2. amps-preamps
  3. 154891-71406

How much sound quality lives inside of voltage swing and gain?

Going to try and tie together a few thoughts as it relates to both tubes and solid state.

I was thinking about how much overall sound quality is tied to correct gain structure in a system and particularly the lack of front end gain and the reliance of establishing voltage swing further down the line.

Take tube preamps of old (and some new), the kind that can output more than 10, 15 even 30 volts before any amount of significant distortion. A principle Nelson Pass used to his advantage with the F4 amp. I will dovetail this with the suggestion that a big reason tube circuits seem more prone to tweaking via boutique parts would be because of those inherent larger voltages impacting the size of the components and thus more of the materials and composition of them acting on the signal. Transformers for input, output, and coupling invariably have an effect but there are few SS designs to compare that. Also a big reason I plan to build a Firstwatt M2 or F6 to hear iron effects in a solid state design.

Conversely some of the more well regarded solid state preamps, Krell Evolution, Pass XP, are also capable of driving difficult loads at greater than the nominal 2V needed for most power amps.

Is there merit to pursue all the system gain as early in the chain as possible? I think so and would like to try out one of the Okto Research DACs or other pro audio units which can output 7-8Vrms. Then use the preamp as a buffer or for a bit of gain followed by a lower gain or purely current drive amp.

A front to back approach would also alleviate noise issues as a quiet circuit with lots of output would eliminate the compounding effect of downstream gain which may only be discarded and handed more noise as it moves through each component.
balodis
erik_squires
16,046 posts
 
Gain is usually the enemy of a quiet system.

Having lots of gain, which you later reduce via a variable resistor (i.e. the volume control) is in my mind not a good idea, but historically preamps have had far too much.  However, with the right DAC circuit, you can adjust the reference level from 2 V up to something else, like 12 Volts. That's not really a question of gain (i.e. voltage amplification).

I’ve often wondered what a CJ PV series preamp would sound like if it’s gain was seriously reduced. Would it be quieter while maintaining the euphonic sweetness? Would channel separation improve?

But yes, having higher than 2 V swing, along with reasonable impedance between circuits, is a great way to limit noise from outside sources.

You might be interested in this curious little headphone amp, which uses 120 V internally. :)

https://spl.audio/studio/phonitor-2/?lang=en


And also, it has VU meters. :) Never heard them.

Best,

E
erik_squires
16,046 posts
 
However, with the right DAC circuit,


I'm going to go away for a day while all the usual suspects skip over this caveat, and then opine vociferously how wrong I am.
balodis OP
1 posts
 
Yes, so take your DAC of choice and build an output stage around it, SS or tubes and power it with some high voltage rails then use that to your advantage and output it into the next stage which also has equally high headroom on the power supply and designed in a way that will allow it to act as the final voltage gain for the entire system. Pair the whole thing with a power amp to provide the needed current, ie a Firstwatt F4. I am also interested in learning of other amp designs where front end voltage gain is minimal and provides mainly current.
I've always found it interesting that whenever I've had certain amps that have level controls on them I enjoyed the sound more when running my preamp higher up in the range and attenuating the amps.

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