Adventures In Audio

Why you need a mono amp in your system - Fosi Audio ZA3 review

Comments on this video

You can comment on this video at YouTube

@IAmThankfulToday:  I quickly realized that I had no interest in the product but stayed for the sarcasm...reminds me of a more verbose version of Granny Crowley, The Dowager Countess on Downtown Abbey. The script was quite funny and so promising that I subbed. Will be more than worth it when he gets his timing down

@allanmoorhead9492:  It's surprising how small an audio power amp can actually be, if you take out the PSU and the radio and phono sections, and the input selection switches. Car audio amplifiers can be very small yet put out a very high level, far more than is needed for the small interior of a car for comfortable listening levels. It seems that many home audio power amps are made larger just to look more powerful.

@PhilipBallGarry:  XLR inputs can be especially useful with an amplifier powered by a switched mode power supply. If you've ever run your hand gently over the case of a device powered by a SMPSU you feel a tingle. That's because they're not fully isolated from the mains supply. It's not harmful of course, it's only a few milliamps but it does represent potential for noise to be imposed on any signal with a common ground. The three terminals of a balanced connector allow true isolation from the chassis of the equipment.

@RomiPetrut:  Thank you very much.

@AudioMasterclass replies to @RomiPetrut: You're welcome.

@RomiPetrut:  Hi, it's a very good review.
I have a question: if I use two za3 as monoblocks with a tube preamp is it a good idea?
...and how is recommended to set the volume controls, at max on za3 using as main volume the preamp?
My respect

@AudioMasterclass replies to @RomiPetrut: Set the preamp volume to minimum then set the power amp volumes to max. Play some audio and advance the preamp volume slowly. It's almost certain this will be OK and you can continue to use your system like this, controlling volume with the preamp. Caution is always good though.

@Douglas_Blake_579 replies to @RomiPetrut: David is correct. But there is a plan B that works too...

Start with the pre-amp at 3 o'clock volume and the amps at 0. Advance the amplifiers until you get the maximum level you are likely ever to use. (for me this ends up around 11 o'clock on the dial). From there use the pre-amp to adjust from zero to your limited maximum.

This has the advantage that the kids won't be able to get you in trouble with the noise police.

@clemmtec9506:  Dose the amp sound better than crown xls1502 ?

@Douglas_Blake_579 replies to @clemmtec9506: Less hiss ... but aside from that, when level matched, it's about a tie.

@Off2Witness:  Started my addiction with a pair of AR 3a, powered by a pair of MAC 60's. Yummy

@stu-po:  These sold out really quick! I'm blaming your very informative review ๐Ÿ˜„

@fosiaudio replies to @stu-po: They are on pre-order on our website.

@immanuelsuresh7739:  Will this be better or equivalent to Marantz PM 6007? In terms of power and sound quality.?

@ChiefExecutiveOrbiter:  Pual McCartney's ears are WORNG!!!

@davelistenstohifi:  Thanks for the review. How does it sound though?

@AudioMasterclass replies to @davelistenstohifi: Not bad.

@jimhines5145:  Listen to the best Toy Matinee release you can find through this amp. It's a true test!

@jerryedwinbennett9695:  Would you PLEASE test the SMSL AO200 mark 2 ??? Uses the German infeneon chip and supposed to be โ€œbetter โ€œ than the amazing Texas 3255 chip, and the integrated amp Ao200 mk2 is only 200$ US dollars right now. I have the aiyima a08 pro itโ€™s amazing for 92$ used , but I am eyeing the fosi zv3 or smsl ao200 mk2. I have Sony cs5 speakers 6 ohm

@pt265:  Yep, to mimic a monoblock setup, I use 2 stereo amps by Parasound 2125v2 and I only use 1 channel on each amp with the 2nd channel unused (nonbridged for quality).

In 4/2023 I've upgraded from 4 delta-sigma dacs (Topping E50, Topping E70, Bluesound Node bought in 12/2022, Arcam AVR5) to the Denafrips Ares II 12th, wow Ares II 12th creates sound in 3D holographic and no listening fatigue after an hour, I can listen for 8+ hours now.

In 11/2023, I upgraded to the Pontus II 12th-1 (and used it with the Denafrips Iris 12th) and wow,
...Apple Music sounds so good.
My Eversolo DMP-A6 is only used as a digital transport streamer for Apple Music, using the Parasound 2100 preamplifier (better volume knob than Eversolo, L/R balance, treble/bass)

@Roddy451:  2:35 ๐Ÿคฃ๐Ÿคฃ๐Ÿคฃ๐Ÿคฃ๐Ÿฟ๐Ÿฟ๐Ÿ‘€๐Ÿ‘€ 14:37 ๐Ÿคฌ๐Ÿคฌ๐Ÿ‘ˆ

After watching that display of a great, wry sense of humor, why the heck wouldn't I subscribe?


@user-tv3nu8zs3s:  This Fosi is for stupid buyers.

@Douglas_Blake_579 replies to @user-tv3nu8zs3s: As opposed to spending $5,000 to get similarly capable audiophile equipment?

@CleartoneAudio replies to @user-tv3nu8zs3s: Trolling...very nice of you.

@Douglas_Blake_579:  From the Williston Labs channel, we now have confirmation that flipping the stereo/mono switch while the ZA3 is powered up is not safe . It puts the chip into protection immediately and we can't be sure it will always come back on after a power cycle.

That switch has no business being on the front of the amp, right in the middle of "Daddy what does this do?" land.

@CristiBaciu:  Imagine a version 2.0 with just HDMI input to connect to tv arc hdmi to control with tv remote

@ufopulse:  cheap chinese junk that clips more then ur grandmas coupons before holidays

@neilw4569:  I like the Grant Wood painting in the background!

@richardgrumbine4867:  Looks like a great little amp... I would have liked to have seen a more standard on off switch... and perhaps no need for volume... and put the mono stereo switch on the back as I would think you would need to be touching very often if at all once you have it set up... but doing so inadvertently like have bad results!

@geevee1045:  Enjoyed your interesting review. Thanks. Just wanted to add that the Fosi Za3 is the first cheap class D amp I've heard that reproduces male voices with body (elevated lower mids perhaps?). It actually sounds rich on my Kef LS50 Metas and manages to inject some warmth into my Maggie LRS+ speakers. So, this is a great relief compared to stereotypical class D leaness, in which hollow body guitars for example, sound like solid body guitars. Just received it today, but so far it's a very pleasant sounding amp. Well worth the cheap investment, for what you get in return. And the sub-out is a nice bonus too.

@ShanePleasance:  My experience with stereo and mono switchable power amps has been to have 2, but keep them stereo mode into biwirable speakers.

@hallmufc replies to @ShanePleasance: How that set up work?

@ShanePleasance replies to @ShanePleasance: Lets say you have 2 x 30 WPC stereo amps that can be switched to mono. Switching them to mono gets you a change to the total output power, and usually a change to the noise figures, not always an improvement. Power usually isn't the issue anyway. Take one stereo amp for each bi-wirable speaker. Y shaped RCA's from source, so one input RCA to 2 Output RCA's - one plug to left amp left channel which connects to the tweeter, other to the right channel of the same amp with connects to the Bass driver. Same with the other amp and speaker (right channel). Then you have - ostensibly - 2 x 60 WPC power amps - and can be done with any two of the same (or same gain) power amps, even if they are NOT mono compatible. Then of course you can have one stereo amp for tweeters, one for bass..... or consider dumping the speaker crossovers and exploring an active crossover twixt pre and power amps, but thats another video... ๐Ÿ™‚

@Douglas_Blake_579 replies to @ShanePleasance: @@hallmufc
Shane has it...
Remove the speaker jumpers.

Amps in stereo mode:
Pre0ut left -> za3#1 L+R -> za3#1L -> left tweeter + za3#1R -> left woofer
Pre0ut right -> za3#2 L+R -> za3#2L -> right tweeter + za3#2R -> right woofer

I just want to add a small note of caution here... the outputs of these amplifiers are in BTL mode. That is they are already bridged. You cannot connect the two black binding posts together, that will cost you an amplifier... So get a meter or continuity buzzer and check your speakers before powering this up, to be sure the bass and treble sections are fully isolated.

@markovlasic1978:  2 mono fosi ZA3 for 2 speakers as mono blocks

@earthoid:  Decades ago I had two NAD 3040 integrated stereo amps that NAD made easy to bridge for mono so I did. Note: the 3040s already had twice the power of the beloved 3020s. Unfortunately the bridged sound was terrible and was only suitable for maybe a PA system. So I left that mess behind but still can't shake the nasty taste that bridging left behind. Therapy might be needed before I can bridge to mono again.

@Douglas_Blake_579 replies to @earthoid: I think you'll find things have moved on considerably since "decades ago".

@gregbailer8701:  Fun Fact: this amp is $100 and gets hot. To all of the 48V( brick) "mono-block" dreamers beware. Your schitt gonna blow up at max level...very soon. It cost Fosi money to drill those holes. Must be a reason?

@Douglas_Blake_579 replies to @gregbailer8701: Naaa ....

@JC-xf5jc:  Love thus GUY๐Ÿ‘๐Ÿผ

@sguttag:  In the fun fact department...the XLR connector (which gets its name from Cannon where that was its connector type)...It was not developed as an audio connector, persay. Have you ever checked the specifications for the 3-pin version? 15A...a bit excessive for mere mic or line level audio! Even its voltage rating is up to 133V on the 3-pin.

@TheRockerxx69:  I love mono!!! I Need 6.

@Projacked1:  How does it work with impedance dips at certain frequencies? Still struggling with that one. ๐Ÿค”

@Douglas_Blake_579 replies to @Projacked1: First ... way too much import is applied to speaker impedance variations. For the most part, amplifiers are voltage sources. As long as they can produce the required current, impedance is largely unimportant.

I have a pair of towers that dip to about 3 ohms in the upper bass region. Far as I can tell my TB10D, which is also a TPA3255 based amplifier, is unaffected by it.

@holycowmanheck:  @10:56 The 20kHz sine wave seems to have a negative bias. The Vmax and Vmin don't seem to line up with what's shown. It looks more like 32V and 41V.

@Douglas_Blake_579 replies to @holycowmanheck: What do you expect from a $65.00 portable scope?
The display is not centered on 0 volts.

@robertbox5399:  If you put 100W into those resistors without a heatsink, they most certainly will burn through that book!

@AudioMasterclass replies to @robertbox5399: Don't worry! I'm a quick worker.

@robertbox5399 replies to @robertbox5399: Until you forget the thing's been left on... The green ones change colour when they get properly hot and you can smell the warmth! Proper audiophile comment that.

@AudioMasterclass replies to @robertbox5399: And then the magic smoke.

@Douglas_Blake_579 replies to @robertbox5399: Sine wave testing is particularly brutal. Most amplifiers are not meant to sustain full on maximum power for more than a few seconds. So one takes their readings then lets things cool off.

I have pairs of those resistors on rather large heatsinks and I've burned fin marks into a piece of scrap wood while working on amplifiers. So far they seem to handle it well enough.

@robertbox5399 replies to @robertbox5399: @Douglas_Blake_579ย  Yes, the difference between PA amps, guitar amps, and home cinema stuff. PMPO rules!

@thomaslutro5560:  Orange knob.... Am I the only person suddenly thikning about US politics now?

@noelmurray1 replies to @thomaslutro5560: You know it should be a BLUE knob!
The only problem is it would cause too much distortion and interference.
Better to go back to the orange.

@riccitone:  lol! No โ€˜kโ€™ ๐Ÿ˜‚

@LucienBill:  The unboxing music is the perfect level of loud and annoying ๐Ÿคฃ

@AudioMasterclass replies to @LucienBill: I aim to please.

@4ujase:  Oh my goodness, I upgraded my Fosi V3 to the 'C'est magnifique Atoll IN100SE! What a sublime amazing sounding beast of an AB amp but not cheap. Two ZA3 in mono I would have considered in a heatbeat, if only it had come out sooner.

@fosiaudio replies to @4ujase: Fosi audio's fault!

@ENGLISHISBEST:  This is audiophile stuff . I enjoy music more than the inners of technology, thats why I buy hifi equipment of hifi quality off the shelf, they do all the technological thought processes & design as its their career. I open a magazine & go on internet to see what is the best rated for the money I have for a component with no real headache worrying about what makes it tick. I then sit back & enjoy my music rather than assessments of the machine. It's when you read comments like you need a machine that reads 10 farads you know it's O.T.T.

@edmatzenik9858:  Mono is sadly lacking in many setups. I think you particularly need a mono switch in a car because not everyone can sit in the middle. And as for cross-talk, in some rooms I've longed for that. In some rooms you just have to put the speakers too far apart, so a bit of cross-talk could be a good thing if you could control it. Maybe.

@PlatinumMastering:  Itโ€™s true some amps have very big crosstalk โ€ฆ and yes 2 mono blocks are better

@paulfriedman4767:  You Sir, are informative and entertaining.

@sjors01:  Hi Audio Masterclass, the back is much more interesting you said, than the front, but the inside is even more beautiful and educational. Could you include this in the next reviews?

@thelowprofile9767:  How do you set it up as monoblock considering that it has left and right rca inputs? Do you just use either the red or the white rca for input?

@Douglas_Blake_579 replies to @thelowprofile9767: The back of the amp is marked ... you use only the right speaker terminals and only the right input channel.

So a dual monoblock setup looks like this...

Preamp out right -> za3 #1 input right->speaker output right->right speaker
Preamp out left -> za3 #2 input right->speaker output right->left speaker

@thelowprofile9767 replies to @thelowprofile9767: @@Douglas_Blake_579 thank you so much. Exactly what I wanted to know. I asked the same question to another vlogger but he canโ€™t seem to understand the question. But you got it right away and answered it in a very clear and detailed way. Youโ€™re the best.

@thelowprofile9767 replies to @thelowprofile9767: @@Douglas_Blake_579 Hi, was this documented anywhere? I was watching another review although it was for another brand which is Aiyima A07 MAX. The reviewer says that he uses the left input instead of the right input. I understand that they are different brands but just wanted to clarify. Ultimately, if I had to set up a monoblock configuration, I can try either left or right input.

@Douglas_Blake_579 replies to @thelowprofile9767: @@thelowprofile9767
Input/output choice in mono mode is not a function of the chip itself, so different designers can implement this differently. Best advice: follow the manufacturer's instructions.

@thelowprofile9767:  The knob will match the Klipsch speakers.

@improbablehandle:  Thanks for that handy nose hair trimmer link.

@Jan-ic9iq:  I have the Fosi V3 with 48v powersupply , hooked it up to JBL L90's ๐Ÿ˜. To my amazement it is capable of handling them. It does get warm, the powersupply stays cool. Two ZA3's would be nice to let those drive the L90's. Unfortunately you can not do bi-amping as far as I know.

@marklawrence17:  I'm an EE. I've had superlative stereos since '79.

Bridged amps, which this is not, deliver twice the voltage and therefore four times the power. The price is each side of the amp sees half the speaker impedance. So, for example, if you bridge into 4ohm magnepans each side of the amp sees a 2ohm load. Few moderately priced amps can reliably handle a 2ohm load. So bridging is for high impedance speakers that don't drop much below 8 ohms. Few modern speakers fit that description. I've never been a fan of bridging. You're all too likely to have stability and overheating and current clipping problems.

Paralleling, as this amp does, results in each side seeing double the speaker impedance. For example, when driving our 4ohm magnepans, each side of the amp sees an 8ohm load. This is much easier for most amps to handle.

You would run this amp in mono mode to handle very low impedance speakers. I've seen some speakers drop below 1ohm in the audio band, dropping below 2 ohms is not uncommon, dropping to 3 ohms is rather common. This amp in mono mode would be a good choice for such speakers, and a lot cheaper than an ampzilla 500 or a mark Levinson.

On the other hand this amp in mono mode would be wasted on a high impedance high sensitivity speaker like any Klipsch. There would be twice the cost and no benefit.

All these considerations really only count if you play your speakers loud. I have a small stereo in my bedroom which averages about 50db never gets over about 80db. Power considerations are just silly.

This amp in mono mode would be a decent choice to drive the magnepans in my living room, which sometimes get quite loud. However, in mono mode each side of each amp sees an 8ohm load and that results in the minor high frequency rise of a couple db. Personally, at age 68 I can't hear anything over about 11khz and I've never measured anyone my age who can. Few over 25 can hear above 16khz, and few under 30 can afford a stereo that works well over 16khz. I've measured several dozen people. No one over 15 in this country can hear 20khz. You may have ribbons that go to 50khz or plasmatronics that go to 200khz, but you can't hear it.

I have trouble imagining someone with $20k speakers using this amp in mono mode. But for my bedroom stereo, elac ubr62 playing soft music, this amp in stereo would be a good choice. For a budget stereo with ss-cs5 or bs22-lr or elac debut 5.2 or emotiva b1+ or Klipsch r41m or rp600m, this amp in stereo would be a very appropriate choice, IMHO.

@daleboylen6427 replies to @marklawrence17: It's NOT bridged according to the lit. They run the amp in a parallel type mode.

@daleboylen6427 replies to @marklawrence17: I'm VERY familiar with bridged amps. I sold high end audio for years. THIS is NOT bridgeable, sorry.

@robertbox5399 replies to @marklawrence17: I'm an EE. What is current clipping? Shouldn't high current cause the feedback loop to increase the drive, ending up with voltage clipping?

@marklawrence17 replies to @marklawrence17: @@robertbox5399 you're correct if the power supply can keep up. If not you get clipping at a lower voltage than you expect. Which some of us call current clipping, as the solution is a power supply with more current capacity.

@Douglas_Blake_579 replies to @marklawrence17: You need to look up the TPA3255 spec sheets ...

The chip itself natively supports ...
4xSE -- 4 single ended outputs
2xSE+1xBTL -- 2 single ended and one bridged output (2,1 stereo)
2xBTL -- 2 bridged outputs (stereo)
1xPBTL -- 1 Parallel bridged output (mono)

The base mode for stereo in these chinese amplifiers is 2xBTL ... that is each channel is already bridged.
For the mono mode they reconfigure the chip for 1xPBTL or Parallel Bridge Tied Load as a means to increase output current capacity.

@mcgovernjimmy:  Lots of infomercials about this product today among "reviewers". "Review for sale"...

@AudioMasterclass replies to @mcgovernjimmy: Fosi Audio sent me this amp. There is no payment or sponsorship.

@mcgovernjimmy replies to @mcgovernjimmy: @@AudioMasterclass Many, like yourself, have been organized by the manufacturer to talk about this product... with the obvious goal of the manufacturer to generate buzz and increase sales. You also stand to profit - which is fine... just be open about it. It would actually be more notable if you spent your own money on the amp. The fact that they sent it to you for free, and these videos happen in unison, is unseemly. It undermines your credibility and puts you in the position of being viewed as being on a bandwagon and "available for hire". This highlights a fact that people need to remember... reviews are just the perspective of another person, and they don't necessarily deserve the credibility that people assign to them. ย 

So many videos about this product suddenly popped up... it's just creepy.

@Douglas_Blake_579 replies to @mcgovernjimmy: @@AudioMasterclass
_ "Fosi Audio sent me this amp. There is no payment or sponsorship."_

... other than a free $159.00 amplifier.

@Douglas_Blake_579 replies to @mcgovernjimmy: @@mcgovernjimmy
" Reviews are just the perspective of another person"

Not really ... Reviews are straight up advertising .

@pauln6803 replies to @mcgovernjimmy: @@mcgovernjimmy This is how Chinese brands get their products known without spending silly money on advertising and paying for What HiFi review stars.
If you've followed Amirm of Audio Science Review, you'll know that he has said he has good relationships with some of the Chinese DAC companies (ASR cut it's teeth on bench testing DACs).
He's said they reach out to him and send products for testing and are happy to answer almost all the technical questions he has thrown at them (ASR is a measurement based community review website, not "audiophile" fluff pieces) and are open to criticism/suggestions for designing the next generation.
The WiiM streamers exploded in popularity because Linkplay threw them at YouTubers.
I can't say that Linkplay were the first to utilise social media platforms in this way, but the rest have certainly cottoned on to this marketing tactic.

@jbrc1322:  One feature missing here that would take this amp to the next level is a high-pass filter for the speaker outs when using a subwoofer. This would take a huge load off the amp if the high demand from the passive woofers was reduced. Distortion would drop substantially at high listening levels and there would be much more headroom for harder to drive speakers. But.... a little birdie told me I just might get my wish in the not so distant future.

@fosiaudio replies to @jbrc1322: Cant agree more.

@deareeMusic:  Your sarcasm has reached levels where I have no idea when u are for real and when u arent and I want to keep it that way

@jerryedwinbennett9695 replies to @deareeMusic: Sarcasm level 9,000 , music enjoyment level, 10,000 !

@mariokrizan399:  ๐Ÿ‘๐Ÿ‘๐Ÿ‘๐Ÿ‘๐Ÿ‘๐Ÿ‘๐Ÿ‘๐Ÿ‘๐Ÿ‘

@SubTroppo:  The outro music didn't make me want to do anything nasty; which is nice. How hot does the power supply run?

@rabit818:  If your fingers has peanut butter while turning it on, fingers slip and you turn the volume loud.

@AudioMasterclass replies to @rabit818: This is a problem I will never have.

@AudioGuyBrian:  Good amp maybe to build a garbage can boombox with. LOL.

@jasontimothywells9895:  Sir , one does not have to have two amps , for your old enough to remember when it was mono . ๐Ÿ˜‚

@tonyfrench2574:  He loves himself and all that irrelevant verbiage he generates

@AudioMasterclass replies to @tonyfrench2574: Who, me?

@rhwinner:  I once caught mono at sleep away camp.

@ThaVoodoo1:  I will be sticking with my Class AB power amp thanks.

@fosiaudio replies to @ThaVoodoo1: Haha, in which case you may turn to class amps?

@davidkclayton:  The Output filter has been optimized for 4 ohms not 8 this is why you get a bump and output at 20,000

@Douglas_Blake_579 replies to @davidkclayton: Actually I did some testing on a couple of these amps using the 10uh coils and 1uf caps, per the development module. The flat response is at about 6 ohms. 8 ohms allows a bit of peaking in the filter. 4 ohms results in a slight roll off.

6 ohms is a good compromise for consumer gear. For pro gear replaceable coils makes more sense.

@marca9955:  Long speaker cables are better than long amp input leads. Better to amplify less noise and distortion than more.

@StrangeBrewReviews replies to @marca9955: Not if your running pro shielded fully balanced XLR cables. Think DIY DJs and smaller mobile audio , small gig musicians...

@Douglas_Blake_579 replies to @marca9955: That's why the balanced inputs. It allows for much longer runs than RCA does.

@Exgol2005:  as always with unique insights or trivia plus wit/humour

@NotSure723:  A YouTube 'play button' is not something you should be seeking to attain, or be proud of.

@saardean4481:  First of all. I love your content. Just a remark as i am listening. โ€žtwo monoblocs two volume controlsโ€œ โ€ฆ not really. Unless i missed something over the years which is quite possible , a monobloc is most times a power amp with no volume control So you will have a single Volume control on your Pre-Amp driving both your monoblocs volume (just wanted to be a smart ass for a second )

@AudioMasterclass replies to @saardean4481: My studio Quad 306 doesn't have a volume control but if I use it as it is then the output level control on my audio interface has to be ridiculously low, and stereo pots often don't track well at very low levels. A pair of 20 dB attenuators is my solution.

@saardean4481 replies to @saardean4481: @@AudioMasterclass i hear ya. Yes i know this issue. Then again even though its a very good amp its an old amp. I stopped
my โ€žaudiophiliaโ€œ beginning of the 2000`s
Now i have active studio monitors and since i spend most my music-sound relevant time in front of them i let my other stuff go. Feels refreshing having a more minimalistic setup. I stopped caring about silver cables and audio expert โ€žfightsโ€œ as like Phil said โ€ži don`t care anymoreโ€œ :-)
I still enjoy watching your channel though

@D-C1:  checkedy check blank book and pen

@AudioMasterclass replies to @D-C1: Puzzled comment readers may wish to know that this comment is a reference to TV game show Blankety Blank.

@D-C1 replies to @D-C1: @@AudioMasterclass you have the best channel on the platform, Happy Christmas.

@crazyprayingmantis5596:  I'll wait until the Za3 pro mk2 plus special edition comes out next week im sure it will "blow the original ZA3 out of the water" ๐Ÿ˜‚

@Douglas_Blake_579 replies to @crazyprayingmantis5596: For certain the paid reviewers will say it does.

@AudioMasterclass replies to @crazyprayingmantis5596: Meanwhile the unpaid reviewers will say what they think.

@Douglas_Blake_579 replies to @crazyprayingmantis5596: @@AudioMasterclass

Way too much gushage going on.

@chuckmaddison2924:  My old Dansette had a " mono block. " and it was tube single end class A.
So, I guess it made me an audiophile.

@AudioMasterclass replies to @chuckmaddison2924: Self-certified audiophiles apply their own criteria.

@supercompooper:  Each driver needs its own amp with at least 10 Farads of capacitance. ๐Ÿ˜Š๐Ÿ˜‹

@Douglas_Blake_579:  For the frequency response test ... the rise in output at 20khz is an artefact of poor output filter design. Fosi is designing for 6 ohm loads as a compromise between 4 and 8. If David tested at 4 ohms he would find that 20khz was down slightly.

For most uses this is pretty harmless, especially since almost nobody would ever hear it.

@niklasschmidt replies to @Douglas_Blake_579: Which is my point. For the segment it is not flawed. And for 500 this problem has been solved. Like in my purifi amp. Fosi provides a path to more to what should matter for an audiophile noise and distortion free gear. Which is often not the case for audiophile brands.

The question is when fosi will provide an amplifier that has addressed the problems of cheap class d

@Douglas_Blake_579 replies to @Douglas_Blake_579: @@niklasschmidt
First, lets understand that the TPA3255 is clearly not "cheap class D" ... The chip was developed by TI for pro-audio use. You will find it in studio monitors, sound reinforcement and public address roles and you will also find it in some high end home theatre gear. To my surprise a couple of the lower powered ICEPower modules are using it as well.

The TB10D version of the TPA3255 tests favourably beside some of the best gear like Naim and Parasound and beats the pants off just about the entire "vintage" market.

Don't mistake the small size and lower pricing for a lack of sound quality. These little guys will surprise you, if you give them the chance.

What they won't do is make your friend's eyes bulge or win you status within a community of audio snobs.

My current main system is a Windows HTPC, DAC, modified TB10D and a pair of Pioneer towers. Total outlay about $1500, including a 60 inch TV. All the electronics fit into a vacant drawer well on my TV stand, with room to spare. I will stack that up against just about any $10,000 system out there on all counts except raw power.

@fosiaudio replies to @Douglas_Blake_579: @@niklasschmidt Great news, we have a big improvement on that.

@niklasschmidt replies to @Douglas_Blake_579: @@fosiaudio. Great!

@carlsitler9071:  Very well sir. I shall sub (not subwoofer, subscribe). Although I am mounting the 2 opposed 10" subwoofer drivers into the box I built for them (4' x 13" x 17"). I was truly shocked at the quality of the Parts Express $44 driver.

@ShazeemKhan replies to @carlsitler9071: Is it a GRS driver?

@matrixplace:  I recently found your channel and felt in love with your sense of humor, cant believe there are people who are triggered :D Keep the great work!

@aesculetum:  I keep wondering if this channel has any common ground with a channel like Techmoan's.

@denis4072:  Every video outro always put a smile on my face. ๐Ÿคฃ๐Ÿคฃ๐Ÿคฃ

@daleboylen6427:  Are you now the more educated version of "Cheapaudioman"?
Pro guy such as yourself reviewing amplifiers your speaker cables will pull off the rack.
I wonder how this does on a pair of Quad ES63's playing the Telarc 1812 with canon shots?
Rhetorical question.

@Douglas_Blake_579 replies to @daleboylen6427: Gee I dunno ... How do you think those speakers will react to a power amp that can dump a clean 250 watts RMS into a 2 ohm load?

And yes the PBTL configuration of the TPA3255, will do that all day long. This isn't some dumb consumer chip amp. The TPA3255 was specifically developed by Texas Instruments for pro-audio uses. You will find them in powered monitors, sound reinforcement, public address and high end amplifier modules such as the ICEPower amplifiers. Also many home theatre systems are based upon this chip.

They are being adopted here because TI is selling them at about $7.00 per chip in production volumes. Combined with the low cost and low parts count, these things end up being a very affordable power house amplifier.

@daleboylen6427 replies to @daleboylen6427: @@Douglas_Blake_579 48 volt, 5 amp power supply. FIVE. Do the math.
250 watts LMAO

@Douglas_Blake_579 replies to @daleboylen6427: @@daleboylen6427
I see you don't understand the purpose of Bulk or Reserve Capacitors. You know, storing a charge to provided extra energy during short term transients...

@daleboylen6427 replies to @daleboylen6427: @@Douglas_Blake_579 I kinda do understand. My Citation 22 has filter caps that are each almostthe size of that Fosi entire unit.
And yes, I understand class D is more efficient. But in the end, it's a 5 amp power supply and the chipset blows up with anything much more than 48 volts. If you LOVE it, buy it. I'm not trading in my Arragon 8008 for a fucking Fosi any time soon.You can feel free to do so if you like.

@Douglas_Blake_579 replies to @daleboylen6427: @@daleboylen6427
Years ago I traded a top line Marantz power amp for a TPA3116 then jumped to the TPA3255 when it became available. I'll stay with the leading edge, no problems.

On my test bench the TPA3255 chip tests in better than about half of the so called high end gear out there. In fact, looking up the specs for your $15,000 amplifier I note that the TPA3255 based amps have about the same power, distortion and frequency response as the Arragon ... at 1/100th the price.

Dump on them all you want, these are good amplifiers.

@CreateListenCreate:  The oscilliscope link is for the fn generator.

@deanodley replies to @CreateListenCreate: Yes noticed this tooโ€ฆ

@AudioMasterclass replies to @CreateListenCreate: Fixed it!

@garyd2698:  Wow that was different. Your witty and somewhat entertaining. Keep it up.

@MichaelBeeny:  You have just found one of the main issues with cheap class D amplifiers. They sound very different on different loudspeakers. All loudspeakers have a very variable impedance curve. These class D amplifiers give a different high frequency response to different speaker impedance. Because of this some speakers will sound extra bright, some over dull. That's the price you pay for cheap class D. Ok for the undemanding use but if you want real HiFi go class AB

@niklasschmidt replies to @MichaelBeeny: Or hypex or purifi

@Douglas_Blake_579 replies to @MichaelBeeny: You do realise that "different frequency response" is about 2db that occurs well above 16khz where almost nobody could hear it.

@jasontimothywells9895 replies to @MichaelBeeny: Even class b and h are awsome power amps , Mitsubishi receivers and amps in the 70s up till mid 80s was awsome , sounded solid and pushed a ton of current .

@davidcorner1174:  thank you.

@stevengagnon4777:  What about an ear test as they are the ultimate testing instrument that maters in the end. Really I would have liked a test with a pair of low impedance speakers with a nasty dip in the base region. Yeah make that a pair with low sensitivity just as a torture test. Maybe you would have a better idea what's going on with that high octave . We could have gotten some words out of Audio Phil he's always entertaining. His highly resolving ears almost never miss anything....especially the stuff I cannot here myself.

@Douglas_Blake_579 replies to @stevengagnon4777: A small change in frequency response in the top octave is not going to affect the bass response. I have multiple tpa3255 amplifiers here and I run them on Pioneer towers that dip to about 3 ohms in the upper bass regions ... no problem.

@StrangeBrewReviews:  They just need to eliminate the vollume knob for a VU meter and make them true mono blocks for $199.

@AudioMasterclass replies to @StrangeBrewReviews: I have a feeling they'll read your comment and do just that.

@StrangeBrewReviews replies to @StrangeBrewReviews: @@AudioMasterclass replce the stereo/mono switch with on/off ....Keep RCA/XLR set of speaker terminals....but now add in full sized bus out XLR and RCA connections for daisy chaining.

@MrRocktuga:  That's basically cheap-fi, and there's no place for it along pro users or audiophiles.

It seems like its output is frequency/impedance dependant like most cheap class D amps.

Audioholics mentioned that they were once measuring a loudspeaker and it was giving strange results, onlh to find out that it was the bad class D amplifier acting up.

So there goes the pro user validation, or the audiophile for thst matter, since many loudspeakers have "difficult" impedance curves.

To be fair, the chinese have all the means to produce amazing amplifiers if they want to.

The obvious question is thst they're not going to be that cheap. ๐Ÿ˜‰

Another usual thing with chinese amps is how they don't deliver the advirtsed power, no matter what additional power supply you buy for it.

IMHO, any used amplifier from a reputable brand is a much better "investment" than this chinese crap, since they hold their value better, they're likely to have spare parts for longer, and they sound better right from the start.

I surely can't hear anything at 20 kHz for quite some time (I'm 50), but that's not a valid reason for buying poorly designed products.

Conventional A/B amplifiers from the last several decades are flat from 20-20.000 Hz (and often beyond), as well as good class D amplifiers.

I personally find that poor behaviour unacceptable in this time and age, and reviewers should call out these chinese manufacturers for selling BS (which is not clearly advertised as such).

This is another case where a product doesn't need to cost a lot of money to be expensive!

It isn't a good value proposition, and even the power switch on the volume button is reminiscent of entry level japanese products from the past (way, way back then).

What I find amazing is how all of this doesn't get stated on a channel like this one!

Anyone who's starting out with audio (both as a listener or maybe music production) should have the most reliable audio it can afford at that time.

Starting out with flawed products doesn't seem to me like the best option.

If decent amplifiers were uber expensive and there wasn't a lot of them in the used market, it might be an alternative.

But that's usually not the case, and these pieces of electronic garbage isn't something that this planet is needing...

It seems like the packaging is still the best part of the buying experience! ๐Ÿ˜‚

@niklasschmidt replies to @MrRocktuga: Why is it flawed? The V3 has better measurements than a 10k Naim.

@pauln6803 replies to @MrRocktuga: I'm sorry to say that cheap Chi+Fi is catching up with and in some cases, beating high priced western gear - see WiiM devices.
I say sorry not because of any anti China bias, but the threat of many European, and in particular British, jobs are going to be under severe threat in the near future.

@scottlowell493:  FWIW: I prefer the polymid tweeter of the B&W Dm100 (or older polyester) to the new diamond anything.

@werner.x:  I like your approach ๐Ÿ˜

@schemkesa:  Ow what a great amp. I need one for my extra Atmos channels. This would be great! Let's waait your review first ๐Ÿ˜‚

@philrobinson4329:  I don't think your music is anoying at all. It's very well mixed and mastered and I can hear all the instruments all the time via my Naim DAC-V1 and Sennheiser HD650s. Nice review BTW.

@AudioMasterclass replies to @philrobinson4329: Gosh, an audiophile listening to my music.

@werner.x replies to @philrobinson4329: Let the mix be good or not - still annoying as a background music ๐Ÿคฃ
I'd assume, by intention. Or what else? ๐Ÿ˜…

@imqqmi:  For audio equipment (6:22), you don't connect shield ground to earth ground but to chassis ground, unless you've got proper filtering of high frequency components. Shield+chassis should work as a faradays cage, but that can be compromised by connecting to earth as it's often a fairly high impedance.
Look up 'How to achieve proper grounding' by Rick Hartley on youtube.

@thrdwrld3:  But what does Audio Phil think about the amp...?

@AudioMasterclass replies to @thrdwrld3: I've a feeling he might be changing all his volume knobs for orange.

@fotouhi:  I wonder if one could use this unit for individual mono channels of a surround system and will the audio improve because of separate power supplies?

@AudioMasterclass replies to @fotouhi: No reason why not other than multiple volume controls. Separate power supplies are good in theory but the improvement would be a tiny fraction of what you could achieve with acoustic treatment in your listening room.

@MrRocktuga replies to @fotouhi: Forget about it.

This is a bad amplifier to start with, and if your AV receiver has the individual line-level outputs for all channels, it should have a better quality amplification than this piece of crap. ๐Ÿ˜‰

If you want or need more power from your AV receiver, try instead:

- buying good external amplifiers (they don't need to cost an arm and a leg);

- Buy only one stereo amp for your main channels, and let the AV receiver handle the rest (the internal power supply won't be as taxed by the main channels).

@jasontimothywells9895 replies to @fotouhi: โ€‹@@MrRocktugaeggszackly. Turn off the mains and loosen up the a/v receiver handle only the soft loads .

@BatteryAz1z:  These type of class D amps have an impedance dependent frequency response, increasing the upper treble with higher impedance, so the frequency response will be different depending on the speaker's impedance curve. It's an issue that is solved by more sophisticated class D designs such as ncore and purifi.

@scottlowell493 replies to @BatteryAz1z: All of the "budget" class D amps that I have tried do that. Not to mention, they modulate noise and the treble is vague and rolled off. Good class D amps are a few thousand, not a few hundred.

@werner.x replies to @BatteryAz1z: I bet, that's exactly designed that way to sound more lively just out of the box without any sound controls added.
And rightly so from the sellers point, because trebles get lost anyway for many reasons.

@niklasschmidt replies to @BatteryAz1z: They are roughly 500 euros. Which would be the entry point hypex. Or 300 if you go for a SMSL.

@niklasschmidt replies to @BatteryAz1z: They are based on ti chips.

@david1rosenthal replies to @BatteryAz1z: Exactly right. This amp is based on the TI TPA3255 chip. We are just on the cusp of seeing implementations of this TI chip with an extra "post filter feedback" circuit that cures this issue, but this doesn't have it. Those more advanced class D amps from Purifi have the extra circuit.

@rf0022:  Balanced audio was first developed by the telephone industry, using transformers for common mode rejection.

@wmrg1057:  Don't like the mono switch on front, its too big & too easy to bump

@Douglas_Blake_579 replies to @wmrg1057: Agreed ... and so far nobody's been willing to flip it while the amp is playing music.

The 2xBTL and 1xPBTL are very different configurations of the TPA3255, and jumping from mode to mode is not guarded by the built in protections.

I, for one, would be very interested to see what happens.

@inonothing09:  a speakon is XLR ? take your payed for bull shit and shove it ...

@AudioMasterclass replies to @inonothing09: Comment readers may like to know that I did not mention Speakon connectors in this video, neither was I paid to make this video.

@Douglas_Blake_579 replies to @inonothing09: They may look like speakons but those are actually dual mode balanced inputs ... you can plug in either an XLR male or a 1/4" TRS plug for balanced input. If they have them wired correctly plugging in a 1/4" TS plug should auto-switch to unbalanced inputs.

@anahatamelodeon:  OK - I'll bite...
First - on PBTL: simply paralleling the outputs is fine to be able to deliver more current and drive lower impedance loads, but you really can't call it "bridge-tied" - surely that means specifically connecting each side of the load to an amplifier output instead of one side to ground. Why not just call it something truthful like parallel mode?

Next - Who invented balanced lines? Probably telephone engineers in the 19th century.

Oh, and I agree about separate switch and volume control, but at least with this type you might be able to switch it on and off without turning the know if you're careful - even so I wouldn't want that arrangement; rocker switch for power is fine for me here.

@glenngundlach9907 replies to @anahatamelodeon: Do NOT try "parallel" mode. Nearly ALL amplifiers wil kill themselves in parallel.

@naibafabdulkobor4301 replies to @anahatamelodeon: When running the channels of a stereo amp in parallel there is usually still an arrangement of resistors one could call a "bridge". Even with both channels' gainadjusted as precisely as possible, this is needed to compensate for tiny differences (so the amps do NOT kill each other).

@anahatamelodeon replies to @anahatamelodeon: @@naibafabdulkobor4301 that's true - I wondered how they balanced the output currents and it would need some sort of current sensing resistor network. I still think BTL is a bad name for that case, because the load is not part of a bridge.

@Douglas_Blake_579 replies to @anahatamelodeon: The mode is PBTL ... Parallel Bridge Tied Load and it is one of several standard configurations the chip is designed to work in.

Do a search for "TPA3255 spec sheet" and see for yourself.

@ac81017:  No such think as budget Audiophiles ๐Ÿ˜…

@Douglas_Blake_579 replies to @ac81017: I know. We're smarter than to give ourselves such a ridiculous label.

@aljosamlinaric8705:  I think you should use termination on osciloskop or at least switch probe from 1x to 10x. That's probably why that voltage difference on oscilloscope.

@werner.x replies to @aljosamlinaric8705: Then he would have seen that same voltage response, when he did check the generator with the same setup, wouldn't he?

@Douglas_Blake_579 replies to @aljosamlinaric8705: FWIW ... that peak in output power is due to the output filters being underdamped at 8 ohms. It's only about 1.5db and it's at 25khz where nobody's going to hear it.

@gteaz:  My centre just needs a mono.

@georgejohnson1498:  Or you could have a really mono only amp! Quad II Forty here. just the one. Fits nicely between my Leak Trough-line Mk 1 from November 1957], and my 1957 Quad ESL [two black inputs on the amplifier inputs as phase does not matter in Mono according to Peter Walker and I agree], so my daily radio set has more years on it than a human lifetime plus half another.

As the great conductor, Otto Klemperer, observed, when requested to remake recordings in stereo, "Stereo is the invention of the fakers!" ... or, on another occasion, "it is a scandal!"

Well balanced mono is far more like what you can hear when listening from a good seat in a real concert hall, unless you insist on sitting in the front six rows, than almost any over separated stereo styles recording!

What I need is a competent way of converting stereo to mono for my very nice set!

Best wishes from George

@AudioMasterclass replies to @georgejohnson1498: Stereo recordings often donโ€™t collapse well into mono. But you can listen to one channel at a time, then you have a choice of two perspectives.

@georgejohnson1498 replies to @georgejohnson1498: @@AudioMasterclass Yes you are quite right, though in the glory days stereo was mono compatible. Sometimes in multichannel mixes, there is the horrible comb filtering effect with phase incompatibility, that ruins stereo to mono!

Fortunately few great artists have made recordings during this era of incompatibility, so I am not much concerned by that.

And if all else fails, then listen to the left channel where the soloist in a concert is [usually], and the first violins. You get a skewed balance like sitting too far to the left in a real concert hall too close to the front. Been there, done that, and got the tea-shirt!

Love your videos!

Best wishes from George

@jasontimothywells9895 replies to @georgejohnson1498: Eggszackly, I always have loved mono , and I still own a old black and white television.

@robturner3065 replies to @georgejohnson1498: @georgejohnson1498 Want to give that Troughline 1 the shot in the arm it desperately needs? Swap the EF80s for EF184s (mine's December 1957!)

@georgejohnson1498 replies to @georgejohnson1498: @@robturner3065 Dear Rob,

My Trough-Line 1 was totally restored and recapped in 2018 and keeping as close as modern capacitors and resistors allow, to original specifications. The valves are either original fitment Mullards or in three [of the eight] cases NOS Mullards of thee original type. Thus it is working about as close to original as is possible. I rather like it. With the equally old ESL and a good Quad valve amp, it has a lovely sound. Very revealing of poor recordings, and fairly hopeless on pop music, but magic on a good live concert relay. I would not want a more modern sound quality. For that I have a solid state stereo set. Rotel radio, Denon integrated amp and Mission QX ! [mk 1] speaker's. That is s nice little set, but not nearly so nicely balanced as the veteran set.

I use the solid state set for iTunes and LPs. It is stereo, but I have only a paper narrow air gap between the speakers, so it becomes effective mono.

Thank you for you nice reply!๐Ÿ™‚

Best wishes from George

@Douglas_Blake_579:  David touched all the key points but lets dive just a little deeper....
Lets ignore the company websites and their hype about power and take a look directly at the "TPA3255 Spec Sheet" ... go ahead do a search...

In stereo mode all these amplifiers operate in 2xBTL (bridged) mode.
The output power is graphed in Figure 8, on page 11.
So here's what you can reasonably expect at 1% distortion ...

[voltage] - [4 ohms] - [8 ohms]
32v - 110w/ch - 55w/ch
36v - 150w/ch - 75w/ch
48v - 220w/ch - 125w/ch

The A07Max and Za3 can both operate in 1xPBTL mode for mono...
This time the output power is graphed in Figure 23 on page 13.
But beware ... this is not a 4-6-8 ohm chart... it is for 2-3-4 ohms, so for 8 ohms we have to take the 4 ohm rating and divide by 2.

[voltage] - [4 ohms] - [8 ohms]
32v - 110w - 55w
36v - 150w - 75w
48v - 250w - 125w

Yep... 1x PBTL mode gives you the same power at 4 and 8 ohms as the stereo mode does.

You do not get the extra power until your speakers dip to 3 or 2 ohms. The graphs show us that at 48volts with 2 ohm speakers, we can expect almost 450w/ch at 1% distortion.

Moreover; since the TPA3255 chip is fixed gain operating at 21.5db ... no matter what power supply is connected, For a given input, the output will be the same. For example: setting a nice volume with the 32 volt supply then plugging in a 48 volt supply will not result in some magical transformation in any of these amplifiers. The output level and tonality will remain the same. All you really get is an extra 3db of headroom with the 48 volt supply. (A 3db jump in maximum volume is barely noticeable, and unlikely to make any difference in home use.)

So... what does all this mean? Well, it boils down to "don't waste your money". Unless you have speakers that get down to 2 ohms there's no real advantage to either the 1xPBTL monoblock mode or the higher voltage power supplies.

Now don't get this all wrong ... I prefer the TPA3255 based amplifiers and use one (a modified TB10D) in my main system. What I am suggesting is that you go with the data sheet, get the real numbers and make your decisions on fact, not marketing hype.

Between TPA3255 amps, you can make your decision on features...

The power switch on the knob is a deal breaker for me.

@richh650:  Your "unboxing" portions are hilarious. I am glad you pointed out how speaker loads can vary greatly with frequency. I dare say most YT reviewers don't comprehend that fact. Thank you!

@Douglas_Blake_579 replies to @richh650: 1.5 and 2 db at 25khz is not "greatly" ... it's "slightly" at worst.

@gurratell7326 replies to @richh650: They can vary if they are badly designed or just cheap. But as already said the difference is just a few dB and can fixed by adjusting your DSP.

@idwalwilliams3713:  Fun

You can comment on this video at YouTube

Thursday January 4, 2024

Like, follow, and comment on this article at Facebook, Twitter, Reddit, Instagram or the social network of your choice.

David Mellor

David Mellor

David Mellor is CEO and Course Director of Audio Masterclass. David has designed courses in audio education and training since 1986 and is the publisher and principal writer of Adventures In Audio.

Learn Pro Tools with our amazing range of video courses

Pro Tools video course catalog

Browse Pro Tools courses...

Learn Logic Pro with our amazing range of video courses

Logic Pro video course catalog

Browse Logic Pro courses...

Learn Cubase with our amazing range of video courses

Cubase video course catalog

Browse Cubase courses...

More from Adventures In Audio...

Hi-Fi comfort OVER your ears? TRUEFREE O1 detailed review

Get the tube sound in your system with the Fosi Audio P3

Any studio you like, any listening room you like - For producers and audiophiles

Hidden Hi-Fi - The equipment you never knew you *didn't* need - Fosi Audio N3

Adding tubes to a jazz mix with Freqport Freqtube

Adding tubes to a rock master with Freqport Freqtube

Adding tubes to female vocals with Freqport Freqtube

Adding tubes to male vocals with Freqport Freqtube

Adding tubes to real drums with Freqport Freqtube

Adding tubes to a bass guitar with Freqport Freqtube

Adding tubes to speech with Freqport Freqtube

Adding tubes to an acoustic guitar with Freqport Freqtube

Parabolic reflector microphone - Sound On Sound latest issue

Your power amp is average - Here's why

MANCAVE REVIEW: In-ear monitors - Better than earbuds?

Can this tiny amp really produce 600 watts? - Fosi Audio V3

MANCAVE - Recreating Olivia Rodrigo's 'Vampire' vocal

Why does this song sound so bad?

Audiophiles - You're all wrong!

MANCAVE RE-REVIEW: OpenRock Pro earbuds in language Audiophiles can understand

MANCAVE REVIEW: OpenRock Open-Ear Air Conduction Sport Earbuds

Can lossy digital audio be better than lossless?

Man-Cave: Microphone mysteries revealed

How I improved my audio - From the Mancave