Jadis DA60

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

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.

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.

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.
_

I also live in Sydney. email me offline and let me know who the technician is. If it is the same guy, he is very experienced and knows what he is talking about.

If not I will give you the othertube guys details

cheers

Hi. I'm from Sydney, and own a Jadis Orchestra Reference; prior to this I had tube amps from Audio Research - these had problems repeatedly. Audio Connection, while very polite and helpful, could not solve the problems - the technicians seem prone to blame any problem whatsoever on "the tubes". I've also had warnings that the "wrong tubes" will "blow the transformers" - frankly, the technician did not seem altogether familiar with recommendations straight from Jadis - thus the Orchestra Reference explicitly is built for KT88s,KT90s,along with EL 34s, but the tech guy said the former tubes would blow the transformers (the original Orchestra was, indeed, built solely for the lower output tubes; but, hey, he had my amp sitting right in front of him, so he knew we were discussing the Reference). Needless to add JJKT88s performed flawlessly for two years.

Given your story, my advice would be to sell the DA60 back to Audio Connection, and trade to something new with a warranty - it's worth asking Joe to give you an extended warranty, which he might well do for free. Otherwise you might well end up throwing good money after bad. Alternately, have you considered shipping the amp back to Jadis for repair work?

All the best,
Rob

Thanks for your responses.

I naturally always have a load connected.

I myself have wondered why the fuse does not blow to protect the amp. The tech at the one Jadis dealer in Sydney said:

"It is true that there is never enough current to go through the valves to "burn out" the output transformer as such. In the instance of Jadis DA60 each valve is protected by a 200mA fuse, which means that if a current of more than 200mA going through, the fuse will blow.This is the theory. But in real life if one of the valve develops a flashover inside the envelop, it may not be high enough current to burn the fuse but the spike will cause a very high voltage back EMF on the primary of the transformer, which adds on the over 470 Volts already there, can and will puncture the thin layer of paper separating the layers of windings between the primary and the earthy potential of the secondary of the transformer."

Does that sound reasonable to anyone?

The transformers are not warrented for life, however Jadis in France did cut me good deal, but having said that they are still expensive.

I heard Treljas DA-60 and had to get one for myself. I thought of using EL-34s as it is my favorite output tube -until recently. I took Jim McShanes advice when retubing a 6550 amp . He said there is only one tube that I would like. It happened to be the Gold Lion Kt-88. I was never a KT-88 fan but he was very certain when I told him I wanted a forward midrange somewhat warm and of course euphonic sound.
I was extremely surprised by his accuracy it sounds great.
It is a very versatile amp. As Trelja says it doesn't seem to get unwound by anything.
Mine is rock steady. It is auto bias and so far has given me no problems. Even when accidently left on idle and despite screwing around with the input/pre tubes.

BTW Try 7613s for the 12AU7s and 5751s for 12AX7s. Personally I switch things around every so often. 7613s are all Heerlen Holland made Amperex tubes but usually labeled for computers they are quite expensive but truly different and truly better IMHO.
The 5751 story need not be repeated here but if you invest they are also expensive, some sound like garbage even if you pay for better tubes. Of note any blackplate will cost you more than a grey and 3 mica more than 2 mica.. It wouldn't hurt to try the Jan Sylvania/Phillips variety for $20. You will get the transparency thing I'm sure.
Last night I put in 2 Tungsram ecc82 and a 7613 in the center and left the Mullard ECC83s for the 12AX7s in place. It sounds great but tubes are a luxury and still and can cost you a lot of money for crap. Now prices are coming off slightly as the market is full of sellers not buyers. Soon they will be even lower but the supply of NOS is just about gone already.
Finally make sure you don't have a modded amp. There is some clown modding an amp that needs modding the least and ruins the sound.
Haven't clipped it so far and I like it loud. Keeping my fingers crossed though.

Yoh,
Hmmm--Sounds like a faulty batch of output Trans poss'-- if you are doing everything right as Trelja states any fault arising from the Tubes will blow the 180R across the tube( you can see it large dark green one). I must admit not having heard of many output Trannies going south ,however Jadis Power ones set for 220v HGK market finding their way to Aust will hoof it with our 240/250 v surges.

Have you tried this Tech-- he poss could help in Sydney

joseph.barkoczy@audioconnection.com.au

Best,
DesW

I used to own an Orchestra Reference, and currently have a DA30 and DA60. In my experience, in addition to being some of the most glorious sounding components, Jadis integrateds are as reliable as anything on the market. In fact, in my system, they've been flat out bulletproof. I've often heard Jadis transformers are warranteed for life, so if you bought the amp new, there should not be too much of an issue for you.

Since Jadis integrateds fuse each output tube, the statement of your technician doesn't seem especially plausible. In my JOR, I had a fully shorted KT90 output tube that caused absolutely no damage to the amp whatsoever. A bad tube would blow a fuse long before a transformer.

I realize this is not going to come across well, but my guess is that the problem is you. Do you have a load (loudspeakers) hooked up to the amplifier at all times? Running a tube amp without a load is a surefire way to blow the output transformers. The vast majority of tube amplifiers that have been built since day 1 have never had a problem with their transformers despite seeing a lot of bad tubes - look at all the vintage Dynacos, Fishers, Scotts, etc. that can be brought back to life even after decades of neglect.