it is a copy of this headphones amp i removed the mosfet because it does not need current gain
NP-100v12: DIY 12AU7 (ECC82) Tube / IRF510 MOSFET Headphone Amplifier
NP-100v12: DIY 12AU7 (ECC82) Tube / IRF510 MOSFET Headphone Amplifier
If you use an ECC81 or ECC82 then yes, it will amplify a bit (not much). It will distort a lot, but I guess that's what you want for a very 'tubey sound'. The ECC83/12AX7 may not work at all at such low voltages, however. (It might work- worth a try)
what if i use a 100v b+ with 10k b+ resistor and 12v heater supply
will it work then. what will the gain be
will it work then. what will the gain be
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It's a simple enough circuit to try, just to see if it works, before making a final version.
http://www.sincitytrader.com/upldr2/files/39_atjyc/SIMPLEPREAMPS.pdf
I have tested the first schematic quite a bit at my office (blackberry preamp) on voltages ranging from 12v to 250v, 12v distorts to much for my taste! 50+v is where it works best.
I have tested the first schematic quite a bit at my office (blackberry preamp) on voltages ranging from 12v to 250v, 12v distorts to much for my taste! 50+v is where it works best.
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The gain from max to min goes 12AX7 -> 12AT7 -> 12AU7
In general you can plug and play between these three tubes without issue, just listen and see which you prefer. The load lines vary of course but they will all still work 😉
Output impedance will be 5-6k (that's high), input impedance will depend on volume control setting, distortion will be in double figures (ditto). You didn't ask, but it will also hum like crazy.
There seems to be a rash at present of people wanting to add distortion to their sound by running valves from 12V supplies. Does this always happen at this time of year?
If you want to add some "tubey sound" to a line source you can do it with a couple of resistors and a silicon diode, no need for a power supply. Put a resistor in series with the signal, say 4K7. Then from the output put a 10K plus a diode in series to ground. This will gently clip signals above about 600mV, and add some distortion to slightly smaller signals. Low level signals will be unaffected. Roughly the same response as a badly biassed valve, but much cheaper.
If you want to add some "tubey sound" to a line source you can do it with a couple of resistors and a silicon diode, no need for a power supply. Put a resistor in series with the signal, say 4K7. Then from the output put a 10K plus a diode in series to ground. This will gently clip signals above about 600mV, and add some distortion to slightly smaller signals. Low level signals will be unaffected. Roughly the same response as a badly biassed valve, but much cheaper.
can somebody give me a circuit for a buffer that uses the 12ax7, 7025, 12at7 tube. it adds 2 to 4x gain and is not too distorted. (normal b+ voltage) and it can have a computer as sound input and a tda7294 as the output.
For a 2-4x gain and low source impedance, those just aren't good choices of tubes. It's like saying, "I need to haul large numbers of people, what's the best among Mini-Cooper, Miata, and Smart?" You want to look at low mu, low plate resistance tubes like 12B4.
Lots going on here, for full explanation and LTSpice sim files:
http://www.diyaudio.com/forums/tubes-valves/173128-tube-can-work-low-volt-fix-your-knowledge-10.html
R2 shoulda been split and bootstrapped off the output of that op-amp.
Plate voltage already so low, grid leak will either pull the bias negative,
and/or rectify like a diode... plate current will get stOOpid small.
6DJ8 and 6922 heaters are hard wired in series for 6V3. The middle tap
given up to a shield between the triodes. No 12V6 option except drop
the excess voltage somewhere else...
Oh, nevermind... I see now the LM317 0A3 current supply.
Plate voltage already so low, grid leak will either pull the bias negative,
and/or rectify like a diode... plate current will get stOOpid small.
6DJ8 and 6922 heaters are hard wired in series for 6V3. The middle tap
given up to a shield between the triodes. No 12V6 option except drop
the excess voltage somewhere else...
Oh, nevermind... I see now the LM317 0A3 current supply.
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