English Channel - Noise Issues

[aziltz]

I was hoping to get some help sorting out some noise issues with my recent English Channel Build.

Here's a gut shot:


As you can see I used the trimmers instead of figuring out the fixed resistors.  Everything in this pedal works as it should, it just has a bit too much noise when I turn up the gain.  I end up using the Cut control to tame the noise.

I've already rearranged the input and output wires so they don't cross like that. Would changing out the trimpots for metal film have a decent effect on the noise?

My other thought was shielded signal wire, but since this isn't a "High Gain" Pedal, I didnt think it necessary when building it.

Any suggestions would be greatly appreciated.  I'm planning a version 2 with Top Boost/Normal Toggle and I'd like to get the noise issues worked out before then

[aziltz]

help?

[kurtlives]

Changing the trims to any type of fixed resistance will help reduce noise.

Shield any high impedance wire.


I did both these things in my build and it is fairly quiet.

[aziltz]

could you elaborate on high impedance wire?  does that mean in the input wire since its connected to the front end of the circuit and theoretically high(er) impedance?

[Paul Marossy]

I built my English Channel using the perfboard layout at ROG. It's a pretty quiet pedal. I also used some shielded wire on the input & output of the circuit.

Anyhow, your layout looks very clean, I don't think it's due to lead dress or anything like that. Maybe changing those trimpots to fixed resistors might help a little bit with that.

[aziltz]

interesting enough to mention, my build sounds quieter with a buffered pedal in front of it, but it doesn't stack as well with pre-gain boosts as it did without a buffer.

[MartyMart]

Is your output jack still wired up without a ground connection as in the photo ?? !!

Mine is made on stripboard and in a case with LONG leads, no noise at all.

MM.

[aziltz]

Is your output jack still wired up without a ground connection as in the photo ?? !!

Mine is made on stripboard and in a case with LONG leads, no noise at all.

MM.

its grounded to the box.   

[Pablo1234]

dump the trimers, use resistors insted. Them things are so noisy its not funny.

[aziltz]

dump the trimers, use resistors insted. Them things are so noisy its not funny.

i plan on doing that anyway, but this puzzles me.

I just did an A/B Test and its clearly less noisey with a buffered pedal in front of it.  This changes my feeling about how much noise is actually from the trimmers.  Why would this be?  Any thoughts?

[aziltz]

So I fixed the problem.  I replaced the trimpots with fixed resistors and add a bit of twisted wire shielding.  This is now one of my quietest pedals!

[Paul Marossy]

So I fixed the problem.  I replaced the trimpots with fixed resistors and add a bit of twisted wire shielding.  This is now one of my quietest pedals!

Cool. 

I didn't know that could cause a problem like that. You learn something new every day!

[MartyMart]

Great - and you also grouded the circuit to your output jack I see !!   

[aziltz]

Great - and you also grouded the circuit to your output jack I see !!   

yes but only to get the blue wire shielded!  it creates a ground loop with the box, since both jacks are touching the box. i think the biggest difference cam from shielding the blue/yellow input & output from the pcb and replacing the trimmers.

[ricothetroll]

Hi,

First of all, thanx for that great forum, and all the knowledges and experience shared here.

I built the English Channel from runofgroove's schematic :
http://www.runoffgroove.com/englishchannel.html

As I wanted pots to be soldered directly to the board, I made a new layout :
http://www.wuala.com/ricothetroll/public/English%20Channel3-2.pdf (there are two connections that appear with thin wires, those are strapped)

I tried to keep the output physically as far as I could from the input, and I also cabled both input and output with shielded cables. Besides, I replaced the trimmers by resistors, and I do have 4.5V on the corresponding fet's drains.

Still, the pedal is very noisy, and even more since I replaced the trimmers : I now have a hiss mixed with the white-like noise. I must admit I don't know what to do to improve it...

Here are some pictures of the circuit :
http://www.wuala.com/ricothetroll/public/DSCF0557.JPG
http://www.wuala.com/ricothetroll/public/DSCF0565.JPG

Any clues are welcome !

Best regards.

Eric

[ricothetroll]

Hasn't anyone here any idea of how to reduce this noise ?