OT: Show us your DIY tube amps

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Originally Posted by alancohen

I guess different strokes for different folks. I can't think of any successful amplifier designer/manufacturer that would include in their marketing literature the phrase, "We could care less if your tubes last 2000 hours or 10,000 hours."

Reliability in any piece of equipment is not the main thing, it's everything. Personally, I would never buy an amplifier where I had to worry about tubes frying every time I turn it on. And I really can't see how pushing a tube to its limits enhances anything. It might boost a little power, but it can't improve its sonic characteristics. I find it hard to believe you have to sacrifice reliability to gain performance.

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The question is what do you define as reliability? The amps themselves are typically bullet proof, at least the ones I've seen him build himself. Tubes are actually a disposable, and when they were in general use, that's how they were viewed. Today, we have a skewed view of them because they are a niche product, and not the only game in town. Even I remember when you could go down to the drug store and stick the tubes out of your TV into a floor standing tester and check them out. If your TV was more likely to pull in that station just on the edge of your viewing area, would you care so much if you had to change the tubes more often?

So in this respect, the marketing would emphasize "greater dynamic range, and more true power to your speakers" rather than "gentle on your tubes" If your tubes last you 2 years instead of 4 years, how does that compare to the investment cost of a couple of Cary monoblocks? Besides, these amps are all designed with new manufacture, and readily available tubes. If you want to put your 60 year old Western Electrics in them, then you might have an tech damp down the bias current and dial back the amp. Lastly, if you can justify your last statement on power versus sonic characteristics with some scientific info, say discussion of various tube curves and power dissipation, I would be more likely to lend some credence to it. Dennis has been building tube amps for close to 50 years, and I doubt there are many people around that know more about it than he does.

I would be constantly listening for audible artifacts due to tube deterioration if the tube plates were glowing.

I have 4 NOS Siemans EL34 that have been cold all their life, i.e. they have never left their boxes. Anybody know where I can get an Octal to TO3 adapter?

If you can not make out the printing on a tube , breathe on it. The moist air will pick up the print.
My last tube amp was a HK Citation II. It had a 6550 short , and took out a 605A . I had replace both the woofer coil and HF phram
Don

If an amp runs tubes hard, the tube can go thermo and red-pate, which can take out a lot of internal parts. I have seen this happen, blowing up not only the fuses, but caps and resistors and even chokes. I had it happen more than once on Cary gear (with all the parts mentioned), and is half the reason I let them go. The other half is that DHTs sounded better...

Dont get me wrong, the did sound pretty good tho. As my tech said, "guitar amps always sound the best right before they blow".

Another opinion I have noted is that overbiased tubes sound grainy??

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Originally Posted by analog addict

The question is what do you define as reliability? The amps themselves are typically bullet proof, at least the ones I've seen him build himself. Tubes are actually a disposable, and when they were in general use, that's how they were viewed.

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My 15W OTL is not self biasing. There are two bias pots on the back that control the bias voltage. With 5W resistors across the speaker terminals the voltage should read zero when no signal is present. Basically it should just idle. I can easily turn it up and increase the volume of the amp, but at the expense of the tubes. Even though surrounding components are protected by local fuses on each tube should they blow, I choose not to alter the design paramenters of the amp for the sake of a few more watts. It runs 5-6 hours a day and hardly gets winded. That's my idea of reliability.

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Originally Posted by gortnipper

Youre welcome!

The Svetlana's are not that great, I have a pair and I am not impressed with them at all. Nor am I with the bog-standard Chinese ones. I think JJ (got a pair with the red amp) and TJ meshies are the good, albeit slightly pricier priced options. I am very impressed with my EML 2A3 tubes (nice birthday pressie!), and I am sure their 300B are great as well, but they are very expensive.

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JJ is local to me, so good option. I'll check them out. The Svets suffer from flimsy grids that flex around and run into the grids at turn on after a number of hours. I prpbably should have added a time delay for the plates........oh well.
They are also quite michrophonic, but that may be the case with all 300B, the grid is long.
On the dull red plates, within a set of tubes, one might glow a smidge, the rest fine. Just not made like the good old days.
I'm still waiting to stumble on a case of NIB WE Engraved base tubes from someones attic. Ha!

I have 4 Heath W5M's modded with 6B4G and have a quad of the Sovtek versions, those are quite nice. Not sure if you can get them anymore though.....a baby 300B sort of.

Tube on dudes!

I have two sets of PSVANE HiFi matched quads ready for my 300B OTLs when the kits arrive. Not sure of the quality, but when you need 8 you need to economize a bit. At $75 each I'm not looking to replace them often.

http://www.hostboard.com/forums/hbmc...2013/05/41.jpg

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Originally Posted by RonSSS

I'm still waiting to stumble on a case of NIB WE Engraved base tubes from someones attic. Ha!

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I have a friend who buys/sells tube down here, and he went to look at an estate with a bunch in the garage. Looking throuh the cases of new and loose bottles, he saw a lot of NIB TV tubes, along with the usual suspects of rectifiers and 12A*7 stuff. But, in a box of loose tubes (mostly audio were six engraved base WE 300B. The owner said, "I dont want you to take all of those new tubes, you have to take some of the used ones as well.

Since he doesnt have a tester that will do four pin tubes, he brought them over and they all tested strong. They sound good, but not that $$$ good. I would rather have EMLs and pocket the difference. He made ~$4k each on a $500 total investment.

6moons audio reviews: 300B Redux
300B Shootout! by Thorsten Loesch

I did quite a bit of research before I bought my batch. The PSVANES have been getting some attention:

Psvane Treasure 300B T-II

It's an interesting story where, how and by who they are made, but they come in various quality levels. I got the lowest HiFi grade for $300/quad. The best go for $900/quad, but I wasn't ready to drop $1800 on tubes yet. Maybe...after I build these amps and they really sing...but that's a lot of ching for a poor workin' stiff.

From my experience, companies that make really fabulous stuff, don't make crap in their economy lines.