I got a new K4040 in January 2009. Assembly of kit was easy and pleasurable. It sounds better than my Accuphase,tube sound is softer and warmer,more detail, but may be bit less bas in first hours. The bias was set and controlled as it is in manual. Now it has run about 35 hours and one of the EL34 has burn off together with R101.
1.Is there a warranty time for tubes.
2. Do Welleman compensate the tube
2. Are the Russian tubes suffisiently good, any recomendations
Regards,
Riho
1.Is there a warranty time for tubes.
–> no.
2. Do Welleman compensate the tube
–> No, we do not direct sales, so it’s not possible.
2. Are the Russian tubes suffisiently good, any recomendations
–> Yes, we haven’t a lot of complaints. They are tubes, not transistors so the lifetime is limited and never sure.
I have had a K4040 since May 2000. A very good amplifier but I have also used many EL34’s in it. There are lots of postings on various forums indicating that the K4040 design pushed the EL34 design specs to their limit. After burning out about 20 EL34’s over the years (I have tried JJ, Svetlana, EH, Sovtek) I decided to convert this amp to run KT88’s. Minor modifications will be needed but the audio quality is better - still running on EL34 biasing and I have heard others who have performed this conversion have never had a KT88 go ‘Chernobyl’…
35 hours life from an EL34 would indicate that there IS a problem. And I have a history of burning out EL34’s in my K4040 - as have many others. The tube biasing adjustments are critical in this amp as is the mains supply voltage. Velleman have compensated me in the past for new power and output transformers as well as new tubes. Thay have been very fair.
If you lose any of the cathode resistors, R97 through to R104 (10ohm, 1W) then also check that R89 through to R96 (180ohm, 1W) are OK as these can take a hiding too!
Martin