Svetlana KT88 VS EH6550

Am needing to retube my SF Power 3 SE's. It came with Svetlana KT88's which do sound good but I have heard that the EH6550 tubes are supposed to be very good as well as more reliable. (One of my KT88's just blew a resistor)

Any feedback on the comparison of these tubes will be appreciated.
I am not sure how the EH6550 qualify as more reliable, Svetlana tubes are pretty bulletproof.

EH are made by Sovtek, I believe, and I have always found Svetlana tubes to be of a higher quality, both in build and sound. EH is Sovtek's go at building tubes which will compete with Svetlana and JJ, as most find Sovtek to be a step down.

I apologize for not knowing the whole Electro Harmonix history...

However, I do know the sound of both tubes. If you are looking for a more drier, more neutral sound from your Sonic Frontiers amp, go for the EH6550. That would mean if you find the SF amp overly warm or lush, which many people do not.

You state that you are happy with the sound of your amp, if that is true to the point where you do not want to push the sound in cooler direction, definitely pick up another set of Svetlanas.

And, if you want a bit more sweetness and bass impact, try JJ(Tesla/Teslovak) KT88. But, I do hesitate to give you a recommendation of this tube as there was a production run in 1998 which was awful. Apart from that group, the tube is reliable, but you never know when you are buying tubes, and I doubt that the JJ KT88 in general is as reliable as the Svetlana.

GOOD LUCK in your search
How old were the Svetlanas? Many people have no problem with them in SF Power amps. I have used the EH6550 in a Power 2 and think they sounded pretty good. You might try the new EH KT88 tubes. Kinda halfway between the Svet. KT88 & the EH6550 in sonics with the best bass of all.
My Svetlana KT88's have about 1200 hours on them. The were original equipment with the PW3 se's. SF's tech department is though discouraging their use and suggesting 6550's but I am hesitant to change as I really like the sound of the KT88's.
This is a timely thread. Thanks for the posts as I am considering getting a SF Power 2-actually I am 90% there. I will be using it on Maggie 1.6's. What I heard was great.

I was wondering if any of you have any sage advice for someone coming into the arena? Are there any other improvements to be made to the Power 2 amps such as, different driver or input tubes, or any tweaks? And, if general living-with-them-type-of-advice is out there I will appreciate seeing it.


Dmailer, did you send amp to SF to repair? If so, I guess they told you not to use KT88. Interesting that SF put them in their SE versions if they consider them unreliable. How do they explain that away?

I thought the SF amps were very reliable, but lately a salesperson who used to sell lots of them told me that they were not reliable. Wonder what others experience is?
Forgot to mention that it could have just been a bad tube. If the tube is bad it will blow the resistor. Doesn't mean the amp is bad design.
The resistor blew yesterday and I suspect it was a bad tube. I plan to call them tomorrow and see if they will send me some new resistors so that I can intall rather than sending it back to the factory. The tech people had told me that the early Svet KT88's had alot of problems and thus they are now not recommending them. Of course they are no longer selling amps but are still maintaining them. If the 6550 is more reliable then they are probably discouraging the KT88's in order to minimize the repair issues.
You should also consider going with KT-90s.

Kevin at Upscale Audio can help you with matched set.
I just spoke with Chris Johnson at the Parts Connexion regarding the recommended tubes for the Power 3's. Chris was president of SFI and knows the product better than anyone. He strongly suggested the Svetlana KT88 tube as the best option. He said the 6550 variations do not sound as good on these amps as the KT88's due to the higher plate voltage. He is sending me new tubes and some replacement resistors. I would suggest that anyone looking to retube an SFI product contact him.
I would say the Svet KT88 is (one of) the best sounding, but not the most dependable. The Power 2SE and Power 3SE were initially shipped with those tubes, but they had problems. So they stopped and went to the Sovtek KT88.

I don't sell those tubes into the Power 2 or 3 typically, and also not into ARC amps like the VT100. I think the problem is they on occasion will draw too much screen current. We check the tubes for that, though I don't think any other place does.

With that I love the Svet KT88. But care should be taken. The Sonic Frontiers power amps have no plate fuse protection so if you make a mistake you have to go underneath and solder a resistor or two. I use them all the time in other amps. They work great in Cary's and many others.

The Svetlana 6550C is the most dependable tube we have. And sounds great. I try to read the customer when I chat with them to see if they are technically adept. If they are not, play it safe.

Hence the problem with on-line tube ordering with no concern on proper use. Gets the customer into trouble. I have wanted to put that into place, but no easy way to do it right.
Kevin, I value your opinion regarding tubes as I have bought tubes from you in the past for several of my components. I am willing to replace resistors occasionaly in order to deliver the best sound. I went with Chris's recommendation that the Svet KT88 does deliver the best sound on these amps. If I find that these tubes begin to cause me excessive problems then I may reconsider the 6550 options as I am sure you are correct in saying that they are more reliable. The original Svet KT88's that I had in the power 3 SE's lasted around 1200 hours before I had an issue. This is something I can live with. If I had issues with them every several hundred hours then that would be a different story.
You might try the new EH KT88's. A lot of people like them, and some are saying they are superior to the Svetlana KT88 -- but you know how opinions go. I wonder if Kevin Deal has tried them yet.