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If any keenos want to do a conversion to a Valve unit then I have a suitable PCB for sale. £10 + £2.50 P&P (UK)
There are only the transformer and rectifier that are particular.
This PCB houses the transformer for generating the HT and the SKRM module, it requires a 12VAC power supply.

I´ve sent an email to you.
Pancho

Sorry, not an email but a PM.

This pcb can also be used in an automation version - I've done it

I'm considering designing and making a PCB that houses the valve pre-amp using an EF86 and half an ECC83 as per the front end of an AC15 for the valve eTaps .
Any thoughts anyone ?
The HT will be lower and are there any special precautions to be taken regarding microphony ?

IME EF86's will be happy and less troublesome with some anti-vibration mounting of the valve socket - maybe consider even a dual anti-vib setup.
EF86's have lots of gain and will give you a huge signal, (in the AC15 it feeds the PI directly) not sure how you will benefit from that before the echo.
What HT?

With one ECC83 you can get the grid leak biased pre as well as a output mixer/buffer as per the original Meazzi. The correct HT for that would be around 170/130v respectlively for the buffer/pre.

A grid leak bias configured ECC83 works better than a EF86 for a echo pre IMO - YMMV

Erik

The HT is about 150VDC.
I don't want to copy the Meazzi circuitry - more the AC15.
Purely for the mystical tone.

In the AC34 circuit the EF86 sees some 300V - in the Matchless clones actually 320V I remember. Can't recall the details of the AC15, but probably the same or close I'd guess. I've haven't tried running EF86's at other voltages - so can't comment on any pros/cons.

There's a EF86 datasheet with resistor value suggestion for different supply voltages - the lowest being 150V - page 2:
http://www.mif.pg.gda.pl/homepages/frank/sheets/010/e/EF86.pdf

For keeping the output signal at a sensible level a split anode resistor setup works nice.

Erik