tubes...

[aliveatfive]

It wasn't the *amp's fault. If you biased the quartets (and I'm sure you did) then somebody was asleep at the tube tester!! I'd send the whole quartet back and request a re-do

*NB it is true that sometimes a driver tube can "run away" and cause the power tube to be overdriven but that usually results in immediate failure of the PT. So I'm sticking to my story

Some NOS tube dealers refuse to sell output tubes if they know they're going into a VT 100. There have been known amp failures in the field. Mine had to be sent back to the factory a while ago, and then re-serviced by an indpendent tech for the same problem on the other channel. Some resistors were allegedly not spec'd prorperly. BTW, the amp has had no problems since the second repair job. I'd just be very careful about watching the output tubes of this amp. Also, I've carefully checked bias frequently. That did not prevent the original loss of a plate resistor with the original 6550s tubes installed.

 

[nsgarch]

There have been known amp failures in the field. That did not prevent the original loss of a plate resistor with the original 6550s tubes installed.

I had the same problem with a pair of M300 MkII monoblocks (8 tubes per side!) I had in the 90's. They would blow plate resistors. But then I had ARC modify them for triode operation and got some matched sets of real winged "C" Svetlana 6550's from Conus Audio in Canada and never had a problem again. Eugene, the Russian owner of Conus Audio, always seems to have the best quality tubes out of Russia. And he does the burn-in and matching himself (a lot of online tube dealers sell 'factory matched' tubes -- not good!) http://www.conusaudio.com/

ARC runs their tubes pretty hard, and it's a good idea to get the amp a little higher off the shelf than the stock feet allow (so the fan gets plenty of air.) I actually made big holes in the shelf of my amp stands right under the fan locations.

 

[twich54]

Nice mod Neil ! Yes proper air flow for tubes as well as Transistors IS IMPORTANT !

 

[User211]

Hola Roberto.....depending how much you'd want to spend, these have had a pretty good couple of reviews in the UK (HIFI+ iirc), but they sure ain't cheap!

http://www.euroaudioteam.com/kt88diamond.php

regards

Looks as though roberto is happy again. I used to buy the E.A.T. from http://www.rpm.fi/ when it was the Tesla Vrsovice, and significantly cheaper. Excellent, but for any other readers, I think I am going to add the provisio that if your tube amp drives it's tubes hard i.e. beyond 75% of rated spec, be aware that these may give up the ghost quite quickly. They did in my Air Tight - but some were replaced under warranty. It IS just possible this issue has been resolved by now, though, I suppose. Lesson - if you are going to buy some, MAKE SURE YOU GET GOOD WARRANTY TERMS BEFORE YOU SPLASH OUT. But when you hear what they are capable of, you will SMILE BIG TIME.

A pair in push-pull are a max rated output of around 100 Watts, so if you own an MC275, Air Tight ATM2 etc, be very careful.

 

[nsgarch]

Justin, I just checked and rpm has the Vrsovice KT88's for basically US $500/quad. I'd bet money they're exactly the same as what EAT sells for 3x that price! I might just have to try them! Air Tight runs tubes very hard. McIntosh the opposite -- one reason being their 'Unity Gain' circuit that draws power from the cathode and the plate, so they run pretty cool for their 90w/channel. Thanks for the link -- I didn't think these were available in the TESLA brand anymore.

 

[User211]

Neil, I can't remember his name now, but I do know he is a very pleasant and honest chap to deal with. Make sure he has some spares before you buy, or at that price, buy a couple extra. If you are sure the Mac circuit is SIGNIFICANTLY easier on the tubes, I think you will be OK.

The chap who sells them makes http://www.glim-audio.com/. So he has great tech knowledge to.

They are a very nice tube. They just oooooooze quality when you have them in your hands and you examine the internal construction. Probably one reason why E.A.T. thinks they can sell them at silly prices - the sound that comes out of them being another.

They look absolutely identical to the E.A.T. tube, apart from the nicer looking Tesla logo. But I think he must have reduced the price to clear his remaining stock - so double check how many he has left, and make your decision.

Also, check this review on the ATM2 - the one at the top is mine: http://www.audioreview.com/cat/amplification/amplifiers/air-tight/atm-2/PRD_124857_1583crx.aspx. I still have very fond memories of that amp.

Now I'd desperately like to try the KR 211 - he sells 845s but they do a KR 211 too - but 4 of those IS expensive! Also, I tried to buy some recently, and was informed there were supply problems... will get my hands on some someday. Current best is the RCA 211, with Amperex running second, GE third, Chinese fourth...

 

[nsgarch]

That's a great shot of the TESLA -- it does look just like the EAT!

 

[User211]

Yup - check http://www.euroaudioteam.com/pdfs/eat_factory_tour.pdf and watch the Tesla - soz, E.A.T. get made if you haven't already...

 

[nsgarch]

Justin, I received the following email:

Sorry, no NOS Tesla KT88 / RE40AK available anymore. Tesla stopped production in January 2006 and EAT bought the machines to Slovakia. I have a contact to EAT and I can ask for a price of a small batch, if you are really interested to buy quad(s). So far the inquiries have been so small that I did not really start with EAT yet.

Regards, Markus

I guess he just hasn't bothered to update his website in 2 years ;-)

 

[User211]

Actually, I am sure he did remove them - they went from where I found them on his site ages ago... can't see them now (didn't look to hard), but obviously you found a reference to them somewhere... must admit I was surprised - last time I spoke to him he didn't have many left from the last batch.

Forget it, then. And I expect the reason no one is asking is because of the price.

 

[roberto]

I had the same problem with a pair of M300 MkII monoblocks (8 tubes per side!) I had in the 90's. They would blow plate resistors. But then I had ARC modify them for triode operation and got some matched sets of real winged "C" Svetlana 6550's from Conus Audio in Canada and never had a problem again. Eugene, the Russian owner of Conus Audio, always seems to have the best quality tubes out of Russia. And he does the burn-in and matching himself (a lot of online tube dealers sell 'factory matched' tubes -- not good!) http://www.conusaudio.com/

ARC runs their tubes pretty hard, and it's a good idea to get the amp a little higher off the shelf than the stock feet allow (so the fan gets plenty of air.) I actually made big holes in the shelf of my amp stands right under the fan locations.

Hola...the tubes are Russians Svetlana 6550Cs...does the C means anything?I am very happy with my new sound, and listening music that I had forgotten...very nice indeed...happy listening,
Roberto.

 

[nsgarch]

for Roberto

Hola...the tubes are Russians Svetlana 6550Cs...does the C means anything?I am very happy with my new sound, and listening music that I had forgotten...very nice indeed...happy listening,Roberto.

New Sensor, the same company that bought the Genalex Gold Lion brand and the Tungsol brand, also bought the Svetlana brand. That is what ARC uses for their OEM 6550C. The REAL Svetlana tube (made in the original St. Petersburg factory) is now called the S.E.D company and they are sold as the "Winged C" and are the genuine Svetlana tube. You can tell by the square holes in the plate and the red base. and the "C" with the wings ;-) Next time you need tubes, get them from www.conusaudio.com They are better and cheaper than from ARC. You can also get them here: http://thetubestore.com/6550c.html

If you want to see a step-by-step bias lesson for the VT100 MkII go here and click on the pictures. It is an excellent reference: http://mycollins.net/audio/artube1.html Be sure to get plenty of sleep the night before!

 

[aliveatfive]

I was under the impression that ARC uses Winged C tubes in its new production. They certainly look like all the Winged C replacement 6550s that I have bought. (And that's quite a large quantity!)

 

[User211]

New Sensor, the same company that bought the Genalex Gold Lion brand and the Tungsol brand, also bought the Svetlana brand. That is what ARC uses for their OEM 6550C. The REAL Svetlana tube (made in the original St. Petersburg factory) is now called the S.E.D company and they are sold as the "Winged C" and are the genuinel Svetlana tube. You can tell by the square holes in the plate and the red base. and the "C" with the wings ;-) Next time you need tubes, get them from www.conusaudio.com They are better and cheaper than from ARC. You can also get them here: http://thetubestore.com/6550c.html

If you want to see a step-by-step bias lesson for the VT100 MkII go here and click on the pictures. It is an excellent reference: http://mycollins.net/audio/artube1.html Be sure to get plenty of sleep the night before!

Neil, I thought I was a KT88 nut, but I think you have me beat Tis a great valve. I wish I could teleport my 211 based amps into all KT88/6550 users homes for a dem, just to see what you all think. It is about time someone invented the Star Trek transporter.

All 211 based amps, and KT88 ones, were not created equal, however. But I can tell you that whilst the Air Tight ATM2 was and is a top rated amp, the 211s I have now blow them away... they are just so easy, musical and emotionally expressive...

I am not trying to get "one above" here, I am just saying what I know to be true. They should give 'em away with cornflakes in an ideal world - so all can witness.

In fact I have just thought of a very good way of putting it - given a sub-standard obviously poor recording, they absolutely make the best of it that they can, whereas a solid stater will expose it for all of it's flaws. I just want to hear it in with the best presentation possible and enjoy it - s*d the poor recording. But when you feed them something nice, they make your jaw drop in the best way possible - and it's presented like they aren't even trying - absolutely effortless - like - this is a cynch!

Waffle, waffle. Anyway, they are good I am sure not everyone would agree, however, and that's one of the things that makes the world an interesting place.

 

[roberto]

New Sensor, the same company that bought the Genalex Gold Lion brand and the Tungsol brand, also bought the Svetlana brand. That is what ARC uses for their OEM 6550C. The REAL Svetlana tube (made in the original St. Petersburg factory) is now called the S.E.D company and they are sold as the "Winged C" and are the genuinel Svetlana tube. You can tell by the square holes in the plate and the red base. and the "C" with the wings ;-) Next time you need tubes, get them from www.conusaudio.com They are better and cheaper than from ARC. You can also get them here: http://thetubestore.com/6550c.html

If you want to see a step-by-step bias lesson for the VT100 MkII go here and click on the pictures. It is an excellent reference: http://mycollins.net/audio/artube1.html Be sure to get plenty of sleep the night before!

Thanks nsgarch, just followed all the Mr. Collins instructions, and everything now is working as ARC made the design. I can not tell the difference prior new tubes and this adjustment, as I did with the new tubes versus my old ones but, I can say that everything perhaps is in a kind of sense of better ground noise, the sense of no noise at all...ideal for listening at late night, and enjoying my music as clean as spring water, fresh and odorless...thanks for sharing these instructions, and very easy to follow!! Happy listening,
Roberto.

 

[nsgarch]

I was under the impression that ARC uses Winged C tubes in its new production. They certainly look like all the Winged C replacement 6550s that I have bought. (And that's quite a large quantity!)

I may not be up on ARC's latest choice for their OEM tubes, sorry When I had ARC amps they were using original Sovtek 6550 (which were terrible!) then they changed to (original) Svetlana (which were very good.) It's certainly easy enough to tell the difference between the real St. Petersburg Svetlanas with the square holes in the plate, and the New Sensor 'Svetlanas' with the round holes in the plate. In the photo I posted for Roberto, it's really hard to see the "Winged C"
on the tube glass, but it's there.

That said, it now appears that New Sensor has decided that they are allowed to use the "Winged C" logo as well as the Svetlana name, I'm not sure. But as I said, if there is any doubt, check the plates! Here is the LATEST S.E.D. "Black Sable" cryoed 6550 from the SED St.Petersburg plant. http://www.tubedepot.com/bsct-6550c-sed.html Tube Depot also sells the regular SV6550C from SED who are obviously trying very hard to distiguish their (excellent) product from the New Sensor copies. Frankly, if I had ARC gear, I'd try to get some NOS 6550 Tungsols ;-)