Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: p2pAmps on January 29, 2016, 04:47:38 am

Title: Concentric 250K 25K pots?
Post by: p2pAmps on January 29, 2016, 04:47:38 am
Guy I know this has probably been covered before but...

I would love to use a 250K / 25K concentric pot on Fender builds like Deluxes and Princeton for Bass/Mis control.  Any change what so ever anyone know of this arrangement?

Cheers
Title: Re: Concentric 250K 25K pots?
Post by: tubenit on January 29, 2016, 05:38:40 am
How about something like this 500k/250k concentric pot :

https://www.allparts.com/EP-4585-000-CTS-250K500K-Concentric-Pot_p_1443.html (https://www.allparts.com/EP-4585-000-CTS-250K500K-Concentric-Pot_p_1443.html)

And then put a 27k resistor across the outside terminals of the 500k pot which is the inner pot .

500k and 27k paralleled = 25.9k 

With respect, Tubenit
Title: Re: Concentric 250K 25K pots?
Post by: p2pAmps on January 29, 2016, 07:19:35 am
Quote from: tubenit on January 29, 2016, 05:38:40 am
How about something like this 500k/250k concentric pot :

https://www.allparts.com/EP-4585-000-CTS-250K500K-Concentric-Pot_p_1443.html (https://www.allparts.com/EP-4585-000-CTS-250K500K-Concentric-Pot_p_1443.html)

And then put a 27k resistor across the outside terminals of the 500k pot which is the inner pot .

500k and 27k paralleled = 25.9k 

With respect, Tubenit

Thanks Tubenit, but what about taper when you throw a 27K across those terminals?

Title: Re: Concentric 250K 25K pots?
Post by: mresistor on January 29, 2016, 07:44:56 am
It's cheaper here and they have some knobs. Don't know what you would do for Fender vintage style concentric knobs? Do they make them?
http://www.guitarelectronics.com/product/CPCS25/CTS-Stacked-Dual-Concentric-Audio-Guitar-Pot-250K500K.html (http://www.guitarelectronics.com/product/CPCS25/CTS-Stacked-Dual-Concentric-Audio-Guitar-Pot-250K500K.html)
Title: Re: Concentric 250K 25K pots?
Post by: sluckey on January 29, 2016, 07:55:10 am
Back in the '60s when there were so many different styles, and combinations of pots, a reputable manufacturer came up with a whole system of replacement pots. You could stack pots and even switches together for your custom needs. There was a front pot style, a rear pot style, and a switch that could all be snapped together. Then you also chose the shaft style, even dual concentric if needed. The system was very versatile, decent quality, and affordable. And if one of the components failed you just replace that component, rather than the whole stack. This system was aimed at consumer electronics, ie, tv, radio, stereo, etc.

I 'think' the manufacturer was Centralab, but I can't swear to it. Maybe someone remembers, and maybe that system is still around.
Title: Re: Concentric 250K 25K pots?
Post by: tubenit on January 29, 2016, 08:29:22 am
Quote
what about taper when you throw a 27K across those terminals?

Check out R.G. Keen's  "Secret Life of Pots"

http://www.geofex.com/Article_Folders/potsecrets/potscret.htm (http://www.geofex.com/Article_Folders/potsecrets/potscret.htm)

See reply #9 on this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=66471.0 (http://www.diystompboxes.com/smfforum/index.php?topic=66471.0)

I've been paralleling resistors across pots for yrs to get what I want from them. There are numerous approaches on how to do this successfully.

With respect, Tubenit
Title: Re: Concentric 250K 25K pots?
Post by: mresistor on January 29, 2016, 09:34:14 am
that first link is especially usefull tubenit    - I had forgotten that this could be done.   I love that pot info page      lots of good info