Why you need two DACs and two turntables
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Tuesday March 19, 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.
@simpaticode: I wonder if anyone has ever made a turn table with more than one stylus and arm? Then you can hold the sound from the first N-1 styli and average the signal add it to the Nth stylus and play it. Yes you get N times the wear on your vinyl for one play, but it should sound great.
@rabb1tjones921: It would be a fun experiment but I am sure there are better digital noise reduction algorithms that would work better for archiving.
@monsieurgolem3392: Cocobolo....
@1974UTuber: Instead of 2 turntables and 2 records which could be different. Why not use 2 needles on the 1 record and have a delay circuit so both signals play at the same time.
Surely that has to be easier than having all the planet's aligned and motors moving at same pitch and speed and 2 exact presses of the same recording
@AudioMasterclass replies to @1974UTuber: For this to work, and it will work if the audio can be synced, it needs two or more copies of the record.
@gilesdavis6345: 🤔
@tristandesade8635: I have a background in statistics.
One point: In theory those 3dB of noise are uncorrelated. In practice they must correlate ever so slightly unless we reproduce infinite loop of music.
Explanation would be long, please trust me on this one.
@AudioMasterclass replies to @tristandesade8635: I think I’ll stick with 3 dB for practicality. I’m sure your long explanation would be very interesting but I’m guessing it’s of a similar order as saying 6 dB for a doubling of voltage when we mean 6.02.
@humblestever24: That aways constant *uckerberg grey T shirt worries me more than your friends Phil , Debbie and Betty.
@AudioMasterclass replies to @humblestever24: I suspect that Zuck's shirt costs a lot more than my Gildan Ultra from eBay.
@darkpatches: I bought an extra turntable because I couldn't afford a Lazy Susan and I like a challenge when I reach for the salt.
@AudioMasterclass replies to @darkpatches: True audiophiles have their three or more turntables on a large lazy Susan.
@stuart.the.pear.1: I use two quantum turntables to have entanglement then listen to the better signal to collapse the wave....
@AudioMasterclass replies to @stuart.the.pear.1: I'm going to send that one to Phil. My guess is that he'll want to work out how to apply Bell's theorem to his system. Whether he can avoid all the loopholes remains to be seen.
@the_kombinator: (where it's at!) I've got two turntables and a digital-to-analog-converter.
@rabit818: “Two turntables and a microphone” - Beck, not Jeff just Beck. I have Audio Alchemy and 90s era California Audio Labs DACs. CAL conked out recently.
@richardmarkham8369: Isn't there a drop in board with 8x DAC's on? I forget the chip, its an old obsolete Philips part (TDA1387), so there are laods of fake copies around now.
@foxtrotzulualpha: two turntables and a microphone
@Xccent-d: How about we buy 1 copy of the vinyl copy it twice to digital. Then wait for a useful AI program to compare the recordings and keep what matches between copy 1 and 2. Anything thing that is random and out of the bounds of the two copies gets deleted. Failing that listen to some "Ambient Lofi " and forget about the whole ordeal lol.
@ShippingExcluded: Of course each vinyl record should be made by a different stamping plant in another part of the world to account for the geographical differences. Preferably the same recording feed recorded to two separate master tapes.
Jk of course, just get a decent digital transfer from the master tape without compressing.
@AudioMasterclass replies to @ShippingExcluded: Your last sentence is of course correct but I did mention in my video that this process would be useful if there was no digital source available. As for master tapes, Google 'Universal Studios fire' and prepare for sadness.
@ShippingExcluded replies to @ShippingExcluded: @@AudioMasterclass Yes, that is indeed very sad. Also kind of strange how many original masters of legendary works were “misplaced”. Thank you for the educative and funny content!
@michal7x7: Common ground conductor causes crosstalk between channels, depending on when is it split between channels.
@AudioMasterclass replies to @michal7x7: You raise a good point and this would depend on how 'groundy' the ground is. I may investigate this for a future video.
@michal7x7 replies to @michal7x7: @@AudioMasterclassyes, with ideal conductors this wouldn't happen. I tested it using a pair of portable Sennheisers and could hear the other channel with one of the channels muted. This wasn't a very scientific test though. Could be crosstalk of the source. But the cables of portable headphones are really thin.
@egotrpn420: As Mazzy would say “ it’s just music stupid”
@LeeBergerMediaProd: How about one turntable with two arms and cartridges? That would eliminate the synchronization issues and require only one copy of the vinyl record. Slight delay between cartridge A and B could be aligned after digitizing.
@AudioMasterclass replies to @LeeBergerMediaProd: No, because the noise will be the same entering each cartridge. It will add 6 dB like the signal because it is correlated, so no benefit.
@LeeBergerMediaProd replies to @LeeBergerMediaProd: I see your point. And I thought I was quite clever 😂
@athathsonty2925: This is one of the very few Audio Masterclass YouTube Videos which I have disliked, lock stock and barrel.
@darkblueturbo: One thing I’m still unsure of: did you want us to leave comments? 😂
@AudioMasterclass replies to @darkblueturbo: You can like and subscribe as well if you wish.
@darkblueturbo replies to @darkblueturbo: Already done sir@@AudioMasterclass
@connorduke4619: FWIW, the experienced chief reviewer at Alpha Audio has stated that double Dac chip dacs consistently sound better than single Dac chip dacs.
@devsysnet: All modern, good quality audio DAC ICs have a balanced output.
@barlow2976: Why would you (physically) need two, or more, turntables? Couldn't the output from a single turntable be reproduced many times, then stacked as you would photographic images?
I'm just checking patent laws right now....
@AudioMasterclass replies to @barlow2976: You're making it too simple for audiophiles.
@barlow2976 replies to @barlow2976: @@AudioMasterclass One wonders what the girls think. I value their opinion over Phil's.
@shpater: 1. When we say 2 dacs we talk about 2 dacs per channel. Other wise there is no 3 db gain.
2. With two turntables it won't work even theoritacly. The reason is that most of the surface noise we hear in the table ( in mid range level) comes from the stamper ( and master tape for analog recording) which has exact the same noise printed on it in both copies.
The rumble noise however comes from the turntable and might be random But then you will ruin the "3db gain" with the table that has the slightly higher ramble level.
3. When I was young I had a 4 track mono tape recorder that could play stereo. I tried to record left Chanel and then right Chanel separately on the same tape and could not synchronize the two. We need to synchronize the two turntables with accuracy of about 1 micro second ( 1 tenth time of a 10 kilo herz signal) in order to avoided phase issues ( similar effect as the azimuth adjustment on tape recorders).
3. I Thank you for your videos and for your compliments on my last comment.
@pompeymonkey3271: This is a process known as "stacking" in the astrophotography community. Not just two images, but often many dozens of images are averaged to improve the signal to noise (which has many sources!) ratio. The signal (correlated) increases in proportion to the number of images in the stack, but the noise (uncorrelated) only increases in proportion to the square root of the number of images.
Of course, there is a point of diminishing returns...
And then there's "drizzle" which can recover data from a stack of under-sampled images which are not exactly aligned.
@erictheis6093: I love these. What a wonderful exercise in critical thinking.
@erictheis6093 replies to @erictheis6093: Are your new glasses balanced?
@spacemissing: My ideal system (not realized due to space problems) would include at least five turntables.
Each would be set up for a particular use, such as LPs, 78s, "good records" "crap records", and so on.
@MrBonger88: The artist Beck has been using 2 turntables for years 😉
@thehoff7479: Great theory!
I think that you will get an extra flanger sound with turning 2x the same record, because there will always be a time difference.
Used to buy 2x the same 12 inch to make this sound in the 80s.
It sounds like a airplane flying over.
But i think you could the following: Play 2 copies on2 different turntables and record with 2 different DACs.
Then subtract both wave-files, so you are left with the 2 noise-files. Then inverse that noise file (like noise cancellation) and and add that to the 2 wavefiles. Then add the wave files to each other and youd should get 3dB more and thr noise filtered out.
@nabman_: Hey David, I glued 4 turntables together, disabled the motors on 3 of them and had the 4th drive them all by putting a Toyota serpentine belt around the platters. I can hear some wow and flutter of around 0.02%. A friend of mine read that audiophiles usually go with Bentley belts. Do you have experience with Bentley belts and would you recommend them? Honest question - no troll here.
@monsieurgolem3392 replies to @nabman_: China makes some third party belts that work fine.
@HeavyCrown2030: Wait one minute have you actually been a parody channel all this time? Ok the jokes on me for taking you serious on the Audio topic
@onepieceatatime: According to Beck, you need "two turntables and a microphone."
@trottophone: You don't need two turntables to demonstrate the '3 dB effect'. If you have a mono LP, just one is enough.
Each groove wall is a separate source of the same music.
Listening in stereo, the music is in the middle, with a panorama of noise from left to right.
Switching to mono, the music stays at the same level, still in the middle.
However, the noise is now in the middle too, and has reduced by 3 dB!
@AudioMasterclass replies to @trottophone: I agree that a mono record should be played in mono. Mono music and stereo noise is not a good combination.
@Roosville1: It's common for Phono (RIAA) pre-amplifiers to use discrete FET (field effect transistors) at the input stage, they have some useful behaviour but some inherent noise. It is common to parallel FET devices to between two and four FETs in parallel, which is exactly the effect you are describing. It increases the signal to noise ratio. I know that there are some DAC chips that are twin DAC design, but can also be set up internally as a single DAC which run the left and right in parallel. Again, as you describe. You have to remember that there are a whole bunch of issues in DAC design, real offsets that rubish the first few bits, not all 1-bit increments result in the same voltage change ect. So it also helps to linerarise the DAC to average this effect.
@billmilosz: Using a balanced signal to drive a headphone transducer results in lower amplifier source impedance as seen by the transducers than the same amplifier circuit used in single-ended mode. Lower source impedance from the driving amplifier results in higher damping factor - a stronger "grip" on the transducer diaphragm by the driving amplifier. In my blind listening tests, this results in improvements in bass. Not necessarily MORE / LOUDER bass, but bass that sounds to me somewhat less sloppy / less boomy and is overall somewhat cleaner and more tuneful. It's not a huge difference, but I will take whatever I can get when it seems to me like a sonic improvement.
@billmilosz: You do not NEED two DAC chips to obtain a balanced audio signal - ANY single-ended audio signal can be converted to balanced by using an opamp or a transformer. But using two DAC chips - one for MINUS and the other for PLUS side of the signal, then you will have a balanced signal that is "closer" to the original data in some ways, and in addition a certain amount of distortion may null out.
@MiltonGrimshaw: I think your commenter on the S/N of a DAC is incorrect as they never considered 32 bit float digital to analogue converters which have far higher S/N ratio that commented
@richardmarkham8369: Classic!
@nitromcclean: I have two Techniscs SL1200 MK II turntables, each with the same Ortofone. I have some 12 inch records which I have two copies of. So I would be able to do this for myself. If somebody can explain to me how to sync the two together, I can have a go .... By the way, I guess the difference of the same recording on a 33 rpm full album and a 45 rpm 12 inch with only one song on one side will be much bigger.
@djtbs1 replies to @nitromcclean: I can tell you that with 2 copies of the same single (whether it's 45 or 33 no matter) on my 1200s with Stanton 5800MP (matched Pair cartridges) the base wow and flutter of the turntable because of the slight variation that exists even with the PLL (phased lock loop circuit) will still give you a bit of flanging effect.
@huubvandoremalen replies to @nitromcclean: Well, without having any digital effect procesor myself at the end of the 80's, my way of creating a phasing effect was playing two identical records at the same time.@@djtbs1
@carlsitler9071: I have 3 dacs, one for my main system, a dongle dac/amp for my phone and one for my livingroom system. I threw my record player away soon after CDs came out.
@enricoself2256: Some years back there was a myth that by stacking up to four TDA1543A (a cheap and low quality DAC made by Philips) you would get an overall better DAC as non-linearity and noise within the DAC would sum as stochastic signals while the actual audio signals would all sum in phase. Theoretically it would make sense. Not so much for vinyls as it is impossible to have the two audio signals perfectly in phase (just the different W&F of the two turntables is enough to misalign the two signals.)
@tonyvink961: The big question that should be answered before we start our dual (npi, well maybe pi) turntable company is "do we need to pay royalties on the 2nd thru N copies of the same disk?
@erictheis6093 replies to @tonyvink961: If you play the even numbered turntables normally, and the odd numbered records backwards, the royalties will cancel each other out. Physics.
@marxman00: Why not Turn your atrocious useless wobbly unbalanced headphone amp up by 6dB to make it sing like the magical not wobbly at all balanced headphone amp ? Perhaps balanced headphones counteract unbalanced people ..so they dont require stabilisers .
@tonyjedioftheforest1364: I actually use 3 turntables in my system but for a different reason. Table one has the best cartridge and I use this for my better records and when I want to fully immerse myself in the music. Sometimes you get an old knackered record that is full of surface noise and this is where table 2 comes in. Second table has a budget conical stylus that doesn’t get all the details of table one but is kind to surface noise. I also use this one for background music saving ware on my better system. Turntable 3 has a dedicated mono stylus which is great for my 1960’s mono records and you don’t get distortion or cross talk like you would from a stereo cartridge. I use a twin shelf wall mount so it doesn’t take up much space. Works great for me.
@richiereyn: In theory, this could be done. Coming at it with the thought processes of a retired video engineer and working on servo systems that accurately control head drum/capstan motor rotation and synchronization, a similar principle could be designed to sync up two turntables to exactly the same speed, servo-locked, so that there is no drift in turntable speed. Direct-drive turntables would definitely be the choice for this. Once locked together, the difficult part would be getting each record placed on the platter in exactly the same position to eradicate phase errors.
But, wouldn't it be much simpler to record each disc on one turntable and then in software line up both copies and play them out in sync?
Oh God, I just realised I fell for this one, hook, line and sinker. My brain hurts!
@stevengagnon4777 replies to @richiereyn: Mine too....think I'm going to put one of my noisy albums on at 70 decibels and let all the other sources of noise down here in the basement. Kitty Kat is doing her best to help. I feel sorry for that little stuffed mouse.
@nigelsilverthorn9188: I was recently watching a vocal review of the Carpenters. There was a comment of the orchestration where it was noticed the numbers of layers of instrument used, no surprise but the commenter noted the use of a maraka so low down in the mix it was really hard to identify it. It was the video of the orchestra that showed it. It occurred that the contribution of a maraka even very low down could mask or 'texturalise' (I made that up) the background noise of the then release media of Vinyl making background noise essentially non-contributory to the sound experienced. I wonder if this a/ makes sense to you, but b/ was that why it was there and was it an often used technique? (or did they need to give the maraka player something to do! )
@michaelsparrow4798: a bridge too far...
@middleearthltd: I believe you possess much useful information/knowledge you could put up for consideration.
You seem determined to resort to poorly contrived sarcasm, smugly delivered.
Do you have a group of pub friends that laugh and laugh at this at this so you are thus encouraged to crack on ?
I believe there was a time when you actually did constructive videos as I subscribed for some reason.
#Subscriber Suggestion Please Put Up Useful Content 🙏
@AudioMasterclass replies to @middleearthltd: I love compliments. Thank you so much.
@Lif-999: You really need to get a grip on that Phil. He's going to break the internet!
@AudioMasterclass replies to @Lif-999: Don’t worry. Mrs Phil is coming to the rescue soon.
@Lif-999 replies to @Lif-999: Mrs Phil? It's a mercy.
Hang on. Audiophiles have partners?
I'm learning so much. 😂
@ziggystardust4627: Could this concept be used on two digital streams? Convert the same source analog audio stream to digital, but separately. Then wouldn't quantization noise be reduced by 3dB? Additionally, let's say you're converting 24-bit to 16 bit. If you did this twice, but with slightly different dithering, would the quantization noise of the 2 audio streams added together be 3dB less?
Of course, it's cheaper and more effective just to do 24 bit audio (even though you're giving up 2-3 bits in your DAC), but an interesting intellectual exercise.
@AudioMasterclass replies to @ziggystardust4627: If the noise is correlated then no. But the noise in each DAC is probably not correlated. Jury is out.
@RadioMattM: Of course the two turntables each need a $17,000 cartridge.
@AudioMasterclass replies to @RadioMattM: I think you mean $34,000.
@stevengagnon4777 replies to @RadioMattM: @@AudioMasterclassit's vinyl and played a hundred times...the 75$ I spent on a new stylus for my Stanton 680 will suffice. And that constant ringing will will certainly cancel out the rest of the noise. And those pops and clicks just add to the ambiance of the fireplace that isn't down here.😊
@edwardcasati3374: There is a much used standard in Digital Electronics called "RS-485" which essentially implements your dual record player concept. Normally a signal is transferred via two wires - a signal and a ground. A problem with this arrangement is that it tends to pick up random noise. For example, if you run the signal wire close to as motor you will get hum, which in some cases can exceed the actual signal. Lots of pops and hisses can change a bit from 0 to 1 or vice versa, resulting in corrupted data. Or you get signal distortion due to long distance parasitic values of inductance, resistance and capacitance.
You can get around much of the problem by using THREE wires (two signal and one ground) and comparing the signals from two signal wires at the far end to see how they differ. (You essentially run two turntables!) The real trick is that on one of the wires you invert the signal at the beginning and at the end of the wire you compare and normalize the regular and inverted signals to each other. It's complicated to explain how the actual comparison is made, but you essentially end up with a clean reliable signal because you are looking at the differences between the two signals. You MUST use twisted pair wire and a common ground, and some other requirements.
I hope that no audiophiles read this, because I don't want to start a new trend making RS-485 required to maintain the purity of the signal before it reaches the DAC.
@stu-po: For the last 20 years, the Library of Congress has been using Photographic process to Archive flat records. Even broken records can be stitched together photographically. This isn't playing the record with a laser, it is capturing the whole record with photographs then using software to play what is in the grooves. Cameras today are remarkable, and maybe soon audiophiles can play and archive LPs with their phones 😃
@andymouse replies to @stu-po: LOL.
@erictheis6093 replies to @stu-po: Better yet - use the digitized 'music' thus extracted to drive lazhers to burn new vinyl!
@GLOBOLG: You gotta get your dacs in a row...😂
@chrisquirk4754 replies to @GLOBOLG: You win the internet!
@jim0_o: I have the head-cannon that the crackle from dust on vinyl is what people enjoy about vinyl be it from nostalgia or just hipster identification. (open to being proven wrong)
@ac81017: My audiophile/audiofool brain has just melted. I just press play and enjoy for the music how it's presented to me in my listening room. If i want to change any form of db, i simply raise of lower the volume knob.
I think Audio Phil hit the nail of the head. 😂😂
@CatOnVenus183 replies to @ac81017: me too, my vintage technics amp even has a remote so i don't have to stand up to do it.
@shipsahoy1793: 😂..you'll never get a perfect sync, but maybe close with the same two turntable setups, but "theortically," you're right potential advantage, but impractical when considering cost differential. Once signals get 75 dB or so below your source signal (including ambient noise) ,
it really doesn't make much of a difference at that point when you're listening to music for enjoyment. People that obsess over 120 versus 130 dB on digital sources and are willing to pay so much extra for every last dB are being plain silly.. good talk, Dave.
@marxman00: good old Dbx noise reduction . I had it on my TEAC V2RX cassette deck .... the recordings sounded terrible played on any other deck ..Luckily now all this is irrelevent.. BUT ..some people like collecting vintage problems
@wmrg1057: April 1st is still 10 days away
@marxman00: and a microphone"
@maidsandmuses: Theoretically this works. You double the signal, but because the noise is stochastic it won't double but only go up by a factor 1.4~ish.
As far as a practical implementation using two turntables is concerned: good luck.
If you insist on using turntables, just use one turntable and play the record quite a few times. You will memorise the songs better every time you play them, but because the noise is stochastic, you won't be able to memorise the noise. Eventually all the songs are completely memorised, with no noise, and then you can throw away your worn-out vinyl(s).
@erictheis6093 replies to @maidsandmuses: Brilliant! Nothing exceeds the accuracy of human memory!
@HeavyCrown2030: Mr Master Class here is the fix 4xDAC or DACs back to back multiples the error reduction lower the noise and maintains dynamic rage.
Most of us call it a digital turntable when you put a DDC in front of the DACs and have the music directly attached for proper time domain during play.
There are DAC chip products that now employee this technique.
@muzammelhaquemukul7089: Ah! That Shania Twain song. That Don’t Impress Me Much.
@earthoid: You have finally gone too far down the rabbit hole for my simple brain to follow. Sixteen turntables! I love it! LOL!
@AudioMasterclass replies to @earthoid: Thing is that the first rabbit hole has multiple rabbit holes in itself. Then each has its own rabbit hole...
@rienpost: You just want audiophiles to waste months of their lives with trying to sync two turntables, right? Fair enough.
@GLOBOLG replies to @rienpost: Actually is quite simple. As someone here commented (not my idea) you just use two platters on the same axis and two tone arms. That way both records are rotating synced. You add to one of the platters a simple mechanism to tweek a bit forward or backward the advance of the said platter. Then you just audibly get them in perfect sync ( using some kind of frequency interference).
But actually you could achieve this even more simply by digitizing two records by playing them one after the other on the same turntable, and the syncing both audio streams by software.
@erictheis6093 replies to @rienpost: I think I would acually be wiliing to pay to watch folks attermpt that.
@Three-Chord-Trick: Can someone explain why I shouldn't use a stack of toilet rolls as a speaker stand? I'm not joking. Wouldn't it be as close to floating on air as possible?
@bluesfish55m51 replies to @Three-Chord-Trick: You would need to use multi-ply. The single-ply crap will impart scratchy overtones and increase signal to noise.
@wlrIII replies to @Three-Chord-Trick: I just use my audiophile-grade liquid nitrogen immersed superconducting plates. A bit more expensive than TP, though.
@Three-Chord-Trick replies to @Three-Chord-Trick: @@wlrIII Honestly, I'm not joking. Ls50 Meta stands cost £400. R3 stands cost £649. The toilet rolls would cost £20 for two speakers. Wouldn't they have zero resonance (as good as)?
@Three-Chord-Trick replies to @Three-Chord-Trick: @@thorniestorange No No. Someone just explain why the toilet roll stand is NOT a good idea. I'm willing to be converted. I have four toilet rolls under my bass guitar amp. The difference with no floor contact is very noticeable.
@maidsandmuses replies to @Three-Chord-Trick: Because one day one of your friends will bring along a Labrador Retriever puppy 😂
Seriously though: most speaker stands are designed so the speaker cabinet can dissipate any cabinet vibration into a heavy "immovable" platform; they are not designed to make the speaker cabinet as free-floating as possible.
@amcluesent: The two turntables should, of course, rotate in clockwise and anti-clockwise directions to null the Coriolis Effect caused by the rotation of the Earth. A veil will be lifted.
@AudioMasterclass replies to @amcluesent: And of course southern hemisphere inhabitants have to mirror image the process.
@ziggystardust4627 replies to @amcluesent: Those veils. The bane of audiophiles everywhere.
@nabman_ replies to @amcluesent: The anticlockwise one will play the demonic embedded messages thus producing undesirable crosstalk between good and evil and resulting in unharmonic distortion and low sin to noise ratio.
@barlow2976 replies to @amcluesent: Absolutely no consideration given to those living on the equator.
@ziggystardust4627 replies to @amcluesent: @@barlow2976When you're an audiophile, you have to choose sides . . .
@bluesfish55m51: Create a turntable with stacked platters and dual tone, arms and cartridges. Now the disks rotate at the exact same speed you can orient them on the platters and quote easily sync the two discs.
@ziggystardust4627 replies to @bluesfish55m51: On the inner groove, the whole wavelength of 20kHz is something like less than a 1/100 millimeter. You still have an incredible phasing and tolerance challenge if you don’t want destructive interference at high frequencies.
@thexfile.: Sounds like audio masturbation? You'll go blind... 😄