Request: Morley JD-10 preamp

Not sure what to say about this circuit. Looks like a fun preamp with a built-in speaker emulation, and it’s supposed to sound really nice. I took the liberty of simplifying the DC input circuitry a bit (the schematic called for a complete bridge rectifier). Also, the original is a buffered effect, but I tried to set this one up for true-bypass wiring instead. Hopefully it’ll work.

Update (20.12.2012): Built it tonight and it works great. I have to say this one sounds really good! Verified.

I know some of you have had problems building this so here are the voltages on my build.

Power supply: 8.89V

All pots at approx. noon, “Rock/Classic” switch set to “Classic” and the speaker emulation set to off.

No.IC1 IC2 IC3
1+4.79V +4.72V +4.77V
2+4.79V +4.73V +4.77V
3+4.35V ~+3.90V +4.74V
40V 0V 0V
5+4.70V +4.78V +4.78V
6+4.72V +4.78V +4.80V
7+4.72V +4.79V +4.80V
8+8.89V +8.89V +8.89V

I made two non-critical substitutions; I didn’t have any 680 ohm resistors and so used 510 ohm ones instead, and I used 220uF/25V electrolytics in place of the giant ones the original calls for.

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7 thoughts on “Request: Morley JD-10 preamp

  1. Hi Kevin,
    When it comes to the pots your guess is as good as mine. As long as you’re satisfied with the result it hardly matters 😉

  2. Thanks for the layout, got it up and running first time and sounds great.
    I built it with all linear pots first but changed them for log which seems
    to work better especially as I go for lower gain stuff,I know the original
    schematic by Award Session is online and shows 220kB but was wondering if
    the B was the old UK mark for Log?
    Anyway thanks again.

  3. i just built this one today and I love it. i first used all 220K linear pots as shown, but I found that log pots work better for the gain, bass and mids control so i used log pots in those positions.

  4. And as a user for 18 years i can recommend these settings for a neutral sound: Treble-0, middle-full, bass-10 o’clock. It takes other pedals really well, try it. It really is a nice little amp in front of your amp….

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