Ampeg SVT-4 Pro

[imix500]

I agree, but the customer wants what he wants. I've been around and around with this guy. When the amp fails again, and assuming it will be within the warranty period of the new board, it will be much easier to deal with. If not within warranty, at least I'll know it's a new board.

[soundguruman]

You are wading deeper and deeper into the crap.

A long time ago, I had a Crate service center. But after realizing that crate amps fail more than cats crap, I refused to work on them, and sent all defects back to the factory.
The factory techs did a horrible job of fixing the amps, and they of course, just failed again and again. (one of the factory repairs caught on fire after 30 minutes of testing at less than 50% power)
What you have there is a Crate amp with an Ampeg logo stuck on the outside.
We both know, it's not Ampeg. It's an Ampeg logo, not an Ampeg amp.
And so, I hope the techs who read this learn something. Don't wax a garbage truck.

[MarkusBass]

I wonder where exactly SVT4Pro is manufactured. I think that SVT3Pro is manufactured in Korea. Is SVT4Pro manufactured in China? Is there any info about it on the internet? I'd like to read it.
I wouldn't be so pesimistic about the amp. As Steve said, this is quite complex amp, with high voltage rails and he is right that "a failure of an output device can take out a lot of parts in a kind of domino effect, and not all of the failures are obvious". If someone does not understand how the amp works, he or she shouldn't start fixing it. Even if he understands how the amp works, it is still not easy task to fix it (due to non-obvious failures, which might not be found). But there is very simple trick, which I use with this (and similar) amp. I usually fix it without output transistors and I add them only at the very end - when I know that the amp works fine).
I found the amp quite reliable. Most problems with this amp came from bad treatment by users (like: using a shorted cabinet wire, trying to set the bias without understand what exactly bias is, throwing the amp from a cabinet onto the floor :-) ). Also guys who fix amps do not pay attention to e.g. MOSFET matching (imix500 - you know what I mean?), bias setting, or checking for proper cooling of the components in the amp (bridge, output MOSFETs). If the power board is not damaged (by poor technicians), it can be always fixed. The solution with a new board is very expensive. I don't remember the price but it is possible that if you replace the power board twice, it may be more expensive than the price of a new amp. What is the cost in your case? Is the old board dameged?

Mark

[soundguruman]

Crate amps became the laughing stock of the prosound industry, due to poor design and lack of reliability.
The Crate factory in the USA went belly up...
Then somebody had a brilliant idea:
Why not use trusted names, like Ampeg, Kustom, and stick these names on the outside of the amps? Then people will buy them again, because they trust the name.
Then they sent sales reps, to tell people that the new SVT was exactly like the old one....etc....etc...
(SVT stands for Super Vacuum Tube)
(SBT stands for Super Bass Transistor)
And when people saw "SVT" they bought it, cause SVT is reliable and trusted, right?
Well what you wound up with is an amp that is not anything like a real Ampeg or a real SVT. It just has the name, and not the guts.
And overall, we get schematics here and there, sometimes complete and sometimes NOT.
But what we don't get is long term parts support, much of the time.
And what we do not get is reliability that matches a real Ampeg. (The real Ampeg used to drop cabinets off of buildings to test the glue joints, etc...)
Real Ampeg made by Magnavox, USA, FYI.

And so, if I stick a "FORD" nameplate on a Volkswagen, does that mean that it becomes a Ford?
I think this may be a rhetorical question.

Switching power supplies have really never worked that well in guitar amps. As a matter of historical note.
All the ones I've seen did not last long, and suffered from poor thermal management.
Switching worked OK for computers, and TVs etc..but not guitar amps.

What you need in a guitar amp is big, beefy hardware, that is battle ready. The amp should be able to run all day, at full power, without overheating.
Unfortunately, the amps flooding our markets from China, etc...just don't fill the qualifications.
And they are putting the real craftsmen out of business. Too bad.

[imix500]

Hey Mark,
This was a special case with this model. I've worked on them before and found them fairly straight forward as far as your typical class ab amp. As with any complex circuit you just break it down into sections and sub systems.
This one has multiple failures that are fighting eachother, not to mention the very missmatched output stage, plus a pcb that disintegrates when looked at the wrong way.

Replacing the board is extreme, but it's the best option for this amp.
Retail on the board is under $700, but I get really good prices on parts from the mother ship.

I'll keep the old board for parts, but it will never go back into service.

[Alex R]

Crate amps became the laughing stock of the prosound industry, due to poor design and lack of reliability.
The Crate factory in the USA went belly up...
Then somebody had a brilliant idea:
Why not use trusted names, like Ampeg, Kustom, and stick these names on the outside of the amps? Then people will buy them again, because they trust the name.
Then they sent sales reps, to tell people that the new SVT was exactly like the old one....etc....etc...
(SVT stands for Super Vacuum Tube)
(SBT stands for Super Bass Transistor)
And when people saw "SVT" they bought it, cause SVT is reliable and trusted, right?
Well what you wound up with is an amp that is not anything like a real Ampeg or a real SVT. It just has the name, and not the guts.
And overall, we get schematics here and there, sometimes complete and sometimes NOT.
But what we don't get is long term parts support, much of the time.
And what we do not get is reliability that matches a real Ampeg. (The real Ampeg used to drop cabinets off of buildings to test the glue joints, etc...)
Real Ampeg made by Magnavox, USA, FYI.

And so, if I stick a "FORD" nameplate on a Volkswagen, does that mean that it becomes a Ford?
I think this may be a rhetorical question.

Switching power supplies have really never worked that well in guitar amps. As a matter of historical note.
All the ones I've seen did not last long, and suffered from poor thermal management.
Switching worked OK for computers, and TVs etc..but not guitar amps.

What you need in a guitar amp is big, beefy hardware, that is battle ready. The amp should be able to run all day, at full power, without overheating.
Unfortunately, the amps flooding our markets from China, etc...just don't fill the qualifications.
And they are putting the real craftsmen out of business. Too bad.

Did you hear that Fender isn't owned by Fender any more?

I mean, it is not really news that brands no longer have any real meaning. I have repaired many modern Ampegs and i never met a customer yet who didn't already know that they are now mass produced items, made where labour is cheap and badged with a familiar brand name. It isn't really news, you know? I only say this because you produce these ideas with such aplomb as though they are original insights or represent some kind of wisdom. But everybody knows already.

I would say though that the fact that something is made in China or wherever doesn't mean anything more than the fact that it has an Ampeg badge on it. China, dude, is quite a large and diverse country, full of human beings who can make good stuff and bad stuff like anyone else. I mean for instance, did you ever look inside the Epiphone Blues Custom 30? PCB amp, made in China, sells pretty cheap, but the PCB is decent quality with nice thick traces well spaced, made to carry HT. Most PCBs are made in China these days - do you turn them all down if they come in for repair?

here's an instructive song for you

[soundguruman]

I have looked at quite a few and repaired quite a few.
And knowing what's inside, or how it's supported, or knowing the reliability, I would never buy one or recommend one to anybody.
Especially since I know how a real one is built, compared to the imitation.

I am quite certain that I was the very first person to point out many years ago, that these are not real Ampegs.
And I mean the first. I said this before anybody else did.
At that time, all involved seriously believed that these were exactly like the original. The sales reps told them so.
And no, not everybody knows this. There are a great many people who think an SVT is a transistor amp, of course it's not.
Only the imitation SVT is transistor, as some people now realize..

And so, "if" this mystery manufacturer were to make a better amp, I would probably say something better about it.

And when I see a well made amp, I do say something good about it. Bruce Egnator, you are my hero.

Want a good bass rig?
Start with a rack mount instrument pre amp, like Rane, Alembic, Furman, etc...etc...There's a bunch of good ones.
Add to this a rack mount power amp, heck, a Peavey CS 400 is supported 10 times better than an imitation Ampeg. And will probably last 15 times longer.
And when you need parts, the Peavey factory sends them quick and for a very fair price.
Sorry, no contest.

I have recommended McIntosh rack mount power amps for bass rigs. I would prefer that to a Peavey, although it costs quite a penny more, it's mondo on the tono.
As you know, the Dead did use McIntosh whenever they could be had. It's sound quality and it lasts.
If I were to set out playing a bass rig, that's how I would do it, cause I know better. (I do play bass, and I like bottom for Days.) I have seen the very best and the worst.

.

[Steve Conner]

What you need in a guitar amp is big, beefy hardware, that is battle ready.

At last the guru said something that I agree with. Unfortunately big beefy hardware costs money, and musicians are mostly broke or stingy, so what is the industry to do? Peddle Chinese crap or go out of business.

There's also the old everlasting lightbulb argument, that if they made amps that lasted for ever, they wouldn't sell many.

Yes, the SVT brand stands for "Super Valve Technology" and shouldn't be used on a transistor amp, but that is ancient history like vacuum tubes themselves.

I wouldn't be surprised if the new transistor units were more reliable than the original tube SVTs, simply because transistors don't wear out. The difference of course is that the original tube one was easier to fix when it blew up, just pop in some new tubes and a couple of screen resistors.

[soundguruman]

At least it could be SBT. Super Bass Transistor.
But it's not anything like a real SBT either.
Do you remember the Ampeg SBT?
Kind of rare nowdays.

[Enzo]

I am quite certain that I was the very first person to point out many years ago, that these are not real Ampegs.
And I mean the first. I said this before anybody else did.
At that time, all involved seriously believed that these were exactly like the original. The sales reps told them so.

What complete and utter hogwash. And you wonder why you are not treated with respect here.


When they first made SVT amps, the name was creared for the reasons you state. Super Valve Technolgy, fine. It is just a product name, not a technical specification. General Motors makes a Chevrolet named the Impala. Wonder of wonders, and no one knows this because I am the first one to point it out, the car is not also an antelope. Seriously, it has tires instead of hooves. A REAL Impala would have hooves. "SVT" is a trade name. They can use it on a transistor amp to associate that transistor amp with the rest of the SVT line if they want. It is not to fool anyone that the amp is full of tubes. Only an idiot will look at a product and think it must be a tube amp because 40 years ago the first amps in the named series had tubes.

[Enzo]

I am quite certain that I was the very first person to point out many years ago, that these are not real Ampegs.
And I mean the first. I said this before anybody else did.
At that time, all involved seriously believed that these were exactly like the original. The sales reps told them so.

What complete and utter hogwash. And you wonder why you are not treated with respect here.


When they first made SVT amps, the name was created for the reasons you state. Super Valve Technolgy, fine. It is just a product name, not a technical specification. General Motors makes a Chevrolet named the Impala. Wonder of wonders, and no one knows this because I am the first one to point it out, the car is not also an antelope. Seriously, it has tires instead of hooves. A REAL Impala would have hooves. "SVT" is a trade name. They can use it on a transistor amp to associate that transistor amp with the rest of the SVT line if they want. It is not to fool anyone that the amp is full of tubes. Only an idiot will look at a product and think it must be a tube amp because 40 years ago the first amps in the named series had tubes.

[Alex R]

well ok Enzo but if you're wrong, the next time a customer brings in an Ampeg and says, as they so often do, I know they make them in China these days, I will be able to tell them that they wouldn't know that if it wasn't for a certain thoroughly well qualified California electrician and all round intellectual pioneer.

[Enzo]

Thanks for covering my vulnerabilities.