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How do you evaluate a vintage tube amp?

Raw Amateur

Raw Amateur

Feb 9, 2011
48
2
Montana
#1
So there is a guy near me who is selling his Ampeg V4, mid seventies amp. I know him, and I am going to go by his place and try it out.

I have done a lot of research on the V4, with the right cab it should be a solid bass set up. He's asking $800 which I think is steep, unless the thing is minty fresh.

I was wondering if there is anything in particular I should take note of when evaluating an old tube amp? When you test one out, is there anything you do to try and find problems with?

I've been playing bass for about seven months now, and I am really interested in tubes. I haven't heard one, if anything I'll get a first hand taste of the sound.

Thanks in advance.
 
#2
You evaluate it like any other amp...play it, look at it, turn all the knobs and switches, etc. The only thing I'd do differently is ask when it was last serviced. And then I'd try to talk him dowm to $600 ;) The V4 is not uncommon and there will be others if this doesn't work out.
 
#4
Make sure the note-to-note volume is at least close to equal when the eq is flat. Check for scratchy pots, and that input/output jacks arent loose/broken. If you can, also see how transformer gets after about 10 mins of being used. If it is burning hot you may have to rebias the tubes, and therefore it would be a good excuse to buy for lower price.
 
#6
When I bought my v4b i searched all of the for sale threads on talk bass to find a average price. $800 seems a bit higher that what i found :eyebrow:
Depending on your location I imagine prices will vary. Not many old ampeg amps in my part of the world (Canada).
 
#7
With tubes, they give a warm mellow sound and energy. Many bassists & guitarists still love this 60s sound. The tubes themselves may need replacing eventually. I know a place where they can be found. Replacements and equivalents are still being made in Russia and Eastern Europe. If you check out an amplifier, there are several issues to consider so ask a veteran electronics specialist for advice first. Good models can cost over the real odds nowadays. A friend just sold a Vox AC 30 Bass biased combo for hundreds of bucks last month. Back in the 60s, I used a variety of valve amps (tube).
Selmer, T'n'B, Impact and several other makes including Fender & Marshall.
 
#8
You can tell a lot with your ears. Listen for hum, pops, crackles, scratchy pots. Those are signs that the amp needs work. Don't even need your bass for that. Turn all the pots all the way up and down. Flip every switch. Let it run and play it for a good long while. If you know the guy, maybe he let's you take the amp to a tech, get it bench tested...

I think it's a fairly safe assumption with any vintage tube amp you are going to need to do some work on it... Maybe you get a good one that's been really well taken care of, maybe the dude selling it already did the work. Maybe not.

Find out how much work has been done on the amp, and let that be a bargaining chip. Caps and Tubes can last a long long time,,, but not forever - it depends on how the amp was used and cared for.

Before you buy, try to think about what work you might have to have done to it. If it needs work then do like Jimmy said,,, try to talk him down to $600!!
 
#9
hennessybass said:
You can tell a lot with your ears. Listen for hum, pops, crackles, scratchy pots. Those are signs that the amp needs work. Don't even need your bass for that. Turn all the pots all the way up and down. Flip every switch. Let it run and play it for a good long while. If you know the guy, maybe he let's you take the amp to a tech, get it bench tested...

I think it's a fairly safe assumption with any vintage tube amp you are going to need to do some work on it... Maybe you get a good one that's been really well taken care of, maybe the dude selling it already did the work. Maybe not.

Find out how much work has been done on the amp, and let that be a bargaining chip. Caps and Tubes can last a long long time,,, but not forever - it depends on how the amp was used and cared for.

Before you buy, try to think about what work you might have to have done to it. If it needs work then do like Jimmy said,,, try to talk him down to $600!!
Click to expand...

Very good advise! Don't even plug the bass in, just fire up the amp and let it warm up (plugged into the speaker cabinet of course). After it warms up, listen for crackles/pops/roars. If there's hum, see if the hum goes away if the hum cancelling trim pot on the back of the head is adjusted. (If the hum does not go away, the amp needs recapping)

I also agree with playing it for a good 15 minutes or half hour and see if anything changes volume-wise. (When I bought my V4 many decades ago, a coupling cap would give out after 15 minutes or so and the amp would go silent)

$800 does sound high, if somebody were to offer me $800 for mine I'd snatch that money out of their hands so fast......$600 sounds more appropriate if it's in pretty good shape and doesn't show any unusual problems.

edit: let me clarify, my V4 is not for sale, Iwas merely using that as a reference point...
 
#10
Oh, as far as the age: If it has toggle switches for the power and standby, it's early 70's. If the power/standby switches are rocker switches, it's mid 70's. If it has master volume on the front panel, it's very late 70's and NOT as desirable--the earlier ones only had a volume on channel one and a volume on channel two.

edit: Here's a pic of mine which is early 70's, note the volume controls and the power/standby switches.
 
#11
nashvillebill said:
$800 does sound high, if somebody were to offer me $800 for mine I'd snatch that money out of their hands so fast......$600 sounds more appropriate if it's in pretty good shape and doesn't show any unusual problems.
Click to expand...

I didn't want to comment on the price too much because I'm selling a V4B right now... didn't want to mess up someone else's sale or something.

But this is a good thread with lot's of good tube amp buying practical advice. So with that... for comparison sake only...

I'm trying to sell my V4B for $875. I priced it that way based on a couple of things... mine is in nice cosmetic shape, comes with a case, and has just had a total cap job, all new pre-amp tubes, two new power tubes, and totally cleaned up by a tech. Complete cap job costs something like $180. Complete tube set from fliptops costs something like $160. I paid to have that work done, and the new owner should be set for a while!

For what it's worth, I've had no interest in my amp so far.

So again,,, think about what work you might have to have done to the amp, and factor that into your decision.
 
#12
Turn it on make sure it's all plugged in, see I it has a 3 pronged plug for ground, turn the volume up and turn all the knobs to check for scratch/pop/etc.
Check all the knobs one at a time on the eq to see if they affect re tone as they should. Check the case for damage, and the transformer for rust.
If it's been around for 30 years who know if it was dropped or kicked or spilled on.
If you can try to push it and see I'd it's loud enough, If the tubes are going it will still sound great at lower levels but will break up really early (like around 5-6 on the master and gain)
That's something you won't notice unless you push it. By then it could be at a show or rehearsal and it's a huge let down and a money pit!
 
#13
For some reason the V4B seems to be priced a little higher than the slightly fancier, more common V4, go figure. The V4 adds reverb and a couple of tone control switches compared to the V4B. The amps are otherwise identical for all intents and purposes, IMHO.

The pricing dilemma seems to be the same whether for cars or amps. A worn-out car might sell for $1000. Take the same car, put $3000 into the engine and drive train and whatnot, and try listing it for $4000...though now it's a pretty good car, it won't get a nibble. Probably wouldn't get a nibble at $2000. When something has been refurbished, the cost of refurbishing it doesn't usually get recouped in the selling price. It's not really fair I agree.
 
#15
FWIW, earlier this year I sold a 1970 VT22 (V4 head in a 212 combo) in strong playing condition and very good cosmetic condition for $500. If I lived in Canada, I'd just look for a clean condition early 70's Traynor tube head, fine amps that are more plentiful and affordable up there.
 
#16
Wow, excellent advice so far. I really appreciate it.

I live in somewhat rural Montana, so any kind of service work on it would have to be shipped out. I'm gonna hold my cards close to my chest before making an offer. I am willing to bet the tubes have not been replaced in a long time. A new set would cost me a little more than $200.

Along with a clip board, I might wear a lab coat too.
 
#18
I open them up and look how they are wired. If everything is all neat and on turrets, like a Hiwatt or something, then I'm happy. Hums and crackles are just price negotiation points, if it is made right, it can be fixed. If it is a horrible spaghetti mess, I don't care what badge is on it, more trouble than it is worth unless it works perfect.
 
#20
Wow, plenty of great advice already, but I'll just ad:

You should expect to get it's max clean volume with the volume knob only up somewhere between 10:30 and 11 o'clock.

That's the way most all the older/master-knob V4/V4B's are supposed to be. (but feel free to turn it up even higher for some riotously overdriven tones if ya wanna!)
 

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