I recently bought a pair of used VTL 750's from an authorized dealer who had completely re tubed these amps with matched Sovtek 6550's.
These particular tubes were TRADE MARKED as "Svetlana" which are the same tubes as Sovtek / Electro Harmonix for those that don't know the name Svetlana was bought by a large distributor.
The dealer said they had 200 hours on them and testing with my Hickok 752A tester showed no shorts, no gas and "new" transconductance readings.
After listening to these for about a month, and unable to get rid of high frequency distortion and dissatisfied with imaging and dynamics, I replaced all 24 Sovtek/Svetlana 6550's with new SED Wing C 6550's.
The upgrade was almost equivalent to replacing the amps. Everyone who visited the next Tuesday listening session (with only 10 hours on them) asked where the upgrade came from.
Can't wait to hear what the Wing C can do when they are completely settled in. I think this is the best new 6550 around and as others have already commented, the Sovtek may be the worst.
If anyone wants these Sovtek / Svetlana, I will be practically giving them away. Look for on an ad at Audiogon soon.
These particular tubes were TRADE MARKED as "Svetlana" which are the same tubes as Sovtek / Electro Harmonix for those that don't know the name Svetlana was bought by a large distributor.
The dealer said they had 200 hours on them and testing with my Hickok 752A tester showed no shorts, no gas and "new" transconductance readings.
After listening to these for about a month, and unable to get rid of high frequency distortion and dissatisfied with imaging and dynamics, I replaced all 24 Sovtek/Svetlana 6550's with new SED Wing C 6550's.
The upgrade was almost equivalent to replacing the amps. Everyone who visited the next Tuesday listening session (with only 10 hours on them) asked where the upgrade came from.
Can't wait to hear what the Wing C can do when they are completely settled in. I think this is the best new 6550 around and as others have already commented, the Sovtek may be the worst.
If anyone wants these Sovtek / Svetlana, I will be practically giving them away. Look for on an ad at Audiogon soon.