Vintage Ampeg SVT - questions
 

Hello,

I recently bought this classic Ampeg SVT. It's far from mint, as you can see, this baby had his time already. It's had a recent checkup and cleaning of all connections and parts. One pre-amp tube was replace, but I don't know wich one :) The seller told me it's 1974. For what I can find surfing the web, that's true.

But I have some questions ...

- Is the date right? (straight corners, black, polarity switch, ...). And, is this a considered to be a amp of a "good" era?

- Those two extra holes on the left side, next to the inputs ... What are those about? Must be a mod. Any idea somebody? It looks like a mini-jack input, but not recent. I have not tested it as input. And the other one looks a (broken) switch? I don't know, can't check it from the inside. Is this a 'known' mod? Looks old, not recent ...

- The front grill cloth is black ... But I think it should be grey. Right? If it's really 1974 ... The seller told me that the guy he bought it from, said it used to be grey ...

- In the back the small horizontal "plate" is missing, normally covering all the outputs, right? The 4 ohm output is labelled, but can somebody tell me where the other outputs are for? :)

- A (good!) link to some info about this amp would be great. I do know google and I can find some stuff. But I think I don't know the right names to search for. SVT and AMPEG, ... there is a LOT about that :)

- Who needs pictures of special parts of the amp, just ask!

I know it's not mint, it had a life. But for me that's not the point, it's all about the tone.

All info about this amp is welcome, thanks a lot in advance!


Peter

fliptops.net is an awesome place to get parts to fix up your awesome new amp, there are links to other sites as well and you can find a lot of information. The beauty of a old ampeg is you can fix them up! and they sound fantastic....

Date is likely right, blue/gray grill cloth was stock (you can still get it...called AV grillcloth), first two are extension amp (line in and out but I forget how they work), main speaker out and extension speaker out. And this is the best resource on the web for SVT info, although www.unofficialampeg.com is also a good place. Really, just do a search on here and you'll find out a ton of stuff on them. Too much, really ;)

Check out this thread for info on how to estimate the date of your amp. Basically you will need to look inside at date codes. You can do this without removing the chassis, but you will need to remove the back grille and a plate on the power amp. Details in the thread.

Fliptops sells replacement face and back plates. They have a pic on their site of an early SVT back plate showing the labels.

Those holes near the input jacks are a mod.

The rust on your input jacks concerns me. This is a key ground point for the amp. If the inside looks like the outside, it would be a good idea to clean the jack to chassis contact areas. You want that ground to be a good as possible. Your amp will sound better if the contact is good. For the outside face, you can buy replacement Switchcraft hex nuts (P2439) and washers (don't have the number with me).

Hey guys, thanks a lot for the info!

I don't know the cosmetics are my main concern ... A perfect amp is cool, but an amp with the right age needs some wear. But the part about the rust is interesting ... The amp is recently services and checked ... So I think that should be okay on the inside.

I'm going to open the back or front to check for dates.

Thanks!

That's a vintage SVT not an SVT classic, many consider this the holy grail. As a rule of thumb, make sure you have some capable techs in your area who can service them, and always factor in repair costs.

If the output tubes have top caps DON"T TOUCH THE TOP CAPS. they can retain a very high voltage even with the amp switched off.

David's pont about the input jacks is right on the money. Without a good connection the amp will never give its best. I'm guessing that the holes near the input jacks are for another input, possibly for a stereo Ric with each pickup driving a separate channel, and a mini switch to link channels one and two.

The switches seem to be missing a standby so that could be the empty hole. iIRC the V4 had three switches on the front panel, Power, Standby and Polarity. David knows these amps way, way better than I so perhaps he'll comment. :)

On that SVT revision, power and polarity were on the front, standby was on the back. Some people modified the amp to put the standby on the front. Especially if a three-conductor power cord was installed and the polarity switch was no longer being used. On the newer SVT-VR the standby is on the front.

A point to remember Peter is that this amp runs with going on for 700V. This is a lethal voltage. If you have no experience working on high voltage tube electronics, please employ the use of a competent tech. I am rabid about safety and worry when folk start poking around inside this kind of amp. A tech's bill will be far less than your life is worth.

Aside from all that, with some proper TLC your amp will serve you well.

Thanks David for the clarification. On a second look at the back I see the switch. I took it as a 1/4" socket at first glance.

I moved the standby to the front panel on my B15N. It always struck me as odd, both as a musician and an engineer, that the Polarity switch you might use once a night is on the front and the Standby, which is used several times a night, is on the back. :D

Yes listen to Paul. You have to have a healthy respect for voltage and current. It doesn't need to be that high to kill you.

I'll be the first to admit that I've been bit a few times over the years when I've got distracted. You feel that surge up your arm and it shakes. You feel sick. If you're lucky and survive being electrocuted, you get an ambulance ride to the hospital where they put you on a heart monitor for 24 hours. Just in case your heart decides to stop.

They call it natural selection. Be smart.

Hi Guys,

Thanks for the good advice. Don't worry, I have no ambition to be electrocuted, I will not touch the inside of the amp. The amp is serviced with a good tech, (left his sticker on the back :) and if needed I have a good one too.

Had my first real play in the band today. Damn! So much MID in this amp, unbelievable! That Hz-switch on the mid is crazy cool! Totally different tone then my AD200B MK2 Orange. A really "hard" and "round" sound cutting trough the mix. I tought "tubes are tubes", but it's totally different. I use little effects (fulltone bassdrive, wounded pawnbatteling ram and zvex whoolly mammoth) for fun and the Ampeg reacts totally different on them compared to the Orange. Just used my '78 Precision, soon going to try my Rippe and Grabber on that beast! I play a 8x10 orange cabinet, I'll post extra pictures soon ...

There is a little "grounding hum" I don't have with my Orange so it's not the guitar nor the location, it's the amp ... Can be problem with the inputjacks?

Interesting toughts about the MOD with the mini-jack and the mini-switch and the Rick! But I tried a mini-jack in there, does not fit ... Maybe it's another type of mini-connection? The switch is broken ...

Here's an extra photo I took just removing the front panel to check the datestamps. 2147440, must be week 40 of the year 1974 if I'm right ... BUT I see some are replaced ... bummer. But also means the amp is serviced (well?) Is there anybody here who can tell me this are "good" replacement parts?

Thanks guys, happy to be with this club!
Peter

O, standby in the back, polarity in the front that's right!

Yes, tubes may be tubes, but transformers are not created equal, and the overbuilt transformers in SVT's are a major reason why they sound like they do. And of course, other design elements, but transformers especially.

I think that he gets it.

Could be. But there are a lot of other possibilities.

There is a hum pot at the back (not the bias, not the balance). Turn it slowly to the left and right a bit to see if the hum is reduced.

This pot balances the heater circuit and is adjusted using your ears to minimize line voltage hum (60Hz in the US). Your problem hum might be at a different frequency and not related to the line hum. If it is, you will hear a second hum as you turn the pot. Turn it to minimize the hum. Try to note where it is before you start.