Gain Reduction without compromise

[Bill Hart]

I should attach my 'idiot' disclaimer here, but the question: let's say a line stage (one I'm interested in trying) has too much gain for the system, overall. I know some preamp/linestages have a switch to 'adjust' gain- is this simply a resistor? I'm loathe to use an in-line attenuator. How is this normally executed in a 'purist' way or is there such a thing?

 

[DonH50]

It may be simply a resistor, which is also what an attenuator includes, but the resistor may actually change the gain of an amplifier stage rather than just attenuating the output (or input). Hard to show without a picture, but visualize the resistor inside a gain block where it changes the gain, rather than in a volume control outside the gain block.

You generally want the most gain early in the system for optimum (lowest) noise but there are always trades.

This might be an interesting topic for a technical article since the where/how/why of setting gain is actually a non-trivial trade among noise, distortion, and other factors and there are different ways to do it.

HTH - Don

 

[LL21]

I should attach my 'idiot' disclaimer here, but the question: let's say a line stage (one I'm interested in trying) has too much gain for the system, overall. I know some preamp/linestages have a switch to 'adjust' gain- is this simply a resistor? I'm loathe to use an in-line attenuator. How is this normally executed in a 'purist' way or is there such a thing?

Hi Whart...just so i understand...how much gain do you actually have? I have 31db in my amp and roughly 25db in my pre...and i dont mind it at all, even though it is on the high side, and the system is totally silent in a silent room...until my ear is within 3-5 inches of the tweeter (depending on age of the preamp tubes).

 

[Bill Hart]

It may be simply a resistor, which is also what an attenuator includes, but the resistor may actually change the gain of an amplifier stage rather than just attenuating the output (or input). Hard to show without a picture, but visualize the resistor inside a gain block where it changes the gain, rather than in a volume control outside the gain block.

You generally want the most gain early in the system for optimum (lowest) noise but there are always trades.

This might be an interesting topic for a technical article since the where/how/why of setting gain is actually a non-trivial trade among noise, distortion, and other factors and there are different ways to do it.

HTH - Don

Makes sense, you answered my question, I think the premise here was that, with the high efficiency horns, there would be no 'range' on the volume control of the line stage. And Don, Thanks.

 

[Bill Hart]

Hi Whart...just so i understand...how much gain do you actually have? I have 31db in my amp and roughly 25db in my pre...and i dont mind it at all, even though it is on the high side, and the system is totally silent in a silent room...until my ear is within 3-5 inches of the tweeter (depending on age of the preamp tubes).

Lloyd, question came up in the context of the output of a particular line stage, given my very efficient horns. And fwiw, the Allnic phono head puts out quite a bit of gain when set to optimize loading for the Airtight cartridge. As it is, I have very little room to work with on my existing line stage- 9 o'clock is pretty loud. I think the concern was, with this other line stage, i'd have virtually no room to work with on the volume control between zero and 'too loud.'

 

[microstrip]

Some preamplifiers from Audio Research could have their gain patched just putting a resistor in parallel with the existing one in the feedback loop or changing it. Unhappily changing the gain also decreased sound quality compared to the original factory setting. . We could also change the gain in early Jeff Rowland amplifiers inserting shorts in parallel with some resistors - again changing the sound characteristics.

As Don says, there are always trades in any change - my advice would be to get in touch with people at the Allnic factory about the best way to solve the problem.

 

[LL21]

Lloyd, question came up in the context of the output of a particular line stage, given my very efficient horns. And fwiw, the Allnic phono head puts out quite a bit of gain when set to optimize loading for the Airtight cartridge. As it is, I have very little room to work with on my existing line stage- 9 o'clock is pretty loud. I think the concern was, with this other line stage, i'd have virtually no room to work with on the volume control between zero and 'too loud.'

Got it...yeah...if 9 o'clock is loud, then not much to play with. I am happy to play from 1 to 28 80% of the time...but on certain MFSL discs...i will bring it up to 30-35...and then when i feel like playing Rutter Pie Jesu from Reference Recordings...well, what can i say...put it to 50 and let the organ fill the room with the choral. So assuming my 50 is 12noon...well, i do have a lot of gain...but probably more flexibility than it seems you might if your equipment has too much gain.

 

[LL21]

...my advice would be to get in touch with people at the Allnic factory about the best way to solve the problem.

+1

 

[Bill Hart]

Some preamplifiers from Audio Research could have their gain patched just putting a resistor in parallel with the existing one in the feedback loop or changing it. Unhappily changing the gain also decreased sound quality compared to the original factory setting. . We could also change the gain in early Jeff Rowland amplifiers inserting shorts in parallel with some resistors - again changing the sound characteristics.

As Don says, there are always trades in any change - my advice would be to get in touch with people at the Allnic factory about the best way to solve the problem.

Right, I don't want to screw up the sound. Just so you know, it is not a problem in relation to the Allnic phono stage, or an Allnic line stage. I can live with the output of the Allnic phono stage with the Lamm L2, but the question arose when I was discussing another possible line stage that apparently has alot of gain, given my speakers. I don't think it would be an issue for either the L3000 line stage or the elusive DHT line stage from Allnic, which I'd like to hear.

 

[Bill Hart]

+1

See my other post, Lloyd, it is not really about the Allnic, but combining various components that are not Allnic. I think if I went with an Allnic line stage there probably would be no issue- indeed, if memory serves, the L3000 can be ordered with an adjustment for gain. As to the DHT, I have no idea (and that's the one I really want to hear).

 

[LL21]

See my other post, Lloyd, it is not really about the Allnic, but combining various components that are not Allnic. I think if I went with an Allnic line stage there probably would be no issue- indeed, if memory serves, the L3000 can be ordered with an adjustment for gain. As to the DHT, I have no idea (and that's the one I really want to hear).

Well, i guess what i meant was...if you want the Allnic but with lower gain...perhaps Allnic can lower it for you by adjusting resistors?

 

[puroagave]

See my other post, Lloyd, it is not really about the Allnic, but combining various components that are not Allnic. I think if I went with an Allnic line stage there probably would be no issue- indeed, if memory serves, the L3000 can be ordered with an adjustment for gain. As to the DHT, I have no idea (and that's the one I really want to hear).

gain matching between components has been my biggest pet peeve. i've had preamps like the joule electra which does one better by adding or subtracting a gain stage rather than resitor networks that pad (dull) the sound. In a perfect world all amps, preamps etc would have adjustable gain to optimize the s/n and lower the noise floor of a given system w/o compromising the liveliness and dynamics.

 

[Bill Hart]

gain matching between components has been my biggest pet peeve. i've had preamps like the joule electra which does one better by adding or subtracting a gain stage rather than resitor networks that pad (dull) the sound. In a perfect world all amps, preamps etc would have adjustable gain to optimize the s/n and lower the noise floor of a given system w/o compromising the liveliness and dynamics.

Yep, i used a Joule for a little while while the Lamm L2 was being fixed, and noted that. Jumpers to bypass a stage.

 

[DonH50]

There is no reason a resistor pad should "dull" the sound in a good design.

Reducing the gain of a gain stage may impact its gain-bandwidth product, feedback factor, and stability as well as noise and distortion, altering the sound as was said earlier. One of those trades to be made...