Digital Processor Reviews

+ Bricasti Design M21. I am looking for a ladder DAC with volume control. :-)

Both Benchmark LA4 and HPA4 have 256-step volume controls ...... So, gain controls may not be a big issue :-) ......

Yes, the Benchmarks are excellent but how one manages system gain best depends on all the components in the chain, not just on the presence/absence of the preamp.

Kal (preamp-less)

I definitely agree, Mr. Reichert. It is often overlooked, but very important. Optimally any attenuation should be minimized, digital (especially) or analog. Ideally everything should be running close to "wide open" at optimal listening levels.

The analog preamp is interesting these days with many DACs having volume control, analog and/or digital. Both the analog output stage and the digital attenuation scheme in these DACs must be excellent.

There was an era where passive preamps rose to prominence (the 90s?). This brings important considerations in impedance. I used a set of EVS "ultimate attenuators" in that era (two small boxes plugged directly into the amp RCAs with a rotary switch selecting individual resistors). Thankfully it was a headphone system so I was sitting next to them. :)

Later I built a transformer-coupled DAC (GREAT sound) that needed minimal attenuation.

Many reviewers found passive "preamps" lacking, especially in dynamics. JA has always emphasized the importance of active line stages, describing them as the most important link. Many preferred a great active line stage to passive, and several since have noted improvement bypassing DAC volume controls and using external line stages.

Back to gainstaging. I sold off my entire system before going overseas in 2012. I was full-on exotica to that point (tubes, vinyl, stats, etc.). When I returned and build back up I did it slowly and less exotically, leaning toward pro stuff and simplicity. I use an RME ADI-2 at its lowest gain setting into a Benchmark amp at its lowest setting and listening with a total of 0.5 to 6db of attenuation (with the volume control in the RME) when listening. It is pretty cool.

If I could get the gainstaging right, I wouldn't hesitate to use the Holo DAC with a bit of digital attenuation.

Best,

Bill

I can see an ad ....... Want cure for audiophile depression? .... buy D'Agostino Momentum HD preamp ($40k, reviewed by Stereophile :-) .......

A volume control should, in almost all cases, really be called a signal attenuation control. It is very, very rarely a gain control and, generally, system gain is determined by a number of elements with fixed gain.

One consequence of this is that the more you attenuate the signal the more you reduce the SNR since the noise is fixed). So gain management consists of adjusting and/or selecting a chain of components that will amplify the signal enough to listen to and not much more.

Of course, that is constraining in use so having a variable attenuator somewhere is useful. Where to put it and how to construct it are separate matters.

Are they gain controls?

Makes money, he's not stupid!

Cheers George

JA2 could do a follow-up comparison review(s) between Pass Labs XP-22 ($9.5k) and Pasound JC 2BP ($4.5k)) and Benchmark LA4 ($2.6k) :-) .......

Interesting Victor, didn't know that, well if right that makes his quote about passive preamps quote look even more legit in what he says.

Nelson Pass:"What could be better? Hardly any noise or distortion added by these simple passive parts. No feedback, no worrying about what type of capacitors – just musical perfection.really - I’m being serious here!".

But there is a impedance matching proviso with 10k passive preamps as their highest output impedance is around 2.5k.
First "the amp" input impedance has to be more than >33kohm input impedance (most are except for some Class-D's), and "if" it has capacitor input coupling, the cap has to be 5uF or higher or bass roll off will occur.
Second "the source" should have a low output impedance, most solid state ones are. But many tubes ones are not.

Cheers George

So, Pass preamps work well with Pass designed power-amps ....... just like, darTZeel preamp and power-amp combo :-) ........

That kind of a combo could provide a transparent window between the source and the loudspeakers (straight wire with gain) :-) ......