I modded my Micro Synth

[Bernardduur]

So I finally had some time to add stuff to my micro synth and must say the unit now sounds really nice I now even love my synth even more!

What I've done:
- Added a switch to switch between bas and guitar version (effect is subtle but does make the unit very nice on bass)
- Added a charge pump to elevate the voltage to 25V (and then down to 24V) so it can be run of a 9V adapter
- Added a expression pedal out for the stop frequency (so I can use it like a "wah" pedal)
- Made it true bypass and made the LED for on / off

[RaceDriver205]

Cool! I hope one day to finish my microsynth too.
I don't suppose you could take a sound clip of this expressed stop frequency in use?
Also, what do you use as an expression pedal?

[Bernardduur]

Ehm, sorry; no clips yet...........

Imagine a synth wah pedal; it sounds just like that.

I use my old Boss as the expression pedal (Boss FV300L)

[sfr]

Seconded for the request on soundclips!

The bass/guitar version difference is just the matter of a few caps, correct? 

Did you DIY this from the start, or is this a modded retail unit?  I've been thinking of attempting this beast at some point in the future . . .

[Bernardduur]

I got one quite cheap so it is a "real" one

The difference is 3 caps and 1 resistor. I used a 4PDT switch for it
On guitar the difference is subtile, on bass it is HUGE!

I will try to make some clips

[Bernardduur]

OK, I made a clip!

Check it out!

Unit is set quite simple:

Guitar + sub octave on full, rest on min. resonance on max. No envelope.

I accidently wired the pedal the wrong way around so now I use it "wrong". Will twist em tomorrow!

[Mark Hammer]

Not sure if there is still anything of value for you in it, but check the Microsynth modifications article here: http://hammer.ampage.org/files/Device1-6.PDF

[Bernardduur]

Yes, I checked em........

Most of the mods were included in my model

Oh, one add-on; the 2k2 near the caps that needed to be changed (between guitar / bass) is replaced by a 22k

[dualaud]

were you able to locate the .01µF mylar cap craig anderton recommends to remove in step #4?
i have a later manufactured device, and can't find the cap at the loaction he describes. all my caps are oriented vertically and not horizontally like shown in Device 1-6.

thanks,
dual

[Bernardduur]

The mods as suggested by Mr Anderton were done in the newer units

So don't look for it

[dualaud]

i had the 68k from input to ground this plus the fact that the device has an internal tranny leads me to believe i have an older unit. i vaguely remember buying it in 97 used.

the lower board reads: PC7901-1B

maybe the only possibility to find out which cap he is talking about would be to trace the circuit and the schematic until i bump into the cap; stupid thing though:
i can't find the .01µf on the schematic i have. could you tell me which part number it is assuming you have the schematic at hand?
is it a cap to ground?
the schematic i have is revision 12/12/78.

thanks,
dual

[Austin73]

Hi Bernard , was it a stock Micro Synth you modded or is it one you made yourself. Very interested in how you did the Stop Freq Expression pedal mod. Got a spar EV5 I feel like sticking in it but not sure if I have to add a resistor in parallel ? I think the EV5 pedal is 500k of hand.

Aus

[StephenGiles]

You might like to think about modding the sweep generator so that the start frequency is controlled by the guitar's peak note strength. Nobody has done this yet and it would make you a hero!!

Puretube mentioned something about a sample & hold, and there is already a peak follower in there!

I think perhaps the best mod would be to disconnect the distortion

[slacker]

i had the 68k from input to ground this plus the fact that the device has an internal tranny leads me to believe i have an older unit. i vaguely remember buying it in 97 used.

The Anderton mods relate to what I beleive is the oldest version. The easiest way to check is to see if yours is the same version is to see there's an Ne5554N chip on the board, if not you've got a different version.
The 12/12/1978 schematic is for the second version and the octave up mod doesn't apply to that version as the circuit is different.
Here's links to the scheamtic for the first and second versions from a post by Stephen Giles.

At last I've found better scans of the Mark 1 Microsynth and Mark 2, which I eventually found on a floppy disc in a box of about 200! They are posted here:
http://img.photobucket.com/albums/v517/uncle_boko/EHmsynth2c.jpg
http://img.photobucket.com/albums/v517/uncle_boko/EHmsynth2b.jpg
http://img.photobucket.com/albums/v517/uncle_boko/EHmsynth2a.jpg

http://img.photobucket.com/albums/v517/uncle_boko/EHmsynth1d.jpg
http://img.photobucket.com/albums/v517/uncle_boko/EHmsynth1c.jpg
http://img.photobucket.com/albums/v517/uncle_boko/EHmsynth1b.jpg
http://img.photobucket.com/albums/v517/uncle_boko/EHmsynth1a.jpg

[StephenGiles]

You might like to think about modding the sweep generator so that the start frequency is controlled by the guitar's peak note strength. Nobody has done this yet and it would make you a hero!!

Puretube mentioned something about a sample & hold, and there is already a peak follower in there!

I think perhaps the best mod would be to disconnect the distortion

Like this:

[StephenGiles]

Ah - I forgot, fuzz boxes take preference

[A.S.P.]

barberpole pulsewidthmodulated dutycycle squares! 

[StephenGiles]

That's the ticket

[Bernardduur]

Hi Bernard , was it a stock Micro Synth you modded or is it one you made yourself. Very interested in how you did the Stop Freq Expression pedal mod. Got a spar EV5 I feel like sticking in it but not sure if I have to add a resistor in parallel ? I think the EV5 pedal is 500k of hand.

Aus

Stock!

The stop freq is just a potmeter; I added a jack with switches (dunno the name) so when I insert the exp pedal it bypasses the stock potmeter. Really cool feature btw! I now use it as my wah pedal (with low resonance) or as a filter (w/ high resonance)

[StephenGiles]

Good idea, now the follower!!