Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: loz_the_guru on April 17, 2019, 10:36:08 PM

Title: Replacing the standard pot - does the resistance matter?
Post by: loz_the_guru on April 17, 2019, 10:36:08 PM

Hi all,

I'm replacing the standard pot and have two options - a Valab stepped/laddered with a 100k resistance, or an Alps black beauty (second hand) at 20k.

I know the standard pot resistance is 20k - the question I have is does it matter if I change this? I need to add 33k/75k resistors to the pot at the same time too, if this is relevant.

Title: Re: Replacing the standard pot - does the resistance matter?
Post by: Tom-s on April 17, 2019, 11:17:08 PM

The standard attenuator has 100k ohm resistance to ground. Get a 100k ohm replacement pot.
If you add the 33/75k resistors to a 20k pot the voltage devision will be different and the padding won't work as intended.
Padding of the volume pot will work with the 100k pot.

IME the Valab is a good pot.

I recently used a DACT type pot with good results in another build. It's really small (convenient for those that need the space) and will work very well in a crack.

https://www.ebay.com/itm/DACT-Type-SMD-Stepped-Attenuator-21-step-volume-control/190844814249

Title: Re: Replacing the standard pot - does the resistance matter?
Post by: loz_the_guru on April 17, 2019, 11:52:09 PM

Quote from: Tom-s on April 17, 2019, 11:17:08 PM

The standard attenuator has 100k ohm resistance to ground. Get a 100k ohm replacement pot.
If you add the 33/75k resistors to a 20k pot the voltage devision will be different and the padding won't work as intended.
Padding of the volume pot will work with the 100k pot.

IME the Valab is a good pot.

I recently used a DACT type pot with good results in another build. It's really small (convenient for those that need the space) and will work very well in a crack.

https://www.ebay.com/itm/DACT-Type-SMD-Stepped-Attenuator-21-step-volume-control/190844814249

Thanks for the reply Tom-s, very useful and glad I included the info RE 75/33 resistors too.

I've heard good things about those DACT pots before so definitely interested in trying one out - in your opinion is it an audible difference in quality over the stock pot? Also, did you need to enlarge the whole in the base plate?

Thanks!

Title: Re: Replacing the standard pot - does the resistance matter?
Post by: Tom-s on April 18, 2019, 04:38:56 AM

Can't answer your questions as i didn't build it into a Bottlehead amp.

But! It is balanced from low levels. So yes, since i listen with low levels, for me it is an upgrade over a slider pot.