6N6P and ECC99 are close enough to drop in. BTW: The last schematic you linked is for a line stage though, not an HP amp. If you want Aikido HP, you want something more like this, if you don't need the noise cancelling (because you have a clean power supply such as the ones I linked) the one I posted in post #2 works fine.
This amp is for 300R headphones but can be modified (similar to the way I did mine) for 32R by changing the 33uF coupling cap to 470uF.
This amp is for 300R headphones but can be modified (similar to the way I did mine) for 32R by changing the 33uF coupling cap to 470uF.
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Hello Cbueche,
The power supply is based on a schematic published in AudioXpress: https://audioxpress.com/assets/upload/files/bicknell2890.pdf
I used a PL36 in stead of an EL34 and an 0B2 in stead of a zener diode.
The PY81 serves as a time delay. It takes a PY81 about 50 seconds (old production) to 30 seconds (newer production) to start to conduct.
The power supply is based on a schematic published in AudioXpress: https://audioxpress.com/assets/upload/files/bicknell2890.pdf
I used a PL36 in stead of an EL34 and an 0B2 in stead of a zener diode.
The PY81 serves as a time delay. It takes a PY81 about 50 seconds (old production) to 30 seconds (newer production) to start to conduct.
Thank you for the pointer, certainly an elaborate way of filtering, but as the article mention, quite wasterful in energy. OK for a headphone amp, but doing the same for a power amp would be even worse. As such I like the capacitor multiplier of Pete Millett better. Not really a regulation but it does a fair job of getting rid of PSU ripple. Or his approach with the Tentlabs MEC is cool as well. Anyway I was intrigued because I have got 40 PL36 tubes, this triggered my curiosity.
Hi, long no see.. finally I arrived to the point where I can begin with this little project
I managed to get my hands on 4x 6N1P and 4x 6N6P tubes (all new) so building is starting. My HP-s are rather 26Ohm, but I think it will still be handled by this circuit nicely.
My father had a looked at the circuit (#2). He told me it's a very forgiving design and tolerates a lot - actually he told me the same what you and others also told me here so I'm happy hearing this.
Another interesting thing he mentioned was the point of amplification: the really amplifying tube part is the triode-half on the bottom-left (6N1P). The other half above it is a current source, the lower-right too (if I remember him well) and the upper-right triode part works as a coupler to the load.
Anyway, a very nice, simple design, he loved it. He only wants me to add a good quality small film cap between the 100k pot and the 300R resistor: he warned me if any DC is entering here at this point, it will go through the whole chain and it might cause a lot of trouble so although not directly needed, better to go the safe route and put it there.
Apart of this minor change that's it for now, tubes are on their way, getting them next week somewhen... I'll put the whole stuff (both channels) into a nice flat case, driven by a somewhat oversized toroid with 2 secondaries (per channel), 1 for filament heatings and 1 for the circuit itself (200V AC, bridge rectifying then).
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One more note: having read this article about fully balanced designs I'm now thinking making a balanced version too and then mod my Cooler Master MH751 (Takstar Pro 82 based).
Until you read up on the disadvantages of this, I wouldn't recommend pursuing it.
No hope for me then..
Back to our topic: my nice little tubes have arrived, 4x 6N1P-EVs (OTK 1) and 4x 6N6P-I-s (OTK 5). As I've read in another topic, OTK marking is an indicator of tube quality, 0 being the best and 9 being the worse, not sure if this is true or not. If it's true I think I'm just fine with my set of 6N6P-I-s with grade "5", in order to use all four of them for 2 little stereo amps.
Back to our topic: my nice little tubes have arrived, 4x 6N1P-EVs (OTK 1) and 4x 6N6P-I-s (OTK 5). As I've read in another topic, OTK marking is an indicator of tube quality, 0 being the best and 9 being the worse, not sure if this is true or not. If it's true I think I'm just fine with my set of 6N6P-I-s with grade "5", in order to use all four of them for 2 little stereo amps.
