Hey all!
After a long time in testing and development, I present the Modular Amplifier 1.
It uses a 6F12P as VA/PI, and 6N8S or 6SN7 (12SN7) as driver, and your choice of over 100 different triode connected tubes for PP output. Beam/Pentode/Tetrode or UL can be achieved by connecting only one side of the screen resistor, too (the other side being connected to the screen supply/UL tap accordingly).
The tube list is as follows:
Modular because each of the above output boards share the same footprint and so are swappable.
The amplifier is designed to run from a voltage doubler/quadrupler from 120V (or single/double on 230V) using an isolation xfmr, and the output can use my interleaved Triad PT as OPT method.
The result is an amplifier varying from 10WPC to 80WPC depending on tubes and iron choices.
PCBs are available. Schematic attached. The VA/PI now use two 100uF/400V caps in series instead of the 47u/600V in the schematic due to availability and cost.
Pictured: 6P36S output and 6P45S output, and 12GE5 output.
6P36S is using a 250VA PT and pairs of 100VA for OPT. 80mA idle
6P45S is using a 625VA PT and pairs of 250VA for OPT. 100mA idle
12GE5 is using a 300VA PT and pairs of 100VA for OPT. 60mA idle (Sold)
Some power numbers (I will update as I continue to run more tests). All tests done with B+ of 320-340V with a 2k2 load unless otherwise specified, 1 kHz sine driving to the point of clipping and backed off 1/10th volt input, triode connection (* audio tubes need higher plate voltage and higher Z loading than sweep tubes):
6DQ6GTB: 24WRMS
6P31S: 37WRMS
6P45S: 113WRMS (1k3 load, 30Hz, 2 tubes parallel)
*EL34: 12WRMS
*KT88/6550: 15WRMS
*6P3S: 6WRMS
12AV5/12GE5/12GT5: 24WRMS
After a long time in testing and development, I present the Modular Amplifier 1.
It uses a 6F12P as VA/PI, and 6N8S or 6SN7 (12SN7) as driver, and your choice of over 100 different triode connected tubes for PP output. Beam/Pentode/Tetrode or UL can be achieved by connecting only one side of the screen resistor, too (the other side being connected to the screen supply/UL tap accordingly).
The tube list is as follows:
Code:
MA-1 6CK Octal - 12AV5 17AV5 18A5 25AV5 6000 6AU5 6AV5 6DB5 6FW5
MA-1 9NH Magnoval - 6P36S 13GB5 18GB5 27GB5 28GB5 6GB5 EL500 EL504 PL500 PL504 6P44S
MA-1 7AC/8GT Octal - 7AC BASE: 12A6 12EF6 12EN6 12L6 12V6 12W6 1614 1621 1622 1631 1632 17L6 17W6 25A6 25B6 25C6 25L6 25W6 26E6 26L6 35L6 36L6 50C6 50L6 50L7 5824 5871 5881 5932 5992 5V6 6046 6550 6AG6 6AY5 6DG6 6EF6 6EY6 6EZ5 6F6 6G6 6K6 6L6 6P6S 6P3S 6U6 6V6 6W6 6Y6 7184 7408 7581 7EY6 8417 9EF6 EL33 EL35 EL37 KT32 KT61 KT63 KT66 KT67 KT71 KT76 KT77 KT88 KT120 KT150 PL33) 8GT BASE: 25E5 25GF6 30P19 30P4 6CM5 6P31S EL36 PL36 TT21 TT22
MA-1 9RJ Magnoval - 40KG6 6KG6 EL509 EL519 PL509 PL519 6P45S
MA-1 9RW Magnoval - 7868 6P41S
MA-1 8BD Octal - 10EG7 10EM7 12SL7 12SN7 12SX7 13D2 13EM7 15EA7 1633 2C50 2C52 5691 5692 5998 6080 6082 6113 6188 6336 6394 6520 6528 6AS7 6BL7 6BX7 6DN7 6EA7 6EM7 6GL7 6N8S 6N9S 6SL7 6SN7 6SU7 7105 7236 7802 7C5 8SN7ECC32 ECC33 ECC34 ECC35 ECC230
MA-1 12BJ Compactron - 6GE5 12GE5 17GE5
MA-1 9CV Noval - 10BQ5 10P18 15CW5 16A5 30P16 30P18 45B5 6BQ5 6CW5 6P15P 6P43P 7189 7320 EL84 EL86 PL82 PL84 UL84
MA-1 12ES Compactron - 6HD5
MA-1 9NZ Novar - 6GT5 12GT5 17GT5
MA-1 9QU Novar - 6KV6 17KV6 22KV6
MA-1 12FY Compactron - 6LR6 36LR6
MA-1 8JC Octal - 6DQ5
MA-1 LW6 Octal - 6LW6 26LW6 36LW6Modular because each of the above output boards share the same footprint and so are swappable.
The amplifier is designed to run from a voltage doubler/quadrupler from 120V (or single/double on 230V) using an isolation xfmr, and the output can use my interleaved Triad PT as OPT method.
The result is an amplifier varying from 10WPC to 80WPC depending on tubes and iron choices.
PCBs are available. Schematic attached. The VA/PI now use two 100uF/400V caps in series instead of the 47u/600V in the schematic due to availability and cost.
Pictured: 6P36S output and 6P45S output, and 12GE5 output.
6P36S is using a 250VA PT and pairs of 100VA for OPT. 80mA idle
6P45S is using a 625VA PT and pairs of 250VA for OPT. 100mA idle
12GE5 is using a 300VA PT and pairs of 100VA for OPT. 60mA idle (Sold)
Some power numbers (I will update as I continue to run more tests). All tests done with B+ of 320-340V with a 2k2 load unless otherwise specified, 1 kHz sine driving to the point of clipping and backed off 1/10th volt input, triode connection (* audio tubes need higher plate voltage and higher Z loading than sweep tubes):
6DQ6GTB: 24WRMS
6P31S: 37WRMS
6P45S: 113WRMS (1k3 load, 30Hz, 2 tubes parallel)
*EL34: 12WRMS
*KT88/6550: 15WRMS
*6P3S: 6WRMS
12AV5/12GE5/12GT5: 24WRMS
Attachments
Last edited:
OT Posts cleaned up.
@Francois G I had thought there were pictures of the boards etc posted here. Apparently, they were posted elsewhere.
I will post more detailed photos of the boards, but here is a pic of the amp guts.
There is a PSU double/quad board at the back (120V in, 300V/600V out), a filter board in the middle, boards for cathode resistors, a pair of output boards, and a left and right VA/PI/Driver boards.
There is also a board for a VR tube to regulate grid bias., and an RC filter board. There is also a 110VDC relay that turns on main power when the bias voltage is present - if there's a bias failure, the amp won't kill itself.
As you can see, everything is mounted on little modular boards.
All my boards are black. The blue one is soft power on off, there's a 12V SMPS for heaters, and a DC-DC boost module to make -110V from the 12V heater which also powers the main power relay.
A complete set of blank boards is 50$. I can also build kits or complete boards.
I will post more detailed photos of the boards, but here is a pic of the amp guts.
There is a PSU double/quad board at the back (120V in, 300V/600V out), a filter board in the middle, boards for cathode resistors, a pair of output boards, and a left and right VA/PI/Driver boards.
There is also a board for a VR tube to regulate grid bias., and an RC filter board. There is also a 110VDC relay that turns on main power when the bias voltage is present - if there's a bias failure, the amp won't kill itself.
As you can see, everything is mounted on little modular boards.
All my boards are black. The blue one is soft power on off, there's a 12V SMPS for heaters, and a DC-DC boost module to make -110V from the 12V heater which also powers the main power relay.
A complete set of blank boards is 50$. I can also build kits or complete boards.
LOL
I decided to convert it to 6P45S because I couldn't waste a 572VA power transformer on a 20W amp. I put the secondaries back in series, and changed the VR tube and bias supply from 110V to 200V (jumper setting).
Almost forgot to add a 10k resistor on the interlock relay though -- ok I DID forget but the relay took 200V for minutes (instead of 110V) without burning out. Lucky!
I decided to convert it to 6P45S because I couldn't waste a 572VA power transformer on a 20W amp. I put the secondaries back in series, and changed the VR tube and bias supply from 110V to 200V (jumper setting).
Almost forgot to add a 10k resistor on the interlock relay though -- ok I DID forget but the relay took 200V for minutes (instead of 110V) without burning out. Lucky!
