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Ampeg SVT Classic - Tubes - Help!

I

iandi.bass

May 20, 2009
30
0
#1
I purchased a used Ampeg SVT-Cl U.S.A.-made almost a year ago and the previous owner had told me that they had only changed one tube since they had purchased it.


So to say the least, I'm looking to purchase and switch the tubes.


My question is, what tubes should I get? Company name etc. etc. And how much of a difference do different tubes make (so long as its the correct tube. I believe a classic uses 6 6550's, 3 12AX7's and 2 12AU7's)?






Also, where could I find and purchase said tubes. I had it in mind to just get some new ones off of ebay stores.
 
#4
I left that part out, but the sound of them has declined since I first purchased it. And periodically(twice at shows) more times at practice, my amp has cut out and the sound was warped incredibly (and it wasn't the bass, or other equip etc.).

And I've got a string of shows of higher caliber coming over the next few months and can't afford to 'just plug into the PA' or use some other bands combo amp when mine ***** out.
 
#5
thetubestore.com has good info on what sets of tubes to get for SVTs... at different price points.

But you're gonna wanna find a respected tube amp tech in your area if you don't already have one.
 
#6
iandi.bass said:
I left that part out, but the sound of them has declined since I first purchased it. And periodically(twice at shows) more times at practice, my amp has cut out and the sound was warped incredibly (and it wasn't the bass, or other equip etc.).

And I've got a string of shows of higher caliber coming over the next few months and can't afford to 'just plug into the PA' or use some other bands combo amp when mine ***** out.
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well you don't know for sure that's a tube problem, and you could easily be throwing money away. and let's say it is a tube problem...it's not very smart to replace all the tubes because one or two are out. a year is nothing for tubes. i've got an amp here with nearly 40 year old power tubes in it.

you're obviously willing to spend money on it to get it working right, so take it to a tech, let him diagnose it, and if you do have to replace some tubes, at least you know for sure that's the problem instead of spending $400 and not fixing it.
 
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#7
Agreed with everyone else. Not sure it is a tube issue. But if you have to buy tubes, get Sovtek or Electro Hamonix, (which is the American name for Sovtek during the cold war). The SVT original 300W head and the classic are expensive to retube, period.
 
#9
I put SED Winged C 6550C's in mine. They are fine tubes. Recomended by many local techs.

http://thetubestore.com/6550c.html

The Winged "C" (SED) 6550C is an ideal replacement for amplifiers with GE 6550A tubes.

From our 6550 tube type listening test:
"The Winged "C" 6550C has very controlled sound - nothing offensive can be found in any part of the frequency response. Also very consistent in detail and separation, with clean highs and exceptional balance throughout."

This 6550 tube is a popular choice in Audio Research amps...
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#10
Great, thanks everyone!

I'm going to try to find someone to check it out for me. I didn't know that there are technicians out there that do this sort of thing, nor did I know that tubes can last out that long. Although the previous owner had the tubes before I did for 3-4 years, so including mine, they should be around 5 years old.


Also, the light that omits from the tubes has declined greatly since I purchased them. I don't know what relevance that has and obviously this is an observation coming from someone inexperienced in tubes, but thank you for the help. And the sites for new tubes are great as well!
 
#12
Question: Does your SVT have the bias lights on the rear ?

If so it's pretty easy to do this yourself. Just get a matched set of 6550's and have at it. Follow the instructions. It's very easy.

iandi.bass said:
Also, the light that omits from the tubes has declined greatly since I purchased them. I don't know what relevance that has ...
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It's relevant.

zachoff said:
You probably don't need to change the preamp tubes.
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True. they last a long time.
 
#13
jackcheez said:
Question: Does your SVT have the bias lights on the rear ?

If so it's pretty easy to do this yourself. Just get a matched set of 6550's and have at it. Follow the instructions. It's very easy.
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the only problem i have with that suggestion is that svt's power tubes work in triplets, so unless you have tubes in both triplet sets out, it's a waste of money to buy a 6-tube matched set. at most you should only need to replace three if one tube goes out. tube sellers throw a lot of hype out there to get you to buy tubes when you don't need to buy them. the matched sextet for an svt is one of them.
 
#14
JimmyM said:
the only problem i have with that suggestion is that svt's power tubes work in triplets, so unless you have tubes in both triplet sets out, it's a waste of money to buy a 6-tube matched set. at most you should only need to replace three if one tube goes out. tube sellers throw a lot of hype out there to get you to buy tubes when you don't need to buy them. the matched sextet for an svt is one of them.
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The SVT-CL manual states...

Power tubes work together in a push/pull configuration and should all be replaced at the same time with matched or balanced tubes.
Click to expand...

I'm not a tech so I'll take their word for it.

The OP is talking about a set that is 4 or 5 years old. Get some good fresh glass in that thing.

The money you save doing it yourself will pay for a few of 'em.
 
#15
why would you not get the Ampeg tubes? a tech recently told me--is he wrong--if you're going to retube the amp.. the CL.. to do both "sides..." and that those tubes should last 20+ years.. if you take care of the amp.. but he was emphatic in retubing with Ampeg tubes.. I think they are made in Russia.. in 2sets of 3.. but I respect this guy.. the tech.. he says you may as well retube both sides if you have a tube problem.. not to ever re tube just one tube and leave the rest remaining..

is he wrong? I really don't know. he's been working on ampegs and other amps for 30 years.. maybe he's a salesman.. lol.. let me know thoughts.. but he is quite emphatic in recommending only using Ampeg tubes and no others.. also, you can get two sets of tubes .. for $300.. and do it yourself..
 
#16
I just paid $350 to have my CL retubed.. all new Ampeg tubes.. it's being done right now.. maybe I got taken, but all the tubes looked "cloudy" visually.. like a white powder within each tube.. then it went out during a show also.. it had not been re tubed since the early 1990s.. so it's due.. and it's been banged around a LOT.. I bought this amp used.. but it's got scratches all over.. so this ampeg guy.. was quite insistent on using the right tubes, explaining only two manufacturers, that he knows of, make sets of 3s.. for the Ampeg.. he claimed Marshall has some also.. but while the tubes might not be "ampeg" brand.. they are what Ampeg recommends.. made in Russia.. once the job is done, he'll give me the box.. I don't have the receipt here in front of me, either.. which lists the brand of tubes.. but his price to retube + labor totals $350.00 USD.. and he claims he's VERY cheap.. does not mark up the tubes. all he asks is for referrals in return... his price includes new tubes and his labor, plus biasing, testing.
 
#17
Ampeg doesn't make tubes. The SVT-CL comes with Sovtek 6550WE's from the factory. It's one of the cheaper tubes purchased in quantity for mass production.

While we're on the subject, Mike Matthews' New Sensor Corp (Electro Harmonix) bought the Sovtek factory in Russia. They are making and re-branding tubes in the names Tung-Sol, Mullard, Electro Harmonix, and Sovtek. They also now produce the highly regarded (and priced) Genelex Gold Lion tubes.

As for tubes lasting 20 years...maybe preamp tubes, but power tubes in regular to heavy use are good for 3 to 5 years, give or take.
 
#18
First: I agree with many of the posts here: take it to a good tube amp tech and have him/her find out what's really wrong with your amp. It might not be tubes at all. And even if it is tubes, you will need an experienced tech to bias it correctly with the new tubes.

Second: Asking for recommendations for brands and models of tubes is kinda pointless according to a real smart guy I know. He (the real smart guy) is a tech and also an amp designer and builder at Savage Audio in the Minneapolis area. He tells me the difference between individual tubes of the same make and model is often greater than the difference between any two tubes from different manufacturers. I believe him.
 
#19
svt's DO work in a push pull system. but 3 power tubes push and 3 tubes pull, unlike most tube amps where each power tube is paired with another for push pull. so you get 3 that match on each side, then you set the bias FOR EACH SET OF 3 SEPARATELY. so all you need to do is get two sets of 3 that match each other within their own sets. once the bias is set properly, each triplet set can be non-matching and it won't matter.

but if it makes you feel better to replace them all, have at it. not my money ;)
 
#20
jackcheez said:
As for tubes lasting 20 years...maybe preamp tubes, but power tubes in regular to heavy use are good for 3 to 5 years, give or take.
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well that depends on how hard you drive it. if you turn it up to 10 every night, you can fry them pretty quickly. one guy fried his within 6 months. but if all i could get out of a set of power tubes at the settings i use was 3-5 years, i'd call them crappy tubes.
 

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