Changing gain pot value in Boss SD-1 mod

A forum devoted to mod, tips and suggestions for upgrading and rehousing your VERY CHEAP commercial stompbox to near boutique excellence.
Post Reply
User avatar
SpikeVelvet
Information
Posts: 14
Joined: 10 Dec 2016, 01:35
Has thanked: 1 time

Post by SpikeVelvet »

I am not sure I really understand how pot value works for the gain control in a circuit. I'm hoping somebody can explain like I am 5.

I modified an SD-1 and changed R6/C3 to give the pedal more gain. It still has the stock 1M pot. I have all the gain I need at about 12 o'clock. Am I correct in assuming that if I change out the pot to a 500k it will have the same amount of gain at max but a more useful and precise sweep of the pot?

Also, isn't there a way to strap a 1M resistor across the terminals to have the pot behave like a 500k?

Thanks,

Kevin

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

Yes, the 500k potentiometer works.
If the 1 MOhm resistor is connected in parallel with a 1 MOhm resistor, the control behavior is no longer linear.
But if the deviation is acceptable then you can do it that way.
Another possibility is to change R6 and C3 again to adjust the gain.
Pot1M_in_parallel_1M_Resistor.jpg
Pot1M_in_parallel_1M_Resistor.jpg (36.54 KiB) Viewed 1958 times

User avatar
SpikeVelvet
Information
Posts: 14
Joined: 10 Dec 2016, 01:35
Has thanked: 1 time

Post by SpikeVelvet »

Thanks Manfred,

I probably will end up changing C3/R6 but the pot issue is something I was trying to iron out my understanding.

Great chart. That is a big help.

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

What are the current values of C3 and R6?

User avatar
SpikeVelvet
Information
Posts: 14
Joined: 10 Dec 2016, 01:35
Has thanked: 1 time

Post by SpikeVelvet »

100n/3k3 for a 482.3 Hz corner frequency

User avatar
Manfred
Tube Twister
Information
Posts: 1937
Joined: 04 Apr 2009, 23:42
Has thanked: 1671 times
Been thanked: 1344 times

Post by Manfred »

For half gain , R6 should be 10kOhm.
For the original corner frequency of 726 Hz C3 would be 22nF and for the corner frequency of 482 Hz 33nF.

Post Reply