The Benson Preamp is pretty popular, but 2M pots are hard to find. This is a modded vero layout using a 1M bass pot. To make this change and keep the same frequency response, resistances are halved, capacitance is doubled. Note that the Drive pot value also had to be halved.
I'll add a regular size layout with normal 1/4 resistor later - just felt like a larger layout for this one.
BENSON PREAMP - MOJO VERO LAYOUT
BENSON PREAMP - MODDED SCHEMATIC
As you can see, the response is nearly identical between the stock and modded values. This will change a little using stock cap and resistor values, but it will still be pretty close.
Hi Andy I hope you're doing well, I wanted to try this pedal for a while and since I had the components I gave it a try, the pedal works and I like how it sounds but I have some issues.
ReplyDelete1. The bass control is not working (is not the pot), drive, treble and volume works fine.
2. It has a ground sound louder than normal (with humbuckers) which increases as I turn up the gain.
Do you have any idea what it could be?
I set the bias for Q2-Q3 at 4v and Q1 with the 12k read about 6.7v, I tried with a 50k pot as well to find the sweet spot but I think is close to that. All transistors are MMBFJ201.
Hello - I'm not sure why that might be. You can send photos to guitarverop2p (at) gmail.com
ReplyDeleteEmail sent, thanks! ✌️
DeleteLayout updated - sorry Felipe, as mentioned in the email. Bass 3 and bass 3 were the wrong way around on the vero. Layout now updated
Delete