SC20 sounds bad

[DirtySteve]

I've been rocking my SC20 for about a year or so without any issues until a couple of weeks ago it started to sound really thin and bright and the distortion has a really staticky harsh sound to it. Then today the volume (or maybe the gain?) started to fluctuate, like I hold a chord and the sustain and distortion just cuts of and then comes back after a second or 2. I've swapped tubes, I took out the V2 hot mod and put it back in, didn't make any difference. It's not cables a or anything like that, I plug the same pedal chain into another amp and it fine.

Any ideas?

 

[fitz]

I've swapped tubes

Pre-amp or power?
Both?

 

[DirtySteve]

Pre-amp or power?
Both?

Pres, I didn't suspect power tubes, they aren't very old and they glow normal. Give me a few minutes...

 

[DirtySteve]

Well I'll be damned. ...this is twice now in 2 weeks.

Thanks!

 

[DirtySteve]

I really am dumbfounded. I've never had to replace power tubes, I play at such low volumes I don't really even get into the power section and these tubes were not very old. Even with my John H I still don't get much passed 2 on the MV. They were JJ 6550s I put in a set of Psvane KT88s and the damn thing came back to life.

 

[fitz]

I really am dumbfounded. I've never had to replace power tubes, I play at such low volumes I don't really even get into the power section and these tubes were not very old.

I'm not hard on tubes either, and I've had a couple go on me.
Brand new preamp tube popped - literally blasted chunks of glass around...
Also lost a KT66 with some similar symptoms as you described.
Got it used, so no clue as to its previous life.

I've heard more than once that tubes can go at any time, for any reason, or no reason at all.

 

[DirtySteve]

I've had preamp tubes go bad after just a couple of hours on them, mostly JJ or Marshall labeled. It's just weird that I have power tubes go bad in 2 different amps at the same time when I've never had issue with power tubes before.

 

[DirtySteve]

Anyway, thanks Fitz, I won't make that mistake again. In fact I'm probably going to suspect power tubes first from now on. lol

 

[cccc]

Yeah , whenever a tube amp starts to sound off, just replace the tubes because in my experience that's what the culprit always seems to be in the end.

 

[PelliX]

I've had preamp tubes go bad after just a couple of hours on them, mostly JJ or Marshall labeled. It's just weird that I have power tubes go bad in 2 different amps at the same time when I've never had issue with power tubes before.

One going bad is just bad luck, a random occurrence. Two is still in the realm of coincidence, but there *can* be contributing factors like lower line voltage resulting in lower heater voltage. The SC is fairly gentle on the output stage but I had a KT88 go south in mine just a week or two back for no "obvious" reason.

 

[DirtySteve]

It already sounds bad again with only about an hour play time since I swapped the power tubes. I don't think that was the problem.

 

[DirtySteve]

Well, I don't know anything else to do. I cleaned the sockets and put the 6550s back in and it sounds fine...for now. There's nothing wrong with the tubes. I'll see if it lasts.

 

[fitz]

Well, I don't know anything else to do. I cleaned the sockets and put the 6550s back in and it sounds fine...for now. There's nothing wrong with the tubes. I'll see if it lasts.

Are you using the loop?
Does the patch cable in the loop trick do anything with those amps?

 

[DirtySteve]

Are you using the loop?
Does the patch cable in the loop trick do anything with those amps?

The loop sucks, it's noisy as can be so I can't use it. I've tried separate power supply for loop pedals and out front pedals and bought brand new nice cables for the loop and none of that helps. I've read that the patch cable doesn't do anything for these amps so I haven't tried. I do leave the loop switch engaged because it cuts volume a little bit when it's on.

 

[Leonard Neemoil]

If you're not actually using anything in the loop, I'd definitely disengage it for a few days and see if that fixes it.

 

[fitz]

Perhaps the Little Devil is just kickin' its ass?
Try running them together with some kinda stereo pedal out front.
The two together will sound better than either alone.

 

[DirtySteve]

If you're not actually using anything in the loop, I'd definitely disengage it for a few days and see if that fixes it.

Yeah, I've tried that and it doesn't matter.

 

[DirtySteve]

Perhaps the Little Devil is just kickin' its ass?
Try running them together with some kinda stereo pedal out front.
The two together will sound better than either alone.

For the most part it is and I have thought of that, lol. But, the other day when I thought my 6550s were bad and I first put the KT88s back in it sounded awesome and held it's own against the Lil' Devil. Then the next time I turned it on it didn't sound as good and hasn't since. Maybe it's me, I have the worst luck with amps, always have. The only 2 amps I've ever had that I didn't have some kind of issue with are my Lil' Devil (except for my recent tube issues that fixed it, unlike my SC) and my Harvard clone that Terry built for me.

This is my second SC, I bought the combo first and it never sounded right to me so I bought the head and traded the combo at GC for my Satin Honey Burst Tribute and a few other bits. The head sounded great up until a couple (maybe 3) weeks ago when it started sounding thin and harsh and lacked the balls it used to have.

 

[DirtySteve]

I think maybe I need to just figure out how to tweak the few eq issues I have with my Lil' Devil and sell my SC. It's superior in every way, I just need to fine tune the eq a bit, but I don't know what to do.

 

[solarburn]

The loop sucks, it's noisy as can be so I can't use it. I've tried separate power supply for loop pedals and out front pedals and bought brand new nice cables for the loop and none of that helps. I've read that the patch cable doesn't do anything for these amps so I haven't tried. I do leave the loop switch engaged because it cuts volume a little bit when it's on.

Yah the loop introduces a transformer or mismatched power tube hum on mine. Turn it off and silent the amp is.

All your cables good? You already checked it straight in right, no condum? Hope you or we can pin it down. Hate those elusive drop outs man.