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dirtbox gain increase and bypass Q

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4/14/2000 5:50 PM

dirtbox gain increase and bypass Q

I recently aquired a Matchless Dirtbox and like the overall sound of the pedal. I wanted to get a little more distortion out of it however, so I removed the 220K resistor right after the gain pot. this increased the distortion to my satisfaction. the problem is, when the pedal is in bypass mode I can hear a faint fuzzing sound on the notes in the background. if you turn the gain pot down while in bypass mode the fuzzing note problem goes away. now, this pedal has true bypass so,how is this happining? could the gain be so high that it is "backwashing" to the input jack? could it be a bad switch?
Ricky

4/15/2000 12:59 AM

Re: dirtbox gain increase and bypass Q - ooooh!

Doesn't immediately sound like a bad switch, more like a non-TB pedal, or a freak cross-talk problem. Can you trace it? It's reputedly the same as a hotbox in drive mode, but with a 3-band eq that's supposedly rather unconventional (guess what I'm interested in..) Tracing the schem will also help you understand what might be going on, and us too.
(and yes, I admit, I REALLY want to know what's in there ;p) If you want to try some stuff out, mail me, we'll do some experimenting to get the fuzz out and/or get TB.

4/15/2000 3:17 AM

I dont have the schem for the dirtbox, but I do have the one for the hotbox availiable at the blue guitar website. its pretty well the same, there are a few things different though to make the dirtbox a little "dirtier"; on the schem the 470K resistor is a 220k. the reason I think it could be the switch is the LED dosen't go on and off like it should, and it is turned on and off with the other half of the DPDT footswitch (I can get in there and connect the lugs manually and it turns on, so I know it works)It is wired to be true-bypass, with one jack connected directly to the other when in bypass. so, what else could it be? I figured removing some of the resistiance in between the stages would be a good way to increase the level of gain without changing the voicing of the pedal itself (as opposed to like jacking up the values of the cathode bypass caps and so on)I mean this thing has 4 gain stages and I know its capable putting out a little more... one other thing, don't know what effect it would have, but my house was built in 1950 and dosen't have 3-prong outlets so I've been using those adapters. Do you think not having a proper ground would do anything?
Ricky

4/15/2000 3:30 AM
Cole	If it only has a DPDT and one half is doing LED switching, then it does not have true bypass. With only one side of the DPDT left, all you can do is switch off the input or output, one or the other will always be connected to the output jack. This would go a ways to explaining the bleedthru problem. BTW, I'd like to see a tracing of the Dirtbox as well...

4/17/2000 7:18 PM

Okay, this is amazing, this thing really deos not have tru-bypass. I really thought it did, but after closer inspection, the input is connected to the first 12ax7 all the time. I guess I'll start by wiring it true-bypass. of course, the LED will have to go, 'cause I'm not going to track down a 3PDT switch. that's okay though. after that, I'm going to remove all the fixed resistors in-between the gain stages.
Ricky

4/17/2000 10:40 PM
Cole	If you've got the green, you can get 3PDTs from Hoffman amps (www.hoffmanamps.com) for $18 a pop. They (Hoffman) have excellent service.

4/18/2000 3:06 AM

yeah, I recently discovered that, but Hoffman has stopped carrying them due to Mike Fuller's (of Fulltone FX, supplier of the 3PDT)shitty additude and apparent inability to keep a constant supply. go over to hoffman amps site and look under switches. he acctually posts the Email he recieved from fuller that uses several 4-letter words. if you haven't seen it you really gotta check it out,its amazing. how unprofessional IMO. anyway, the lack of LED indicator is not that big of a deal, I'll gladly trade it for true bypass any day. I found a really good deal on the carling DPDT, $9 at clark parts.
Ricky

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