E&MM Harmony Generator project PCB

[StephenGiles]

<Is this the same one as the EH Micro Synthesizer ?>

No this one.


http://img.photobucket.com/albums/v317/StephenGiles/EHsynth1.gif

[freddd]

Andre do you have a parts layout to go with your trace? I can't read the schematic at marks site! My poor eyes! Awsome work btw, I really wanna build one.

[Andre]

Thanks for the schematic diagram Stephen.

freddd, I think you missed it.
I already posted a parts layout earlier in this thread.

André

[markusw]

<Is this the same one as the EH Micro Synthesizer ?>

No this one.


http://img.photobucket.com/albums/v317/StephenGiles/EHsynth1.gif

Stephen, one question: as far as I understood the most right part (with the two 3094s) is the tracking filter. So when fed with a guitar signal it should provide a rather pure sine wave (and a square wave). What exactly are the "muting" and "loop" controls doing?
For improving the tracking of the EMM would it be sufficient to add the tracking filter (or e.g. an adaptive Schmitt trigger like the one found in the EH mini synths or the Boss octavers) or would it need the whole thing you posted?

Thanks for your help in advance! 

BTW, how fast does the adaptive filter "lock in"?

Markus
 

[StephenGiles]

Markus

I think the muting & loop in the EH Guitar Synth are for the VCA control, so would not be needed. You would need the compressor (or similar) and the adaptive filter which is much more efficient than the adaptive Schmitt trigger in the Microsynth. The adaptive filter is very fast, I found the tracking in that synth to be very good, albeit monophonic.

Stephen


 

[freddd]

Sorry for causing so much fuss but - Where abouts is the layout? Do you mean the picture of the finished board?

[markusw]

Markus

I think the muting & loop in the EH Guitar Synth are for the VCA control, so would not be needed. You would need the compressor (or similar) and the adaptive filter which is much more efficient than the adaptive Schmitt trigger in the Microsynth. The adaptive filter is very fast, I found the tracking in that synth to be very good, albeit monophonic.

Stephen

Thanks!! 

Sorry, another dumb Q: which part in the schem would be the compressor? 

And another one: would it be hard to mod the adaptive filter for 13700s?

Markus

[Andre]

freddd,

Is this what you're looking for ?



André

[markusw]

Sorry, another dumb Q: which part in the schem would be the compressor? 

Markus

Would it be the 4558 with it's +ve input connected to "C" plus the 3080 below??

Markus

[Coriolis]

Nice demo - I heard Inca Roads in there...

C

[Andre]

Inca Roads is my all time favorite Zappa song, but the little part I played in the demo is also the only part of it I can play 

[freddd]

I finally got it. Seems firefox didn't like the picture and just wasn't displaying anything. I had to surf through your webspace and download it Thanks a lot.

[StephenGiles]

Sorry, another dumb Q: which part in the schem would be the compressor? 

Markus

Would it be the 4558 with it's +ve input connected to "C" plus the 3080 below??

Markus

Correct, and in answer to your point about modifying the 3094s to 13600s in the adaptive filter, I don't know - much easier to pay out for 3094s from Smallbear.

[Andre]

I recorded another soundclip to show that, with the right gain settings,  you get this thing to track much better.

http://www.xs4all.nl/~jvcn0028/HarmonizerDemo2.mp3

I think it's still far from being a usable effect, but it's not that bad also.

I tried to replace the 741's with TL071's but this resulted in a lot of sizzling, squeeling and howling, so had to put the old 741's back.
I also used a LF351 in the first stage as listed in the partslist but this also resulted in lots of unwanted noise.

Markus, removing the connection between pins 10 and 13 of the 4046 did not change anything, as we both expected.

André

[AdamB]

That sounds amazing. OK now I want one.

What size enclosure would you recommend for this thing? That PCB looks pretty big.

EDIT:
Also,  have you tried the envelope trigger out yet?

-Adam

[markusw]

Correct, and in answer to your point about modifying the 3094s to 13600s in the adaptive filter, I don't know - much easier to pay out for 3094s from Smallbear.

Thanks!! You're right. Better first try with 3094s and then try to sub them for 13600/13700s....

I recorded another soundclip to show that, with the right gain settings,  you get this thing to track much better.

http://www.xs4all.nl/~jvcn0028/HarmonizerDemo2.mp3

I think it's still far from being a usable effect, but it's not that bad also.

I tried to replace the 741's with TL071's but this resulted in a lot of sizzling, squeeling and howling, so had to put the old 741's back.
I also used a LF351 in the first stage as listed in the partslist but this also resulted in lots of unwanted noise.

Markus, removing the connection between pins 10 and 13 of the 4046 did not change anything, as we both expected.

André

Thanks again for sharing your observations!! Also for checking the pin 10 - pin 13 connection! 
Any ideas why the TL071 doesn't work in this circuit?

Markus

[Andre]

What size enclosure would you recommend for this thing? That PCB looks pretty big.

It's about 10.5 x 8.2 cm. If you build this thing, make sure you pick an enclosure big enough to fit the harmonizer as well as
some extra circuits for in- and output filtering.  And please keep in mind that the rotary switches have a diameter of about
3 cm, so that's a lot of space.

Also,  have you tried the envelope trigger out yet?

No, not yet. I didn't even put the transistor in, since it was not necessary for testing.

Any ideas why the TL071 doesn't work in this circuit?

No, I was hoping that by using TL071 I could reduce the voltage drop of the negative power supply, but it did not
help a thing, so I still have to solve that issue.

André

[AdamB]

Yea, I think maybe I'll add a square-wave fuzz type circuit on the input too, as I like horrible distorted synthy noises and I think there is a chance it will improve tracking.

I was thinking something like this:

from Tim Escobedo's Circuit Snippets.

What sort of filtering would I need on the input and output? You mean to cut bass/highs like on a fuzz face?

[Andre]

It is sure worth to try this square wave shaper, although I don't think it will completely remove the unwanted harmonics of the guitar output, so using a fundamental extractor as discussed earlier will give the best tracking.

As far as output filtering concerns:

The output is generated by switching the envelope of the input signal to the output, in the rythm of the generated harmonics.  Then this signal is mixed with the input signal. The reason for this is that the output follows the envelope of the input.
Disadvantage of this method is that the harmonics sound very distorted, because of the hard switching.

It would be much better to filter the harmonics, reshape the envelope with some VCA and then mix it with the input signal.

Because of the wide range of the generated harmonics you would need a switchable Low Pass Filter.  If you drop the 3 octave down option, which is too low to be useful anyway, you can do with  a 6 position rotary switch.
You can now use the other part of the switch to make a switchable output filter.

I'm afraid I'm no Mark Hammer or R.G. when it comes to explaining things,     so I hope you understand what I mean.

André

[markusw]

... so using a fundamental extractor as discussed earlier will give the best tracking.

IMHO, at least you will need some lp filtering before the signal is squared. Currently, I have a PLL circuit on breadboard that at the moment is fed through a gain stage -> active lp filter -> LM311 comparator and tracking isn't really a problem. Sure, at the very end of the notes it's jumping between the octaves, but for normal playing it's pretty fine. Alternatively, instead of the comparator there is an adaptive Schmitt trigger between the lp filter (like in the EH Micro Synth or the Boss OC-2) and the PLL but, to be honest, it doesn't really change that much.
So IMHO the EMM unit already would benefit quite a lot from adding a lp filter before the signal is run into IC4.

You can now use the other part of the switch to make a switchable output filter.

Cool idea! 

reshape the envelope with some VCA and then mix it with the input signal.

Have a look at the Electrax synth. The schematics should be somewhere here around. IIRC, there is a VCA used. Also there is an attack/decay generator which might be used instead of the natural envelope for some (I would assume) pretty cool sounds.

Markus