Extensive testing with power tubes in JVM - KT77, E34L, EH6CA7, =C= ..

doomsdaymachine

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I finally had a chance to do some extensive testing of a few different power tubes in the JVM205H, and thought I would post my findings, for those interested...

My volume was at 10:00 on the master, and 10:00 on the channel, which is pretty darn loud! I biased them all the same, at 37mV. Seems just about right, for all. Keep in mind, I play from older Gary Moore hard rock, to heavier 80's thrash, and Drop-D, chunky rhythms. I like a searing lead tone, thick with harmonics, and sustain for days, (but, who doesn't)??

I only utilize 3 channels/modes on the JVM - clean green, and orange & red on the OD's. I boost both OD's, with a Wylde OD - It's THE BEST I've found for boosting a Marshall, boutique or not! I've tried them all..

First up - JJ E34L's: NICE midrange, and good "EL34" sound, with a bit more THUMP, than other EL34's.. I dialed in good tones, NICE 80's/90's Mercyful Fate tones, but after some time, I just didn't find it "TIGHT" in the bottom end. It was more, but I found it "muffled", to some degree. Could be dialed out, but they just didn't "wow" me..

Next, EH 6CA7'S: Immediately, I thought, "BIGGER" tone than the E34L's. Certainly more highs, not as pronounced in the mids, but surely brighter, & clearer than the JJ E34L's. NICE thump! More bass? It's close, but I did find it clearer. These were a step up in tone, to the E34L's, but they have some high end, I found apparent. I like them well enough to keep them for spares, but still no "wow".

Next, the stock =C= SED's: I started experimenting right away, when I got the amp, but never really spent a whole lot of time, and was never really extensive about it. But, putting these back in, and biasing up to 37mV, (I think stock, I tested them at 26mV), these really sound good. Clear as a bell, nice punch, nice mids, nice aggression, but a tad bright. SWEET harmonics. Tighter bass than the E34L's, but not as warm. These do have some "wow" factor, biased up a little warmer I do like them, and have no problem keeping them in there!

Last - JJ KT77's: These are said to have an extended low end, as well as highs. They're also said to have LESS bass than E34L's, and not as aggressive. I BEG TO DIFFER. They have less mids, yes. Extended highs? I'd say clearer is more accurate. Extended bass? More than the SED's, more than the 6CA7's, and TIGHTER than the E34L's. I find it plenty aggressive, and MEAN AS HELL. If you're a metal guy -THESE ARE FOR YOU. I'm extremely pleased with them. They make my JVM sound "pissed off", for lack of a better description. Harmonics are abundant, chunky rhythm tones are tight & aggressive, and for me, these have that "wow", in spades. They will STAY IN!! The SED's would be my go-to back-ups, 6CA7's my third choice, and E34L's, may last. They ALL are more than adequate replacements, but the KT77's are the shit, for my JVM. They kick all sorts of ass!
 

big dooley

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the JJ KT77's were a winner in my DSL and my JVM as well, when comparing with others... and i'm not even a metal player
but i'd like to try the JJ 6CA7's next time...
 

mickeydg5

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Thanks for sharing and great descriptions.
I will have to try KT77 tubes one day.

One question please, did any of the tubes have ratings like soft-med-hard or numbers? If so please share.

Thanks man!
 

doomsdaymachine

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i'd like to try the JJ 6CA7's next time..

ME TOO! The EH's are kinda bright. I just wonder if the New Sensor Mullard EL34's are like that. I tried the Tungsol EL34B's in my Blackstar I had, but the KT77's beat them out too. Just like they did in my Laney TT50 - They shit all over the stock TAD's, (Shuguang). They REALLY sounded badass in the Peavey JSX I had.

I think I'm seeing a trend - they seem to get it done in all my amps.:wtf: :lol:
 

doomsdaymachine

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Thanks for sharing and great descriptions.
I will have to try KT77 tubes one day.

One question please, did any of the tubes have ratings like soft-med-hard or numbers? If so please share.

Thanks man!

E34L's, & 6CA7's came from Tube Depot. KT77's came from Bob at Eurotubes. I generally ask for an earlier break-up.

Any GOOD tube supplier will test, and grade, with numbers on the box.
 

diesect20022000

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I found i MOSTLY agreed with your tonal comparison/contrasts. I like the E34L's more than the SED's and the EH6ca7's.

I found the SED's to be harmonicaly dense but, feel apart in the lows ESPECIALY once turned up and the 6ca7's were a bit stiff and harsh.

the KT-77's are my power tube of choice though.

I find they retain MOST of the EL34's mids while adding a ruby 6l6gcm-str type glassy top and round bottom on them and stay tight or rather get TIGHTER with volume and, meaner yes.

They are the clear winner for me, second is E34L's, next SED's and last and least, EH6ca7's.
 

FFXIhealer

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FFXIhealer

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I thought it was a vacuum tube. Maybe you should explain to me what you mean by "snake oil." Are they, uh, padding their page to make it sound better? Should I just get another EH 12AX7 in there instead?
 

RobS

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Good review.

Have you tried the standard JJEL34?

I have a set of these in my 800 at the moment and really like them.

rob
 

big dooley

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I thought it was a vacuum tube. Maybe you should explain to me what you mean by "snake oil." Are they, uh, padding their page to make it sound better? Should I just get another EH 12AX7 in there instead?

they say that it's better when you put a balanced triode tube in the PI position... what they don't tell you is that the circuit itself isn't balanced at all... it's just a way to get more cash out of your wallet.... snake oil....
 

Adrian R

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What I like about the E34Ls is their apparent extended headroom..They have great mids, as ALL JJ tubes have..but the 34Ls just GET LOUDER, and are priced very reasonably...great tube FOR THE MONEY....

The KT77s imo sound ALLOT like the E34Ls..

T/SOL 34bs..real bass heavy...
 

Fusedbrain

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I'm not the op ( this is an old thread ) but they bias up exactly like EL34's. Bias at 60% - 65% and your results will likely be similar to the op's.

The exact milliamp number is not always transferable between amps. The plate voltage will determine what the exact milliamp value would be for a given % plate dissipation. The bias in my Ecstasy 101B is set at 28ma, but the plate voltage is 540volts, so the current is set way lower than if the plate voltage was only 420volts

I run the KT77's in my DSL100 & Bogner at around 60% in both amps. Sounds killer!!! Great for the heavier styles :hbang:
 

Diego OS

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Hi
do you have to make any modifications to use KT77? just adjust the bias?
 

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