The high octane phono preamp

Hi Pawel,

from a quick look it seems that this is a very cartridge specific issue and certainly not standard. I don't fully understand what's the point of that, so I have difficulties recommending a way to get there. But sure feel free to experiment!

to get quality of MC cartridge

Actually to get there, I would always recommend a AT150MLX or - even more delicate - a AT150ANV for most joy. These are one of the very few modern MM designs with low inductance, requiring a low input capacitance mm phono pre just like the high octane is. And they sound simply amazing ;)
 
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Hi Pat and Russell! That's great to hear! Happy building!!

@noviygera: the 2sc2547 are the hard-to-get parts, and unfortunately it seems there are also fakes on the market. Of course they can be substituted easily with whatever low noise bjt you have on hand. However, I really like these parts and it won't hurt to have a number of them in the parts bin if you can get them.

For more info on that part, see e.g.

http://www.diyaudio.com/forums/solid-state/17285-ultra-low-noise-transistors.html

http://www.diyaudio.com/forums/analogue-source/154394-hps-4-0-phono-stage.html
 
NEW BOARDS!

Dear all,

on our national holiday today the weather was great, but quite unexplicably I resisted and worked out new boards!

There are a few changes to the previous board, e.g. to make mounting of the board easier (it has now mounting holes) as well as it will fit into a normal Hammond 1455N1601 enclosure.

Then it also corrects a few warts and bugs of the previous version (C6/C106 are gone, CP1 is fixed and goes now to ground).

Oh - and of course the new board is RED :cool:

The boards are currently manufactured and will be available in a few weeks. If you want to preorder one, just let me know!

Price of the new board will be 11 Euros, together with shipping that will arrive in total at 19 Euros.
 
Hi Joachim!

Basically, the opamp simply compares the voltage from the LED (a 1.6 V red LED in my case) with the fraction 1/25.5 of the regulated voltage which is again 40V/25.5 ~ 1.6V. Any difference between these two voltages is compensated by adjusting VGS of the shunt mosfet.

When the output voltage never raises up to the intended 40V, please check that you have a 1.6V LED (not an 1.2 V or so) and your two sensing resistors RP2, RP3.

Hannes

Hannes,
i have a bunch of red and green leds and all of them have Vf in 1.8-2.0 range. Can i adjust the 25.5K resistor to keep the ratio 40V/RP2 = Vf led?
Thanks for your support,
Adrian