EHX - Micro Synth XO Version  [schematic]

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Re: Micro Synth XO Version EHX (half-schematic)

Postby Liquids » 26 May 2012, 17:14

generally in low voltage electronics, 1n914 and 1n4148 are the same. I think some diodes I got the other day actually were labeled 1n9148. I have a strange sense of humor, but I found that funny.

Those two diode types are more or less 'generic' silicon types. They're not for ultra high voltage, ultra high current, or ultra high speed applications. Pedal effects rarely qualify as even one of those.

However, it's education to look at the datsheets for the two types of diodes, from the same manufacturer (mouser.com is a great source for such datasheets), and examine the difference, or see if they put the two on the same datasheet, even!

1N4001/1N400X type diodes are different. They're 'over design' for audio portions of most circuit, kind of oversized, clunky, etc on vero and perf. IF you have them, use them. Again though, look at the datasheet for a 1N4001. You'll probably see that its a datasheet for 1N4001-1N4007 diodes, with minor differences between variants ending in 1-7 other than max voltage. Most pedals are low voltage and I think the 1N4001 has the lowest voltage tolerance - at 50V. Which is why you may see it called for in a pedal for power supply stuff from time to time...50v is plenty and some may like it's other specs better for power supply areas or the like.

Gnerally to anyone....you can learn a lot of datasheets. Read some, be inquisitive of them...compare one to another...look at how good designs utilize them in circuits or where detailed schematics suggest a number of diode/transistor types will work equally well, and try to understand why....

OF course in The Art OF Electronics, it explicity says that any circuit that is dependent upon a specific component types characteristics is a symptom of 'bad design.' Think Germanium fuzz face in the modern world (back then maybe it wasn't) =^)

Hope that is more information than you asked for...
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Re: Micro Synth XO Version EHX (half-schematic)

Postby ecollins12 » 24 Jun 2012, 01:05

Hi Bernard,
Thanks for the schematic. One thing... Can you confirm V+ and V- on the cd4013? The original schematic shows a little different. Can you also check if pin goes to gnd or V-? I am problems simulating in multisim. Thanks.
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Re: Micro Synth XO Version EHX (half-schematic)

Postby Bernardduur » 25 Jun 2012, 06:51

I'll check!
'No more....... loud music.......'
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Re: Micro Synth XO Version EHX (half-schematic)

Postby Bernardduur » 25 Jun 2012, 06:56

Ah look, you were right. The S on the second part of the 4013 goes to V-; pin 14 goes to GND, pin 7 to V-
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Re: Micro Synth XO Version EHX (half-schematic)

Postby ecollins12 » 28 Jun 2012, 18:04

Thanks for checking man!
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Re: Micro Synth XO Version EHX (half-schematic)

Postby ecollins12 » 29 Jun 2012, 19:00

Can anybody explain how the "Sub Modulator Track and Hold" circuit works in the XO version? It seems as if the whole transconductance amp was by Q9 and Q1. I just can't figure out how it works. Thanks
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Re: Micro Synth XO Version EHX (half-schematic)

Postby ecollins12 » 01 Jul 2012, 04:55

OK, Bernard could you confirm the Q9, Q1 circuit? I don't believe the source of the JFET should be tied to the Q' of 4013 (and neither should R86, 4.7k).
-ecollins
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Re: Micro Synth XO Version EHX (half-schematic)

Postby uncleboko » 01 Jul 2012, 09:28

ecollins12 wrote:Can anybody explain how the "Sub Modulator Track and Hold" circuit works in the XO version? It seems as if the whole transconductance amp was by Q9 and Q1. I just can't figure out how it works. Thanks


EH secret :lol:
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Re: Micro Synth XO Version EHX (half-schematic)

Postby Liquids » 01 Jul 2012, 12:15

From what I understand, it's not unlike the Boss OC-2...clean signal and sub-octave signal blended....buta bit like a VCA where the clean signal acts like the gate for the suc-octave signal. Maybe the stompboxology article on sub-harmonic synthesis will help. Even if not directly addressed there you'll learn another approach...

Lastly, on could sim it in LTspice...
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Re: Micro Synth XO Version EHX (half-schematic)

Postby ecollins12 » 01 Jul 2012, 18:39

OK, I have figured it out. Thanks to reading the Stomboxology article. This is for the xo version...The transistor is basically a switch. The clean guitar is on the emitter. When turned on via the divided square wave, only half of the AC signal is passed. Kind of like a /2 sine wave. The jfet just buffers the signal which is then filter a bit by the 220nF cap. I was thrown off because the schematic has the sognal from the Jfet tied to square wave from the 4013, which i believe is NOT correct.
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Re: Micro Synth XO Version EHX (half-schematic)

Postby lufox15 » 13 Jul 2012, 16:37

I everyone I've just built this circuit on a breadboard but as always it doesn't work, so what do you think it's happening?, the Diode BIAS on the LM13700 it's unconnected? or to ground? I'm not shure about that, but in the circuit when I put all the pots of signal to ground The signal of my guitar is alive yet, so I guess that something with the LM13700 maybe, I'm lost here, but I'll try follow the signal with a oscilloscope later.
:?: :?: :?: :?:
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Re: Micro Synth XO Version EHX (half-schematic)

Postby lufox15 » 13 Jul 2012, 16:39

another thing sorry. I'm using instead TLC2272 a TL072 and a TL084 could be those the problem? should I change them for a pair of RC4558? I'm using RC4558 for all the OA as the schematic looks. only for the TLC2272.
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Re: Micro Synth XO Version EHX (half-schematic)

Postby lufox15 » 13 Jul 2012, 16:42

instead BC850 = BC549, BC857 = BC558 or 2N3906 or 2N5087, and for the fet BF5484 = BF245C those are correct? should I used another replacements?
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Re: Micro Synth XO Version EHX (half-schematic)

Postby Liquids » 13 Jul 2012, 20:25

I don't know that I'd trust the schematic. One thing you can do in some areas, if things are on the breadboard, is refer to the arrangement of components on the earlier versions, for reference...there may be errors in the schematic, a personal error you made in duplicating it on the breadboard, a wrong assumption about how the breadboard is configured. Lots of breadboards had breaks in continuity along what might otherwise seem like continuous power rails...I always say beep it out, and even still I got caught the other day assuming that with a new breadboard that LOOKED like the 'twin industries' type I am the most fan of, but it was cheaper...and good, but had breaks in the power rails.

Of course, there are points in the schematic where component configurations are different due to the difference in voltage...but sometimes it's the same, just a different value...sometimes it's even the same value. It may help you on the breadboard.

The TLC2272 op amps are likely used predominantly in cases where their ability to swing rail to rail helps ofset the single sided 9v of this design as compared to previous version that were powered with +/- rails. In some cases, such as op amps used as a comparator, you might find a 4558 does fine or better - I've heard some say LM358s work well compared to other op amps, when configured like a comparator. I've read documents that really say 'use a comparator if you want a comparator' but also heard other experts say, there's no reason one shouldn't use an op amp as a comparator...within a general audio or at least within a specific circuit context.

IF you're using NPN where an NPN is called for, and PNP where a PNP is called for, I wouldn't sweat that as the reason for things not working.

That attack decay / final OTA are and how it's configured has always been the least intelligable to me. I'd ignore that until everything else is clear to a point. But really...an audio probe is your friend. Start at the beginning...once audio signal starts splitting, figure out ALL the places id dies (it's the kind of circuit where it may be dying in multiple places). With some good analysis, that should help you narrow the problem quite a bit more quickly than back and forth posting.
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Re: Micro Synth XO Version EHX (half-schematic)

Postby lufox15 » 17 Jul 2012, 06:13

Thanks for the help Liquids, and now the circuit is working almost, well the first part, I have guitar clean signal, octave up, and square wave but I don't have sub octave, I'm not sure if my Cd4013 is dead or something goes wrong with the schematic.

Bernardduur a question.
In the schematic in the part before the first flip flop there is a 4558 U5 that have its non-inverted inputs (+ +) connected? looking at the big version schematic I've noticed that these are not connected, so is a mistake? on the schematic you can see on A15A and A16B the connection is between a inverted input and a non inverted input, anyway I've made this change and the sub octave signal doesn't work. I need to buy another CD4013 and I'll change it to see what happens.
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Re: Micro Synth XO Version EHX (half-schematic)

Postby Liquids » 17 Jul 2012, 07:17

make sure you've got it oriented in the correct direction/pins. Like a previous poster said, check out the stompboxology article too. Audio probe...see if you get a big loud signal out of the 4013 at any point...
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Re: Micro Synth XO Version EHX (half-schematic)

Postby lufox15 » 20 Jul 2012, 23:05

Well looks like still no working the sub octave, but I simulated on Proteus and works, but I have no idea where is te mistake because my oscilloscope stop working and now I can't see the track of the signal in that stage so, I don't know what to do.
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Re: Micro Synth XO Version EHX (half-schematic)

Postby microsynth » 09 Feb 2013, 16:38

Can someone explain to me why this pedal doesn't work with daisy chained power? I know I'm not exceeding the wall wart's current rating, because I can power several pedals along with the microsynth, but the microsynth won't pass signal if the signal chain involves pedals it's powered with. I don't get it.

my scenarios:
works:
guitar -> Tuner -> Compressor -> Overdrive -> Microsynth
----------|-----------chained power-----------| |own power|

works:
(Tuner -> Compressor -> Overdrive) /signal disconnect/ guitar -> Microsynth
|------------------------chained power-----------------------------------------------|

doesn't work:
guitar -> Tuner -> Compressor -> Overdrive -> Microsynth
-----------|------------------chained power--------------------|

doesn't work:
guitar -> Microsynth -> Tuner -> Compressor -> Overdrive
----------|-------------------chained power--------------------|
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Re: Micro Synth XO Version EHX (half-schematic)

Postby microsynth » 09 Feb 2013, 18:36

Waaaaait a minute. Could it have something to do with the fact that the microsynth runs at +4.5V to -4.5V, instead of the standard 0 to 9V? So the microsynth's power return path is at a different voltage than the other pedals it's chained to? :hmmm:
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Re: Micro Synth XO Version EHX (half-schematic)

Postby fbiramba » 17 Feb 2013, 09:18

on the schematic, we don't know where C51 goes? I think to the ground ?

what are the characteristics for ferrite bead? how much Henry?

thaanks a lot for this topic !

Franck
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