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Dylan 10th April 2011 05:19 AM

6DJ8/6922 rolling... any general consensus on these?
I picked up a handful of tubes to play with in my new (and first) DIY amplifier, based on the Van Waarde 6DJ8+6AS7 OTL headphone amp. I got these for $5 a piece (braggart!) at a local antique mall, so how could I go wrong grabbing a bunch of brands to try?! :D

Here's what I picked up:

Amperex "Bugle Boy" 6DJ8/ECC88 (three of them)
Amperex plain white label 6DJ8/ECC88
Amperex "Orange Globe" JAN-6922 (Gold Pins)
Sylvania Green label JAN-6922 (Steel pins). There's a whole jar of these available if I want more.

All test good.

So how would you guys rank these tubes? I'm a newbie to critical tube listening, so I don't know quite how to describe them.

I personally am torn between the Amperex vs. Sylvania 6922. The Amperex seems a little more detailed, but almost too much? It seems there's not a thing in the signal path that doesn't get through this tube. The Sylvania is nice, with a bit less "edge." The Bugle Boys seem to have a quality I can't put my finger on, similarly for the plain white label. I seem to keep going back to the BBs.

I know it's ultimately up to what I like, but I was curious about other opinions given the huge selection (and prices!) of these tubes out there.

By the way, what's the usual going price on the Sylvania Green 6922? If anyone wants a few to play with without paying the $50 everyone seems to want, I could grab the rest of that jar I saw and pass them on for a bargain price.

Dylan 11th April 2011 07:33 AM

I just learned a lesson that might be helpful to other amp building newbies.

Don't immediately assume your design is perfect because it worked the first time, and that certain tubes you try later are "noisy."

I was about to can the Amperex 6922 as an option because I always heard an incredibly faint, but noticeable hum, but only when using that tube. I decided to open up the amp and do some poking around, because surely a tube wouldn't hum like that?

Turns out my amp likes the heater supply ground tied to B+ ground. Until now it had been floating. No more noise whatsoever, and the Amperex 6922 is finally getting a proper listen. It might become a favorite.

SY 11th April 2011 11:45 AM

Small differences in operating points will swamp any differences between those tube brands. Get the topology right, get the operating point right, and the tube brand won't matter very much except to collectors.

One other thing- layout. I had tried a particular ECC88 variant some years ago and found it to be noisy and microphonic compared to most of the others. All the others seemed fine. I stuck them back in my tube box and there they sat for 25 years. In the meantime, I had learned a few tricks; I pulled them back out of the box and tried them again. Dead quiet. The difference was their propensity to oscillate- they needed more effective grid-stopping than my old design provided.

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