Can I do this?

[Xavier]

Can I add an input gain trimmer to my pedals?

A 500k pot should be fine?

[Travis]

If I read you right, you want to add a pot between the guitar and effect, right?  Just an additional guitar volume knob?  You can do this, but the effect will vary.  On effects where turnign down your volume knob has a pronounced effect, this will work nicely.  

Depending on the strength of your guitar's signal, you may have some tone-sucking just because the path to ground is of too low resistance.

[Peter Snowberg]

Pay special attention to Travis' post. As you load the signal down you will suck the tone out of the signal.

Because this control is cutting the level, it's called an attenuator and as Travis indicated, in the right setting this is a very cool thing to have around.

If you want to attenuate the signal between your guitar and the first effect, I would recommend using a value more like 1 meg to keep the tone loss from loading of the signal down to a minimum. This brings up another problem... as you turn down the control you will experience more and more series resistance which will also kill tone. Luckily you can address that to an extent by placing a small capacitor between the input and output lugs on the pot. You see this same cap in lots of guitars. Just look at the schematic of a better model Strat or just about any hod-rod guitar. The value of that cap varies depending on the pickups and the value of the level pot, but I would start with something like 0.001uF (film caps are preferred). See how the tone is affected and raise or lower it as needed for your setup. Inside amps, this cap is often in series with a switch called "Bright". That's a clue . Go too small with the value and it will get brill sounding. Experiment for best results.

If you want to control the level after an effect and your effect lacks an output level control, you could use a much lower value is most cases. Try 100K or 250K there. With some effects that have low impedance output buffers, you could go all the way down to something like 5K, but 25K or 50K is more realistic.

Any resistor you place in the signal chain will affect tone, so play around with values until you are satisfied, and then play around some more after you think you have the right value. A week later it might not sound as right to your ears.

I hope that helps.

Take care,
-Peter

[Xavier]

Well let me elaborate a little bit.

I have a DS1 in the loop of my Boss GT6. The signal in the loop is pretty hot because this way I overdrive better my Hughes & Kettner Tube Factor.

But my DS1 doesn't seem to like this, it sounds pretty saturaded, like a fuzz. So I thought an internal trimmer for the DS1 would help in balancing everything.

Thank you

[Peter Snowberg]

That sounds like a good idea. I would try 100K in that case. You could probably do just fine with any value from 10K to 250K. Good luck, and please post your results.

Take care,
-Peter

[Xavier]

Next question is where in the signal chain should I put it? I was thinking about just after the input hits R1, but I'm afraid that would affect the un-effected signal when the pedal is in "bypass" too, since Boss pedals are not "true bypass" but buffered. I only want the trimmer to affect the input gain when the pedal is "on"

[Gearbuilder]

Hi,
I don't know the GP6 effect loop but on my ME5 i've got the same  problems with my TS9 I think  it's an impedance mismatching .When i use it ,i put the TS in front of the ME5 or directly in the amp . The two solutions sound better than in  the loop.
Some loops aren't good with some pedals because they are line level input and output.Even if you put a pot ,you'll loss some signal and maybe get a bad high-end signal.Try to Buffer  and adapt  the impedance with an active preamp like the MXR Micro amp,and listen to, with or without.Choose the best or chnage the place of your pedal!
Bruno