Building a Mutron Biphase

[bvanesch]

Hello everyone, I´m cloning the Biphase and have arrived at powering it up and tweaking the LFO´s. Phaser B on it´s
own with Generator 2 works perfectly: sinus and squared it does real slow(+-12 second cycle) to fast, with amplitude
control by way of  R127.

The problem is Generator 1. Either with A and B or just A, the Rate-pot has one small turn spot halfway where it
goes from superfast to hyper in a few degrees, resulting in a strobe on the effect-pcb. Generator 1 is pretty
different from 2 and I haven´t come up with anything obvious doing a signal trace from start to finish. The actual
LFO(either square or sinus) seems to be 213 A and B but the rate pot does virtually nothing there. Also, LFO trimpot
adjustment R126 and amplitude trimpot adjustment R128 don´t do anything. 212A looks like a log amp, 212B a non-
amplifying inverter and 215 A a buffer.

I looked at the original schematics and they look the same except for R68 which on the original says 20k, but the 1
may have faded.. Testing this made no difference though.

This is the famous page where many a Mutron-fan resided for hours and hours: Patroche´s blog:
http://www.crazy-patroche.com/article-mu-tron-biphase-musitronic-plans-et-clonage-108652497.html , where you
can find all the schematics. Relevant here is the "Schema de Controle" and then the bottom part of it.

I´m not allowed to post foto´s of the pcb or a simplified schematic so Patroches page will have to do.. Components were all checked and everything so far looks physically ok on the pcb.
I´m studying up on building LFO´s but so far I haven´t been able to figure out where the problem lies here, and I
would appreciate your opinions and knowledge,

Many thanks in advance, Bram.

[bvanesch]

Found it! Pin 2 on IC212a and pin 3 on IC213a were not grounded at C52/C50 due to having made a mistake on the redrawing of the board! It´s working fine now. Next setting up the LDR´s and audio!

Any questions about my project I´ll gladly answer.

Greetings, Bram.

[tommycataus]

Brilliant mate. I've been trying to build up the courage to do this... Do you know whether anyone has done a vero layout for this? I know Mark at tagboard effects mentioned it as a possibility a while back but I don't know whether he got around to it or there is anything already out there.

I built a Phasor 2 and love the sound of it. What would you say the difference is, what does the biphase have in the way of features that makes it so much more popular and well known? I'm wondering how those extra features could be used practically and how they differ.

[bvanesch]

I have never worked with vero boards, but I imagine this layout would be pretty big? The original control board was A4 size, I´ve managed to get it to half that with no nasty side effects so far(the original separates audio and lfo pretty well). I´m already thinking of doing another one with some more improvements and a tidier layout. Why? Because this one sounds really good already! I´m amazed at how little I had to tweak and fiddle around for it to sound good after hooking it up the first time! Mind you I stuck to the original schematics and components as much as possible.

The schematic for Phasor 2 is ,as much as I can tell on the lousy quality pics I found, the same as it is for Phasor B on the Biphase. The A channel LFO is different, CV controlled, and I haven´t been listening enough yet to know wether they sound different. It´s still on the workbench as I´m waiting for a rack unit to mount it in. Maybe it´s different because of the pedal use options..

As for the possibilities: I´ve been loving the input A slow/ input B fast phasing, the sound is very rich and clear. Only when it´s in a box I can test it in stereo at home. The next step will be the pedal, that will really open up the possibilities: sweep rate/sweep by itself. The normal/reverse is also very nice and will be very cool in stereo. When using generator 1 channel B will do the oppposite phase of channel A. All in all it´s a great project so far, although not cheap. I´m up to 230 euros so far. Only thing to buy now is the rack unit to build it in and finishing touches.

Good luck with a build and any questions I´ll be happy to answer. I wish I could show pic here but I can´t!

[tommycataus]

That sounds pretty good, despite the size. I've got a few things I'll be completing before I come back to phasers but this is most definitely on the list. I love the thought of the two phasers going in stereo. The Phasor II can give some amazingly subtle textures that really jump out when you step on the fuzz. Damn I can't wait!

[bvanesch]

Hi there, finally got around to some experimenting with youtube to be able to show the result. This is just a first effort with terrible lighting and a bit "dull" sound, taken with a compact Sony TX-10:

https://youtu.be/pjL9kBJLly8

Greetings, Bram.

[stringsthings]

That sounds great    And looks super cool also.

I'd be very interested in any developments that you make ( especially PCB related ).  I love phase shifters and I've made
a few ( including the Mutron II ).  If you don't mind, what are the specs on the LDR's and where did you get them?

( I'm too lazy to translate the page, but I know that's an option )

[bvanesch]

I´m looking forward to building another one soon, with some minor changes to the pcb´s, so any questions feel free to ask. An obvious change I made but forget to mention is getting rid of the single multicable link between pcb´s. Seperated them all and use 2,54 connectors for everything but audiopaths.

I live in Portugal and was fortunate to find some LDR´s here relatively cheap: http://www.castroelectronica.pt/product/ldr-200-volts-14-x-265-mm , as you need 12 for the phasers. The ones for the signal pass I bought here: http://www.newtone-online.nl/catalog/product_info.php?cPath=22_77&products_id=474 in Holland(where I´m from btw). If you snoop around this excellent store you´ll find many LDR´s, vactrols and other cool components.

Again, any questions go right ahead. Greetings.

[tommycataus]

Great work mate. I'm just reviewing the schematic and I am confused as to the identity of J1 etc. I'm guessing jacks, but whatys with all the connections, for example J1-12? I'm confused as to what connects where. Please can you shed some light on this? I'd be most grateful. Thanks!