Looking for schematic, design and/or plans for a 2a3 interstage headphone amplifier. I think SonnyMarrow posted one he made but he couldn't post the full schematics because it was similar to Eddie current studio T. https://www.diyaudio.com/community/...stage-transformers-venue.390795/#post-7136376
Does anyone have one they built or know of that sounds good they can post?
I am interested in using tamura and electraprint output transformers in this project.
Thanks.
Does anyone have one they built or know of that sounds good they can post?
I am interested in using tamura and electraprint output transformers in this project.
Thanks.
Most headphones are very efficient. They only require low power. That means very low hum can still be heard.
Interstage transformers pick up hum. Keep them spaced away from the power transformer and B+ choke. And you must orient the interstage angular direction to be different than the power transformer and the B+ choke. Use an aluminum chassis; magnetic steel = hum.
You must use DC to power the 2A3 filament.
You must carefully control all ground loops, especially the input connector to input tube wiring; and the ground loop to the first B+ cap.
Hum is very distracting, because most headphones shut out all ambient noise.
Have fun designing, building, and listening!
Interstage transformers pick up hum. Keep them spaced away from the power transformer and B+ choke. And you must orient the interstage angular direction to be different than the power transformer and the B+ choke. Use an aluminum chassis; magnetic steel = hum.
You must use DC to power the 2A3 filament.
You must carefully control all ground loops, especially the input connector to input tube wiring; and the ground loop to the first B+ cap.
Hum is very distracting, because most headphones shut out all ambient noise.
Have fun designing, building, and listening!
wanderer47,
I do not use headphones.
I build low power tube amplifiers, mostly for speakers that are about 2.5 feet away (near field listening at the computer, or in the bedroom).
I used to design and build lots of 2 stage single ended amplifiers; but now I mostly design and build push pull and balanced amplifiers.
Most of my amplifiers have less than 100uV of hum and noise; good for speakers; but not low enough for most headphones - unless you use a proper pair of resistors to load and attenuate the amplifier output.
If headphone operation is what you want, and not for speakers, a lot of headphone fans read these threads.
They can find some good schematics for you.
It might be helpful if you tell them the manufacturer(s) and model(s) of your headphones.
If you also list the sensitivity specs, and the impedance specs, It would be helpful too, so that an appropriate schematic can be picked.
Example:
A set of electrostatic headphones, generally requires a more powerful and complex headphone amplifier.
Have Fun!
I do not use headphones.
I build low power tube amplifiers, mostly for speakers that are about 2.5 feet away (near field listening at the computer, or in the bedroom).
I used to design and build lots of 2 stage single ended amplifiers; but now I mostly design and build push pull and balanced amplifiers.
Most of my amplifiers have less than 100uV of hum and noise; good for speakers; but not low enough for most headphones - unless you use a proper pair of resistors to load and attenuate the amplifier output.
If headphone operation is what you want, and not for speakers, a lot of headphone fans read these threads.
They can find some good schematics for you.
It might be helpful if you tell them the manufacturer(s) and model(s) of your headphones.
If you also list the sensitivity specs, and the impedance specs, It would be helpful too, so that an appropriate schematic can be picked.
Example:
A set of electrostatic headphones, generally requires a more powerful and complex headphone amplifier.
Have Fun!
Most headphone fans will be familiar with those models, or they will look up the specifications.
Things like impedance, Ohms; and sensitivity, dB/milliwatt.
Things like impedance, Ohms; and sensitivity, dB/milliwatt.
This is my current circuit. Transformers are LL1692A PP and LL2774 80mA. And the driver tube I'm using now is triode connected C3m.
Few modifications are needed to change it to a 2A3 amplifier.
Every power supplies need to be carefully filtered because headphones are much more sensitive to noise comparing with speakers.
There's a mistake in the previous circuit. One side of the cathode capacitor "bridge" was not connected to the cathode of the tube.
I would think it would be easier to use an indirectly heated tube like the 6a5g or even a 6av5 worked in triode. Would eliminate any possibility of heater hum.
True, indirect heating is easier . . .
But 2A3 tubes with DC heated filaments is known to work Extremely well.
I think 2A3 glass envelopes look better than many octal tube glass envelopes.
But 2A3 tubes with DC heated filaments is known to work Extremely well.
I think 2A3 glass envelopes look better than many octal tube glass envelopes.
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4-65A tube's beauty level, is in between the 2A3 and the 100TH.
I built using 2A3, and 4-65A, 100TH is more than I care to design, get parts for, and build.
The only problem with Thoriated Tungsten Direct Heated Filaments, is for those who care to listen in the dark!
The 100TH looses in that scenario, even if the plates are not glowing orange/red.
I built using 2A3, and 4-65A, 100TH is more than I care to design, get parts for, and build.
The only problem with Thoriated Tungsten Direct Heated Filaments, is for those who care to listen in the dark!
The 100TH looses in that scenario, even if the plates are not glowing orange/red.