Replacing volume pot from 100K to 50K reduces gain?

ad010685 · 30th January 2013, 06:50 PM

Dears, is the above a tactic to reduce preamp gain? Or nothing related to this? preamp is a noval aikido with 6n1p input and 6n6p output tubes.
Checked replacement of the input tubes to reduce gain, but theory says it will not be enough. I am near to pad input volume with resistors but a pot replacement might be a simpler choice? Thanx for response, please basic style as i am extremely basic. Thanxs

Mooly · 30th January 2013, 07:06 PM

Changing the pot shouldn't alter the gain at all. As you mention valves though, its possible the lower value would load whatever stage drives it... which is something you don't want.

The best way to lower the gain may be just a simple attenuator at the input. Altering gain by altering the feedback internally in the amp may cause other problems and require other alterations.

ad010685 · 30th January 2013, 07:13 PM

If I dont have space inside the preamp, can I go from source (phono stage in my case) to a passive stepped attenuator preamp?Its output would then go to the high gain preamp. Is this too crazy or possible without compromising signal?
Thanx

Mooly · 31st January 2013, 06:26 AM

Certainly its possible and could work well in practice.

Its just that amplifying a signal (the phono stage) and then attenuating the signal only to amplify it again is never the best solution from a purist view. Each stage of gain adds noise and distortion.

ad010685 · 31st January 2013, 06:49 AM

Thanxs Mooly, appreciated your courtesy. So maybe it would be better and more purist If really take a solder gun to decrease 10dB from pre input with two resistors.
I wanted to avoid but in fact it makes sense?
Cheers

30th January 2013, 06:50 PM	#1
ad010685 diyAudio Member Join Date: Apr 2003 Location: ITALY	Replacing volume pot from 100K to 50K reduces gain? Dears, is the above a tactic to reduce preamp gain? Or nothing related to this? preamp is a noval aikido with 6n1p input and 6n6p output tubes. Checked replacement of the input tubes to reduce gain, but theory says it will not be enough. I am near to pad input volume with resistors but a pot replacement might be a simpler choice? Thanx for response, please basic style as i am extremely basic. Thanxs

30th January 2013, 07:06 PM	#2
Mooly diyAudio Moderator Join Date: Sep 2007	Changing the pot shouldn't alter the gain at all. As you mention valves though, its possible the lower value would load whatever stage drives it... which is something you don't want. The best way to lower the gain may be just a simple attenuator at the input. Altering gain by altering the feedback internally in the amp may cause other problems and require other alterations. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

31st January 2013, 06:26 AM	#4
Mooly diyAudio Moderator Join Date: Sep 2007	Certainly its possible and could work well in practice. Its just that amplifying a signal (the phono stage) and then attenuating the signal only to amplify it again is never the best solution from a purist view. Each stage of gain adds noise and distortion. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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30th January 2013, 07:13 PM	#3
ad010685 diyAudio Member Join Date: Apr 2003 Location: ITALY	If I dont have space inside the preamp, can I go from source (phono stage in my case) to a passive stepped attenuator preamp?Its output would then go to the high gain preamp. Is this too crazy or possible without compromising signal? Thanx

31st January 2013, 06:49 AM	#5
ad010685 diyAudio Member Join Date: Apr 2003 Location: ITALY	Thanxs Mooly, appreciated your courtesy. So maybe it would be better and more purist If really take a solder gun to decrease 10dB from pre input with two resistors. I wanted to avoid but in fact it makes sense? Cheers

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