Dim Preamp Tubes.

[nonamemx]

My main amp is a Laney Pro Tube head, 100w, all tube. Its got 4 JJ's EL34L and 2 Electro Harmonix 12AX7EH's in the V1 and V2, and then two JJ ECC83S tubes in the V3 and V4.


The Electro Harmonix tubes sound wonderful, I love them in this amp. But. . .they are very very dim compared to the other tubes, you can barely see any light at all being emitted from them when the amp is on. The JJ's glow regularly, and no matter where any of my Electro Harmonix tubes are placed, they simply dont glow much at all! The thing sounds WONDERFUL, but. . .I did have it fail on me the other day, but all was fixed when replaced the Electro Harmonix tubes out of it.

So. . .it leads me to believe that the EH tubes simply aren't compatable with other tubes in the same amp. Its very strange, and I REALLY want to use the Electro Harmonix because they are the best sounding, lowest noise tubes I have.

Can anyone help me sort this out? thanks!

[DonP]

Different manufacturers use different materials. The whole idea of the heater is to get the cathode pumping out electrons to the plate. Some cathode materials are more efficient and don't need as much heat.

Cool amp - I have an AOR 50 head and a 1x12 AOR 50 combo.

[toejam]

The Electro Harmonix tubes sound wonderful, I love them in this amp. But. . .they are very very dim compared to the other tubes

Since they sound fine, they are fine. Preamp tubes aren't really supposed to glow all that bright compared to power amp tubes.

[nonamemx]

Different manufacturers use different materials. The whole idea of the heater is to get the cathode pumping out electrons to the plate. Some cathode materials are more efficient and don't need as much heat.

Cool amp - I have an AOR 50 head and a 1x12 AOR 50 combo.

Yeah, but these are the only tubes that Ive seen do anything like this. They dont even look like they're lit unless you examine them really closely.


Its definately a cool amp, I love the thing. I've had it for a year just about (I
got it last June I think) and I'm still enjoying the tone. Its far from perfect, but the character is so unique, its so punchy, gainy, juicy, twangy, clear, deep, beefy, bassy, glassy, natural, organic, the adjectives go on forever. It impresses me every day.

Since they sound fine, they are fine. Preamp tubes aren't really supposed to glow all that bright compared to power amp tubes.

I know that power tubes are obviously brighter, but Im talking about the preamp tubes only. It has 4 preamp tubes, two are JJ's (V3 and V4) and the other 2 are the Electro Harmonics (V1 and V2). The JJ's glow fine, but the Electro Harmonics dont even seem to be lighting up at all, unless you get out a magnifying glass and then you can see that there is a pin-head sized dot of orange glow inside them.

I used to assume that if it sounds fine, it is fine, BUT a couple days ago I had a mixture of chinese, GT, JJ and EH in it, and I had a EH in the V1, and the thing did a very wierd cut out. I hit the standby, and I usually start hitting chords for fun when it starts to "Fade In" (you know what Im talking about) It would work until it had faded in completely to the normal level, at which point it would go "THUNK!" (Kind of a thumping sound, not extremely loud) and then I would get NO sound at all, just a strange buzzing. I turned the amp on and off a couple times, trying to see if it was just a fluke, but the problem remained until I swapped out the preamp tubes, then it worked fine and has been. I somewhat suspected the EH tube, since it wasn't glowing much at all compared to the other 3 preamp tubes.

[parntz145]

[QUOTE=nonamemx]Yeah, but these are the only tubes that Ive seen do anything like this. They dont even look like they're lit unless you examine them really closely.

This is normal. Have you ever checked out the Sovtek LPS 12ax7? You cant even tell they are on. Dont worry about the tubes they are fine. When I had a Mesa triaxis I used the same tubes as you and they did the same thing. Your tubes are fine.

[nonamemx]

ok, Great. Rests my concerns at ease.



New Question:

Electro Harmonix are made in Russia. Does this mean they are made by Sovtek? if they are, are they the same as normal sovteks? (I.E. Relabeled)

[toejam]

This is normal. Have you ever checked out the Sovtek LPS 12ax7? You cant even tell they are on.

Yeah, I've got a pair of those in my THD Univalve head at the moment. I also noticed they were even less bright than the EH, JJ, GT or Mesa tubes that I sometimes use.