EH KT90's or Ei KT90's which ones??

[robster]

O.K. I'm ready to try KT90's in my VRD's which have the Valve Art KT88's now,what brand do yo prefer? EH KT90's or Ei KT90's and where should I buy them,Tube Depot or Upscale Audio? also what's u'r favorite 12AX7 in your VRD's Mullard,smooth plate Telefunkens or Bugle Boys?

Cheers,

Robert

[Lurch]

Check out the following from Jim McShane's website.....

Ei KT-90 Type I & II - All tubes have arrived! Matching underway now! I currently have a waiting
list for the tubes, and all may be spoken for. If any remain after the folks on the list are covered
they'll be posted here in a few weeks. Citation II owners need to know the type I (even singles) is a superb tube for the amp, I used them myself for 11 years! Pricing for either type will be 44.50/single, $87.50/pair, and $174.50/quad (if available).

New Update - KT-90 Type III Status! I burn in and match all KT-90s at 465 volts plate and screen,
and -50 on the grid. Current production type III KT-90s want to run 120 ma. or higher at that setting, so I have to adjust bias voltage to keep them from burning up. I adjust the bias to give me 85 ma. at 465 volts, or 39.5 watts, well under the dissipation limit of 50 watts. Within 60-90 seconds there's significant red on the plate. Many show red with as low as 65 ma cathode current, which is only 30 watts.

I cannot in good conscience sell these as full capability tubes until production quality improves. There are currently type III KT-90s being offered elsewhere - but not from me. If you purchase current production tubes you need to know that some vendors will not guarantee the tubes won't have the red plate issue. If you buy current stock - just be sure you know what you are getting and are okay with that. There was a recent report stating current production (last few months) type III had improved, so in June 2005 I purchased some from a major distributor to check. Here are my observations:

1. Build quality - the pins were soldered properly and the bottles were straight. That is an improvement over over what was being sent out 6-12 months ago. The lettering appears to be a paint now (a la JJ) as opposed to the prior Telefunken-like chalky lettering. In this area the tubes are better than a few months ago.

2. They still have the red plate problem, it is still apparent. Large numbers of screen grid wires glowing white hot, red in the plate creases at less than 40 watts dissipation (the tube is rated at 50 watts), the red is visible in just a minute or two in a room with low light levels (one shaded outside window, no artificial lights on). Clearly the screens are still misaligned - and as Eric Barbour said, this will shorten tube life and increase distortion.

So there may be some hope - in that the "visible" quality issues seem to have improved. But the internals are still suffering from the same problems as they have for the last few years. As always, there may be a small percentage of the tubes that end up without the red plate/glowing screens problem, but most apparently still have it. Therefore I cannot recommend the type III at this time. If you buy type III for a Citation II or any high dissipation application you do so at your own risk IMHO. If you want to use these tubes in low stress aplications that's up to you, but I won't be stocking them at this time. I will re-sample again in about 90 days. Maybe they are on the road back - but they aren't there yet...

I'll try to keep everyone posted on this issue since this tube is perfect for Citation II (and many other) amps.

Some good news! I've conducted some careful listening tests of the Electro-Harmonix KT-88 in the Citation II amp. Is it as good as an Ei KT-90? Well, no. Is it far better than an EH KT-90? Yes! Is it a darn nice sounding tube? Yes! I gotta say, I like 'em! They have more of a top end tilt than the KT-90, and they don't have the incredible bottom end, so they tend to sound a bit less balanced than the Ei KT-90s. But after 4-5 hours use the bottom end gets better - which is good, 'cause at first they are really shrill sounding. Once broken in they make very nice music in a Citation II. They are definitely best when biased at 75 ma. Don't exceed 75 ma., as this stresses
the tube beyond it's ratings (or at least right to the limit!). They are very stable at 75 ma. as well.

They do nothing for me in triode though - the Ei KT-90s in triode still KILL anything else in triode. I recommend using the EH in the stock (ultralinear) configuration only.

The bottom line? They aren't as good as the KT-90s, but they are very enjoyable in Citation II gear. I can certainly recommend them, and my stock is tested at or over 75 ma. and ready to go! Electro-Harmonix KT-88s sell for $49.50 per pair, and $99.50 per quad.

He's up on the KT-90 situation because they are touted as the tube of choice for Citation IIs.

[robster]

Thanks Lurch,I've bought a few tubes from Jim McShane for my Fisher 400,he is SO NICE!!!

Cheers,

Robert

[mark1101]

So far I've tried the JJ KT-88s. They are definitely better IMHO than the Valve Arts, but they cost more too. They do sound better to me. I haven't tried any KT-90s. The EH tubes I've used in the past always performed well. I always liked the EH tubes.

What made the biggest difference though in the VRDs is the small tubes. By far. I have tried, JJs, Bugle Boys, and Telefunken smooth plates (12ax7 and 12au7) in addition to some other cheaper brands. By far the cleanest and detailed sounding to me are the bugle boys and they cost less than half as much as the Tele.

This is just my opinion, but one of the best examples of audophile nervosa is believing all the hype about the tele smooth plates. There are tubes that cost way less and sound better, period. I spent the money, tried several types and found that out for myself. The Telefunkens sound great, but they are NOT worth some of the ridiculous prices that are asked. I have the ribbed plates as well. Don't get burned. Bugle boys are a fantastic starting point. They are plentiful and fairly inexpensive.

After about $1500 worth of rolling I decided to just start listening to the music.

[robster]

Thanks Mark,

where's a good place to get the Bugle Boy's 12AX7's? Brent Jesse has them,but kinda pricey.

Cheers,

Robert

[mark1101]

Check out Antique Electronics.