Tuesday, 13 September 2016

Euro build notes for a Serge Resonant EQ Mk. II

These are my build notes for a Euro format Serge Resonant EQ Mk. II.
Mk. II daughter board and Mk. II panel by Clarke

 First the virgin PCBs.
This Euro version still uses Ken Stones CGS 202 pcb.
http://www.cgs.synth.net/modules/cgs202_reseq.html

Above is a pic of a vintage Serge Res equaliser.
It's the 3rd module from the top. It's very compact in comparison to the Euro version and doesn't have
the extra outs from the 10 filter bands. And pot's are used instead for sliders.

 Official BOM for the daughter board:

SMT Components
[3] TL074 (SOIC-14)
[10] 330R Resistor (0805)
[25] 47k Resistor (0805)
[2] 0.1uF Ceramic capacitor (0805)

Through-hole Components
[18] Kobiconn 16PJ138 jacks
[10] Bourns or Alpha 45mm LED sliders
[2] Alpha 9mm pots or similar, value 50k Audio.
[10] LED Current-limiting Resistors - value varies by slider brand and LED color.
        I'm using 1.2K.
[2] 22uF Electrolytic capacitors
[2] 1N4001 Diode
[1] 2x5-pin Eurorack power header
These are the 330R resistors.... outboard resistors.

Next the 47K SMDs.

[2] 0.1uF Ceramic capacitor (0805)
[2] 22uF Electrolytic capacitors
[2] 1N4001 Diode
[1] 2x5-pin Eurorack power header

SLIDER Pots, jacks, etc.


Now for the main PCB.
Resistors & headers 1st.

What capacitors should I use ???

Ken Stone's site says this:
"Traditionally, polystyrene capacitors are used for all of the smaller value capacitors in this module. I have not tried using other types and cannot say whether using the polystyrene capacitors makes any audible difference. From 10n, up greencaps were used. In modern terms these would be MKT or MKS. Note that there are also 10 x 10n decoupling capacitors. These decoupling capacitors can be MKT, MKS, monolythic ceramic, or anything else that will physically fit."

For this build I'm using ceramics for the 680pf & 220pf. The jury is out on whether axial polystyrene sound better. The price difference is considerable.
I'll use Axial poly's in my next build if I can detect a difference between this build and my vintage
Resonant Filter. .


It's now time to wire up the two PCBs.



Headers can also be used like this:


 This makes for easier trouble shooting.




This is not part of the original CGS build. Took a bit of schematic study and trial & error to work out where
to where to make the connections. they were basically the outs pins of the ten TL072s.. pins 1 & 7




Links:
1. Muff wigglers
2. Ken Stone - CGS
Video 1
Video 2


5 comments:

  1. So have you had any trouble with the ceramic caps? I'm building mine now and I used poly box caps for everything but the 220pf and 680pf filter caps and the decoupling caps, and I'm trying to determine whether I should go ahead and order the poly caps for the remaining filter caps.

    ReplyDelete
  2. So have you had any trouble with the ceramic caps? I'm building mine now and I used poly box caps for everything but the 220pf and 680pf filter caps and the decoupling caps, and I'm trying to determine whether I should go ahead and order the poly caps for the remaining filter caps.

    ReplyDelete
  3. Hello John,
    I haven't had any trouble with using ceramics for the 680pf & 220pf. I haven't yet done a second build. I have been comparing this one with my vintage serge resonant filter and they sound similar. So I'm quite happy with the ceramics.

    ReplyDelete
    Replies
    1. Hi Jon

      Very useful build notes thank you and for your very interesting site.

      For the led sliders did you use 10K or 100K or else?

      All the best

      Delete