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

[jacobsteel]

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?

 

[Cybercow]

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.

 

[giovanni]

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.

 

[jacobsteel]

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?

 

[jacobsteel]

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.

 

[Betty Wont]

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.

 

[jacobsteel]

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….

 

[jacobsteel]

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

 

[giovanni]

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.



View attachment 26871

In/out-rear side scale 1:1
View attachment 26872

Top side scale 1:1
View attachment 26873

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

 

[jacobsteel]

@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...

 

[giovanni]

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

 

[jacobsteel]

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...

 

[giovanni]

And did you ground the shields?

 

[jacobsteel]

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:

 

[giovanni]

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

 

[jacobsteel]

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!

 

[jacobsteel]

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

 

[Alan W]

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.

 

[andare]

Very cool thread, lots of useful tips, thanks.

 

[jacobsteel]

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