EH - Bass Micro Synth

DrNomis · Post by **DrNomis** » 04 Aug 2010, 09:55

You should be able to use a BC549 in place of a 2N5088,just make sure you have the transistor orientated properly,that is,the emitter,base,and collector terminals going to their correct solder pads,otherwise it won't work correctly,you could even use a BC549c transistor too,the BC549 transistor is a Silicon NPN high gain transistor with a maximum gain of about 700,the BC549c is a low noise version of it.....

borislavgajic · Post by **borislavgajic** » 04 Aug 2010, 17:20

Hi, first, great job in the pcbs and layouts Borislav!

.............thank you

"HIGH ON SILENCE", what does it means?

...that means when there is no signal at input (you do not hit guitar string) ,there will be HIGH (+voltage) in that spot...

I used BC549 tranzistors......your problem is ...what OPamp chips you used? it wont work good with TL082,TL072.........you must use 4558,or similar IC-s......try to fix that

cheers

Could you post some picture of your build?

Boris

lufox15 · Post by **lufox15** » 04 Aug 2010, 20:23

Hi, thank you very much for your answers!

i'm using the 4558 for all.
well, i find the problem, there was a little error on my pcb the pin2 of the IC A14 was not grounded

jeje. i'm using the 4558 for all.
But now i listen all the waves, and the attack delay works, but the filter stage doesn't work

, the stop freq pot defines the frecuency, like a "tone" pot. i think that the start freq pot doesn't work, i don't know what can i do? i made version for guitar using R69 2.2k and the other caps.
Could be a error on the sweep rate pot?, or maybe with the IC A13?

Thanks.

PD. i was looking too close the photo of the new version of the microsynth and i guess they use 4 LM13700 and only one need 2 transistors BC850, maybe the Bc549, in the filter stage IC A13, maybe it's possible think about a new version of the pcb using LM13700.

lufox15 · Post by **lufox15** » 05 Aug 2010, 14:46

Hi, I see that in the schematic the R89 is 4.7K, and in the drawings of Borislav R89 is 47K. this could affect the filter stage?, and R83 is 33K or 3.3k? i put 3.3K

. well, those are the differences i see on my circuit.

Thanks.

lufox15 · Post by **lufox15** » 05 Aug 2010, 16:56

Hi, again.
I was testing the circuit with a multimeter and i found that i don't have response on the IC A7, i change the 4558 and equal, when i touch with my finger the trigger pot the filter stage works, but i can't find the error, R30 is 2.2k?, i used four 1N4148 instead of 1N914, it's that right?

, i have delay attack response and the point 6 on the schematic works

, so i guess the problem is only in the IC A4A but i don't know what can i replace or change?, please can you say the voltages on the pins of the IC A4A log amp?

Thanks, sorry about my english.

borislavgajic · Post by **borislavgajic** » 05 Aug 2010, 17:04

sorry , I dont have microsynth here .......so no voltages.....

I used 1n4148 diodes......they work....
if your filter is reacting , than just seek error on trigger part....it is something simple...use picture of originall PCB to see resistor values......

Boris

borislavgajic · Post by **borislavgajic** » 05 Aug 2010, 17:06

give us some pictures of your build!?

lufox15 · Post by **lufox15** » 27 Aug 2010, 00:42

Hi

I was trying to draw the schematics of the new version of the Microsynth and well, i think that most are there, but there are tracks that i can't see on the pictures on the other topic viewtopic.php?f=1&t=3176&p=35038&hilit= ... nth#p35038 and someone could help to complete the stages that are not clear on the pictures, especially the delay attack stage it's diferent and the power supply.

sorry about my english

Thanks.

borislavgajic · Post by **borislavgajic** » 27 Aug 2010, 16:07

Great !!!...thanks a lot.......

Boris

uncleboko · Post by **uncleboko** » 20 Sep 2010, 21:02

lufox15 wrote:Hi
I was trying to draw the schematics of the new version of the Microsynth and well, i think that most are there, but there are tracks that i can't see on the pictures on the other topic viewtopic.php?f=1&t=3176&p=35038&hilit= ... nth#p35038 and someone could help to complete the stages that are not clear on the pictures, especially the delay attack stage it's diferent and the power supply.

sorry about my english
Thanks.

Have you managed to get any further with the schematic?

lufox15 · Post by **lufox15** » 24 Sep 2010, 00:18

Hi, well i think that is hard with the pictures, especially the attack delay, and the filters, and the power supply

, maybe someone with a microsynth could help us.

S. Thompson · Post by **S. Thompson** » 26 Oct 2010, 17:25

Hi all,

Does anyone know if C10 is an electrolytic, ceramic, or film capacitor? I've been trying to hunt down the exact one I need. Also, the measurement is in mf, correct?

Boris, thank you for all of this information!

- Steve

borislavgajic · Post by **borislavgajic** » 27 Oct 2010, 13:19

S. Thompson wrote:Hi all,

Does anyone know if C10 is an electrolytic, ceramic, or film capacitor? I've been trying to hunt down the exact one I need. Also, the measurement is in mf, correct?

Boris, thank you for all of this information!

- Steve

Hi Steve.......I am glad you like all this....

thanks!
if you think about capacitor *c10 0.1 0.056 -> guitar..........it is block capacitor 100nF for bass version,or 56 nF for guitar...........

have a nice day...and please post results of your work!!!

boris

devastator · Post by **devastator** » 27 Oct 2010, 19:29

someones worked on a guitar/bass version ? EHX schematic says there're only for elements to change in the guitar model to make the bass model.

It'd be interesting to make that switching with a 4PDT (or a rotary switch) .

S. Thompson · Post by **S. Thompson** » 27 Oct 2010, 20:13

I was actually discussing this with my constituent as a possibility (the guy who actually does the hands-on work for me) and he is convinced you would need a separate board if modding the factory pedal to contain the other components.

From what I understand, the bass version tracks better and sounds thicker, so I'm not sure why you would want to go back to the guitar version.

I'll let you know in a few days after my parts arrive though!

- Steve

borislavgajic · Post by **borislavgajic** » 28 Oct 2010, 15:23

you can use this switch,solder fiew components to it and wire it to original PCB.......so you can make bass/guitar version easy

good luck

Boris

JiM · Post by **JiM** » 02 Nov 2010, 22:55

borislavgajic wrote:you can use this switch,solder fiew components to it and wire it to original PCB.......so you can make bass/guitar version easy

I thought about that, when i did compare these schematics ...
Depending on the actual circuit (i don't remember exactly), it might be possible to use a switch with less poles, by adding components in parallel and/or shorting components in series.
One good example of that : http://hammer.ampage.org/files/fast-slow.png

S. Thompson · Post by **S. Thompson** » 03 Nov 2010, 01:08

Any variation between models of this pedal or a chance that maybe EHX used oddly colored/marked components to confuse cloners?

The resistor at R69 that needs to be changed out to convert the pedal to the bass micro synthesizer appears to be a way different value than expected.

- Steve

S. Thompson · Post by **S. Thompson** » 03 Nov 2010, 13:24

Here is a picture of the resistor in question for anyone who has messed with these before.

- Steve

tuemmueh · Post by **tuemmueh** » 03 Nov 2010, 18:03

There seems to be some incorrect information around ...
According to the factory schematic, the following parts need to be changed for the bass-version:
C6=2u2 (1u)
C7=1u (0.47u)
C8=0.1u (0.056u)
R62=12k (2k2)

original values are written behind the bass-values.
As C6&C8 are both connected to ground, you could also use a 3pdt, switching ground for C6&C8 bass/guitar-version.

Timm