What I don't understand about my Inspire KT88 SE amp is that many small tubes sound stressed and harsh in it, like 6V6, 6P3S-e, and 5881. But when I use EL84 plugged into an octal adapter, they sound good. At some point I may have to waste a few more dollars and pick up a couple 7189.

Easy to drive electrostats. I've driven them to more than adequate levels with my Inspire Fire Bottle KT88 SE amp.

I'm curious if it's possible to sample a pair of Tungsol KT150's in that amp? Does anyone know the answer to that? Thanks in advance for the assist. Oh, and the amp was built in 2014.

https://www.youtube.com/watch?v=jlR9B22kOiM

Kt150
 

Not even breathing hard or taking advantage of what it can do. One other designer I know doing safety stress testing was pushing way beyond the 650/850v max spec up to ~900/1100 volts held there sixty days straight just to see if they could burn it up. Not a glitch. I can hear a difference manually biasing each KT150 tube between 40,50,60 ma. 45ma per tube is a sweet spot in my current setup.

KT150 Spec sheet:
https://www.tungsol.com/specs/kt150-tung-sol.pdf

There wouldn't be much reason to use a KT150 in the "12wpc" Inspire amp. That is the version that produces 12wpc using KT88 tubes. The KT88 can produce that much power in a typical SEP design at acceptable distortion levels. If you install KT150, it will still produce 12wpc.

That is unless you happen to prefer the sound of a KT150 over a KT88. Personally I find that they sound fairly similar in that amp, comparing the new production Gold Lion KT88 vs the Tung-Sol KT150. YMMV.

Oh really. I was thinking that the Tung Sol KT150 would have a different sonic signature. So using the KT150 in the amp is a non issue but you don't feel their would be any sonic improvement over the KT88 Gold Lion's? Thank you for replying.

Here's the full description of the version I purchased.

An aside, the guy I purchased it from kept the GL KT88 and NOS RCA 6SN7. He include a pair of JJ KT77, an unlabeled 6SN7 and a JJ GZ34. But I got a good price, so I had no problem with that.

"FIRE-BOTTLE"
NEW HIGHER POWER
17 WATT PER CHANNEL
SINGLE-ENDED STEREO AMPLIFIER
KT-88/6550 TUBE
SINGLE-ENDED CLASS A

SPECIAL EDITION

"LATEST HO EDITION"

INSPIRE TUBE AMPLIFIER by DENNIS HAD FEATURING THE KT-88/6550 BEAM POWER VACCUM TUBE AMPLIFIER IN A SINGLE-ENDED CLASS A 17 WATT DESIGN

"INSPIRE FIRE-BOTTLE"

CLASS A, 17 WATT SE
KT-88 GENALEX OUTPUT TUBES
6SN7 INPUT DRIVER
5AR4, GZ-34 RECTIFIER TUBE
REGULATED OUTPUT KT-88 SCREEN GRID B+ VOLTAGE
REGULATED DC, B+ VOLTAGE ON DRIVER TUBE
REGULATED DC POSITIVE CATHODE BIAS ON DRIVER TUBE

INDIVIDUAL FILAMENT TRANSFORMERS FOR EACH OUTPUT TUBE

CUSTOM DESIGNED AIR-GAP 20 WATT OUTPUT TRANSFORMERS TO MATCH KT-88 TUBES AT FULL BANDWIDTH

I have designed and built in just about every special part but the kitchen sink in this new high output SE amplifier

Every Inspire amplifier and preamplifier is a new cool thing that never existed before today. I just love designing, building and sharing these single-ended class "A" amplifiers with music lovers in all corners of the world. After all these years I just love it!!!!!!!

This afternoon I am offering a special version of the original Fire-Bottle, powerful single-ended class A amplifier featuring the famous KT-88, 6550 output tubes. I gotta tell ya, the sonic presentation delivered by this amplifier will revitalize your musical enjoyment. You'll be listening to your record/music collection as if you were hearing the performers for the first time. This jewel delivers the emotion of the music ... big time. The amp plays like a 50 watter with amazing control and slam. I consider this a "life-time" amplifier.

If you have ever wondered about this single-ended vacuum tube audio craze ..... now is the time for an Inspire "Fire-Bottle" SE amplifier in your home listening room. No matter the choice of music you enjoy or the playback equipment you use, this affordable Inspire will reward the listener with the emotional impact and realism of the original score.

Thank you for your interest in the Inspire KT-88 HIGH POWER SPECIAL EDITION FIRE-BOTTLE offering and have a great day .........

Dennis J. Had W4USR Radioman731
retired Founder and President of Cary Audio Design

The tubes included with the Inspire "fire-Bottle" a pair of Genalex KT-88 output tubes , RCA 6SN7 NOS input tube along with a 5AR4/GZ34 rectifier tube

****** chassis finish is powder coat, Harley Black ******
Power Transformer 120/240 volt dual ac primary for operation in any country

Join the Inspire fun!!!!! .... Every body needs a single-ended class A Inspire audio amplifier ....

Dennis

I haven't seen Dennis post any new amps on eBay with more than 10 wpc for some time now. He seems to really like his "INSPIRE 6FLV-V SEP AMP." I'm sure it sounds wonderful.

He even seems to favor running it with metal 6F6 tubes, which would produce only 5 wpc. Anyone hear ever listen to this amp with the 6F6 tubes?

I heard the 6V6'er last week with all sorts of tubes including the 6F6 metals. They really did sound good, much to my surprise...

Have you run them with a 5Y3 rectifier?

Yes, and surprisingly to me, it made very little difference. A slight less harshness. Also tried 4 different pair of 6V6, all vintage. Treble forwardness, detail, and energy were well above what I hear from KT66, EL34, 6CA7, and KT88. Even noticeably above KT77, which is more detailed in a more natural sounding, open way.

Likewise the EL84 sounded good with 5Y3, 5V4GA, 5U4GB, and GZ34. I thought they would sound more relaxed and better with the lower voltage rectifiers. And maybe they did just a bit. But given that my Inspire EL84 amp came with a 274B as the stock rectifier, maybe this isn't too surprising.