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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Can you SEE (construction) how a tube SOUNDS?

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I've been wondering again;)

My amplifier uses 6U8 driver tubes, and I have tested some 8 different brands of these. Most of them look very alike (inner construction). I have found that the most pleasing to my ears (but it certainly isn't always easy to hear the difference!!!) are in this case EI, which have the most robust construction (getter is not mounted on a simple 'stick' but rests on a whole construction of metal pieces, there are also two little rectangular metal pieces that look as if installed to re- or deflect something:)). My second choice are the RCA's which have black plates on the triode-section, but for the rest look very much like the other brands I've listened to.

Can any of you experienced tubelovers tell me if I can generalise these findings to all the tubes, and secondly, can two tubes of the same type but of different makes that look quasi-identical have big differences in sound quality between them? If so, what is the invisible factor? (I've had Telefunken that look very much like cheap unlabeled Chinese tubes, but seem to sound better, although the 'name' might have influenced me a little!). And last but not least: what's the advantage of 'black plates'?

Many thanks,
I was wondering something similar and would also appreciate anyone with experience commenting! My experience wasn't about sound per se but still about seeing the difference in quality in construction.

I built a pair of monoblocks with 5U4-G rectifiers. The first set of tubes were Chinese and a few days after completion one of them began to flash on startup. After that is seemed OK and voltages and currents were fine. Worried about the flash I replaced them with Sovteks.

When I took the first Sovtek out of the box is simply looked more robust than the Chinese tubes. After several months now I've not had a single flash or other issue with the Sovteks.

I understand that my sample is not sufficient to draw any real conclusions but just anecdotally (sp?) in this case it seems that a quality difference is visible . It would be very interesting to hear if sound differences might be "seen".
Hello Sherman,

I've experienced the same 'flashing' of tubes when powering up and asked what it was in another forum: I'm not gonna go into the details, but in short it has something to do with the resistance of the filament when cold. It's no problem at all, no manufacturing error, doesn't hurt anyone or anything, so you can just use those tubes.

Interestingly the Ei tubes I rate so highly suffer(-ed? I don't know if they still do!) from it, and in the beginning I even heard some crunchy noises in the speakers when warming up. Quite some tubes exhibit this 'noisy start' and in my experience it disappears after a little while, I think it's just the flashes being (sonically) amplified. I don't think it's in any way related to the quality of the tube.

Another thing I forgot in my previous post: are D-getters better than Halo-getters? (they are surely more exotic)

DigitalJunkie said:
The filament "flash" is normal in some tube types,but is not the same thing as a rectifier arcing over.
I've had 2 Sovtek 5AR4's arc over in my ST-70,both in the exact same spot,the same side of the tube,right at the bottom of the cathode,it seems the gap there between A and K is really close.
Maybe Sovtek has recently fixed that?

My Chinese tube initially just flashed right at the top of the tube. After a few more days of use and being turned on and off two or three times a day the flash became longer in duration, starting at the top and moving toward the base, almost like a florescent light turning on.

No consensus was reached here that it was dangerous or even a serious fault. However after the time (and money) I put in on the amps I decided caution was in order and replaced them.

The Chinese tubes had something like a mica piece at the top while the Sovteks wrap the wire around a very different structure which to my untrained eye just looks more solid.
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