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Old 1st April 2009, 05:00 PM   #11
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Quote:
Snap !Must have purchased about same time..
I couldn't have done better if I tried. I still have about 20 of these tubes still new in the carton. I have used them to test ideas that I am not sure of. I have about 3 of them that I have banged on pretty hard over the years. They have survived for 10 years, so I guess that they were built right.

I don't put these things in any circuit where rare of expensive components are at risk, since I have seen them fry in some violent ways. I think the biggest bang I got was when a cathode bypass cap exploded after the tube shorted and the resistor opened.

Here is one of them being used in a clip lead test amp. This is a CCS loaded trioded KT88. The big sweep tube is the CCS and the OPT is isolated form DC by a big oil cap. Nothing expensive will blow if the tube shorts since the CCS keeps everything in line.
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Old 1st April 2009, 07:37 PM   #12
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Have used Valve Art KT-88's for last two years in my ELLA Amp - haven't missed a beat...

430 volts, 55mA - biased using the DIYHS Auto Bias circuit - rock solid.
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Old 1st April 2009, 08:43 PM   #13
PB2 is offline PB2  United States
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Quote:
Originally posted by tubelab.com

The EH KT 88's in UL with some cathode feedback to lower the output impedance make the most powerful bass that I have ever heard come from a single ended amp. I run them hot at about 400 volts across the tube and 100 mA of current. The bass can be heard inside the house across the street. It is solid and not boomy. I have tried a bunch of other tubes in the same system and some give more detail, but none rock the house like the EH KT88.

Wondering if you've measured the output impedance, and perhaps peak power with the EH vs. other tubes.
Freq response as loaded by the speaker might also better demonstrate the differences. I'd expect more bass impact with higher output impedance actually since the LF rolloff Q will be higher.

I'm seriously interested in what gives the EHs better bass.

Pete B.
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Old 1st April 2009, 09:43 PM   #14
rknize is offline rknize  United States
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I have not tried EH KT-88, but I do have a set of SED KT-88s (then Svetlana). I ran them quite hard in an older amp and they survived just fine. I plan to try a pair in the SimpleSE biased good and hot once the chassis is done.

I can also vouch for the Tung-Sol 6550 reissues sounding nice (good bass on inefficient speakers), but I have only tried them in the Dynaco which doesn't push them very hard at all.

Russ
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Old 3rd April 2009, 12:44 AM   #15
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As far as current production tubes go my experiences with the EH output tubes has been very positive. Except for some 300B's I've used their tubes mostly in guitar amps, 6V6, 6L6, EL34, 6CA7,6550 and KT88 are the ones I've tried. The 6CA7 seems to be especially good and right now I'm using them in a Sovtek Mig 60 where I used to use the JJ E34L. They have a lot of headroom and they sound terrific in this amp. I want to try a set in my Hiwatt DR504 head too.

For what it's worth I have not cared for the EH small signal tubes but I've only used the 12AX7 and 12AY7 so I can't speak for all of them.

I do think there is some good stuff on the market if you're willing to give it a try.
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Old 3rd April 2009, 07:51 AM   #16
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I have a quad of Reflector 6550s lying about. Can anyone comment on their sonic characteristics? Their construction looks solid.
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Old 3rd April 2009, 03:26 PM   #17
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I've got the Tung-Sol reissues. Are you referring to Svetlana or Sovtek branded tubes?
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Old 3rd April 2009, 04:23 PM   #18
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Quote:
Originally posted by wrenchone
I have a quad of Reflector 6550s lying about. Can anyone comment on their sonic characteristics? Their construction looks solid.
Ah ha....don't be fooled by the construction...The ill-fated Ei KT90 with a plum sized anode looks beefy enough, but on many just wrap the tube with a knuckle and the fireworks start on the innards. Tube amps sitting on top of bass bins looks good, not the right place for these tubes.

ps. A good and reliable substitute to the 12AX7 is the JJ ECC83S. The batch of 100 I had were remarkably consistent. Agree ?

richy
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Old 3rd April 2009, 05:09 PM   #19
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I have a quad of Reflector 6550s lying about.
There have been a lot of Reflector sourced tubes that contained the digits 6550 over the years. I used Sovtek 6550 WA in some of my monster guitar amps of years past. They worked very well in that respect, and held up well. I still have a few. They take a long time for the bias to stabilize (some are in the 5 to 10 minute range) but they have been used a lot. In fact these were my favorite tube until New Sensor lost my business and respect over some junk Sovtek 300B's. I did not use any New Sensor tube until I bought a box full of returns cheap and discovered the EH tubes.

They sound good in a Simple SE, but have less bass then the current production EH tubes and really don't like to eat 40 watts either. I have a set of vintage GE 6550's that have a much cleaner sound, but even less bass. Again these observations are with the Simple SE connected to 15 inch OB speakers. The EH tubes are cranked to 100 mA, the others at about 75 mA.

The picture changes when I connect my Yamaha NS-10's. All tubes have similar bass response since the speaker is the limiting factor, although KT88's and 6550's have noticibly more bass than EL34's or 6L6GC's.

Quote:
The ill-fated Ei KT90 with a plum sized anode looks beefy enough, but on many just wrap the tube with a knuckle and the fireworks start on the innards.
Ditto the original Chinese KT88. It looks wicked until the fireworks start. You don't even need to thump them, they will fry all by themselves, but put them in a guitar amp that sits on top of the speaker and watch the light show. Wicked sounds come out of the speaker too!
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Old 3rd April 2009, 07:37 PM   #20
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I have a quad of EH KT90s that I bought years ago but never used. I went to put them into the ST70 recently after a JJ KT77 exploded and noticed one of the cathodes had slide down out of the top mica. I was able to smack it against my palm a few times and get it back into place. They all biased in fine after that and I put a few dozen hours on them before I finally got replacement JJ KT77s. They sounded good and gentle tapping didn't not move the cathodes. These were the tall, skinny ones that I believe are modified sweep tubes of some sort (PL509?). They sounded good and looked at home in the Dynaco.

Russ
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