Have you seen my thread?
6SN7 push pull flea amplifier project
It uses the 6SN7 as outputs, and the 12AU7 would work if biased correctly. I need to send out a few PCBs to testers soon, as soon as I have a open day off to do it. There are a handful of dual triodes that will work well.
6SN7 push pull flea amplifier project
It uses the 6SN7 as outputs, and the 12AU7 would work if biased correctly. I need to send out a few PCBs to testers soon, as soon as I have a open day off to do it. There are a handful of dual triodes that will work well.
I haven't built such a flea but if you're starting the conversation with 12--7 family of tubes, I recall that in a post somewhere here, smoking-amp made a point about the 12AT7 having transconductance curves that made it particularly suitable for differential use.
I took a quick look and found one of smoking-amp's posts here in a list of search hits here.
I took a quick look and found one of smoking-amp's posts here in a list of search hits here.
Lingwendil, I am thinking that a variation on your 6SN7 using parallel Push Pull 12AU7 would be nice. I am hoping that both halves of each bottle can share a single Rk to keep the garter simple. Are you running class A or AB?
Smoking-amp, The chassis I have in mind for the resto has sockets on 1.4" centers. Do you think that will be enough clearance for the 1.2" diameter bottles?
Smoking-amp, The chassis I have in mind for the resto has sockets on 1.4" centers. Do you think that will be enough clearance for the 1.2" diameter bottles?
I have only traced the 6HZ8 curves on the tracer here, which look quite nice. Amplifiers using it seem to be scarce, if existent at all. If ever there were a sleeper....
Almost a sub for ECL86, similar to 6HC8 also.
The 9DX basing brings something over 20 base compatible tubes for rolling options. Some with frame grids like 6LY8, 6JT8, 6LQ8, 6KR8, 6KV8 (all on the $1 list).
On Ebay, there are a couple examples of 6HZ8 in the slim form 9 pin mini tube, from Greece and Italy. Whether that is -really- a 6HZ8, or some re-labeled ECL86 or something, dunno.
With the 1.4" available spacing limitation, if you could mount them with the low power triodes facing each other, and the higher power pentodes facing away from each other, then probably going to work fine.
Some other $1 list similar/competitive tubes around too: 6MF8, 6KY8, 6AG9, 9AH9, 12/6T10, 6AL11, 16AK9, 17JZ8
Almost a sub for ECL86, similar to 6HC8 also.
The 9DX basing brings something over 20 base compatible tubes for rolling options. Some with frame grids like 6LY8, 6JT8, 6LQ8, 6KR8, 6KV8 (all on the $1 list).
On Ebay, there are a couple examples of 6HZ8 in the slim form 9 pin mini tube, from Greece and Italy. Whether that is -really- a 6HZ8, or some re-labeled ECL86 or something, dunno.
With the 1.4" available spacing limitation, if you could mount them with the low power triodes facing each other, and the higher power pentodes facing away from each other, then probably going to work fine.
Some other $1 list similar/competitive tubes around too: 6MF8, 6KY8, 6AG9, 9AH9, 12/6T10, 6AL11, 16AK9, 17JZ8
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Class AB, I think it gives about 500mW class A, and I've squeezed 1.3W per channel out of it without audible distortion. You could run it hotter if you want a higher class A idle, just watch the dissipation doesn't get out of hand, some tubes can take it, some can't. I don't see higher than 1/2W often so AB works great with my speakers.
As for the single Rk per side, it should work reasonable enough, so long as the tubes are reasonably well matched. Garter bias works really well keeping each half in nice balance, but I've not experimented with parallel connection on common cathode loads, my gut feeling is to run everything separate, but that's a lot of doubling up on parts, in such a case I would rather run a bigger dual triode instead and just do it up once.
Also to throw an idea out there, if going for baby-power push pull, you would be hard pressed to find a better match of a speaker than if you build a Karlsonator, wide dispersion, great bass performance, and super realistic imaging, great way to take advantage of a lower power build and let it show it's best qualities.
Mini Karlsonator (0.53X) with Dual TC9FD's
I've built two sets, and they are really, really fun speakers for general use, and low output. Don't let the foamboard fool you, these are some real giant killers, and could easily be made of plywood or hardwood, and they have the "look" to match a vintage style amp.
I've had a pair as my main setup for months, and love them.
Mini Karlsonator (0.53X) with Dual TC9FD's
I've built two sets, and they are really, really fun speakers for general use, and low output. Don't let the foamboard fool you, these are some real giant killers, and could easily be made of plywood or hardwood, and they have the "look" to match a vintage style amp.
I've had a pair as my main setup for months, and love them.
Here's one with ECC99:
There's a transformer up front because it's the evolution of a Raven-style circuit. See that circuit here: The Amity, Raven, and Aurora
There's a transformer up front because it's the evolution of a Raven-style circuit. See that circuit here: The Amity, Raven, and Aurora
The Karlson Horn was a popular DIY speaker cabinet in the 1950's and 60's. My childhood neighbor had built a pair some time in the late 50's.
He offered to show me how to make them after I built his Heathkit AR-13 receiver, but I was more interested in 4 X 10 inch guitar cabinets then, so that's what we made.
Flea powered HiFi........a small SE amp with a 45 tube can't be beat. it's the best sounding 2 watts you can build. A properly outfitted TSE with all the audiophile parts including $$$ OPT's can get expensive though.......
Can't spend the big bucks for 2 WPC, make a SE amp with triode wired 12V6's, use the Edcor XSE15-5K OPTs ($24 ea), an XPWR202 power transformer ($58) or an Antek 1T275 ($35) use 12V6 tubes because they're $4 each and a 12AT7, 12AX7 or similar dual triode for the driver. I prefer the 5965 because they are $3 each. Add some small parts, stir well, simmer for an hour or two at the proper soldering temperature and you can make a fine sounding SE HiFi amp for $150 or so.
He offered to show me how to make them after I built his Heathkit AR-13 receiver, but I was more interested in 4 X 10 inch guitar cabinets then, so that's what we made.
Flea powered HiFi........a small SE amp with a 45 tube can't be beat. it's the best sounding 2 watts you can build. A properly outfitted TSE with all the audiophile parts including $$$ OPT's can get expensive though.......
Can't spend the big bucks for 2 WPC, make a SE amp with triode wired 12V6's, use the Edcor XSE15-5K OPTs ($24 ea), an XPWR202 power transformer ($58) or an Antek 1T275 ($35) use 12V6 tubes because they're $4 each and a 12AT7, 12AX7 or similar dual triode for the driver. I prefer the 5965 because they are $3 each. Add some small parts, stir well, simmer for an hour or two at the proper soldering temperature and you can make a fine sounding SE HiFi amp for $150 or so.
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