Found a little simple headphone amp circuit.
Its a 12au7 gain stage into a mosfet source follower.
The mosfet has a lm317 current source.
Didn't work to start with but then found a dry joint on the tube socket.
Then found a 2k2 pot in place of the 22k pot which killed the gain.
Got there in the end.
Its a 12au7 gain stage into a mosfet source follower.
The mosfet has a lm317 current source.
Didn't work to start with but then found a dry joint on the tube socket.
Then found a 2k2 pot in place of the 22k pot which killed the gain.
Got there in the end.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Hi,
I was thinking to build this, that is very similar and include some improvements as a delay on/off but I don't know wich is the better and most simply building.
NP-100v12: DIY 12AU7 (ECC82) Tube / IRF510 MOSFET Headphone Amplifier
What do you thing??
I was thinking to build this, that is very similar and include some improvements as a delay on/off but I don't know wich is the better and most simply building.
NP-100v12: DIY 12AU7 (ECC82) Tube / IRF510 MOSFET Headphone Amplifier
What do you thing??
I found my amplifier doesn't work well with all 12ax7's.
I suspect 12 volts is a little too low for it.
I found an article where someone had the same problem and they found making the grid a bit more positive helped.
I have a 100k grid resistor so added a 1 meg pull up resistor and the amp works much better with marginal valves.
I suspect 12 volts is a little too low for it.
I found an article where someone had the same problem and they found making the grid a bit more positive helped.
I have a 100k grid resistor so added a 1 meg pull up resistor and the amp works much better with marginal valves.
It tries. Does not always work. Especially on external images.
If you click on the image it shrinks to fit your screen. (At least on my FireFox Win7 PC.) Yes, that is counter-intuitive.
If you Refresh the page (F5), it tries to re-size the images. On this thread I had to do it twice; some threads take more F5 beating, some just never fit.
The current forum software is VERY old. The plan is to replace it with new software "soon". In the meantime we live with little annoyances. Any attempt to change the old software would be time-consuming, time better spent in preparation for moving to new software.
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