CapnCrunch Posted July 10, 2002 Share Posted July 10, 2002 I apologize in advance for my lengthy description of this problem. If you actually read through this entire post you are either a personal friend of mine or one of the most considerate people around (how's that for motivation I have a Sovtek Mig100 high gain head. It is a very simple amp that I have been able to get good sounds out of it with minimal tweaking. My problem started a month ago when I very gradually (it was hardly noticeable at first) started to loose volume (dB) whenever I used any kind of pedal (especially distortion) through the low input. I then noticed that I was beginning to loose volume even when I was clean. This became more and more apparent until I could hardly hear myself at practice (my band's drummer also began to have trouble hearing me). Considering that every other part of the band still cuts through I don't consider mass hearing-loss to be the cause of this (yet) This volume usually drops more the longer I have it on (the first hint I was given that it could be the tubes to blame), but now it does it almost immediately after I let it warm up (couple minutes). Now I get to the most recent and worst part of the problem. The gain seems to have increased a little when the amp is clean (not too much of a problem), but when I throw on distortion or effects it makes the "fart of death" through my 1960a cab. Everything rattles and sounds way too flabby... picture a hissing cat mixed with a big fart and that is the sound it makes in place of distortion. Note that I am used to a decent (although maybe a little muddy) tone through the 1960a, but this crap is just unacceptable. If I increase the main to compensate for the drop in volume the hissing and farting escalate while the volume doesn't go up that much. I am guessing that right now anyone who had read this far figures I am a dumb #(@! who has done one of the following things: 1. Blown / Shredded his speakers. Heck that's what I would think, they are GT-75's after all. 2. Boosted the level on his pedals too high and screwed up the circuitry in the amp. 3. Damaged the circuitry in the pedal(s) so they produce bad freqs. Unfortunately, I am fairly sure none of these are the causes for my "fart of death", otherwise I would not be posting a topic on this. I plugged a band-mate's Fender ToneMaster (vintage 30) 4x12 into my amp and the distortion and volume were just as crappy and unacceptable (taking into consideration the vintage 30's are a bit louder than the gt-75's and the bottom end was clearer through the tone master). I then replaced my distortion pedal with his (same model) and had the exact same problem. I then tried his guitar and had the same problem. By this time I am pretty sure it is the amp to blame. Since I have lost about 50% of the precieved volume out of the amp, and I wanted to focus on the simple fixes first I replaced the 4 5881/6L6 power tubes (Sovtek Mfg.) with Fender (still Sovtek Mfg.) 5881 replacements (two matched pairs). I put them in and powered on the amp and got the exact same "fart of death" distortion. At this point I felt the problem was heading into unfamiliar territory and took the head to my local music shop. They tested the original power and preamp tubes (which were all still good and were not burnt up looking at all). They cranked the amp clean, but since they hadn't heard it before and they didn't try and pedals they couldn't really hear anything was wrong with it. After some additional research I personally think that it is a capacitance problem on the low input (since the way the signal is interpreted with a pedal versus straight through is different on most amps). I have never liked the high gain input on this amp (hence the pedals) and buying another amp is out of the question. Any help or insight would be greatly appreciated! Aaron -- You and the captain, make it happen. Link to comment Share on other sites More sharing options...
Dak Lander Posted July 10, 2002 Share Posted July 10, 2002 Post it on feel free to ask Myles. He'll see it there an will respond quicker. Good luck Our Joint "When you come slam bang up against trouble, it never looks half as bad if you face up to it." The Duke... Link to comment Share on other sites More sharing options...
Tedster Posted July 10, 2002 Share Posted July 10, 2002 The "fart of death" sounds like a torture devised by Dr. Evil for Austin Powers. "Cisco Kid, was a friend of mine" Link to comment Share on other sites More sharing options...
Tedster Posted July 10, 2002 Share Posted July 10, 2002 The "fart of death" sounds like a torture devised by Dr. Evil for Austin Powers. "Cisco Kid, was a friend of mine" Link to comment Share on other sites More sharing options...
DC Posted July 10, 2002 Share Posted July 10, 2002 All through your description I was thinking tubes, but if they're okay, you need to ask Myles. You changed out your pre amp tubes too? I'd definately be saving for a Boogie. -David http://www.garageband.com/artist/MichaelangelosMuse Link to comment Share on other sites More sharing options...
Gabriel E. Posted July 10, 2002 Share Posted July 10, 2002 Gee. That sounds like a preamp problem of some kind. Do you have the same problem when you plug the guitar straight into the amp sans pedals? I was unclear on this. The first thing I would do is swap out the preamp tubes. If that's not it, you could have a fried resistor or blown cap in the preamp citcuit. You should check for bad solder joints too. If you open the amp up, be sure to discharge the filter caps before touching anything. If you don't know how to do that, take it to a tech. "You never can vouch for your own consciousness." - Norman Mailer Link to comment Share on other sites More sharing options...
CapnCrunch Posted July 12, 2002 Author Share Posted July 12, 2002 Yes, both the preamp and power tubes tested fine. I tried going straight from guitar to the low input (with a different cable as well) and got the same results. A friend had a similar problem that turned out to be his second stage power transformer. I am betting that it is either a joint on the transformer or something in the preamp circuit like Gabriel suggested. Oh well, ended up letting the tech have his way with it so I guess I will wait and let ya all know what he finds. Aaron -- You and the captain, make it happen. Link to comment Share on other sites More sharing options...
Binky_dup1 Posted July 15, 2002 Share Posted July 15, 2002 Sounds like a big cap to me, what did Myles say? Link to comment Share on other sites More sharing options...
not coaster MODERATOR Posted July 15, 2002 Share Posted July 15, 2002 Capn Crunch ehh??? Arg matey!! Ya gots a great name. In the Cereal kingdom of course. Link to comment Share on other sites More sharing options...
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