Jadis DA60

I quote an email from Jadis to me:

dear Sir
the DA 60 can work with all this kind of tube
after the choice is a question of personal taste
on my side I like the KT88 GENALEX because Ilisten a lot of jazz and voices I like the warm in the high frequency
for big orchestra the KT90 are more dynamic and have a very good control of the bass but the high frequency is less sweet
best regards

So I bought two matched hand matched quads of Genalex KT88 and supplied them to the Sydney dealer who is doing the repair (new output transformer, caps, resistors etc). They completed the rapair and returned the amp but have refused to give me a warranty on the work because they say the DA60 cannot use KT88s. They further say that in all likelihood that the KT88s will destroy my amp beacuse of the extra current draw and heat generated over 6550s.

When I drew their attantion to the fact that the recommendation to use KT88s came from Jadis, I was told by the boss that the their tech new better than Jadis.

So I fear that rationality has left the building and has been replaced with bluff, bluster and bs.

I welcolme any comments.
_

Jadis DA60 can use any tube among the EL34/6CA7/KT77 and 6550/KT88/KT90 variants. Jadis says it themselves, and I've done so as well in mine with no problems whatsoever. Why do you need anything more than what the people who build the amplifier have to say on the matter?

For the record my preference is EL34 first, KT77 second, then KT88, but that's why they make vanilla and chocolate. Use whatever sounds best to you knowing that the amp will play beautiful music with no issues whatsoever with your choice. It's difficult for me to think of a better, more musical amplifier than the Jadis integrateds.

When I picked the amp after its repair I was told that all the problems were my fault for using the wrong valves (Tung Sol 6550 reissues), and that the new Genalex KT88 reissuess could not run in my amp and would soon destroy it. And there woud be no warranty on the repair.

Without plugging the amp in I took it to David Peach of Peach Audio at Balmain in Sydney. He found that the heater voltage was set to 13.85V instead of the correct 12.6V (two KT88s in series), and there was a dry solder joint on a new cap.

I asked him to make the amp reliable and he designed and made the following changes:

· Removed the cathode fuses and instead fused the anodes as per http://www.audionote.co.uk/articles/tweak_fusing_valves.shtml

· Each pair of valves was previously cathode biased. Now every valve is cathode biased.

· He protected the output transformers from back EMF by installing shunting diodes.

· Changed the transformer taps from 4 Ohms to 8 Ohms to suit my speakers

· Reset the heater voltage

My amp is now back and sounds and works great. Peach Audio is highly recommended.

http://www.audionote.co.uk/articles/tweak_fusing_valves.shtml