Adding a pre amp

[Fitzcaraldo215]

5 hours ago, KingRex said:

How does a DAC perform volume attenuation?   It has to have some sort of material inside it that varies something in order for the amp to know it needs to send more or less power to the speaker.  I'm asking out of pure ignorance.  My question on a passive vs internal in the dac volume control was to understand just this.  I get what an Alps pot, Autoformer, resistive ladder do.  I was once told how Pass Labs does it but don't fully get it.  I thought it had something to do with a semiconductor that had a ladder inside it. I really don't know.  If your going to say its all software, what is the software driving.

Thanks. 

A digital volume control, as in many DACs, AVRs, HT prepros, etc., does not function by increasing/decreasing resistance, like the Alps pot, etc. It functions by merely shifting bits in a register without the necessity for moving parts or "wipers" or switched resistive ladders, etc. routing and thereby affecting the signal.  The digital control is, of course, done with the signal in the digital domain prior to any analog output stages.  

 

The digital volume control is noiseless and distortionless.  That is impossible to achieve with an analog domain volume control in an active or passive circuit.  Getting the analog control even close to the performance of the digital control is also expensive, requiring expensive parts.  The digital control is easily and inexpensive to implement and is already built into some DAC chips. 

[Fitzcaraldo215]

40 minutes ago, GUTB said:

Nelson Pass is an authority in amp design based on his public work in amp design, long experience and well-known expertise in the subject. Everyone knows preamps sound better, and Pass isn’t an exception. 

But, Pass also makes and sells analog preamps.  So, would his opinion not also be highly biased, as is, of course, your own? 

 

Everyone? I sold a very nice, very costly Levinson 380s line stage 10 years ago when I realized how much transparency it was taking away vs. direct play via a digital volume control.  That model had been John Atkinson's reference for a fair number of years at Stereophile. The 380s did sound great with analog sources, but did not fare well in direct comparison to digital straight to the amps with a digital volume control.

 

Actually, everyone knows that adding devices to the analog signal path cannot possibly make the signal better.  Unless heroically and expensively engineered to minimize its own inherent noise and distortion below audibility, it cannot come close to even a cheap digital volume control competently engineered, which really is not hard to do.

 

 

 

 

[Fitzcaraldo215]

3 minutes ago, diecaster said:

Fitzcaraldo215,

 

That is all well and good in theory. But, in practice, that's not how it works out. At least not for everyone. You go ahead and be concerned with what the signal looks like. I will care about how that signal sounds. With my 40 years of experience, I'll take a high quality active tube-based preamp over a passive preamp or a DAC with digital volume control.  

There we have it, as it were, in a nutshell.  If some prefer the added "sounds" of the preamp added in a constant and fixed way to the original signal, I staunchly defend your right to do so. I am not concerned with what the signal looks like either.  I just prefer that it not be distorted or have noise added to it as much as possible.

 

I have also been at this for a very long time in decades myself. Count me out on tubes or analog volume controls. Been there, done that.  They  definitely add something, but not positively, in my experience.  YMMV.

[Fitzcaraldo215]

7 minutes ago, mansr said:

Yes, but it's class A bias.

Yes, classy, and expensive, by the way.

[Fitzcaraldo215]

5 hours ago, sandyk said:

 

It can't improve the quality of the source signal it receives, but it may be able to reduce the degradation that occurs when there is a relatively long distance between the DAC and the power amplifier ,due to it's often improved cable driving capabilities,  or when the power amplifier has a lower input impedance such as many recent Solid State power amplifiers with around 10Kohm input impedance. (Most Preamps have an input impedance of greater than 20Kohms. with many around 50Kohms.)

Some Preamps are also capable of correctly driving 75 ohm terminated coax cables over vastly improved distances than the DAC itself is capable of, without HF roll off.. 

I currently use the following setup:

 

HTPC via USB to an Exasound E28 directly to amps and sub in a 7.1 Mch configuration

 

The front, center and sub channels are 1-2 meter XLR  analog interconnections.  The surround and rear channels are all 10 meter XLRs.  There is no problem whatsoever.  There is no audible or measured HF rolloff. There are no issues with system dynamics or anything else.

 

And, it delivers by far the highest quality sound I have ever had in my room.  Higher, in fact, than my previous stereo using a Levinson 380S to Krell KAS-2 Class A monsters.  As previously stated, the Levinson colored the sound noticeably when used in its HT unity gain mode for the front channels, bypassing its very exotic volume control.  So, I got rid of it, and also the Krells, BTW, both a long time ago.  Also, since my PC provides all audio and video, I have no need for input switching via a preamp.

 

Thus, as usual, results are highly system dependent.  There is no single, one size fits all answer that is universally true in all circumstances.  Insisting otherwise is foolish, driven purely by biased beliefs, not broad experience.

 

Enjoy your preamps, those who prefer them.  To me, they add nothing but extra cost and system complexity, and they can slightly degrade sonic performance.  

[Fitzcaraldo215]

33 minutes ago, mansr said:

Digitally controlled analogue attenuators are common. Is that what you meant?

Yes, but to avoid confusion, a digitally controlled attenuator for use in an analog circuit is still an analog device, albeit with digital controls.  It attenuates signal purely in the analog domain, and no a-d or d-a is necessary to use it.

 

OTOH, a digital volume control operates entirely in the digital domain by shifting the bits in each PCM signal word.

[Fitzcaraldo215]

13 hours ago, cjf said:

 

I was initially going to do exactly that because I think it would have addressed the JRiver VOL issue mentioned previously but as it turns out, my current Trim level (+4dBV) is already not enough to drive the Amp fully. So dropping it would make things worse and of course, increasing it would only exaggerate the original issue because JRiver VOL would need to be attenuated even further then it already is.

 

Its interesting because the Hilo is probably one of the most flexible DAC's out there by allowing 8 different Output Trim Levels to choose from. So the fact that none of them can address this specific issue, using this specific Amp does beg the question of what percent of others attempting a DAC Direct to Amp setup run into the same problem and or are not aware of this issue to begin with?  Keep in mind that most DAC's are not as flexible as the Hilo in terms of finding a proper Output Trim Level to drive an Amp fully but also at the same time trying to maintain as much digital resolution/bits as possible. It seems like a very tricky line to walk by also needing to use as little digital attenuation as possible within the DAC or Software VOL control.

No such problems here driven by my Exasound e28 into 3 different amps - a Spectron,     A 20-year old Bryston PowerPac 120 and two Parasound A23s, plus a JL Audio sub - all via XLR.  I also use JRiver, but currently only with the Exa master volume control, as the Exa-JRiver volume integration tool has not been working in software. It all functions exactly as it should with channel level trims in Dirac Live.

[Fitzcaraldo215]

1 hour ago, barrows said:

Exasound volume controls work at 32 bits (or is it 48 bits, cannot remember, anyway at least 32), so allowing for 21 bits for full resolution any DAC is capable of still gives you 11 bits of attenuationn with no worries.  So you can even go to -66 dB!  Not really a concern here...

The Exasound is 32 bits, which is common these days in DACs, AVRs and HT prepros, even cheap ones.  I did not see a spec for cjf's Lynx Hilo.

 

 

[Fitzcaraldo215]

15 hours ago, cjf said:

I see what you did there

 

I've certainly made no claims that the Lynx Hilo is SOA in terms of its resolution, but with that said, it does do things few other DA's can do which is why I bought it. I just acquired it about a month ago to explorer all its capabilities and to determine how best I will integrate it into my existing system. At $2500 beans I had no expectation that it would be a world beater but it does hold its own when compared to my Meitner which is impressive.

I am not criticizing your choice of the Lynx at all.  I respect it.  It just seems that it may have limitations on the volume control front that some other DACs do not.

 

There is a guy, dallasjustice, at ASR Forum who has a very sophisticated active crossover setup, and he is one very credible guy.  He has tried many, many things in perfecting his system.  He chose the Lynx Hilo.  

[Fitzcaraldo215]

1 hour ago, Panelhead said:

  Noise level is a limiting factor. The 32 bit is mostly hype. 

  In my application I want a 32 bit dac chip for digital attenuation. The one in my Pulse works flawlessly. Just not a fan of the rest.

Not at all.  32-bit is a straightforward, well engineered way to implement the digital volume control with no downsides.

 

Yes, of course, digital source material is 24-bit, with even the LSBs being just noise.  Putting that into 32-bit words just adds more noise bits.  But, that prevents loss of resolution with volume attenuation in most all circumstances.