GE-7 Still hisses too much after mods

trotskyismyniece · March 23, 2011, 03:46:07 PM

So awhile ago I bought a GE-7 and modded it by switching out the stock DIP IC's with TL072's, and replaced all the tantulum caps with poly film. It was very quiet after that, but recently I noticed that the 100 hz slider was not functioning. It turns out that from leaving long leads on the new film caps and bending them around to fit in that enclosure put pressure on the pads in the PCB and broke one. I put jumpers in a few places where I noticed the pads lifting and got the 100hz slider working again, but that introduced an extremely loud hiss like wind blowing. I figured it was the electro caps, and replaced them real quick with new ones from Radio Shack. The hiss lowered substantially but there is still a lot, probably on par with the amount you get with a high gain dirt pedal. there's possibly more hiss than when it was stock, but I don't remember how it sounded.

I'm not sure what I should be looking for. Would bad solder joints cause hiss? I thought that would only cause pops and crackles, but I'm not sure what else would be causing this. It seems to be on all bands. Just cutting the 100hz doesn't get rid of it, in fact, it seems like it's the worst at 3.2khz.

petemoore · March 23, 2011, 04:14:20 PM

I noticed the plastic alternative was less noisy than the metal box unit.
Hiss' is more along with the "gain everything up and then turn most of it back down" than 'solder joint'. Solder joints generally either 'just connect', or not.
Eq's have natural tendancy to boost noise of course, just used to get better idea of what is ''relevant for Eq'', then find a less 'boost-whatever-noise-is-there' alternative to leaving an eq on.

Paul Marossy · March 23, 2011, 06:43:58 PM

Quote from: trotskyismyniece on March 23, 2011, 03:46:07 PM
I'm not sure what I should be looking for. Would bad solder joints cause hiss? I thought that would only cause pops and crackles, but I'm not sure what else would be causing this. It seems to be on all bands. Just cutting the 100hz doesn't get rid of it, in fact, it seems like it's the worst at 3.2khz.

Could possibly be a bad solder joint somewhere, but the fact that it's on all bands to me points to something else. Maybe you need to try some even quieter opamps, something like an OPA2134 maybe would be slightly less noisy. No matter what you do, an EQ pedal can only get so quiet, especially in those higher frequencies.

trotskyismyniece · March 23, 2011, 09:14:26 PM

Well, I know that there's the potential for problems with boosted noise, but it was much much quieter when whatever circuitry pertaining to the 100hz band was basically cut out. It seems strange that restoring it would add that much noise. Maybe the fully functioning circuit really is this noisy and the inadvertent 'mod' was giving me false hope for how quiet it could be?

Paul Marossy · March 23, 2011, 09:50:52 PM

Quote from: trotskyismyniece on March 23, 2011, 09:14:26 PM
Maybe the fully functioning circuit really is this noisy and the inadvertent 'mod' was giving me false hope for how quiet it could be?

Maybe. I have a GE-7, but I've never really used it. I'm not sure how noisy it is. I'm sure there is probably a lot of hiss if you boost the higher frequencies.

alfafalfa · March 24, 2011, 11:27:32 AM

I have a Ge-7 and can assure it's not hissy , even with TL022 opamps . Your noise problem will probably be the result of your lifting pads. There must be connection you didn't see imho.

Check it again.

earthtonesaudio · March 24, 2011, 11:50:56 AM

Quote from: alfafalfa on March 24, 2011, 11:27:32 AM
...Your noise problem will probably be the result of your lifting pads. There must be connection you didn't see imho.

Check it again.

I agree with this much.

I have a GE-7 also. I felt mine was a bit too hissy so I replaced the TL022's with TLE2072's. It's better now. Not dead silent or anything, but no longer bothersome.

Paul Marossy · March 24, 2011, 12:15:37 PM

Quote from: earthtonesaudio on March 24, 2011, 11:50:56 AM
Quote from: alfafalfa on March 24, 2011, 11:27:32 AM
...Your noise problem will probably be the result of your lifting pads. There must be connection you didn't see imho.

Check it again.

I agree with this much.

I have a GE-7 also. I felt mine was a bit too hissy so I replaced the TL022's with TLE2072's. It's better now. Not dead silent or anything, but no longer bothersome.

Good to know. I think I might mod mine just for kicks. I think it also depends on if you have the new or old version of the pedal. I'm sure mine's probably the old one as I got it new about 1998.

earthtonesaudio · March 24, 2011, 05:06:11 PM

Yeah, I don't remember which one mine is. There are pictures of old and new versions here... according to these pics mine is the "new" version, so I only replaced the 3 DIP-8 op-amps.

Paul Marossy · March 24, 2011, 05:34:45 PM

By new and old I mean that there are two different PCB designs and (I think) slightly different components.

earthtonesaudio · March 24, 2011, 09:54:47 PM

You're right Paul. There are pics on the Monte Allums Mods site that show the two different boards. The newer one has two SIP op-amps and 3 DIPs. The older one has one SIP and 4 DIP op-amps, but I don't know more than that.

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GE-7 Still hisses too much after mods