Lowering Gain?

pg33 · 2421

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Offline pg33

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on: June 04, 2023, 09:23:07 PM
My system (source, preamp, and Quicksand) has too much gain and I would like to reduce Quicksand gain, if possible. Is there some way to do that?



Offline Paul Birkeland

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Reply #1 on: June 05, 2023, 11:28:42 AM
You can plug a pair of inline attenuators into the Quicksand to nudge the gain down.  You didn't mention what speakers you are using, which can also certainly contribute to the issue.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline pg33

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Reply #2 on: June 12, 2023, 07:35:18 PM
I've used multiple speakers with it--the issue is there regardless. I used some DIY TABAQ TL's, Bose, and Bang & Olufsen. The Bose are the only ones that aren't efficient.

Here's all the details:
I've built a power amplifier (no volume control) which is comprised of a Pass B1 with Korg and Bottlehead Quicksand. Both are running off a 24V battery; I upgraded the components to compensate for 29V-20V. Together, both units are spec'd for 36dB of gain. There is a voltage divider employed between the source and B1, so as to limit the ceiling/make it play nice. The source is a DAP with volume control.

This isn't a big issue. I feel like the amplifier's floor is too high, not dark at all. I'm guessing that's because I am well over the ideal gain with my creation.
« Last Edit: June 12, 2023, 07:52:28 PM by pg33 »



Offline Paul Birkeland

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Reply #3 on: June 13, 2023, 04:38:41 AM
Padding at the source is the least ideal location for padding in general.  Is there an earth reference for this system?  Are you hearing noise with nothing plugged into the Quicksand and its inputs shorted?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline pg33

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Reply #4 on: June 23, 2023, 11:34:06 AM
The voltage divider at the input was required to make the B1 operate correctly; I omitted the volume pot, which is required to operate correctly. There is no earth, but I don’t think I have a ground problem. I experimented with a ground in the past.

I have not tried the experiment you’ve described. How do I short inputs?

I should be more descriptive. I wouldn’t call this an issue. The system is just hyper sensitive. I can hear changes in the noise floor when tracks change; the DAP also makes a click between tracks, this can be heard with headphones, but it is much louder on this system. I am trying to figure out how to make it less sensitive without adding a pot somewhere (I have nowhere to put one).



Offline Paul Birkeland

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Reply #5 on: June 23, 2023, 01:07:39 PM
The B1 Nutube probably should get the full signal from your source if it can handle that much signal voltage, then I would attenuate between that and the Quicksand, as the Nutube isn't the quietest tube ever and microphony is a bit of an issue as well.  Since you have the two built together, shoring the inputs doesn't necessarily make a ton of sense as a test.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline pg33

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Reply #6 on: June 27, 2023, 04:28:59 PM
If I wanted to attenuate between the B1 and Quicksand, how would I go about that (technically speaking)?



Offline Paul Birkeland

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Reply #7 on: June 27, 2023, 04:45:26 PM
Use a voltage divider between the output of the B1 and the input of the Quicksand.  I would try a 10K/470 ohm voltage divider to get you about 27dB of padding, if that's too much just swap out the 470 ohm resistors for 1K resistors instead.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man