# Duo-Phase build, panel layout and LFO mod question...



## jacobsteel (May 21, 2022)

Hi there, I building a DuoPhase, sketching up a printable sticker (using Eurostile, but wider spaced) for the panel.

*Font used on the Mu-Tron Bi-phase?*
I guess Mu-Tron used something like the font "Eurostile" in the original design.
Here's a discussion on whether they used Microgramma or Eurostile. Still, you can approximate the Microgramma if you space the letters a bit wider.


However, I'm thinking of adding a few mods:
• *Input selector *(Pre A, Post A, B straight) for channel B is simple (but not yet drawn into the sketch below).

•An *expression pedal* would be cool, but cooler still would be to be able to use a common 200K volume pedal:
_Question 1:_ has anyone added a circuit for that?

•* Sine-Square wave LFO mod*.
_Question 2:_ Has anyone built a good sine-to-square-wave conversion?

*• CV.* I might add control voltage (CV), that's perhaps simpler than doing the Sine / Square mod. Or a toggle to external sync could be rectified and you'd have a crude envelope follower?


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## Cybercow (May 22, 2022)

From my experience with MicroGamma and Eurostile, the primary difference is that MicroGamma has a slightly wider character shape and the kerning is a bit tighter. With Eurostile the character shape is not as wide as MicroGamma and the kerning is a bit wider. (In the 90's I worked at a local printshop and worked extensively with hundreds of font types.)

IMO, when working clone enclosures, being the ball-park with font selection is a fair approximation of capturing the "look" of the pedal.


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## giovanni (May 22, 2022)

Fonts are a fascinating topic. Josh Scott from JHS had a show about vintage EHX fonts and how sometimes they would use the wrong letter to get the visual they wanted.


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## jacobsteel (May 22, 2022)

Finished tonight. Took around 4 hours total; wise from previous debugging I built slow and careful and measured at regular steps. Checked components before soldering. Desoldering that board would *not* be easy. I found one bad LED (white) but had some spares.

Either way, it sounds good, yet I also get the clicking sound in some combinations. But still, sounds good. 

Also, what sort of waveform is that LFO (didn't bring out the Oscilloscope tonight)? I would like it to be more even... tried the trims a bit and I will most certainly try to add a manual expression pedal... but trimming, any thread here that deals with trimming the Duo-Phase?

And/or adding more feedback, adding a feedback stage?


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## jacobsteel (May 24, 2022)

White LEDs gave good control over the very bright light-range. However, to my taste, that's not where the fat phasing's happening.
So, I changed to red LEDs and voila! *Very* good control over the darker range and in spite of the waveform outputted from the driver (not very sine-wavy) a nice sine-wavy phase transition was easily set.

Lesson learned:
1) Wave form does not translate exactly to phasing-sound (probably because the LDRs are somewhat slow as well... )
2) Red LED = better control over the "dark end". Dark end = more squelchy phasing.
3) Rightmost trim: adjust darkness (+ "length of darkness", but not in changing the waveform). Leftmost trim: bright-end-trim.


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## Betty Wont (May 24, 2022)

The Deadendfx Lola Phase has the square wave and expression pedal functions. I don't think they are simple hacks to add to this board. Ticking can be eliminated by making sure none of your wires (especially the in/out wires) go near the lfo sections of the pcb. Route the wires around the areas and it will be silent. The recommended "correct" leds for the vactrols in this circuit are yellow diffuse. I've built a ton of these and always keep the trimpots at noon. It should be pefectly calibrated with the correct LEDs and LDRs.


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## jacobsteel (May 24, 2022)

Betty Wont said:


> The Deadendfx Lola Phase has the square wave and expression pedal functions. I don't think they are simple hacks to add to this board. Ticking can be eliminated by making sure none of your wires (especially the in/out wires) go near the lfo sections of the pcb. Route the wires around the areas and it will be silent. The recommended "correct" leds for the vactrols in this circuit are yellow diffuse. I've built a ton of these and always keep the trimpots at noon. It should be pefectly calibrated with the correct LEDs and LDRs.


Thanks! Sold out right now… But, I might build versions of the Shulte Compact Phasing while waiting…. 😊👍


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## jacobsteel (May 29, 2022)

*Done*! (I might add knobs, not sure yet, see what my local store, TEMA has)...

*Fonts =* I went for the Eurostile font (tried Microgramma too, but Eurostile actually looked more like the original (when re-kerned, letters re-spaced).

*Internal LEDs *= I mounted yellow LEDs, and as far as my old ears can tell no enormous difference to red. However, there might be more phasing-action to be had if the outer limits could be even further stretched, as of now you can reach end points in extreme positions but not _both_ end points at the same settings, i.e. one trim setting allows for very good top-end phasing, another for superb low end. And playing music and trimming you can hear there's a few versions of trimming pattern to be had). 
Something for future experiments I guess.

*Solved!* = Ticking noise problem. I made *all input cables shielded* (center leading signal and earth/sleeve grounded in one end, as used in some cassette recorder designs). After shielding+grounding all input cables (including those to input-switch for phasor B) I could not provoke any ticking noise any more.

*Front panel:* I took the two files (included below) to the local photo-print store and hade them printed at 10x15 cm. Then glued them to the box. Some photo-stores machines alter the scaling ever so slightly, but this may be one way of getting front panel decals sort of inexpensive. I include my designs below, some small changes might still be necessary but could easily be made in Photoshop even.

So, thank you all for a nice build and a most impressive PCB layout. Phasing-wise most of the old Mu-Tron appears actually to be there (although the original added some extra control functions).

Here's a short stop motion film of the building and a sound example.







In/out-rear side scale 1:1




Top side scale 1:1


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## giovanni (May 29, 2022)

jacobsteel said:


> *Done*! (I might add knobs, not sure yet, see what my local store, TEMA has)...
> 
> *Fonts =* I went for the Eurostile font (tried Microgramma too, but Eurostile actually looked more like the original (when re-kerned, letters re-spaced).
> 
> ...


That looks amazing! What do you mean you made the input cables shielded?


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## jacobsteel (May 29, 2022)

@giovanni - thank you! 

*Shielded*: Instead of using single lead cables* (the colored ones that Das Musik Ding included) I used multi-leaded ones (single center lead with a metal shield around). Pictures below.

The "shield" (the braid/metal mesh around the insulated center lead) is connected to the ground and will provide cover from electromagnetic interference (such as may stem from the Voltage regulation or the LFO drivers, which could theoretically produce a small magnetic signal when switching). Every lead that has a current flowing through it will generate a magnetic field (although often these are too tiny to notice). [Faradays law].

Wiki puts it better:
_"The shield acts as a Faraday cage – a surface that reflects electromagnetic radiation. This reduces both the interference from outside noise onto the signals and the signals from radiating out and potentially disturbing other devices (see electromagnetic compatibility). To be effective against electric fields (see also capacitive coupling), the shield must be *grounded*."_

Potential sources of magnetic radiation _inside_ the little metal box:
The TC1044SCPAs DC-to-DC converters that boost the voltage for the TL072 opamps (which sound a lot better when feeded more Volts)
The 2N4401 transistors that boost/regulate the current through the LDR-phasing-LEDs.

Magnetic radiation dissipates with squared distance [inverse squared law], so further distance from these components will make things quieter. However, distance is limited inside a box. So from magnetic radiation from _inside_ the box extra shielding works. From radiation from _outside_ the box the box itself will provide cover.

Shield cable:



picture source: https://www.globalsources.com/Electrical-cable/Electrical-cable-1186181720p.htm

in contrast to



picture source: https://zwcables.com/single-core-cable-or-multicore-cable/


* RE: single lead, technically more like "single conductor, multi-core" as there are several small copper wires...


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## giovanni (May 29, 2022)

That’s what I thought. I just couldn’t picture it inside a pedal. Can you post a gut shot btw?


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## jacobsteel (May 29, 2022)

Certainly! A lot is covered by "just-to-be-sure" tape...  





... but I took closeups on where the shielded cables end up. I chose the ground connection to be by the input jacks. 





and by the switches only the center lead was soldered...


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## giovanni (May 29, 2022)

And did you ground the shields?


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## jacobsteel (May 29, 2022)

Yep! They're grounded on the ground tab on the input jacks.

input jack end (*EDIT*: actually I just now notice that this jack is the output jack of Phasor A, I added an _"Input B = Input A / B / Output A"_ switch, and this is the output switch).
Either way. The _inputs_ are all shielded (here the shielded cable goes on to my added input selector switch, so even the input cables to the input selector switch are shielded):




other end / switch end:


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## giovanni (May 29, 2022)

Gotcha. This is one of my next builds so I want to be prepared to bust that ticking!


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## jacobsteel (May 29, 2022)

giovanni said:


> Gotcha. This is one of my next builds so I want to be prepared to bust that ticking!


I also read the forums here before building. Great forum!  

I noticed someone had trouble with desoldering so I took the added precaution of mounting little soldering pins to points I knew I might be fiddling with later on (e.g. changing LEDs).

Best of luck!


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## jacobsteel (Jun 3, 2022)

Got some off-white knobs to finish off. Like the look. Great kit!


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## Alan W (Jun 11, 2022)

Nice work, and beautiful graphics. I’ve got one loaded except for the LDRs and pots, will be soon!

I make my own shielded wire for pedals, using braided desoldering tape and shrink wrap, I find it’s easier to work with. As you say, just ground at one end. Here’s a photo using this process.


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## andare (Jun 11, 2022)

Very cool thread, lots of useful tips, thanks.


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## jacobsteel (Jun 11, 2022)

Thank you! And wow, beautiful work! Cool tip with the shrink-and-braid too!


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## andare (Jun 11, 2022)

Alan W said:


> Nice work, and beautiful graphics. I’ve got one loaded except for the LDRs and pots, will be soon!
> 
> I make my own shielded wire for pedals, using braided desoldering tape and shrink wrap, I find it’s easier to work with. As you say, just ground at one end. Here’s a photo using this process.View attachment 27330


From the picture I can't tell how you make the shielded wire. It doesn't look like the desoldering braid is wrapped around the wire and the shrink wrap doesn't look shrunk (also first time seeing transparent shrink wrap)


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## fig (Jun 11, 2022)

From what I’ve read/experienced, shielding is really only necessary for the input side but there are always points for symmetry!


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## Alan W (Jun 11, 2022)

andare said:


> From the picture I can't tell how you make the shielded wire. It doesn't look like the desoldering braid is wrapped around the wire and the shrink wrap doesn't look shrunk (also first time seeing transparent shrink wrap)


First I measure out the length of wire that is needed, and strip the ends. Then, I have a 1/16th diameter piece of steel wire that I ground a soft pointed end on (a very fine knitting needle works great for this instead of the steel wire) that I use to open up the flat braid. (This is the only finicky part.) I push the wire into the tube of braid, and pull the braid taut. Then, measure out some fine shrink wrap. I like clear, just because the copper braid is pretty. Before shrinking the wrap, cut a small piece of wire to attach the ground at one end. On this wire, I strip out 3/4 of an inch and poke this into the braid shield, then shrink the outer wrap.

If a pedal has any gain, any noise picked up by the input wire gets amplified by the gain, so   inputs that reach all the way to the footswitch get this treatment. I do also do the out feed; on most pedals this is not necessary, but ones with noisy internal parts (LFOs, etc.) seem worthwhile, and, as Fig has noted, symmetry can’t hurt. Once you are used to making the “coax” it goes very fast. I did this initially because it was faster than cutting and stripping/isolating coax. (Plus, I do this in audio equipment builds, and I strongly prefer solid core wire.)


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## andare (Jun 11, 2022)

Alan W said:


> First I measure out the length of wire that is needed, and strip the ends. Then, I have a 1/16th diameter piece of steel wire that I ground a soft pointed end on (a very fine knitting needle works great for this instead of the steel wire) that I use to open up the flat braid. (This is the only finicky part.) I push the wire into the tube of braid, and pull the braid taut. Then, measure out some fine shrink wrap. I like clear, just because the copper braid is pretty. Before shrinking the wrap, cut a small piece of wire to attach the ground at one end. On this wire, I strip out 3/4 of an inch and poke this into the braid shield, then shrink the outer wrap.
> 
> If a pedal has any gain, any noise picked up by the input wire gets amplified by the gain, so   inputs that reach all the way to the footswitch get this treatment. I do also do the out feed; on most pedals this is not necessary, but ones with noisy internal parts (LFOs, etc.) seem worthwhile, and, as Fig has noted, symmetry can’t hurt. Once you are used to making the “coax” it goes very fast. I did this initially because it was faster than cutting and stripping/isolating coax. (Plus, I do this in audio equipment builds, and I strongly prefer solid core wire.)


Thanks a lot. The shielded wire I have is kinda ugly to work with. The insulation is very thick and the wire is heavy. It tends to pull the small braided wire away from the lugs. Using solid wire and adding the shielding seems a bit fiddly but more durable.


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## jacobsteel (Jun 15, 2022)

Sorry for slightly off topic but I finished the Krautrock phaser. 

The relevance to this discussion is: "But how do lightbulbs sound in contrast to LEDs" - and how could you add CV?

Because of the smallish footprint of the DuoPhase I tried the CV and lightbulbs in this one. Reveal: Lightbulbs appear to give much longer and more nuanced "dark-time"... but bulbs consume much more power (needs their own cooling and PSU...   )
As lightbulbs' darkening takes some time phasers controlled by Lightbulb-LDR will sound different (slower, but at times crunchier in the dark-end).

Link to Shulte Compact Phasing A / Krautrock Phaser project thread


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