Need guidelines for making ckt board

Posted: 2/17/2014 8:09:47 PM

From: Austria

Joined: 10/23/2013

@Thierry :

It is Headphone Volume, but there is no headphone amp on this board.

I put the board into one of my existing theremin housings for testing only.


@wannes_dn@ :





I have two more suggestions :








1. Add a decoupling transistor for -12v to front pannel (found somewhere in this forum)







2. Move the DC input jack to position of U1/U2

I get some unwanted volume modulation, when I am grabbing the DC power cable.


The reason might be, that the input jack is near volume oscillator, because I obverved this only on this PCB


and not on my other EW Theremins








Posted: 2/17/2014 8:18:06 PM

Joined: 1/12/2014

"This is my EW Theremin based on wannes_dn' s board, with a few modifications"


That looks neat! I wonder how well it works compared to factory build etherwaves.

Posted: 2/17/2014 9:05:53 PM

From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as . ...................................

Joined: 12/7/2007

" I had a working but not yet so good prototype in my Etherwave in March 2009 in Lippstadt during the Without Touch festival."

Which means that when you said buffering the oscillators was not the solution, and would affect linearity, you KNEW that this was dishonest advice.. Your "reasons" given dont stand up - as proven by Dewsters design.

By far the worst possible scenario - you deliberately steered a community endevour in the wrong direction and betrayed the trust we had in your competence and honesty, in order that the TW project never interfered with your plans.  I understand why the idea of  "deception" is so frequently floated by you. You are guilty of it!


Posted: 2/17/2014 11:00:02 PM

From: Colmar, France

Joined: 12/31/2007

... Which only means that totally decoupling the oscillators was not the perfect solution. I ran into linearity and stability problems with that and that's exactly what I wrote in the time on TW.

Fred, please stop this deliberate misinterpreting and twisting of my words! What you do here is simply sick!

I tried to stay calm and to answer your repeated and unsubstantiated reproaches in a polite and factual way while you were always looking for something more which you could twist until it fitted your delusional ideas. Thank you not only for poisoning this thread, but also my day and the general atmosphere here.

Posted: 2/18/2014 4:49:12 PM

Joined: 9/30/2012

"Instead i placed a 1X2 header (jp1) to connect the switch to." - wannes_dn

And you connect pin 1 and 2 from the 10x1 connector with the 1x2 connector via cable? If i route these connections on the front side of the pcb, will it affect the function of the circuit?


"I am also working on a board for the 5 potentiometer + the headphone amp circuit. If you want to use it, just let me know."

You are talking about the amp circuit shown in the "Hot-rodding your EW" file plus a potentiometer? Won't harm if you post that! :)


thanks a lot for the help!

Posted: 2/20/2014 9:09:47 PM

From: Northern NJ, USA

Joined: 2/17/2012

"@dewster: I'll look up in my notes tonight, this action was already last summer and I don't exactly remember the details. In ever case it was a very strange story."  - Thierry

Thierry, anything to report from your notes?

Posted: 2/20/2014 9:56:18 PM

From: Colmar, France

Joined: 12/31/2007

@dewster: yes, I found them. Detailed writing here this weekend.

Posted: 2/25/2014 4:53:46 PM

From: Northern NJ, USA

Joined: 2/17/2012

"Detailed writing here this weekend."  - Thierry


Posted: 2/25/2014 7:17:19 PM

From: Colmar, France

Joined: 12/31/2007

Please accept my apologies if I have other priorities, a day job, a family, several theremins waiting for repair or upgrade, instead of loosing my precious time ruminating stories from last year, especially since I feel forced after some recent discussions to look up every word in order to prevent hurting sensitive souls...

But since you insist:

Last summer I got a phone call from Italia. The guy had bought a yaewsbm for 25€ from another Italian guy who had told that he was a friend of the late Barbara Buchholz. He had installed it and found his Etherwave basically working again with deeper bass, but with a thin, rather sinusoidal timbre. When he switched it on the next day it made no more sound at all. I told him that I couldn't solve that at distance but he could send me his instrument in what he did.

When the instrument arrived there was no audio signal but the classical chirping when touching the volume loop. Opened it. Fixed pitch oscillator was found working but with reduced and asymmetrical amplitude. Variable pitch oscillator didn't work at all. There were only about 5V on the +12V line while the -12V line was ok. I removed the yaewsbm and restored the original wiring. No change. The 78L12 didn't get hot, so the 5V instead of 12V was obviously not an actual overload problem. Replaced it and had +12V again. The fixed pitch oscillator worked now correctly again with the fixed supply but the variable oscillator still did nothing. Found Q1 with a B-E short and C open. Replaced it and the VPO worked again. But the sound was still thin and rather sinusoidal as described. Found C2 with extreme capacitance loss, only about 5pF remaining. Replaced it too and had a correctly working Etherwave again.

Called the owner and told him what I had found and replaced. Asked him if I should now install the yaewsbm again and try to debug it if needed. He declined and preferred to get an ESPE01 installed. So did I and sent the upgraded Etherwave back together with the yaewsbm. I didn't look closer onto the latter, but at a first glance it seemed neatly built on veroboard with clean solderings.

These were the facts. 

I can't tell if it was "only" one of these rare "power on" accidents or if it was perhaps initially a short in C2 which overloaded Q1 who took the 78L12 with him in heaven while C2 burned down to the reduced capacitance (highly speculative)... That's a discussion which I let up to the experts.

Posted: 2/25/2014 8:52:16 PM

From: Northern NJ, USA

Joined: 2/17/2012

"But since you insist:"  - Thierry

You're jumping on me for holding you to your promise?


1. 78L12 with ~5V out, replaced.

2. Q1 with shorted BE and open C, replaced.

3. C2 with low capacitance, replaced.

My bet is ESD.  Q1 & C2 are electrically right at the pitch antenna, and the regulator could have gotten zapped through C1 or L5+L12.  NP0 capacitors don't generally go changing their values without serious voltage overload; regulators tend to fry and open up rather than change their regulation point.  You having two exceedingly odd things like this along with a fried transistor, all tied to a convenient ESD entry point.

I fail to see how any of this can even remotely be traced back to a correctly constructed and installed YAEWSBM module.

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