If Preamp Gain is Set to High-What Consequences?

Newbee, I don't see that Foster_9 has confused anything, given the clarification provided in his second post. He is saying that the gain of the preamp has been set internally to 15 db. Nothing has been set to 15v or 15 volts. Which means that when the volume control of the preamp is turned all the way up, its output voltage will be 15 db greater than its input voltage. That corresponds to a ratio of about 5.62x, meaning that the output voltage at any instant of time will be about 5.62 times as great as the input voltage at that instant, with the volume control at max.

And, yes, reducing the volume control setting from its max position will reduce the actual gain provided by the preamp from the specified number, since the specified number is based on having the control at max.

Concerning whether or not reducing the internal gain setting would result in improved sonics, IMO it's anyone's guess, as there are many preamp-dependent variables that are involved. Anecdotal evidence seems to suggest, though, that having a gain structure which results in running the volume control in the upper part of its range often (but not always) provides best results. Personally, though, my instinct under the circumstances would be to leave it as is.

Best regards,
-- Al

Hi Newbee,

Depending on the specific design, the volume control can be located at or near the input of the preamp, or somewhere in the middle of its internal signal path (following an active input stage that receives the input signal), or even at the output in at least one case that I know of. See some of the preamp schematics shown at the Bryston site for examples of designs having the volume control function somewhere in the middle.

That is really a side issue, though. Regardless of where the control is located, if the preamp's gain is specified as 15 db it means that the output voltage is 15 db greater than the input voltage when the control is at max. Reducing the setting of the volume control from its maximum position will reduce that number correspondingly, most likely to negative numbers (corresponding to the output voltage being less than the input voltage) in the range of positions Foster_9 is using. That is very common these days, especially with digital sources.

Personally I think there are too potential many tradeoff's trade offs to bother unless one is trying to minimize pre-amp noise, typically seen in a tubed unit.

I agree, as I indicated at the end of my earlier post. Unless, that is, it is readily possible for Foster_9 to change the internal gain settings himself, in which case he may want to experiment a little. A consultation with Joule would also seem to be in order, as you suggested, to see if they feel that with this specific design any particular part of the volume control's range would be significantly more optimal to be using than other parts.

My pre-amp has noise as seen by the amp. The line stage has 26db (a lot, I think, for old amps with more than 1.5 input sensitivity.) This noise is constant and doesn't change, with VC at 0 or max setting. It only changes when I put an in line attenuator between it an the amp. It doesn't change when I put an inline attenuator between a source and the pre-amp input.

That would simply say that the noise is being introduced at some point in the preamp's internal signal path that is "downstream" of wherever the volume control is located, assuming it is not being introduced in the interconnect cable.

Best regards,
-- Al