MXR micro chorus  [schematic]

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MXR micro chorus

Postby bluesbreaker62 » 10 Aug 2009, 16:47

Hi all,

I've been enjoying this forum for too long without contributing anything.

I hope you like it:

Image
Image
Image

If you need more pics, just ask

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Re: MXR micro chorus

Postby Fermusicman » 14 Aug 2009, 22:09

Thanks BB, good pics, :D We can to know the caps values?, :wink:
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Re: MXR micro chorus

Postby lolbou » 14 Aug 2009, 22:18

Thanks, nice and useful pics!

:shock: A double-sided PCB... Will need a second layer on the SVG file :wink: ....

Still the date interests me! And the wiring (color - device)...

Cheers!!
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Re: MXR micro chorus

Postby Fender3D » 07 Sep 2009, 16:22

I reversed engineered it:

Image

or PDF http://www.wizardinside.it/foto/schemi/micro_c-sch.pdf

I assumed the values for RV1, R28, C1, C9, TR1 from MXR micro flanger's schematic values (I reversed engineered it as soon as I bought it some years ago... both are really similar :wink: )

I only hope bluesbreaker62 list the caps value too 'cause they're too much different from flanger (please do it :cry: )

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Re: MXR micro chorus

Postby Dirk_Hendrik » 07 Sep 2009, 16:44

Thanks!
Those 3 diodes give a serious :scratch:
Sorry. Plain out of planes.

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Re: MXR micro chorus

Postby Fender3D » 07 Sep 2009, 17:02

3 must be the perfect number :lol:
'cause the same 3 diodes were in micro flanger and in DOD effects too :hmmm:
they'll avoid the BBD bias setting
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Re: MXR micro chorus

Postby analogguru » 07 Sep 2009, 17:09

No mistakes on Rev 1.00 deserves the missing capacitor values, here you go:
C1: 50n
C2: 1n
C3: 1n
C4: 200p
C5: 300p
C6: 30p
C7: 10n
C8: 1n
C9: 50n
C10: 1n
C11: 1n
C12: 0,33µ
C13: 200p
C14: 20p
C15: 10n
C16: 20p
C17: 10µ
C18: 10µ
C19: 0,33µ
C20: 0,33µ

Please DON´T save the schematic as .jpg.

USE INSTEAD black/white .GIF or .PNG !

The schematic drawing will stay sharper and the file will be smaller.

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Re: MXR micro chorus

Postby Fender3D » 07 Sep 2009, 18:09

Thanks analogguru :D

Sorry for double post, but I really don't know how edit the previous :scratch:

Updated schematic with the caps values.
Added PNG http://www.wizardinside.it/foto/schemi/micro_c-sch.png
and GIF http://www.wizardinside.it/foto/schemi/micro_c-sch.gif,
but...
IrfanView blurred them too when converting from PDF :shock:
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Re: MXR micro chorus

Postby analogguru » 07 Sep 2009, 21:33

:hmmm: I didn´t know that you work directly into .pdf.

Anyhow here is the .pdf converted to .gif - first with ghostscript to .bmp and then with XnView (Freeware) to .gif - to show you what I mean.

resolution .jpg: 1123 x 793 (~ 100 dpi)
file size .jpg: 143.092

resolution .gif: 3508 x 2479 (300 dpi)
file size .gif: 95.015

the rest you can see below.

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Re: MXR micro chorus

Postby estragon » 07 Sep 2009, 21:40

Fender3D wrote:3 must be the perfect number :lol:
'cause the same 3 diodes were in micro flanger and in DOD effects too :hmmm:
they'll avoid the BBD bias setting

Take notice biasing is set in practice to VREF minus four (4) diode drops, as Q1 is an emitter follower whose output is one diode drop below its base. This arrangement varies with temperature. Wether it matched the variation required by the SAD512 or not, that's another story.
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Re: MXR micro chorus

Postby distortion_gfx1 » 17 Apr 2010, 09:15

Q: Can i convert this chorus into a flanger(Mxr micro Flanger)? though chorus and a flanger has some similarities..
tnx :lol:
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Re: MXR micro chorus

Postby mictester » 17 Apr 2010, 09:40

Dirk_Hendrik wrote:Thanks!
Those 3 diodes give a serious :scratch:


They're just there for the 3-diode drop they provide.
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Re: MXR micro chorus

Postby distortion_gfx1 » 18 Apr 2010, 05:47

distortion_gfx1 wrote:Q: Can i convert this chorus into a flanger(Mxr micro Flanger)? though chorus and a flanger has some similarities..
tnx :lol:


anyone?
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Re: MXR micro chorus

Postby analogguru » 18 Apr 2010, 09:45

Why do you want to convert it ?
If you don´t like it as it is, sell the BBD-chip and you can buy two cheap flangers.

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Re: MXR micro chorus

Postby mistral » 18 Apr 2010, 13:59

SAD512D Replace or equivalent?
where i can buy it?
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Re: MXR micro chorus

Postby Dirk_Hendrik » 19 Apr 2010, 19:09

mistral wrote:SAD512D Replace or equivalent?
where i can buy it?


Both questions get the same answer, Nope.
SAD512D's are made of dried Pygmee foreskin leather which is even rarer than unobtanium.
Sorry. Plain out of planes.

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Re: MXR micro chorus

Postby mictester » 19 Apr 2010, 20:40

mistral wrote:SAD512D Replace or equivalent?
where i can buy it?
Regards


You might sometimes see them advertised at stupid prices on Ebay - DON'T bother buying them. You're very unlikely to get one that works, and any that you do get will be desoldered from broken equipment.

I remember this as being a sweet little chorus (correct me if I'm wrong, please), and I was thinking of reworking one to use something obtainable like an MN 3007. The delay with the 3007 will be too long, so the clock frequency will have to be increased to get similar results to the original. This could help with the aliasing problems....

OK. Updated Micro Chorus on the way!
"Why is it humming?" "Because it doesn't know the words!"
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Re: MXR micro chorus

Postby theehman » 19 Apr 2010, 20:51

mictester wrote:
mistral wrote:SAD512D Replace or equivalent?
where i can buy it?
Regards


You might sometimes see them advertised at stupid prices on Ebay - DON'T bother buying them. You're very unlikely to get one that works, and any that you do get will be desoldered from broken equipment.

I remember this as being a sweet little chorus (correct me if I'm wrong, please), and I was thinking of reworking one to use something obtainable like an MN 3007. The delay with the 3007 will be too long, so the clock frequency will have to be increased to get similar results to the original. This could help with the aliasing problems....

OK. Updated Micro Chorus on the way!


If you could come up with a way to replace the SAD512D in non-working pedals with an MN3007, you'd be revered as a veritable GOD!
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Re: MXR micro chorus

Postby mictester » 19 Apr 2010, 22:03

theehman wrote:
If you could come up with a way to replace the SAD512D in non-working pedals with an MN3007, you'd be revered as a veritable GOD!


It won't be a pin-for-pin replacement, but there's no reason why you couldn't have a little "above" board with a 3007 and some biasing components. You'd also have to change the clock frequency because the 3007 is twice as long as the 512...

I'll do a rework of the Microchorus, and see where we get from there. I'll do a Vero layout as well.
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Re: MXR micro chorus

Postby mictester » 20 Apr 2010, 06:47

Here we are:

A reworked MXR Micro Chorus using an MN3007 and a few component changes. I also added presets for the BBD bias and for the mix between straight and delayed signals, so you can maximise your chorus sound. It's breadboarded, and works well as shown. I'm going to play around with the values in the multivibrator to shorten the delay, and recalculate the values in the filters to get more top end through the delay path.

Microchorus3007.png


Veroboard and PCBs to follow soon.

Enjoy!
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