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Old 23rd April 2012, 04:48 AM   #31
popilin is offline popilin  Argentina
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Recall that the TV vertical output amplifier needs linear valves, nobody likes to see a distorted image.
Today we see the 6SN7 in hi-end audio, at a time was very common to see on TV (so the TV had vertical adjustment in the front )
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Old 23rd April 2012, 05:12 AM   #32
AJT is offline AJT  Philippines
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prices of sockets from china are going down, just the other day, i ordered 54pcs assorted sockets for just U$88 from goodcomponent.com.....
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Old 23rd April 2012, 12:51 PM   #33
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The tubes could be free, but a bigger tube with fewer sockets could still be cheaper.......Using 12GC6 you can make a very nice tube amp with cheap output transformer.
The 12GC6 is a good sized octal tube. The other ones I have in mind are even BIGGER!

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Recall that the TV vertical output amplifier needs linear valves
The 6SN7 was one of the first vertical sweep tubes. The 6BL7 and 6BX7 evolved from the 6SN7. The dual dissimilar triode came next, followed by the triode pentode combination like the 6LU8 or 6LR8. All make good audio amps. In fact the vertical output transformer from some TV sets work good as an audio OPT. The tube / transformer doesn't care if it is driving a deflecion yoke or a speaker. Most of the transformers are small enough to have good frequency response. You need one with 4 wires asince a few are autotransformers.

The horizontal (line) output tube operates as a switched CCS and was not designed with linearity in mind, however many work quite well as audio amps.

The video output tube is usually quite linear, has excellent gain into the VHF region, and also makes a good audio amp but are limited to 10 watts of dissipation and under. Some are good audio driver tubes like the venerable 12BY7.
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Old 23rd April 2012, 05:26 PM   #34
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Originally Posted by popilin View Post
Recall that the TV vertical output amplifier needs linear valves, nobody likes to see a distorted image.
Today we see the 6SN7 in hi-end audio, at a time was very common to see on TV (so the TV had vertical adjustment in the front )
The same about 6P15P: large linear swing. Nice as driver, and for small power outputs.
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Old 23rd April 2012, 05:53 PM   #35
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OMG! I just looked at vaccumtubes.net and they have another super sale on!!
Thanks to the smoking amp guy I couldn't say no. I just bought 1000 more tubes from VacuumTubes.net. If you spend an hour on the phone and buy enough tubes the price gets cheaper.
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Old 23rd April 2012, 07:39 PM   #36
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Holy Cow! Any interesting tubes left?

By the way, ESRC has an interesting 24 Watt sweep for $3, the 26DQ5.
Almost the same as a 6HJ5, but with a cap and octal base. Looks like a 6CB5.
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Last edited by smoking-amp; 23rd April 2012 at 07:44 PM.
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Old 23rd April 2012, 09:33 PM   #37
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Holy Cow! Any interesting tubes left?
I had been hesitant to mention a certain number since the Chinese had been buying them from ESRC by the 1000's. I discovered this gem when it hit the $1 lists over a year ago, but at 35 cents each I bought 500. It is the 6HA6/6HB6. This guy is a 6BQ5/EL84 with an odd pinout and twice the Gm. It can bang out 20 watts per pair in P-P without breaking a sweat. They can be seen here in one of Pete's red DRIVER boards putting out 7 watts in class A P-P. That will drive the grids right out of your favorite sweep tubes! Pin compatible with a 6EJ7, they plug right into Pete's board.

In the sweep tube department I grabbed 100 25DN6's. The specs show 15 watt plates, but the tubes say otherwise. I have extracted over 100 watts from a pair at the edge of glow. The plates of the RCA's and Sylvania's that I have in hand are about the same size as the 6HJ5's plates.

Speaking of 6HJ5's......I bought enough stuff to get a nice price on 100 of them. Expect some more BigWatt amps in the future. I will wire a few 6HJ5's together and see what happens.

I also got enough 50 cent tubes to make complete kits for the next Tubelab project board. It is amp 1.3 that was created in this thread:

The Hundred-Buck Amp Challenge

The picture shows the amp as it was last November. I still haven't finished the cabinet yet though. The schematic is still going through some changes. I have added a mosfet phase inverter so that the output tubes can run in class AB and crank out about 6 watts.
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File Type: jpg AlmostDone_A.jpg (251.8 KB, 1192 views)
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Old 24th April 2012, 02:38 AM   #38
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Very nice. Gotta love surfin' on the edge. Nice app! (to use the current vernacular).
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Old 25th April 2012, 12:37 AM   #39
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Did the big dumb blonde one stop to think how much 1000 tubes would weigh? NOOOOOO. The UPS man deposited two very large and heavy boxes on my front porch while I was at work today. Total weight 68 pounds.

I couldn't say no to these guys at 50 cents each! The 6922 is just for size comparison......those were not on sale. Actually they were free......I pulled them out of a junk scope.

Now I just need to find the time to light a few up.
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Old 25th April 2012, 02:11 AM   #40
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Interesting, they sure look bigger than a typical 15 Watter. Will be interesting to see what your "stress test" will produce. Might check the filament current draw just to see if the later versions still pull as much current as the 1955 datasheet specs. The 1955 date on the Sylvania datasheet would likely be using an old high temp cathode, while the later tube types got lower temp cathodes. Maybe they upgraded these later too.
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Last edited by smoking-amp; 25th April 2012 at 02:17 AM.
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