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MDAC First Listen (part 00110111)

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BigDog

pfm Member
clivem2 said:
There's a new Regen which includes galvanic isolation; hence the higher price.
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Sorry to have mislead... I should have said "new ISO REGEN" which is on the order of $325 and which includes galvanic isolation, a redesign of the original REGEN which is still available for $175.

Based on comments in this thread by those who I have come to know thru their posts, I have no doubt that John's DETOX will surpass the REGEN in both improved sound quality as well as construction based on number of machine screws if nothing else. :) I have less confidence in the performance of the ISO REGEN if only based on my personal experience.

C'mon DETOX!
 
EIffel said:
Regarding the streamer, will one (you) need to make some physical alterations to the Compute Module board before it can be plugged into the streamer board, or will it be possible to buy a regular CM3 and plug it in the streamer board?
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A standard module (CM3) will work but the CPU on the module will not be clocked-locked to the Audio Master Clock.

My intention is to hand rework Modules under a microscope to allow external clock synchronisation - I might only do this for the P&P sponsored units (without extra cost).

We have used an unused I/O pin on the CM3 DIMM connector as a 19.2MHz clock input (PLL'ed from the Audio Master Clocks) and I'll hand modify the module to route this pin to the CPU's XO circuit.
 
dimedrol said:
JohnW, please help me out here...

My mdac listening volume is about -40db. I found your posts here on PFM saying that this amount of digital attenuation is sub optimal, so you recommended Rothwell in-line attenuators. I ordered those (RCA version) per your advice. Upon further searching I also found other posts where you say Rothwell attenuators are not good because they don't attenuate the Common mode (not sure if it applies to RCA as well or XLR only).

Furthermore you said that in-line attenuators increase source impedance which is not good either.

So at this point I am confused.
Without in-line attenuators I have high digital attenuation which is bad
With in-line attenuators it is not good either.
what do I do then?

update: I was thinking of maybe taking the preamp route, but upon checking out one of the Schiit preamps I found that it's output impedance is 72Ohm, which means in that regard it's no better than the Rothwells. Please advise.
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Sounds like you have a power amplifier with very high gain or very sensitive speakers?

I'd not worry about it too much, there is no neat affordable solution.
 
BigDog said:
Based on comments in this thread by those who I have come to know thru their posts, I have no doubt that John's DETOX will surpass the REGEN in both improved sound quality as well as construction based on number of machine screws if nothing else. :)
C'mon DETOX!
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Have I missed Fusion's view of the Detox, or hasn't he posted it yet?
 
No, you didn't miss anything. Unfortunately I have yet to deliver a final statement on the Superior DAC and the Detox.

I'm sorry, but after my nephew was born 10 days ago, I had a lot of family business going on. This week should be calm enough for me to get more stuff done.
 
JohnW said:
Sounds like you have a power amplifier with very high gain or very sensitive speakers?

I'd not worry about it too much, there is no neat affordable solution.
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Mine is a 200W@8Ohm power amp (input impedance 50kOhm) with no gain controls. Most listening I do is at night, hence MDAC volume has to stay below -40db and I saw people on this forum (including you) saying that this is not the best mode for the MDAC, yet it's the mode I need most. So in my situation, is there anything I could do, including opting for a different DAC etc? Or is this particular problem not worth resolving (considering the drawbacks of known approaches)?
 
The whole gain of your system is too high, it is really common, with DACs having increasingly high output, a DAC with a variable analogue output would solve the problem.
Keith
 
Analogue attenuation decreases the signal and the background noise, digital attenuation decreases the signal but not the back ground noise, that is why it is not good practise to use too much digital attenuation.
Keith
 
Purite Audio said:
The whole gain of your system is too high, it is really common, with DACs having increasingly high output, a DAC with a variable analogue output would solve the problem.
Keith
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It may be situations such as this that Mytek anticipated and made allowance for by offering jumpers to lower the gain by 6dB as required. In extreme cases, the Mytek DACs as well as others, I surmise, can overload the amp(s) resulting in distortion.
 
I understand that some standalone/built-in preamps operate in analogue domain, I just don't understand how are they beneficial to in-line attenuators I already ordered. In-line attenuators are fixed level passive preamps (that is my understanding). And there's a lot of opinions on the internet about them degrading sound.
 
Purite Audio said:
Analogue attenuation decreases the signal and the background noise, digital attenuation decreases the signal but not the back ground noise, that is why it is not good practise to use too much digital attenuation.
Keith
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This does not apply to a decent digital front end where the significant noise contribution is basically the output impedance of the DAC array.

The MDAC has a balanced Dynamic range of 126dB in standard form any pre-amplifier including a passive pot over most of its operating range is going to add more thermal noise.

Where a Passive pot / "Good" pre-amplifier is going to help is that any Common Mode noise is also going to be attenuated at lower levels - where as the RF "Hush" is outputted at full level at all times with a Digital preamp.
 
JohnW said:
Where a Passive pot / "Good" pre-amplifier is going to help is that any Common Mode noise is also going to be attenuated at lower levels - where as the RF "Hush" is outputted at full level with a Digital preamp.
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Now the question of the year is: under what condition will an analogue preamp (attenuator) be beneficial to the MDAC's digital one, provided the listening level is -40db? Are there known implementation meeting that criteria?
 
dimedrol said:
Now the question of the year is: under what condition will an analogue preamp (attenuator) be beneficial to the MDAC's digital one, provided the listening level is -40db? Are there known implementation meeting that criteria?
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Relax. My situation is similar to yours. I use -15dB Rothwells. Everything sounds great.
 
No problem with the MDAC at -40db (or less)
From my listening sessions with some properly implemented balanced attenuators (built by John) I (marginally) preferred the sound without, but any differences were minimal and potentially at the imaginable level.

By all means get some attenuators and see what you think, but I wouldn't unduly worry about it
 
On some well produced tracks my MDAC is running at +3db ....and I still want more....:D:D:D

(not really, the system is close to total breakdown at that sound level)...All the amps and the MDAC are really hot after a listening session....worryingly hot, but John assured me the MDAC can't go past about 38 Celsius...so maybe I imagine things.
 
timola said:
On some well produced tracks my MDAC is running at +3db ....and I still want more....:D:D:D

(not really, the system is close to total breakdown at that sound level)...All the amps and the MDAC are really hot after a listening session....worryingly hot, but John assured me the MDAC can't go past about 38 Celsius...so maybe I imagine things.
Click to expand...

I am all in favor of volume settings appropriate to the genre of music being played and find that almost nothing sounds good in a whisper.

38degC?! My Pass Class A monos idle at 60degC/140degF. Not a good thing during the warmer times of year.
 
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