EH - Bass Micro Synth

borislavgajic · Post by **borislavgajic** » 13 Jun 2011, 14:16

Izvini Druze Orgasmer.....nikad nisam koristio veroboard........

PCB uopste nije komplikovano za napraviti........

translation.... sorry my friend Orgasmer........I have never made veroboard........Pcb is not difficult to make......

cheers

Boris.......

P.S.

I would love to see more finished builds...posted here

nothingmaker · Post by **nothingmaker** » 03 Oct 2011, 14:44

hi, anyone have a schematic of new Micro Synth XO series?
I'd like to mod the pedal for more sustain of the effect...

Thank you so much

zerbino · Post by **zerbino** » 30 Jan 2012, 20:20

Could somebody help me? I've built EHX MicroSynth on 3080 + Darlington couples (instead of 3094). Signal goes through the entire schematic and stops on the final cascade. I've read that there is a mistake in schematic and 2 pin of A14 should be connected to ground. I've try that, but in vain. Still nothing on the output.
What should I do?
Thanks
Sorry for bad english

Jellevanlys · Post by **Jellevanlys** » 31 Jan 2012, 13:04

Hello,
I am new here. After building a minimixer I would like to build something bigger. So as a bassplayer I'm very pleased to see that you can make your own Bass Microsynth. I already downloaded the files from Borislav Gajic and i'm very enthusiastic about making that box. The only problem is that i don't know where the connections of the footswitch, the in- and outputs of the jacks and the DC-input wires have to be connected on the PCB.
Can anyone clear this out?
Thanx
J

borislavgajic · Post by **borislavgajic** » 31 Jan 2012, 16:30

I am glad to see such positive spirit......if you manage to make all parts done, than two jacks and AC wires would not be a problem.....

go for it, and I think there are markings on PCB that saz IN, OUT...there you connect input and output.......ac from traffo goes to grec bridge rectifier......

cheers

Boris

Liquids · Post by **Liquids** » 31 Jan 2012, 20:26

I never noticed the fine, though only partially complete work of tracing the XO version was done and offered here.

From what is drawn, the values and connections look quite similar to the bipolar voltage version of the schematics from Dec 1978. The filter looks different though and that (to me) is the critical area...and where some of the voltage differences are more significant and require value and layout changes.

Seems like EHX got penny-wise and instead of using 2x value caps in the smoothing filter of the bass version, they simply use 2x value resistors instead.

In some ways it seems more trouble than it's worth to me to try and get this to work off of 9v, but I'm curious anyway, because I believe David Cockerell who worked on the original is back at EHX and is behind this version too...

The early versions used the boosted guitar signal for bypass, which made the 'clean/bypassed' output not only incredibly hot, but oftentimes distorted. If you compare the microsynth sub-octave/etc signal levels to the 'true bypass' signal, the effected signal can get VERY loud. But if your bypass reference is the boosted guitar signal, the effected signal seems to have trouble keeping up and you also send a really hot signal through the OTAs.

bunyaman · Post by **bunyaman** » 29 Feb 2012, 16:47

Hi, men! borislavgajic, I have a question for you. I have a schematics(attached). There is pin 2 of A14 isn`t grounded, but on Your PCB(from first post) this pin is grounded. Is it bug of this schematics, or error on pcb? And i didn`t found schematics of this device in a topic. What schematics did you use?

eh_bassmicrosynth.pdf: (116.69 KiB) Downloaded 544 times

bunyaman · Post by **bunyaman** » 29 Feb 2012, 16:57

Oh, and now I found the post of lufox15, where he corrected the mistake with grounding of pin 2 of A14! I hope, will soon begin the building of this great device!

Sorry for my bad english...

bratpilot · Post by **bratpilot** » 06 Mar 2012, 12:51

Hi!
I think it's not so difficult to replace CA3094 in old design to LM13700 like in XO version.
Thanks to Lofox15 for his "Half - schematic" ( viewtopic.php?f=1&t=14650 )
That I can see new design is not very different from the old.
difference in the nominals are likely caused by change of voltage - 18V to 9V
replaced by a transistor OTA (after Octaver)
on the principle of replacing the CA3094 to LM13700 is quite understandable.
so I think it is quite possible "modding" old version.
scheme of the old version I have in the Proteus. Today I will think about it.

borislavgajic · Post by **borislavgajic** » 15 Mar 2012, 22:31

...Го фор ит !!!!!!

I wanted to say...........Go for it !!!

rtstef · Post by **rtstef** » 02 Apr 2012, 07:25

Hi,

No news for xo model schematic or lm13700 adaptation?
I really want to build one microsynth but no money for ca3094 et no knowledge for improvise.

Thanks all
Stephane

nb: great job in that subject !

Liquids · Post by **Liquids** » 02 Apr 2012, 13:42

rtstef wrote:Hi,

No news for xo model schematic or lm13700 adaptation?
I really want to build one microsynth but no money for ca3094 et no knowledge for improvise.

Thanks all
Stephane

nb: great job in that subject !

If you are an ambitious DIYer - that is, don't need a paint-by numbers perfing/vero layout done for you, and not afraid of generating & regulating bipolar power off an AC regular, I have plenty of info posted on the 'other' forum via schematics and posts.

zerbino · Post by **zerbino** » 29 May 2012, 10:47

Are there anybody to help output volumes of vocies about equal? suboctave & octave signals are too small, square wave signal just TOO high...
Help!

lufox15 · Post by **lufox15** » 30 May 2012, 02:59

I think that you can change the resistor near to the pot's, I don't remembet well, it have maybe a 10K to 22k value you can reduce it and in the case of the square wave you could put a high resistor.

borislavgajic · Post by **borislavgajic** » 24 Jun 2012, 21:18

I made mine as a exact copy of original unit that was at repair in my place

so do not bother about schematics.....do all like I have shown on PCB layouts....they are 100% working! if there are some errors try to find where you made short connection or cold solder spot......in my clone TL082 did not work OK...so I put 4558 or 1458 there.....it works great.....I even made foot controlled pedal , and switch that kills filter sweep...

good luck....it is a big project

boris

bs_ane · Post by **bs_ane** » 07 Apr 2013, 07:42

Hi..
I read this topic and confused..so many information....

Can anyone post the correct schematic for bass and part list???

sadrew · Post by **sadrew** » 21 Apr 2013, 08:23

hey boris where can i buy slide pots that fit in your project? do you have a product number and maybe an online shop in EU that sells them? thank you

Effectsiation · Post by **Effectsiation** » 10 Mar 2014, 16:25

Does anyone have a stock version of the 90s-version Microsynth? I'm looking for a few pictures or an explanation of where the wires come off the boards and where they go (to switches/jacks).

All the pictures I can find of that Microsynth are post TB mods.

Basically I have one that I'm trying to fix and the guy I bought it from did a bunch of mods (including a failed TB job) and I'm trying to basically just get this thing back to stock.

Thanks for any help you can give!!!

Liquids · Post by **Liquids** » 11 Mar 2014, 13:51

With the schematic in hand, you should be able to locate the components/wires that feed the input and output of the circuit via continuity.

daemons · Post by **daemons** » 23 Aug 2015, 18:34

bs_ane wrote:Hi..
I read this topic and confused..so many information....

Can anyone post the correct schematic for bass and part list???

I share your sentiment.

bratpilot wrote:Hi!
I think it's not so difficult to replace CA3094 in old design to LM13700 like in XO version.
Thanks to Lofox15 for his "Half - schematic" ( viewtopic.php?f=1&t=14650 )
That I can see new design is not very different from the old.

I'm willing to help LoFox15 trace the XO version. I would very much prefer building an LM13700 9V version of this pedal myself.
I tried viewing the pictures beavis posted, but they don't load anymore from his website. A temporary issue perhaps..
I think much of the missing parts can be drawn from the old circuit, not directly, but in a sense of what it does, and how it does it. Just need to find the right values to achieve the same results. This is no small project though. But I guess it's nothing compared to an Akai Deep Impact.

Edit: posted this too quickly.. looks like Bernardduur has already done the job https://www.freestompboxes.org/viewtopic ... 50#p188186 . Guess I'll be ordering a few LM13700s in my next Digikey order.

Dae.