Problem with Ampeg SVT 4 Pro

[carbonfold]

I had a Ampeg SVT-4PRO and had several problems with it. A common and a pain in the butt problem with the Ampeg SVT-4PRO, SVT-5PRO, and the B4R is the master pot that sync up both power amps inside. Sometimes when that pot starts failing, it can screw up both sides or just one.

Check both output power amps and see if you get the same problem. Don't bridge them together and run them in stereo. Bypass your preamp and try amp A first, then try amp B. If you still have the problems with the power amp while bypassing the preamp, I would guess it could be the master pot or a problem in the phasing or "Y" of the amp.

The only cool thing that I do like about those amps is the fact there are two amps inside of it. So if one side fails, you can always check and see if the other side is having the same problem. And if you have the same problem on both sides, it is usually in the preamp or the phasing section to the power amplifiers or the output section from the amp to speakers.

 

[georgestrings]

Yeah... I don't see it either....... if it was done right, it shouldn't need adjusted later, Mosfets are pretty stable devices.

That's what I thought - no offense intended towards anyone, but I've never seen ANY "biasing" done on an SS amp, and EVERY time I've seen it mentioned, it was by a tube amp proponent...

I thought it sounded like the stuff urban legends were made of, to be honest...



- georgestrings

 

[BassmanPaul]

He does play an Active bass but we tried a Passive and it did the same thing. Since it was B Stock, we only had a 90 day warranty which has expired already...

Did a credit card get used to pay for the amp?

Many CC companies extend warranty periods on items bought with the card. You may well discover you still have a warranty.

Paul

 

[southgabass]

I am the fabled bass player in this question... its an 8ohm cab btw and i do play an active bass..... we tried it all.. cleared corrosion (there wasn't any but for good measure took out my electronics kit and made sure)... new cab... instrument, everything... sent it off to technician... when it got to them they found nothing wrong... sent it back... played beautifully at the shop that sent it off... when i got to practice we got through about 2 and a half songs when it suddenly died out again... a little more odd this time... everytime the drummer would hit his kick drum i would see the limit light and peak light up and the only way to get sound was to use the limit defeat and get a super distorted sound... decided to stop playing out of frustration... took it back to the shop and they couldn't believe that i was back with it... when they checked the signal... it wasn't sending a signal but about 15v out.... our drummer being an electrician took his voltmeter to it and found a grounding issue in one of the tube plugs...

 

[southgabass]

and the beginning of the issue with the blown speakers i think was my fault for letting someone else use it... our band isn't used to sharing the stage but it was for a dedicated fan's party... so the band that followed us used my bass equipment... didnt find the busted speaker or the issue for a little bit (we took a 3 week break from gigs to relax a lil) when we returned to practice... needless to say i wasn't a happy camper... so my guess is the guy in the band following us just went to town with it and blew it all up... our guitarist just happens to check into these forums a bit more often than i do... so i guess he wanted to post on it =p

 

[pedulla1]

Glad to hear you resolved the problem. That amp sounds great even better than the SVT 3 pro. Good luck.

 

[deaf pea]

...but I've never seen ANY "biasing" done on an SS amp...

Adjusting the MOSfet bias of the SVT-3PRO is a common "fix" for a "bad sounding amp" . . . . . .

 

[southgabass]

the problem was not resolved though.... got it back to practice and it cut out... only way to get sound is to use the limit defeat then its really distorted and im afraid its gonna damage itself and my cab... and now its sending out about 15v from both power amp out-puts... quite odd.... so I'm going to try to get it fixed again... but in the mean time I'm looking for another set-up... thinking about the Carvin BX1500 and a new cab... or some sort of combo that has some customability and great sound like the SVT 4... I love that amp... makes me smile every time i got to play on it (and it worked)....

 

[Jerrold Tiers]

What you need is to get it fixed right.

It sounds like there is a common problem, affecting both channels, which simplifies it a bit for the tech.

 

[southgabass]

well my theory to that was a loose component that "wiggled back in" during shipping... when it returned to the shop here I played it sounded wonderful... worked fine for a few songs at practice before suddenly just quitting... i say there was no sound without pressing the limit defeat.... but there was it was almost a whisper though.... who knows... just makes me a sad panda... looking at getting a Carvin BX1500 and 210 cab as a backup though... until i really get a chance to play that it will be the backup, because I don't know of anything that gives me that SVT4 sound that I love... my backup GK that i had did a good job but just not 100% there you know...

 

[aRun]

Did you ever have any luck with this man??

Ive got an SVT4 pro sitting collecting dust which has an identical problem. Has been the was for some time. The only local tech I have is full of poopie, and very useless.