Single Pot in parallel to control 2x identical gain controls

BobTPH

Joined Jun 5, 2013
9,284
I'm not so sure. From the post #14 pic it looks as though the module's signal input terminal connects directly to the top of the pot, and the attenuated signal from the wiper goes to the IC input. The IC could be configured with a fixed gain.
If so, the signal at the wiper could feed a second module. Hence one mono pot could replace both trim-pots and both modules would have the same overall gain.
How does that work when the input of one is the output of the other, as the OP has stated?
 

Alec_t

Joined Sep 17, 2013
14,411
How does that work when the input of one is the output of the other, as the OP has stated?
I thought from the thread title and post #1 that the plan was to have the two modules in parallel?
If the modules are in a series chain, then why not just set one trim-pot to max (or some other convenient level) and replace the other trim-pot with a volume control?
 

boostbuck

Joined Oct 5, 2017
570
Well they're gonna be in series with each other so one will get it's input from the clean audio signal and the other with get its input from the output of the first one...
The trimpots do not 'control' the gain of the module. The signal for the module is fed THROUGH the trimpot. Therefore you can't control two modules with one trimpot, unless the signal from the trimpot wiper is provided equally to each module i.e. they are in parallel.
 

Thread Starter

PattyT

Joined Nov 7, 2019
16
I'm not so sure. From the post #14 pic it looks as though the module's signal input terminal connects directly to the top of the pot, and the attenuated signal from the wiper goes to the IC input. The IC could be configured with a fixed gain.
If so, the signal at the wiper could feed a second module. Hence one mono pot could replace both trim-pots and both modules would have the same overall gain.

thats what i was going for
 

Thread Starter

PattyT

Joined Nov 7, 2019
16
There is no way around not having a separate resistances for each circuit if you want two separate (stereo) outputs.
I assume that's the reason for having two amps.

the amps are to be mono and in series to increase gain enough to match the other half of the effect circuit.

This has been done by a maker online BUT the caveat to this is that only one of the modules in the series pair was controlled by an external Pot, the other just had the factory trim pot cranked all the way up
 

Thread Starter

PattyT

Joined Nov 7, 2019
16
The trim pot shown in your pics is 10k, not 1k.

I originally wanted to use a 1k to minimise the amount of signal distortion through the pot so the clipping diodes have cleaner signal to deal with.

10k will suffice, and I decided to change to 10k before posting photos
 

boostbuck

Joined Oct 5, 2017
570
thats what i was going for
No, it isn't. That would be in parallel, and you want to use them in series:

Well they're gonna be in series with each other so one will get it's input from the clean audio signal and the other with get its input from the output of the first one...
You would gain much understanding by drawing a circuit of how you would like the pot to be used, I think.
 
I'm in Australia and the shipping on that is worth more than double the component cost in AUD. Our local electronics stores carry some components but not a double ganged pot
https://au.rs-online.com/web/p/potentiometers/7377726
Sorry it's linear. The construction is fairly typical, I wonder if you could dismantle it and insert the track with pins from a single pot?
Or would a slider potemtiometer do the job, with a frabricated or 3D printed knob which slides them together?
 

Alec_t

Joined Sep 17, 2013
14,411
Here's what I think your options are :
1710329768749.png
It now seems your intention is to use the series arrangement, to maximise gain.
The parallel arrangement would provide a greater load on the signal source unless the trim-pot were removed from module 2.
 
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