Low Distortion J-FET + Tube Preamp Preamplifier PCB Board Fit for 12AX7 / ECC83
Jul 08, 2018
This FET/Tube amplifier is an amazing performer once a few changes are made to it
I agree with it being a good quality and would only recommend if a few modifications can be made to it.
First you'll need to understand that the Tube socket itself has to be inserted on the opposite side of the PC board, and maybe at that point, also populate the other components on the other side of the board. This will need to be done in order to get any performance out of it.
Second, You’ll have to remove resistors R5 and R6 (10K and 15K) and replace with a single 68k resistors for each channel. The single 68K resistor will replace both 10K and 15K on each channel.
Once the above is done, and in my case I've added a 12 regulator to drive the filament, you should then experience very clean and amazingly transparent sound performance.
MPmods..
I built my own low noise tube pre-amplifier, using regulated filament supply (IC) and super buffed up capacitance for the plate supply. But still had detectable noise, so gave this board a try out. far exceeded my expectation and did so with only two capacitors in the main supply. Really made a huge difference in lowering the noise floor, and easily made an overall better sounding pre-amp.
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