New tubes -Ampeg SVT CL

Sandermann · #1 03-29-2012, 03:55 AM

Hey guys!

Ok, so this is the situation:
I have an old SVT CL. One of the power tubes no longer light up when I turn it on, and the bias indicator for the tube doesn't light up either, so I'm guessing that since I bought the amp used, the previous owner must have worn them out..

I am considering to replace the old power tubes with either Sovtek 6550WE's or Electro-Harmonix 6550's, and I was wondering if anyone have any experience with these products?

And if anyone knows wether I can do something to "save" the tubes I currently have?

Love the forum btw

Downunderwonder · #2 03-29-2012, 04:29 AM

I would guess differently, but I'm not an amp tech either. Could be there is a fault. If I was the previous owner I might have thrown in a new valve and when it went poof too I might have given up and sold it as is.

Better find a good tech who will test your old valves and tell you if they are still good. JimmyM says most techs help themselves to your good vintage ones and sell you a whole new set as a rule. Good vintage valves are worth big bucks.

coreyfyfe · #3 03-29-2012, 05:10 AM

The sovtek 6550WE is the one with the small plastic base right? I think those are typically preferred in guitar amps. I'd go with the EH tubes of those two.

If one tube is not lighting up it could be more than just the tube, as said above. To test this, swap the tube into a different slot. If the tube remains dead then it's likely the tube, if the different tube in the same slot is dark then you probably have a failure in the bias circuit and you should bring the amp in for service.

Randyt · #4 03-29-2012, 05:32 AM

im going throught the same process of purchasing back up tubes for my CL too!....what i have come up with so far is that JJ 6550's have recieved higher ratings than others..(some of these reviews can be scewed) The Genelex Gold lion (RI) are excellent yet at a higher price range. Ampeg stocks all their new SVT's with JJ (from what ive read)
What you might also look at is replacing with KT88's??...im kinda thinking about going with KT88's...but the big question is ...do i go with the red glass or blue glass??LOL...i wonder if there is a diffference in coloured bottle glass? (JJ's or eurotubes offers different colours.
good luck

Sandermann · #5 03-29-2012, 05:49 AM

Thx for the replies! I tried switching them around and the same tube is still dead, so I'm pretty sure I have to buy new ones.

Seems likely since the powertubes are the sovtek ones and if they are primarily used for guitar amps, it makes sense if they are worn out I guess..

Time to decide wether I want funky color tubes or if I should listen to my wallet!

JimmyM · #6 03-29-2012, 11:06 AM

Tubes are tubes, and the only difference is build quality, and has nothing to do with what kind of amp they go in. Some folks don't care for them, but I've never had much of a problem with Sovteks. They're some of the longer lasting new tubes on the market IMHO. But they will go toes up sometimes.

However, one power tube going bad is no reason to assume that they're all about to go on you. Tubes don't wear like that. One can go out and the rest could last years. With SVT's, power tubes are generally replaced in triplet sets, so if one tube goes out, you should only have to buy three at the most, and that's only to make sure you get matched tubes. Won't talk you out of a full set if you insist, but it's a waste of money.

hodgy · #7 03-29-2012, 11:21 AM

Ampeg currently ships all VRs and CLs with the Sovteks. Heritage CLs get the JJ's. I like the EH's and Svetlanas I kinda like too, but as Jimmy says, tubes are tubes.
Of course, there is still the possibility that there is something else problematic in the amp (one I see very often is a blown resistor on the tube PCB) and in that case I'm afraid you'll have to see a tech.

coreyfyfe · #8 03-29-2012, 02:05 PM

Quote:

Originally Posted by JimmyM

Tubes are tubes, and the only difference is build quality, and has nothing to do with what kind of amp they go in. Some folks don't care for them, but I've never had much of a problem with Sovteks. They're some of the longer lasting new tubes on the market IMHO. But they will go toes up sometimes.

It looks like the ones I was referring to were the 6550WD (have the little plastic base, not the wide metal base) which are out of production according to tubedepot. Had them in my V4 when it first got it and they totally lacked balls and had a pretty harsh breakup. Most reviews I found on them said they were great in old marshalls, bad in bass amps. The sovtek 6550WE reference in the OP's post are indeed supposed to be a decent tube for bass.

Hodgy - you might be able to shed a little light on this. Ampeg used to ship with Svetlana branded Sovteks and now ships with straight up Sovteks. Is there are reason? Most reviews/comparisons I've read treat them as the same tube (as they are made in the same factory) so why the switch?

hodgy · #9 03-29-2012, 03:33 PM

Quote:

Originally Posted by coreyfyfe

It looks like the ones I was referring to were the 6550WD (have the little plastic base, not the wide metal base) which are out of production according to tubedepot. Had them in my V4 when it first got it and they totally lacked balls and had a pretty harsh breakup. Most reviews I found on them said they were great in old marshalls, bad in bass amps. The sovtek 6550WE reference in the OP's post are indeed supposed to be a decent tube for bass.

Hodgy - you might be able to shed a little light on this. Ampeg used to ship with Svetlana branded Sovteks and now ships with straight up Sovteks. Is there are reason? Most reviews/comparisons I've read treat them as the same tube (as they are made in the same factory) so why the switch?

I believe the reason is that the Svets were getting harder to find the quantities of at the price that was needed. Really no more reason than that the supply wasn't there.

DannyZ · #10 03-29-2012, 03:44 PM

I have an American SVT-VR that was re-tubed a year ago when I bought it. I only use channel one. Instead of replacing the whole 6 tube set, can the tube set be rotated to lengthen tube life and possibly get a better tone? I guess it wouldn't hurt none to do so. Based on the picture which tubes service channel one and which serve channel two? Can the preamp tubes be rotated or do they run both channels? Any help would be appreciated.

coreyfyfe · #11 03-30-2012, 07:07 AM

In the picture you're only showing the power amp chasis, so all of those tubes are related to both channels. The pre-amp tubes are mounted into the pre-amp chasis. Remove the four bolts on the top and it should slide out. I believe in the VR the positions of the channel two gain stage tube and the collector tube are reversed (compared to the vintage amp) and the 12AX7 for channel two is listed as V5 on the schematic. Where exactly that is in the amp, I'm not certain, but if you can look at the schematic you may be able to figure it out based on what is around it on the circuit board.

Either way, yes you can swap around the channel 2 tube with the others (or even remove it and still have channel 1 be functional), but it really wont matter in terms of life span as pre-amp tubes have a very long life in general. If you want to swap them around and try to get different tones then by all means. A few TB members who have swapped in NOS tubes in their VR pre-amps say they are nearly indistinguishable from vintage SVTs.