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Do Transports Matter--or are bitses bitses?


The Monkey

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Being an engineer I never went down the transport rabbit hole, but recently have experienced significant SQ differences with different USB transports, especially when I modded my Hiface to batteries. Got me thinking the EE's may be missing something. Tried to measure the differences with FFT software but nada so it could be placebo but sure doesn't sound like it comparing the modded Hiface with a TerraX. Then there is Jocko's USB transport that he posted a 3ps measurement of for only $500 which I haven't tried.

Still I have been eyeing $3-$5k transports.

Are you saying this is big waste of money? What about Steve N's products ?

Didn't you get banned recently from HF? What happened?

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Are you sure about this? I thought they had to be bit-perfect in order for DTS to work. I thought running a DTS DVD (or CD, if you can find one) into a DTS-decoding receiver was another way to check bit-perfection.

To be honest I'm not sure but I know that each of my DVD players in their stock settings did DSP on the digital outputs from a CD. I don't know about DVD stuff.

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Didn't you get banned recently from HF? What happened?

Ooooh, ooooh, that's a fun story...... can I tell it?

Regal made a fairly long post, where he detailed some listening comparisons between his brother's Apex Pinnacle and one of his own DIY creations (a Stacker, I think?). He claimed that while the Pinnacle was quite good, and it did respond to 6SN7 tube rolling, it didn't have the typical DHT magic and that the DIY amp sounded better overall to his ears.

Problem is, Todd called him out on this bullshit. Only two Pinnacles existed at the time and it was impossible that either of them were in the possession of Regal or his 'brother'.

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Lynx and Transit will both lock on to the Assemblage HDCD filter with HDCD encoded discs. They didn't sound the same.

How did they not sound the same? Was it a blind test with the two transports set up identically (both using optical)? Also I'm not familiar with the Assemblage but does it reclock? If not it could be jitter.

Expectation is a large part of what we hear, that is a fact. In the end if you think the Lynx sounds better it probably does.

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Not necessarily the same, this is more about the DACses than about the transports: pro HD shootout.

Thanks for that link. Very very interesting though not truly double blind but single blind. What they should have done to really make it good was to have someone switch up the cables again and make sure that they could identify which was which....

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Expectation is a large part of what we hear, that is a fact. In the end if you think the Lynx sounds better it probably does.

I know I am just banging my head against the wall here, but just because you "couldn't hear a difference" between your higher and lower priced DACs in a blind test a couple of years ago doesn't mean that there are no differences between modern DACs other than subjective perception and placebo. And bit perfect output doesn't translate to equality.

OK, I just had to get that out. Carry on.

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I know I am just banging my head against the wall here, but just because you "couldn't hear a difference" between your higher and lower priced DACs in a blind test a couple of years ago doesn't mean that there are no differences between modern DACs other than subjective perception and placebo. And bit perfect output doesn't translate to equality.

OK, I just had to get that out. Carry on.

You are absolutely right that it doesn't mean that it's not possible that there aren't differences or that I don't have lead ears.

My point is that you should prove it to yourself using a scientific approach before stating definitively that there are differences when the measurement apparatus is so susceptible to perception and placebo like (with regards to Hirsch) effects.

The same test was done and I could hear the difference between the DACs and the Benchmark DAC1. I am not nor have I ever argued that all DACs sound the same. At loud volumes even my two DACs now sound different because the noise floor is better on one than the other.

I hope that removed any wall that you think you were beating your head on.

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Actually, you're kind of agreeing. The alternative viewpoint could be phrased thusly:

Expectation is a large part of what we hear, that is a fact. In the end if you think ...
...they won't sound different, then they probably won't.

And I don't know of any DBT that could refute that particular placebo effect.

And kudos to all for keeping this potential charged subject civil. Cheers!

df_kudos_366.jpg

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Actually, you're kind of agreeing. The alternative viewpoint could be phrased thusly:...they won't sound different, then they probably won't.

And I don't know of any DBT that could refute that particular placebo effect.

But you can use DBT to disprove the converse (for you and your setup). Also if you do include one DAC that does not DBT within the test set then you can check for this too because if you don't find a difference between any of them then your test (or test subject) is flawed anyway.

For some reason it appears that some around here believe that I am dogmatic about "all DACs are the same" but I never ever said this. I presented a test I did that proved to me and to my ears that 3 DACs that I thought sounded different did not at regular listening volumes. I assure you I did not think they sounded the same at the start of the test, I was dying to keep the Weiss.

Edited by Dreadhead
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where can i buy one of those external perception machines?

I can build you one out of Ebony.

Was it at least single blind, volume matched, and are you sure that they were truly bit perfect or just claimed to be bit perfect?

It's a pretty common trick to pump up the volume 2/3dB which will sound "better" but will not be that noticeably different. I don't trust my ears anymore on volume matching and use a voltmeter across the headphone out along with a test tone.

I was absolutely 100% convinced I could hear the differences between my two DACs at regular listening volumes until I did a couple single blind tests and couldn't tell shit with any accuracy.

While I would have thought the volume to be nearly the same you make a good point about that being hard to interpret.

Ooooh, ooooh, that's a fun story...... can I tell it?

Regal made a fairly long post, where he detailed some listening comparisons between his brother's Apex Pinnacle and one of his own DIY creations (a Stacker, I think?). He claimed that while the Pinnacle was quite good, and it did respond to 6SN7 tube rolling, it didn't have the typical DHT magic and that the DIY amp sounded better overall to his ears.

Problem is, Todd called him out on this bullshit. Only two Pinnacles existed at the time and it was impossible that either of them were in the possession of Regal or his 'brother'.

That was some funny shit! Hmmm, no reply from Buick boy yet? :P

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My $.02

Transports: Real Time error prone reading of physical media by optical means (That's Shiny Platters to you) vs "Computer Based" HD / SSD sourced bits.

Any system that cannot reliably output the sourced input bits is broken by definition. It either works perfectly or it fails.

How would you feel if your bank only accepted some of the bits of your paycheck?

The HDCD light test is a good test for bit-perfectness.

A decent transport should deliver the right bits at the right time. This is where we get into jitter. Lots has been said on this, but recovering an invariant clock from a push based protocol with no error correction / retransmit control seems somewhat backwards compared to a local clock based pull protocol - but thats hard to do with unbuffered real-time reading :)

Does any of this make a difference.

Bit correctness: Yes - its either right or wrong.

Jitter: Possibly - If you can't correctly differentiate transports to a statistically significant degree - then by definition its imperceptible to you. Save your money and be happy.

If you can, then you have your answer.

If you are undecided, and want confirmation of your biases, we''re here to help.

If you want an objective measure of output differences may I suggest Audio DiffMaker

Other people have suggested perception is reality, and there are many, many things that alter perception. You might enjoy some of them.

Final words: Whatever makes you happy. Me? I'd be happy with some Kaizen, so we end up with demonstrably "better" products at lower prices over time. How hard could it be. :) Look at what Moore's law has done to your 'phone. I live in hope.

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How did they not sound the same? Was it a blind test with the two transports set up identically (both using optical)? Also I'm not familiar with the Assemblage but does it reclock? If not it could be jitter.

Expectation is a large part of what we hear, that is a fact. In the end if you think the Lynx sounds better it probably does.

Nope not blind test, but I want to try it in the future. Levels were matched. The Transit is toslink, the Lynx was coax. But by your theory that bits is bits it shouldn't have mattered that they were using different digital outputs.

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Nope not blind test, but I want to try it in the future. Levels were matched. The Transit is toslink, the Lynx was coax. But by your theory that bits is bits it shouldn't have mattered that they were using different digital outputs.

I never said that it didn't matter what input was being used. It's common enough that some inputs are treated differently on DACs as far as clocking so it may well be audible.

Also I have had problems with coax and galvanic noise in my setup so I avoid it but that's not a good reason for anyone else to avoid it. I am not saying any method is inferior/superior. In pro audio they seem to use them interchangeably (while specifying 75 ohm cable for coax to fight jitter) except that clock signals are almost always done with BNC's for some reason which makes me think optical is bad for clocking. I don't know.

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I built these two DACs. Both use a CS8416 receiver, a WM8741 DAC, and the same output stage. One uses a Wolfson receiver between the 8416 and the 8741 to reduce jitter, the other an ASRC. The ASRC is upsampling which may be a bigger difference than the jitter, so the test is not quite fair. I'll need to retest with a different clock speed to equal that out. But, the jitter is one of two main variables, so take it as you will.

THD and frequency response differences shown below. Note that there is 0 feedback in these designs (not even source follower local fedback), so THD is higher than for an opamp output stage, but still very good and the sort of distortion that generally does not sound bad.

8804 has (very slightly) higher 2nd harmonics, ASRC has higher everything else. 8804 has higher noise floor which I can't explain. (The 60Hz/120Hz/180Hz/... bumps are an artifact of the soundcard.) The frequency response for the 8804 looks slightly better, too.

I think the ASRC sounds better.

Colin has heard both so he may be able to comment further.

8804 THD

8804_thd.png

ASRC THD

asrc_thd.png

8804 FR

8804_fr.png

ASRC FR

asrc_fr.png

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^ x2. I thought the idea was to differentiate transports and if they have a unique sound signature or not???

Also, on the subject, an earlier post claimed different volume levels from switching transports. I don't see how a different transport or digital input could possibly effect the output level of the DAC, if the same DAC were used for both? Maybe I'm missing something...

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^ x2. I thought the idea was to differentiate transports and if they have a unique sound signature or not???

Yes, yes, but you can consider everything up to the DAC chip the "transport". That is, comparing the effect of two different jitter reducers is one way to decide if you think jitter matters. Plugging in two different transports is another -- I just happened to have these graphs on my HDD and thought they might be interesting.

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Also, on the subject, an earlier post claimed different volume levels from switching transports. I don't see how a different transport or digital input could possibly effect the output level of the DAC, if the same DAC were used for both? Maybe I'm missing something...

Probably my post. I should have clarified and said that if both were bit perfect then by definition the music was at the same level. That said it's not always the case with DVD transports and or computer transports and it happens that sometimes some DSP to be done in transports/software that ruins the bit perfect nature and/changes levels.

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Yes, yes, but you can consider everything up to the DAC chip the "transport"

Hm, I'm not sure I'd agree 100%, although I see what you're getting at. I'd say there is a clear division in this case. The transport is responsible for digital transmission and the DAC for digital reception. The assumption is that there is a two box solution here and a cable between the two devices.

But yes I see your point about jitter, so carry on :)

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