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Old 21st March 2014, 12:27 PM   #1
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Default All tube cap tube amp?

Hello,
Can anyone lead me in the direction of an amp schematic using 807 6sn7 and 6sl7 tubes? I'm looking from anywhere to 10-20 watts se or push pull. My plan is to make the amp with all grid cap tubes such as 2 2c22 tubes in place of 6sn7 tubes and 6c8 in place of the 6sl7. If anyone could provide a schematic it would be appreciated!
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Old 21st March 2014, 03:02 PM   #2
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The 807 is a 6L6GB with a different base and a top cap. So is the 6BG6. Most 807's have additional shielding around the lead frame that doesn't matter at audio. You can use any schematic that was drawn for a metal 6L6, 6L6GA, or 6L6GB since all of these tubes cary the same 19 watt plate and 270 volt screen grid ratings. A 6L6GC schematic could be used provided these ratings are not exceeded.

Some 807's and 6BG6GA's were built with 6L6GC and even 7027A guts inside. These were manufactured late in vacuum tube production usually by Sylvania/Philips, but I have seen some GE 807 with 6L6GC guts. These are not too common. They can be spotted by comparing the guts to a regular 807 and a 6L6GC. If you are sure that you have these tubes, ANY 6L6GC circuit can be used, and a pair of these can put out 50 watts, all day long, forever. Here is an example.

6BG6 To 6L6 Vacuum Tube List

When I got some of these they were $6 each. I got the adapters and stuck them in a Fender Bandmaster which would eat Chinese 6L6GC's in about 6 months. They are still in there (about 6 years ago).


If you really want uniqueness, get some 7193 tubes. They are 1/2 of a 6SN7 with TWO caps, one for the grid, and one for the plate.

I breadboarded an amp about 10 years ago that used an 815 for the P-P output tube. It has two pentodes with two plate caps and can make 15 to 20 watts output. It had two 7193's for the LTP splitter, and a pair of tiny HY-615 tubes for the first LTP. It is a short octal tube with a cap for the plate and grid that is similar to the 6C4. I never got around to building the complete amp and gave all the tubes to a friend a few years ago.
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Old 21st March 2014, 03:17 PM   #3
Magz is offline Magz  United States
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Tubelab,

He mentioned the 2C22, that's the same tube as the 7193. It's an excellent tube! Approximately 1/2 of a 6SN7, but much better sounding to my ears; they also like to run higher current than 6SN7. I was running them at 14.5mA in one of my preamps, and the sound is better than at the lower currents typical of the 6SN7.

I liked them so much I bought about 30 of them...then I discovered DHTs for preamps.


.

Last edited by Magz; 21st March 2014 at 03:22 PM.
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Old 21st March 2014, 03:51 PM   #4
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Quote:
Originally Posted by tubelab.com View Post
The 807 is a 6L6GB with a different base and a top cap. So is the 6BG6. Most 807's have additional shielding around the lead frame that doesn't matter at audio. You can use any schematic that was drawn for a metal 6L6, 6L6GA, or 6L6GB since all of these tubes cary the same 19 watt plate and 270 volt screen grid ratings. A 6L6GC schematic could be used provided these ratings are not exceeded.

Some 807's and 6BG6GA's were built with 6L6GC and even 7027A guts inside. These were manufactured late in vacuum tube production usually by Sylvania/Philips, but I have seen some GE 807 with 6L6GC guts. These are not too common. They can be spotted by comparing the guts to a regular 807 and a 6L6GC. If you are sure that you have these tubes, ANY 6L6GC circuit can be used, and a pair of these can put out 50 watts, all day long, forever. Here is an example.

6BG6 To 6L6 Vacuum Tube List

When I got some of these they were $6 each. I got the adapters and stuck them in a Fender Bandmaster which would eat Chinese 6L6GC's in about 6 months. They are still in there (about 6 years ago).


If you really want uniqueness, get some 7193 tubes. They are 1/2 of a 6SN7 with TWO caps, one for the grid, and one for the plate.

I breadboarded an amp about 10 years ago that used an 815 for the P-P output tube. It has two pentodes with two plate caps and can make 15 to 20 watts output. It had two 7193's for the LTP splitter, and a pair of tiny HY-615 tubes for the first LTP. It is a short octal tube with a cap for the plate and grid that is similar to the 6C4. I never got around to building the complete amp and gave all the tubes to a friend a few years ago.
Would you happen to have a schematic or any rough design parameters? The whole point of the build it build a unique amp and that sounds very interesting!
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Old 21st March 2014, 06:02 PM   #5
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Quote:
He mentioned the 2C22, that's the same tube as the 7193.
Cool, I never heard of the 2C22, didn't know it was the same thing.

Quote:
Would you happen to have a schematic or any rough design parameters?
I am in the process of packing up all my stuff and moving it all 1200 miles. I can't find S#$% right now. Some of it's here, some of it's there, and I am lost in the middle!

5 or 6 years ago, I did a remote design....I guessed at the design, and ChrisH tested my guesses on the other side of the world. Together we designed an amp that used 6SN7's and 6L6GC's to make anywhere between 20 and 50 WPC. Chris made a nice looking pair of mono blocks out of the design, and I still have my breadboard. The breadboard has been tested with everything from 300B's to big sweep tubes, and it works great. I will build an amp with that design, once I am settled into "retirement" whatever that is. I'm currently thinking 125 WPC with sweep tubes, but I also have a nice set of UTC LS57 OPT's and some DH pentodes that work in the breadboard, so maybe....two amps.

That design uses two LTP's DC coupled to each other. Most of my experiments have used 6SN7's for both tubes. This gives plenty of gain for any 6L6 type, even with some GNFB. It could drive triode wired KT88's to the 80 WPC range, but didn't quite have enough gain for big sweep tubes, 300B's or sweep tubes in screen drive. For those experiments I used a 6SL7 for the first stage. This required some resistor value changes.

When you need some boring reading to put you to sleep at night, look at the design thread....warning it is long, but if interested enough you can learn something.

6L6GC AB2 Amp
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Old 21st March 2014, 06:31 PM   #6
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The 6F8G is a twin triode that's electrically equivalent to the 6SN7, but has a top cap.

Once you have a 6SN7 equivalent, no other small signal type is needed. Use Williamson style topology.

If more power than that available from 807s is wanted, consider the TT21. The guts of the TT21 are identical to that of the KT88, but the plate is connected to a top cap.
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Old 21st March 2014, 06:53 PM   #7
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I have heard of the 6f8 but like I said I want to go a little more unusual tube lineup instead of the typical 12ax7 6sn7 807
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Old 21st March 2014, 07:47 PM   #8
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Quote:
Originally Posted by Tubes4321 View Post
Hello,
Can anyone lead me in the direction of an amp schematic using 807 6sn7 and 6sl7 tubes? I'm looking from anywhere to 10-20 watts se or push pull. My plan is to make the amp with all grid cap tubes such as 2 2c22 tubes in place of 6sn7 tubes and 6c8 in place of the 6sl7. If anyone could provide a schematic it would be appreciated!
I can do that: Vixen. This design can give you a definite 30W of output. 807 finals, and uses both the 6SN7-oids and 6SL7.
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Old 21st March 2014, 09:59 PM   #9
multi is offline multi  Australia
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If more power than that available from 807s is wanted, consider the TT21. The guts of the TT21 are identical to that of the KT88, but the plate is connected to a top cap. _Hope Tubes4231 has very deep pockets; TT21 cost a fortune, 807's dirt cheap!!
Phil
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Old 22nd March 2014, 03:26 AM   #10
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Quote:
Originally Posted by multi View Post
If more power than that available from 807s is wanted, consider the TT21. The guts of the TT21 are identical to that of the KT88, but the plate is connected to a top cap. _Hope Tubes4231 has very deep pockets; TT21 cost a fortune, 807's dirt cheap!!
Phil
12E1 are still available at not too ridiculous prices, but still not as cheap as 807's.
If enough space is available, the cheapest option is still parallel 807's.
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