SVT Distortion

HometownLetdown · #1 12-20-2011, 11:05 PM

I have searched and cannot find exactly what my problem is.

I have and SVT Classic with 8x10 and a Pbass.

When I am playing sometimes the sound will start to distort for 10-30 seconds almost like I am running it through a distortion or fuzz pedal and then go back to normal. I changed out the speaker and instrument cables and still have the same issue. I cant replicate by any specific means it just happens out of the blue.

The bias is set to green on both lights after the amp has warmed up and has no signal running through it.

Current EQ Settings:
Gain 5
Bass 6
Mid 8
Freq 3
Treb 7
Master 4

Thanks for any suggestions on what this may be.

JimmyM · #2 12-20-2011, 11:46 PM

First thing I'd do is check all the tubes and make sure they're seated in the sockets properly. Doesn't sound like power tubes are the problem. If you have any spare preamp/driver tubes, you might try swapping them out one at a time to see if you have a culprit. Someone else might have some ideas, but beyond that and you're always better off taking it to a qualified tech, especially if you know as little about them as me

James Judson · #3 12-21-2011, 12:54 AM

Quote:

Originally Posted by JimmyM

First thing I'd do is check all the tubes and make sure they're seated in the sockets properly. Doesn't sound like power tubes are the problem. If you have any spare preamp/driver tubes, you might try swapping them out one at a time to see if you have a culprit. Someone else might have some ideas, but beyond that and you're always better off taking it to a qualified tech, especially if you know as little about them as me

+1 for Jimmys suggestion.

Intermittent problems are usually bad/intermittent connections. Any connector is subject. Tube? Tube socket? Potentiometers? Input/Output connectors?

A word to the wize. There are high voltages inside that thing so if you don't know where they are stay out.

Because the problem is intermittent, taking it to a tech may get your amp back with NPF (no problem found). So I say live with it as long as you can. A good Tech does have ways of making intermittent problems surface.

Thats a great amp and well worth fixing.

Mastermold · #4 12-21-2011, 01:04 AM

Preamp tube might be the culprit. It's a cheap fix if it is.

HometownLetdown · #5 12-21-2011, 01:04 PM

Cool I may just have to take it to a tech as I know nothing about working on these. My first tube head so kind of lost.

If I swap out the preamp tube will it need to be biased?

JimmyM · #6 12-21-2011, 01:10 PM

Nope, no biasing required. The hardest part of changing preamp tubes is getting inside the amp. After that, anyone can do it. But if you're unsure, definitely take it to a reputable tech.

KramerBassFan · #7 12-21-2011, 01:22 PM

Get a bigger amp

HometownLetdown · #8 12-21-2011, 02:09 PM

Quote:

Originally Posted by KramerBassFan

Get a bigger amp

Lol yea, I am picking up an additional 8x10, I actually already own it just havnt picked it up yet.

rtslinger · #9 12-21-2011, 02:18 PM

Yup Tube problem

RED J · #10 12-21-2011, 02:50 PM

Quote:

Originally Posted by HometownLetdown

Lol yea, I am picking up an additional 8x10, I actually already own it just havnt picked it up yet.

SVT + 2x8x10...blowing out walls for 40 years. First time I heard one in a club is an indelible memory !

HometownLetdown · #11 12-21-2011, 04:19 PM

Quote:

Originally Posted by rtslinger

Yup Tube problem

Preamp tube?

HometownLetdown · #12 12-21-2011, 04:19 PM

Quote:

Originally Posted by RED J

SVT + 2x8x10...blowing out walls for 40 years. First time I heard one in a club is an indelible memory !

I love it, I had a small hiatous and sold all my gear but before I was running 2 8x10's with a mesa m6, awesome sound, loud loud loud

Now I am purchasing gear again, I got the SVT and 8x10, finally got the second one

JimmyM · #13 12-21-2011, 04:29 PM

Quote:

Originally Posted by HometownLetdown

Preamp tube?

You said that the power tube indicator lights glow normally and don't show any faults. Therefore, it's highly unlikely you have a bum power tube. Not impossible, but unlikely.

chadds · #14 12-21-2011, 08:50 PM

Quote:

Originally Posted by RED J

SVT + 2x8x10...blowing out walls for 40 years. First time I heard one in a club is an indelible memory !

I heard one two cab back in the day. The guitarist had a 100 watt 2 - 4x12 Marshall stack. With, wait for it..... the vinyl cover on the top cab. It was moving.

rickdog · #15 12-21-2011, 09:19 PM

Quote:

Originally Posted by HometownLetdown

When I am playing sometimes the sound will start to distort for 10-30 seconds almost like I am running it through a distortion or fuzz pedal and then go back to normal. I changed out the speaker and instrument cables and still have the same issue. I cant replicate by any specific means it just happens out of the blue.

The tube suggestion is a good one, but... have you tried connecting a patchcord from PREAMP OUT to POWER AMP IN on the back? That power amp in jack has a switch in it (to disconnect the internal preamp when you plug in an external one). Sometimes the contacts corrode and cause weird stuff like this to happen. Sometimes just inserting and remove a plug in that jack is enough to clear up the problem.

Usually JimmyM suggests this... is he getting old and slow?

JimmyM · #16 12-21-2011, 09:45 PM

punkrockmike · #17 12-21-2011, 10:27 PM

where was your 810 made/what year is it? try it with a different speaker cabinet. i had a somewhat similar problem and it turned out to be my ampeg 810. it was one of the ones made by loud technologies in vietnam. mud city. almost sounded like you're describing. tried it with a different cab and it sounded as smooth as butter.

dukeisdog · #18 12-22-2011, 06:30 AM

What bass are you using through the rig? Is it an active bass? If so, switch out the battery.

HometownLetdown · #19 12-22-2011, 09:04 AM

Quote:

Originally Posted by punkrockmike

where was your 810 made/what year is it? try it with a different speaker cabinet. i had a somewhat similar problem and it turned out to be my ampeg 810. it was one of the ones made by loud technologies in vietnam. mud city. almost sounded like you're describing. tried it with a different cab and it sounded as smooth as butter.

I have an old 8x10 before they were made in Viatnam, but I will try another cab as soon as I pickup the other 8x10.

Quote:

Originally Posted by dukeisdog

What bass are you using through the rig? Is it an active bass? If so, switch out the battery.

No it's not an active bass. Before I was using a MM Sterling and I checked the battery still had issues, now I am trying with a Fender Pbass with SD Q-Pounders SDB-3

JimmyM · #20 12-22-2011, 09:16 AM

Quote:

Originally Posted by punkrockmike

where was your 810 made/what year is it? try it with a different speaker cabinet. i had a somewhat similar problem and it turned out to be my ampeg 810. it was one of the ones made by loud technologies in vietnam. mud city.

Funny how people hear things differently. I hear the newer Ampeg 810e's and they sound not the least bit muddy to me. It's the SLM cabs that sound muddy to me.