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Old 30th June 2008, 12:28 AM   #1
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Default A few pretty pictures and an ugly picture

About 10 years ago I bought a box of tubes at the Miami hamfest. It contained 3 Western Electric 367A's and some other WE tubes and goodies. The 367A is like a 350B with a different pinout in a strangely shaped bottle. Both are relatives of the 6L6GB. Whatever piece of WE equipment that used these tubes must have used 3 of them because they seem to be found in threes. I have been saving these for eventual use in a P-P amp with the UTC transformers that I have also been saving. This would require 4 tubes. I have been looking for more of these but they seem to be expensive. A recent auction on Ebay for 3 used 367A's closed at $528! OK, it looks like these things have gone FAR out of my price range.

I decided to modify a Simple SE amp to accept the 367A's so I could see what tubes could possibly be worth that much money.
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Old 30th June 2008, 12:35 AM   #2
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I set the Simple SE up in triode mode with no feedback using the big Edcor 5K ohm OPT's. This setup is the most revealing of the tube's true sound. I put in two of the 367A's, let them run in for about 20 minutes and made some measurements. I set the B+ at 380 volts which puts about 350 volts across the tube. Current is about 55 mA per tube. Power output is 4.2 watts on one channel and 4.4 on the other channel at 5% distortion. Distortion at 1 watt is 1.2 and 1.3%.

The picture below shows the setup running at 3 WPC.
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Old 30th June 2008, 12:45 AM   #3
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I hooked up a pair of speakers and the CD player and listened for a while. These tubes DO sound nice. Far better than my usual Chinese 6L6GC's. I believe that they sound better than any of the 6L6 types that I have tried, but A-B comparisons are impossible due to the unusual pinout. Note the second pair of tube sockets sky wired on top of the originals.

I let the amp play all day long, stopping in to listen to it for a total of about two hours. I am trying to justify keeping it.
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Old 30th June 2008, 12:54 AM   #4
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Earlier this evening I put in the third 367A tube. When I powered up the amp the tube lit up like one of my gassy 6V6's. The resulting arc blew the screen grid resistor in half, then the 5 watt cathode resistor opened, followed shortly by the cathode bypass capacitor exploding! This is the same board that blew its 63 volt capacitor during the 6V6 experiments, so I had installed 160 volt caps in preparation for some more toasted tubes.

I guess that I have 2 good 367A's. Maybe I'll put them on Ebay and use the money for some Edcor OPT's. I have too many amps already, and a whole bunch of wild ideas that beg to be tested.
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Old 30th June 2008, 03:35 AM   #5
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Cool stuff tubelab. Looks like them WE tubes had a little too much to eat, kinda got a flat tire goin'. Yea I'm sure you could much more wondrous things with the money raised by pawning them than you could with them. Keep the gassy tube pics a coming, they are always neat to look at.
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Old 30th June 2008, 06:27 AM   #6
DougL is offline DougL  United States
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George,

I am very happy to see that there is a lot of general interest in your work. Its well deserved.

Good Luck;

Doug
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Old 30th June 2008, 08:35 AM   #7
Salas is offline Salas  Greece
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I like very much the tubelab experiments. The gassy tubez series in particular. I have saved some pics and use them as wallpapers.

Also the tubelab amps are really hard test proven and great projects. Original DIY spirit included by the boatload.
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Old 30th June 2008, 11:41 AM   #8
poynton is offline poynton  United Kingdom
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Those are really sexy tubes - almost pornographic !
Maybe that's why the prices are so high?


Andy
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