A headphone amp with mystery features you might love - Fosi Audio SK02
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Tuesday January 30, 2024
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.
@parthabhatta1963: Excellent video mainly for the teardown and preamp portion explanation.
I have a Exposure brand amp without tone controls which is ok for all sources except while playing old cassettes where high frequencies get substantially cut off owing to the age of the cassettes. I am planning to put this device between my cassette deck and amplifier to give the high frequencies a boost and this video has helped me to make a decision. 👍👍👍 Thanks to uploader.
@arthurriaf8052: Most of my equipment has Tos link cables and I USE them! They're noise free and even a 10' long cable is not expensive. I wouldn't think of buying a light link cable for hundreds of dollars or pound or speckles or whatever currency you name. Light is the way to go. 1 cable and the sound is perfect as can be. I've used light link in the professional world for 40 plus years and can even repair cables with the right equipment. All the High voltage connections to our tools were light links. Perfect transmission and testable with the right gear.
@TeSp00kie1: I know very little about this stuff but it is my understanding that balanced outputs also have the benefit of a lower noise floor. Also, if you're looking for a streamer, all the Wiim products are magnificent.
@billmankin6204: Wow. >$700 for a TOSLINK is _criminal_. Any computer engineer <- will tell you digital cables either work, or they don't. The difference (unlike analog cables - that's a different fight) is ZERO if the cheap cable is good enough to carry the signal - I take from your other videos you agree. This does look like a fun gadget, and I think it will be great for traveling. I go to pool tournaments regularly and despise listening to TV and movies on the integrated speakers.
@JHDundrum: "TOSLINK is a trademark of Toshiba Corp." Toshiba is the Tokyo Shibaura Electric Co., Ltd., therefore I go with a pronunciation starting with a word sounding like "toss". Now, if anyone can outline why Tesla is pronounced tezla, I'd be ever so etc. : )
@mtinhk: Isn't the "Optical In" useful if you want to use the SK02's own DAC/AMP without coloration by previous DSP?
Whether or not all DAC chips sound the same, a "DAC" is usually more than the DAC chip itself, isn't it? For example, I have my projector connected via optical output to my SMSL SU-1 and can get better sound out of this combination (even if at fixed volume, and even if I lose Dolby Atmos) than I could get out of the projector's own 3.5mm analog output.
In another use case, I don't want to use the "DAC" of the HDMI extractor connected to my Roku to have sound DSPd by the extractor itself before it reaches my SMSL DL200. As in the previous case, I am assuming that the converstion from digital to optical does not alter the sound in the ways that convertion to analog + amping would.
I do agree that one's levels of interest in very high sample rates might be directly proportional to the seriousness of their ADHD, but other functions here may have their use cases even if one is not a flamboyant audiophile, isn't it?
I would have been more interested in learning how the SK02 sounds. For example, I have the Fosi Audio DS1. Does the SK02 sound similar to it?
@AudioMasterclass replies to @mtinhk: I have a feeling that people often get overexcited about DACs. Having said that, I've just had two sent to me for review. Maybe I'll change my mind.
@danrussell9357: Hope to see a DSD video!
@1donjuego: So I just browsed the Fosiaudio official website. No SK02 to be found. Just an SK01 which appears to be quite different. Wanting to be clear ... not that it is sold out. It doesn't exist according to Fosi.
@AudioMasterclass replies to @1donjuego: I think the situation is that it hasn't been released for sale yet. Hopefully soon.
@mortenjohansen4120: Why don’t you use thr headphones they use in studios, AKG k240 or Behringer hps 3000???
@AudioMasterclass replies to @mortenjohansen4120: Wot? Behringer HPS3000 for $15? Sure you don't mean Beyerdynamic DT100? Anyway, here's my affiliate link for the Behringers. Buy, buy, buy - https://amzn.to/3HXox4n
@kristianlarsen7694: Ere we go again, facing endless amounts of rewievers, producing avalanches of statements and verdicts of this, they may believe is a new thing.
Its not new, you made a balanced output yourself, and i as a very practical amateur did with the xlr output of my Lynx one soundcard. I had a pair of sennheiser 410 that were 600 ohm. They had cable for each side into 6,5 mm jack. I cut it and soldered each side + and - to xlr, and plugged it into the output of my soundcard. Used it for tracking. I may not be the only one to do that. It was in use until microsoft with an "upgrade" of their OS turned the sound card obsolete. I am glad that microsoft OS is not part of my car.
Is it correct that noise mostly hits high impedance connections? Headphones with 32 ohms are low impedance, so is there a problem to fix? As the saying goes. If it aint broke, dont fix it.
There is allways a fair amount of trolling in your videos just 0,0001 mm below the surface.
Thanks for the fun.
@D1N02: too bad I can't read lips
@middleearthltd: I Heart stick up the arse Brits who love to hear themselves talk
I would rate this sarcasm at SK02 level
@gustavehenry: Tos-link sends a digital signal, therefore, there is no way to amplify it.
That is a major disadvantage of using it as audio output from a tv, you can't use the tv volume control for your volume any more. You have to change the volume on the receiver.
The advantage, is that it's a 1 thin cable, 5.1 signal with no interference possible. (therefore, you'll only fear interference from the 10+ other cables linking your speakers and other devices....)
@JustLearning: I may have missed it but did you provide a link for the Fosi Audio SK02? You had loads of links to everything but the SK02?
@AudioMasterclass replies to @JustLearning: I got my spreadsheet in a twist and released the video too early. From what I've been told so far, the SK02 will be released in February.
@Bizzle65 replies to @JustLearning: I had a quick look and from what I can gather it’s still at the Kickstarter stage. I just backed the project for £65!!
@simonegleton1790: Thank you for this; am wondering if you, or any followers, know what the retail price will be?
@AudioMasterclass replies to @simonegleton1790: No idea but I wouldn't expect it to break the bank.
@peters7949: As usual, great video Dave.
Re: mini TOSlink cables, I have a few Mac Mini computers, late 2014 & older, that have this feature, which I use to feed AV (HiFi) amps, not only does this mean the audio files I play are passed to the AV system as the creator intended, WAV etc, and not decoded by the computer’s DAC & head phone amplifier, it means that DTS encoded PCM files play in full 5.1 surround. For many years the only readily available way of playing surround music files was DTS encoded WAV burnt to CD, which connected to AV amp via SPDIF or TOSlink (which is carrying SPDIF for the majority of uses; ADAT Lightpipe was another TOSlink audio format) gave me many hours of surround sound music pleasure in my listening room, I now use one of the older MAC Minis as a music player.
It was a sad day when Apple dropped the combined headphone/TOSlink connector.
TOSlink was short for Toshiba Link, so while I & everyone I know, calls it TOS Link, perhaps it should be Tosh link?
As to anyone who pays more than a few pounds for TOSlink cables, they are living in cloud coockoo land, especially ones with gold plated connectors (I’m looking at you Audio Phil). The core is 1mm diameter multimode, so bit spread limits SPDIF to max 10m or so, and is designed to work fine using plastic fibre.
The major factor for TOSlink connectors is how well they lock in place, and some of the expensive connectors are large & heavy, the weight of the cable & leverage of the long connector can damage the socket. So so called premium grade connectors are vastly inferior to cheep ones in the long term.
@AudioMasterclass replies to @peters7949: Some audiophiles can, apparently, hear the difference between a plastic and a glass toslink cable. The glass cable, as you would expect, is "smoother" and has "slightly less sibilance". It is also "weightier and darker but just by a tiny bit". I asked Phil but he started going on about the skin effect.
@peters7949 replies to @peters7949: @@AudioMasterclassmy immediate response is a word beginning in B, that is probably baned by YouTube. As John Watkins (the digital audio design guru) said “if changing the interconnect cable, changes the sound, the interface electronics was badly designed” All that comes out of TOSlink, SPDIF & AES3 is one’s & zeros. Only if the cable is long enough for HF losses or bit spread to prevent the receiver distinguishing between a one & zero can it have any effect on the audio carried, and the result will be loss of signal, which may be intermittent, but cannot affect audio transients or smoothness.
@thefloop2813: Your unboxing music might indeed be absolutely abysmally horrible.
It does sound really good though, especially for a youtube video.
P.s. Ill poke my nose into the cable and capacitor issues whenever i get the chance, but i just like to chuckle from the sidelines when it comes to the whole usb/coaxial/optical thing. Gotta choose your battles, ya know?
And SCSI? Why did you have to remind me, the night terrors are gonna come back now.
@dmikelyn: Nothing subtle about this gentleman’s sarcasm and innuendo. It certainly speaks to my jaded audio soul! So I say “More of the same Good Sir!” if you please. :-)
@ЛюбомирРусев-ф6в: Very interesting device. Strangely enough, it reminds me about (almost) similar on functionality and internal parts DAC/phone amplifier Fiio K3 new. Not sure about the prices' comparison.
@marcbegine: Toshiba link (Toslink)
@davidkclayton: They have been using encoders in audio equipment for quite some time now. I have not yet seen a system that doesn't remember it's settings. If that's the case in this piece I think that's an oversight.🤨
@davespagnol8847: I guess the biggest fun with Toslink is getting the connector from Poundland for .... a pound, and finding that it sounds no different to a £300 one.
@gustavehenry replies to @davespagnol8847: One of the major advantage of optical is the quality of the signal. Because, an optical signal can't have interference. (It light, not electrons). Therefore the only thing that could go bad in a optical cable is... if you break it.
The only potential problem of your dollar (pound, euro, who cares) cable, is that it might be too fragile. But event that... if you don't try to hang yourself after figuring out that the 300x more expensive version that you bought first is no better, there is little chance that you would damage it if you care ^^
@markphilpot8734: You spoke of fun in your review. Sarcasm seems to be your fun and why not. Cheers !
@nicc5122: Hang on, there's no 32kHz sample decode? More optical comments. I use a DAC on a laptop to generate an OPTICAL output (electrically isolated) then feed it into a DAC, so USB in and optical out does make sense (just digital pass through)
@AudioMasterclass replies to @nicc5122: At some point someone is going to say they like the sound of optical.
@nicc5122: Optical eliminates ground loops. That's why I favour it PARTICULARLY from laptops which have inherently noisy power supplies (especially HP...) I've several transformer balanced humblocks too but can introduce more problems and you need to part with a lot of money for good transformers.
@deejayiwan7: Fun fact: older Mac Book Pro models had optical out in headphone combo out
@AudioMasterclass replies to @deejayiwan7: I try to learn something new every day. I can relax now.
@jimhines5145: While your reviews are extremely good and well thought out, I liked your channel better before you started this...review thing. Sure free stuff is always great to get, but this is really cheap stuff. Don't get me wrong, some cheap stuff is great quality and I do have a few Fosi audio components myself. I just feel like you had a great channel before you started doing equipment reviews. Please don't do many of them and get back to your original ideas, which are great videos.
@AudioMasterclass replies to @jimhines5145: My secret plan is to work up from cheap gear to high-end. I don't know whether the high-end manufacturers will dare though.
@chaoticsystem2211: what?? 4?
@AudioMasterclass replies to @chaoticsystem2211: Correct. You're the first and only to answer so far.
@chaoticsystem2211 replies to @chaoticsystem2211: @@AudioMasterclass But how? The only way i can think of, is to use separate transformers for each channel. Without common 0V, you could save one wire.
But does that even work?
@AudioMasterclass replies to @chaoticsystem2211: @@chaoticsystem2211 I didn't use transformers, I used two op-amps. Each side of the headphones is connected across the outputs of the two op amps (one is inverted). Two pins x two channels = a four-pin XLR.
@chaoticsystem2211 replies to @chaoticsystem2211: @@AudioMasterclass i see... thanks. analog circuits are like magic to me anyway :D
@atoptip6193: TOSLINK, the only ever application of fiberoptics in audio, is actually very useful — it eliminates any ground loops that may raise their ugly heads. If only it did not remind me of TOSsr@gs…
@AudioMasterclass replies to @atoptip6193: Your asterisking is commendable.
@atoptip6193 replies to @atoptip6193: Thank you. But what asterisk? You mean the @ sign?@@AudioMasterclass
@AudioMasterclass replies to @atoptip6193: @@atoptip6193 Debbie, my editorial assistant, advises me that replacing letters with symbols, any symbol, is widely known as 'asterisking'.
@shipsahoy1793: I am not using the optical output
on my TV either.
I use the HDMI connections on my TV, just for the bloody FUN of it!🥁
@PeTroL420: I don't understand. Wouldn't a balanced output be mono? On a mixer's XLR inputs, you have to run two balanced cables and have a two channel capable DI box or use two DI boxes to achieve stereo.
@Wuppie62 replies to @PeTroL420: A standard XLR cable is wired in a certain way that it transports 1 signal. But with (mini-)jack plugs you have variants like TR, TRS, and TRRS, where T stands for Tip, R for Ring, and S for Sleeve. Therefor a jack plug can be mono, stereo, unbalanced or balanced.
@PeTroL420 replies to @PeTroL420: @@Wuppie62 I don't think you understand what I'm saying. TS, TRS and TRRS are all unbalanced. TS is mono, TRS is stereo left/right and TRRS is stereo left/right plus mic. A stereo balanced plug would need something like a TRRRS because you'll need two positives, two negatives and a ground to get the signals balanced.
@Wuppie62 replies to @PeTroL420: @@PeTroL420
6.3mm jack plugs cables can be used for one channel (mono) Balanced. Just like XLR. I have them and use them as such. TS jack plug is unbalanced mono.
Bytheway, search for and look for instance at " iFi Audio 4.4mm to XLR cable ".
@peters7949 replies to @PeTroL420: Headphones, being a relatively high signal level & low impedance (like loudspeakers) do not need a screen, just 2 wires per driver (ear) so an XLR with 4 or more pins would be ideal, preferably wired so the output is on a socket, and. The head phones on the plug, so it’s not possible to touch the ‘live’ contacts when not plugged in. The voltage is almost certainly not large enough to cause harm, but shorting the pins might damage the headphone amplifier.
@artysanmobile: A decent Toslink cable should cost you $10 or so. Note I said decent. The reason being it is optical and as a result is a go/no-go proposition. There is no ‘quality’ involved. It either works to absolute perfection or it is dead silent. I have many of these cables left over from a project with Yamaha consoles. Audiophiles are welcome to them for the ‘nephew’ price of $200 apiece. I’ll mark them North and South to make installation more special for them.
@mathumphreys: You reminded me that I have had a couple of laptops that had 3.2mm optical out. I never used it though.
@artysanmobile: Macintosh computers have used a dual function 3.5mm audio out jack for many years. It has a tip-ring-sleeve construction just like you’d expect but also, way in there, an optical transmitter exactly suited to the Toslink Mini plug you’ve shown. I don’t know 3 people who realize it’s there.
@MrAdopado replies to @artysanmobile: The optical is not there any more ... in fact it's been a few years since they (unfortunately) dropped the optical out that was combined with the 3.5 socket.
@artysanmobile replies to @artysanmobile: @@MrAdopado I knew it was no longer, but it was such a secret in the first place I didn’t expect an announcement. Probably 2015 or so.
@JHDundrum replies to @artysanmobile: An Asus Xonar DS 7.1 PCI sound card I bought in 2011 had this feature too and even came with a Toslink-mini to standard adapter. The Google Chromecast Audio had the same 3.5 mm copper / Toslink-mini dual purpose socket.
@IncognitoChild: The only thing I ever remember seeing a mini toslink on was Sony Mini disc portables..... But now I think of it, I've seen it on Sony TVs as well for headphone/optical connection.
@MrAdopado replies to @IncognitoChild: Apple had it for years ... but then unfortunately dropped it in 2016.
@IncognitoChild replies to @IncognitoChild: @@MrAdopadothey only started using it in 2006, strange how they dropped it so quickly.
I only used Mac's in the 80s, so I don't know the Apple consumer products.
It was sold as "surround out" - did HDMI replace it?
@MrAdopado replies to @IncognitoChild: @@IncognitoChild Apple used many different ways of delivering a digital output over the years that could be used for high quality audio. Early days was SCSI then Firewire 400, Firewire 800, Ethernet, USB versions 1,2,3, A,B and C variants, Mini DisplayPort, Thunderbolt versions 1,2,3,4, HDMI ... I may have missed a few! ... so Optical was just one of them. Presumably they found that the optical option wasn't frequently used by their customers so decided to drop it (like they dropped many of the previous standards when they became less in demand). Keeping optical for 10 years is a long time in the computer world ... and you can still do it with a "dongle" of course. Optical is still often used for domestic audio (TVs and Amps) and my own TV has no other method for me to easily get a discrete audio out to my amplifier.
@timf-tinkering replies to @IncognitoChild: Not just Sony. Pretty-much all portable Minidisc recorders had a combined 3.5mm analogue / optical digital input connector.
@IncognitoChild replies to @IncognitoChild: @@timf-tinkering yeah, you're right I should have said not exclusively limited to. Although they were the first (I only ever bought Sony)👍😎
@SparK17299: It's toslink, not tozlink. Toshiba invented it and the term stands for toshiba link
@AudioMasterclass replies to @SparK17299: Aha, toshlink then.
@SparK17299 replies to @SparK17299: @@AudioMasterclass 😂
@dangerzone007: It doesn't sound like any more fun than a regular DAC amp. Nowhere near as much fun as a Mojo 2 with its EQ and crossfeed features. And then there's trying to remember what the lights do.
@Kevin-sh1sx replies to @dangerzone007: Oh, 650$
@MrBenherrmann: Can this thing be used as a preamp also - or is it just a Head Amp? I have an SK01 and enjoy it, and as you know it is both a head amp and a preamp (albeit a preamp out with only a 3.5 MM). I like the added DAC feature also.
@Kevin-sh1sx replies to @MrBenherrmann: It looks like this can be used in conjunction with SK02.
@MrBenherrmann replies to @MrBenherrmann: @@Kevin-sh1sxWhen I got it, I immediately saw that it can be used as a Preamp, with a 3.5 output. Attached to both the V3 and ZA3, I found the combinations to be outstanding. This is a really good DAC and I prefer it over my iFi ZenDac Mk II and some of my Schiit gear.
@Synthematix: Toshiba Link
@williamobrien6936: Many modern TV's can transmit audio through their USB ports. The SK02 could be used as a preamp.
@chefsteve8381: Balanced will stop ground loops.
@PeTroL420 replies to @chefsteve8381: Not all the time. You can still get a buzz with balanced cables.
@apigge8723: Thanks for emphasizing "fun" here. I believe it's always good to take some time out for that!
@slinkman79: 4:07 <I listened to "Tales From Topographic Oceans" by Yes... so you don't have to> 😂😂😂😂😂😂😂😂😂
@kevinmcgrath3591 replies to @slinkman79: I do like their good stuff (rare but great) but this album is a prog rock car crash of the worst kind imaginable so I totally get his remark. Im old enough to remember when it was released and being stunned by its meandering, soul less dreadfulness compared to the preceding 'close to the edge' , a wonderful LP in 1972
@rhodaborrocks1654 replies to @slinkman79: @@kevinmcgrath3591 I couldn't agree more, I bought a copy when it was released on the strength of their previous records but could not figure it out .. I eventually gave it to my sister, because I didn't like her.
@slinkman79 replies to @slinkman79: @@kevinmcgrath3591 Indeed! I don't rememeber being able to listen to a single side of this double LP in one seat, I always get bored...
As for "Close to the Edge", it remains one of my favourite album of all times.
@rienpost: I love the subtle undercurrent of sarcasm in your videos.
@thefloop2813 replies to @rienpost: Subtle?
@rienpost replies to @rienpost: @@thefloop2813 That whas sarcasm from my side.
@thefloop2813 replies to @rienpost: @@rienpost Yea def seems pretty obvious now. I was probably drinking, does tend to be when i make the poor choice to enter youtube comment threads lmao. Generally if there's a beer in my hand im on youtube talking shit about something instead of just listening to or making music like i should be doing
@amcluesent: Not sure if this was meant to be humorous, but satirising your core audience doesn't seem the smartest of moves.
@hansfijlstra5932 replies to @amcluesent: What do you think his core audience is?
@canthandletruthhuh replies to @amcluesent: Oh chill out
@peters7949 replies to @amcluesent: I’m with Dave on this one, satirise away.
@ChrisStoneinator replies to @amcluesent: I don't think you're his core audience mate. Sorry.
And yes, it's hilarious actually.
@AdriaanW1966 replies to @amcluesent: Don't take yourself too seriously
@gregwmanning: I used duplex (tx/Rx) "single mode" optical fibre patch cords at work (telecommunication) of varying lengths upto 30m, that carry a 10Gb signal, (some patch cords even carry dozens of 10Gb wavelengths or "colours"). Some of my equipment have 100Gb ports. The patch cords cost depends on their length. I dont see the invoices now days, but previously they were about $20-$100. In my industry stuff get cheaper and better (and faster) as time passes.
My short investigations of Toslink, says it is a multimode optic fibre system. Manufacturing tolerances required for multimode fibre are a lot lower than single mode, so therefore should be cheaper. Is it possible audio fibre systems, is marketing hype over substance?
@chrisbartram3034 replies to @gregwmanning: It's the pricey Toslink cables that are hype over substance, plenty for under a tenner on Amazon, and TBH, it's either going to work or not.
@georgebliss964 replies to @gregwmanning: I am not sure why Fosi chose Toslink over SPDIF which is more popular and user friendly.
@Wuppie62 replies to @gregwmanning: @@chrisbartram3034
I'm using a very affordable Amazon toslink cable between my TV-mediabox and an external DAC for TV-audio, and it works perfectly. Why? Because all the other ports on my external DAC are already occupied by other digital sources, my amp has only one unbalanced audio input (which is connected to my DAC's audio out), and I also prefer the sound of my external DAC over the TV-mediabox' internal DAC.
@edwarddodge7937: Too bad there are no PCM multiples of 44.1kHz
@peters7949 replies to @edwarddodge7937: Whilst not common they do exist, 88.2kHz, 176.4kHz. Although I can’t see the point of the, in this day & age. In the dim & distant past down conversion from 88.2 to 44.1 was much easier, but with modern sample rate converters this is no longer a problem.
@Kevin-sh1sx replies to @edwarddodge7937: It seems to include, but there is no separate light display, classified as adjacent lights, for example, 88.2KHz will be placed in the 96KHz light.
@obsprisma: Great video sir. Could you give a link where you can order this Fosi SK02? I can't find it on Amazon yet.
@AudioMasterclass replies to @obsprisma: I think it's going to be on general release in February. Perhaps Fosi could advise you.
@ac81017: As an Audiophile DSD is useless unless you like classical music. Last time I checked there was only 1000 odd albums in DSD.
@Jacob1451 replies to @ac81017: Honestly, after 124kpbs, I realistically can't tell objective sound quality differences. I still wonder what the benefits of all the extra file size of hi-res files actually is for the listener. Far as I can tell it at best, mostly benefits producers making music
@Jacob1451 replies to @ac81017: @tinetannies4637 Oh yeah, I got 2 DAPS, 3 DACS, and balanced cables already too. Slowly building up a decent song library. Loving this journey 🤟🤟🤟🤟
@steverobertsbbc: "I abstain." No sh*t, Sherlock! :D