Interested in applications of 6GT5 sweep tubes for PP audio amp design...
Not a whole lot out there- far as history of usage. Pic below shows what seems to be rare example-
I know Tony T has used these in SE design, and KodaBX has used them in PP...
Q's:
1. Are they a viable candidate to design low distortion good sounding 50w+50w in non parallel PP design? Or are they better suited for guitars?
2. Can anyone supply an audio amp schematic they've successfully built and recommend?
3. What kind of B+ is needed?
Thx,
Jim
Not a whole lot out there- far as history of usage. Pic below shows what seems to be rare example-
Grommes Precision S-100
I know Tony T has used these in SE design, and KodaBX has used them in PP...
Q's:
1. Are they a viable candidate to design low distortion good sounding 50w+50w in non parallel PP design? Or are they better suited for guitars?
2. Can anyone supply an audio amp schematic they've successfully built and recommend?
3. What kind of B+ is needed?
Thx,
Jim
Attachments
The 6GT5 plate curves look OK for typical tube linearity. Compare with ECL86, EL506, KT77, 6CB5, 10/6JA5, 7355, 38HE7, 6AV5, 6HZ8 pentodes for quite good curves. Spacing should be near uniform at higher currents for the class B portion of class AB, where only one tube is conducting. Probably looking at like a 3.3K to 4.2K Ohm P-P OT for the 6GT5. The problem with 6GT5 is the Novar socket. Very hard to find good Novar sockets these days. The ones from China typically state Magnoval/Novar, but they are tight on Magnoval and loose on Novar tubes. (you can tighten the socket pins with a small tool, but tedious work.) I would suggest the Compactron socketed 10JA5 Vertical Amp tube as a more practical choice, with excellent curves and low cost. Even cheaper is 38HE7, which (on most) allows operation of just the pentode with 21V Htr across pins 10 and 12. Can be uprated to 15 Watt Pdiss without the damper tube powered that way. And even has good triode mode curves too.
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12/6GE5 - 12/6JN6 Sweep tubes are quite decent for linearity too and have been used in amplifiers here. They are quite similar to 6GT5, so any circuits using those should work for 6GT5 as well.
Most TV Sweep tubes can be made to work well, maybe needing a little more N Fdbk to bring them up to par. Plenty of "audio" type tubes that need just as much N Fdbk to fix them up. 21HB5 and 22/17KV6 are some likely decent sleeper Sweeps.
Most TV Sweep tubes can be made to work well, maybe needing a little more N Fdbk to bring them up to par. Plenty of "audio" type tubes that need just as much N Fdbk to fix them up. 21HB5 and 22/17KV6 are some likely decent sleeper Sweeps.
With the 0A2 150V screen V, it is running with the datasheet curve set. 60V knee Voltage and 440V B+ leaves delta 380V operating peaks (and delta 500/2 mA peaks + bias current per tube ). To get 100 Watts would lead to a 2900 or 3000 Ohm P to P OT. This would translate to a 6K P-P OT at the same B+ for a single set of tubes. The highish 440V B+ would indicate its optimized for power and efficiency, which it can well afford to do ( still low distortion) with the straight line plate curves. ( low screen current distortion allowing higher Z loading )
The 550 mA peak tube rating would readily allow (single tube set ) operation with a 3000 Ohm P-P OT at 330V B+ ( delta 360 mA peaks + bias current ) (providing tube diss. Watts are in bounds). Although the tubes will likely last longer at the lower 500/2 peak mA + bias current (per tube) used in the above schematic..
The 550 mA peak tube rating would readily allow (single tube set ) operation with a 3000 Ohm P-P OT at 330V B+ ( delta 360 mA peaks + bias current ) (providing tube diss. Watts are in bounds). Although the tubes will likely last longer at the lower 500/2 peak mA + bias current (per tube) used in the above schematic..
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I saw this schema too, thx. Doing this project for friend w/ 2000 sq ft man cave.
At first, thought the the S-100 was 2 channel. But with 1 opt showing- it's 100w (rated) mono block.
Like to divide that circuit up into 2 x 50w- that schema provides good basis to begin.
Jim
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sa,
450-500V B+ is what I was thinking for a 2ch pair... at least 300, if not 350ma supply. I have pr of Hammond 1650h's (6.6K) which should work.
Found the load graph below- you have something more or different? Novar base same as noval? Did quick inconclusive search.
Compactron suggestions are good, but I'd like to stick w/ 9 pin if possible since I have bunch of those sockets & footprint already in my PCB lib.
12GT5's are cheap like others- $6 vs $7.50 each, which is important cuz this guy likes it loud and bass heavy ;<)
AX7 / AU7 drive system is simple enough. Can single cathodyne inverter be used in place of AU7 to drive 50W pair?
Thanks for input,
Jim
http://www.r-type.org/pdfs/6gt5.pdf
450-500V B+ is what I was thinking for a 2ch pair... at least 300, if not 350ma supply. I have pr of Hammond 1650h's (6.6K) which should work.
Found the load graph below- you have something more or different? Novar base same as noval? Did quick inconclusive search.
Compactron suggestions are good, but I'd like to stick w/ 9 pin if possible since I have bunch of those sockets & footprint already in my PCB lib.
12GT5's are cheap like others- $6 vs $7.50 each, which is important cuz this guy likes it loud and bass heavy ;<)
AX7 / AU7 drive system is simple enough. Can single cathodyne inverter be used in place of AU7 to drive 50W pair?
Thanks for input,
Jim
http://www.r-type.org/pdfs/6gt5.pdf
Sounds like a good plan.
The Novar sockets are bigger than Noval sockets. More like a Compactron socket, but with 9 pins. Most of the big 9 pin sockets around are Magnoval sockets from China. They have bigger diameter pins than Novar though. Some sockets are advertised as Magnoval/Novar combo, but really aren't. They don't fit either properly. But you can tighten the socket pins with some tedious work. Good Novar sockets may set you back $17 each.
The 9NZ socket pin-out for 6GT5 is compatible with the 9QU socket pin-out if you do not use pin 6 for grid 1. This would make 6JG6, 6JR6, 6JT6, and 6KV6 and 6P41S tubes useable when pin 6 is grounded. (do not ground permanently or 6GT5 will not work)
The Novar sockets are bigger than Noval sockets. More like a Compactron socket, but with 9 pins. Most of the big 9 pin sockets around are Magnoval sockets from China. They have bigger diameter pins than Novar though. Some sockets are advertised as Magnoval/Novar combo, but really aren't. They don't fit either properly. But you can tighten the socket pins with some tedious work. Good Novar sockets may set you back $17 each.
The 9NZ socket pin-out for 6GT5 is compatible with the 9QU socket pin-out if you do not use pin 6 for grid 1. This would make 6JG6, 6JR6, 6JT6, and 6KV6 and 6P41S tubes useable when pin 6 is grounded. (do not ground permanently or 6GT5 will not work)
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The 6DQ6B tube and 6FW5 tubes are nearly the same as 6GT5. Most likely can find Amplifier schematics using those tubes.