6550 tube vs KT88

Thanks Tvad I'll order that issue. I think the issue here is that my Seas speakers area MTM design rated at 87db, so its just not a match for the KT88 I demoed nor the EH88's that I rolloed in my JOR.
db rating must be 90+ to be effective.
This is the one drawback with Seas speakers, few tube amps can bring out the dynamics. The Jadis is one that can meet these demands, as their web site says, "our amps can drive any speaker" and they can. I've put their smallest amp to the test.
Not sure how the Jadis 88 tubes image? vs the 90's I'm using.
The thing is, if I order a Jadis amp in the future, I may just stay with the 90, as I like the sound. And may not be willing to give up the characteristics of the 90 in order to gain some benifits of the 88's or 6550's.
Trade off's are a part of this audio realm. But if it isn't broke, don't fix it.

Bartokfan,

>> I think the issue here is that my Seas speakers area
>> MTM design rated at 87db, so its just not a match for
>> the KT88
I do not understand this convoluted logic! what does 87dB SPL/W/m have to do with compatibility with KT88 output tubes?

what is the bias voltage set at for the KT88 tubes?
(for example, in my 502A the recommended bias voltage for 6550 tubes is 50mV. However, KT88 work better in this amp when their bias is set at 55mV i.e. driven slightly harder).

As far as I can tell: you do not have sufficient power amp output wattage to drive is mid-low efficiency speaker. Correct?
If so, please do not blame your lack of output power wattage on the sonics of the KT88!

Bartokfan, you should do some homework before writing, because you really don't know wtf you're talking about.

Your Jadis Orchestra (correct?) at 40wpc simply does not have enough power to drive 87db/1w/1m loudspeakers. It doesn't matter what tubes you're using. You don't have enough juice to recreate dynamic passages, especially in classical music. Period.

The following is taken from a review of the Orchestra here on Audiogon.

The limited power output means it struggles with vivid dynamic passages at loud volumes. It really can't render a concert grand without clipping - as a trial I'd suggest Emil Gilels' recording on DG of Beethoven's "Pathetique" - the chords crash and so does the amplifier. Yet, turn down the volume to what you might experience twenty rows back in an auditorium, and everything is fine - fantastic ambience, wonderful tone.

You might find some KT88 tubes that work well in the JOR, and they might be found in the Vacuum Tube Valley Issue 19, but your problem with the sound of KT88 tubes has nothing to do with the tubes, and everything to do with your mating of a 40wpc tube amp with 87db/1w/1m loudspeakers.

I owned a KT88 tube amp that produced 110wpc, and it created clean sound pressure levels of 105+db in my listening room with moderately sensitive loudspeakers like yours.

IMO, FWIW, Amen, All Praise to Allah.

Kumbaya.

Tvad, I beg to differ on a nit. Bartock fan does "know wtf" he's talking about. He understands himself perfectly. The problem is that nobody else does!

Perhaps in his ability to judge the performance of tubes sans amps (other than his JOR) and drivers without speaker systems (other than his Thors) his is an idiot savant, perhaps sans savant. For the life of me I don't know why anyone evens bothers to respond to his posts, they always evolove into a testimonial for KT90's (since I guess he decided against the KT88 based Cayin) and the superlative Seas drivers. I believe that is his initial intent when he posts. Too bad the word introspection is not one with which he is familar. If it were not so sad it would be funny.

IMHO, FWIW, Amen, All praise to Allah, and God Bless America............

I'm only reporting my experiments as a note to others who can use the info I provide. I'm saying that when I rooled the 90's to a quad of EH88's, all the timber/dynamics/sepaaration of bass/mids/highs had virtually disappeared when compared to the 90's.
Maybe the issue is that when you roll the JOR to 88's, the amp needs to be biased properly. Not sure how biasing could bring the 88's resolution up to the superior dynamics of the 90's. Maybe the Jadis stock 90's are a highly select tube for this amp. Gabriel did say Jadis 88 replacement tubes are expensive, possibly fora resaon. Not all tube amps are equal, maybe not all 88's are equal.
I also demo-eda 88 tube amp recently and found the very same results in the sound vs the JOR/KT90's.
The orchestral was flat, no peaks valleys in dynamics of fq's. Blues/jazz hada increase in dynamics, but not equal to the JOR90, not even close.
I should point out that the JOR does have tone controls and i use them to the max, at say 95% open. When I have the tone controls at neutral, 12 oclock, then the Jadis sounds exactly/very close like the 88 tube amp i demo-ed.
Maybe some feel that's not true musical image with the treble up, which beams the highs/steely, cold. But its the way i like it. I love the tingle and sparkle.
With the tone controls up to 95/98 % open I get to hear recessed instruments in the orchestra that CANNOT BE HEARD when treble is at say 50-75% open. Bass is also greatly extended at 95% open.

Its like the apature on a camera, more open lets more light in. Here the tone open allows a greater band width and more music comes through.

So open 95% the music is alive in the room. At 75% open the music has a image that its in the next room.
btw I listen with vol control at a very comfortable 25% open, 9 Oclock, maybe a tad more, but rarely. Its too loud for my taste at 10 oclock. I should also mention even at 11 pr 12 oclock vol, the sound is clean, not distorted.
With tone open 98% and vol at mid way, then the music is shattering loud.

The 88 tube amp i demoed vol at 9 oclock or 12 oclock, had little effects. The seas's showed no change in response.
Its kinda like that Audio esearch VS110 with 8 KT88's/LS12 pre with the Magnaplanars i heard the other day.
the salesman said, "if I turn the ARC to 10 oclock or up all the way, its the same, the maggies will not respond to any increase in vol" And it did so, sure enough, no change.

It was at that time I realized impedence load, some drivers were beasts on amps. I also realized how powerful Jadis makes its amps, even the tiny JOR has its muscle.