Thoughts on Genalex Gold Lion KT88's in Ampeg SVT CL?

[JuanB]

I've done a search and wasn't able to find too much on this. Just curious what others think of the new production Genalex Gold Lion KT88's in modern Ampeg SVT CLs. Thanks!

 

[Wasnex]

@coreyfyfe may have some experience with that tube.

 

[coreyfyfe]

@coreyfyfe may have some experience with that tube.

Not in an SVT, but I did try some in my science mother. They didn’t seem to handle the high voltage well, a lot of noise. In a lower voltage guitar amp they were okay. Plenty of reliable 6550 options on the market, I don’t really see a reason to try these KT88 in an SVT. I currently have the new sensor tung sol reissues in mine.

 

[JuanB]

Not in an SVT, but I did try some in my science mother. They didn’t seem to handle the high voltage well, a lot of noise. In a lower voltage guitar amp they were okay. Plenty of reliable 6550 options on the market, I don’t really see a reason to try these KT88 in an SVT. I currently have the new sensor tung sol reissues in mine.

Thanks, coreyfyfe.

 

[JuanB]

Not in an SVT, but I did try some in my science mother. They didn’t seem to handle the high voltage well, a lot of noise. In a lower voltage guitar amp they were okay. Plenty of reliable 6550 options on the market, I don’t really see a reason to try these KT88 in an SVT. I currently have the new sensor tung sol reissues in mine.

Where did you buy your tubes? Maybe they didn't burn in the tubes at the operating voltage of your amp.

 

[rickdog]

About 8-10 years ago I had a couple of Tung-Sol reissues fail (internal arcing) in my SVT-CL after not too many hours of light use. Maybe I just had bad luck and got some from a bad manufacturing lot. I replaced them with JJ KT88s, which seem to work just fine. I can't say I've put a lot of hours on them, though, I just don't have a need for that much power these days.

The SVT-CL plate voltage is right around the maximum spec for a 6550, KT88 has some margin. I know @agedhorse has advised there are theoretically risks with this substitution (simply because they aren't the tubes the amp was designed for) but I think that practically speaking it works reliably.

I got my JJs from Eurotubes.com.

 

[Wasnex]

The SVT has fairly high plate voltage, but the screen voltage is much lower (about 1/2). Some amps run the screens a few volts below the plates.

There are quite a few threads across the web where people are concerned with using the more recent New Sensor designed KT88s in amps with high operating voltages. AFAIK, recent designs include Electro Harmonix, Tung-Sol, Gold Lion, and Mullard. Not sure if the Svetlana KT88SV falls into this category is it may be the discontinued Sovtek KT88 with a new label.

The only tubes in this list I have any experience with are Electro Harmonics KT88 and 6550, which appear to be the same tube. I have received multiples of each in used amps I bought, and all were either bad or failed in short order. So I suggest avoiding EH 6550 and KT88.

I also have a sextet of the discontinued Sovtek KT88s in a Trace Elliot V6 which runs similar voltages to the SVT. The matching is right at the edge of acceptable (15%), but the amp sounds fabulous.

Older New Sensor designs like the Sovtek 6550WE seem to have a decent reputation for reliability, but some users don't like the sound. My impression is Sovtek 6550WE, Shuguang 6550, or JJ 6550 are probably your best bet for reliability if you want to stick with 6550. AFAIK Ampeg runs JJs in standard SVTs and Sovteks or Svetlanas in the 50th AV.

I have a fairly large collection of amps and JJ KT88 has been very reliable, but some people report extremely bad luck with JJs.

Any brand/model of tube can fail. This best thing you can do is buy from a good vendor who does an extended burn-in before matching. Even better if the vendor can match the tubes at the operating voltage in your amp. Many matchers do not approach the voltage in high powered amps. I believe TC Tubes does this, but they do not offer a wide variety of new output tubes, and the ones they do offer are New Sensor designs.

The other thing is to find a vendor who offers a long warranty (6-months VS 90 days). One potential problem here is the vendor may be reluctant to honor the warranty, and claim any problems that occur are due to the amp. My impression is Eurotubes may fall into this category, and they are the premier JJ dealer.

The set of KT88s I bought from Eurotubes was almost perfectly matched. I did have a problem, but it actually turned out to be the amp (loose pins in the tube sockets) . After the initial problem, they offered to test the tubes, but I got the impression I was responsible for postage. I checked the working voltages in the amp, retensioned the pins, and the amp has been fine since.

 

[agedhorse]

There are variables other than plate voltage that come into play.

Since different variables come into play with different designs, and different tube types have different variables, it should be clear that the performance and reliability of different designs will be different with different tube types.

This is why I don’t recommend playing tube type roulette without a confirmation from somebody who really understands the risk. A catastrophic failure can damage some expensive components in addition to the tubes themselves.

 

[JuanB]

Thanks, @agedhorse. I've read quite a few reports of people using KT88s in SVTs. I've not run across any negative reports. I may stick with 6550s moving forward.

 

[agedhorse]

Thanks, @agedhorse. I've read quite a few reports of people using KT88s in SVTs. I've not run across any negative reports. I may stick with 6550s moving forward.

The problems people report and what they attribute the problems to are often just wild guesses. That's why I don't take what I read on the internet as the truth unless I know more about the source of the information.