Phase Revolution - Perf & PCB layout for R.G.'s Phase 180 Plus

[frequencycentral]

I've done this layout, took a while, designed to fit into a Hammond enclosure (can't remember it's code) 4.7" L x 3.7" W x 1.34" H. (120mm x 95mm x 35mm). The layout is designed for the enclosure to be 'landscape' as opposed to portrait'. I used LM324 quad opamps to keep the size down. A 5 knob build. I know the chances are very slight - but anyone care to check it over for any obvious errors before I start building it? Thanks!





Link to GEOFEX article: http://www.geofex.com/FX_images/p180plus.gif

[frequencycentral]

Here's the PCB version and PNP just for the hell of it, still needs to be verified though:

[nelson]

Make sure and buy 20 bazillion fets to match!

[frequencycentral]

Make sure and buy 20 bazillion fets to match!

Wot? Won't 8 be enough then? 

Just thinking out loud - I haven't got enough 0.047uf caps in stock to make this ATM, though I do have 20 bazillion 0.1uf. I'm just wondering how much difference it will make?

[Slade]

Hi,
I'm working on something pretty much like this and I just want to say that you could add a second trimmer to adjust the bias of the second 4 transistors to avoid the matching, maybe it could give you more possibilities to get nice and deep phase.
Let me know
Greetings.

[frequencycentral]

Hi,
I'm working on something pretty much like this and I just want to say that you could add a second trimmer to adjust the bias of the second 4 transistors to avoid the matching, maybe it could give you more possibilities to get nice and deep phase.
Let me know
Greetings.

Hi, nice idea, but I'm planning for the bias to be a panel mounted pot, as interesting variations are available. I've got a bunch of 2n5485, and I'm using sockets in my build for the FETs, so if the batch I have don't match up I'll just have to get some more! At least with the sockets I'll be up and running, just not quite there

[frequencycentral]

Just a quick note, I did this layout using LM324 quad opamp packages for two reasons, one to save some space, and two because I have a bunch of LM324's that need using. TL064's and TL084's have the same pinout as LM324's so they are options too!

[Slade]

That's fine
I don't really think that a external control for the BIAS could be very useful, let me know if it's so or not, please.
I'm doing mine using NE5532 Opamps, they're really clean and nice sounding, have you tried them?

[frequencycentral]

That's fine
I don't really think that a external control for the BIAS could be very useful, let me know if it's so or not, please.
I'm doing mine using NE5532 Opamps, they're really clean and nice sounding, have you tried them?

There's an external bias on my Phase Evolution: Phase 45 with JC Malliet's mods, to which I added two extra stages. The bias control does add some extra interesting flavours.

Yup, I've got some NE5532, but I've got a glut of LM324 which I'm trying to deplete!

[Slade]

Excellent, excellent..

Finally, what would be the function of the Regen control in this phaser? Can´t find it looking at the schematic, is it the 47k pot (I thought this is a trimmer) before the mix pot?

[frequencycentral]

Excellent, excellent..

Finally, what would be the function of the Regen control in this phaser? Can´t find it looking at the schematic, is it the 47k pot (I thought this is a trimmer) before the mix pot?

The Regen is a resonance control, or a feedback control. It feeds the output back into the circuit and accentuates the notch frequencies. It can sound very filtery and chewy.

[Slade]

Ok, so that is what I'm doing by replacing the 22k (common mod) for a 100k pot in series with a 15k resistor. I'm not doing the Mix mod, but I'm doing a "Depth" control by changing the 1M resistor to the BIAS for a 620k resistor in series with a 1M pot, by increasing the value of this resistor you lose depth of the phaser and get a change in the tone and by decreasing it you get more deep phase sound, I think you should try it, it works perfect and gives you pretty nice textures
Greetings.

[frequencycentral]

I'm doing a "Depth" control by changing the 1M resistor to the BIAS for a 620k resistor in series with a 1M pot, by increasing the value of this resistor you lose depth of the phaser and get a change in the tone and by decreasing it you get more deep phase sound, I think you should try it, it works perfect and gives you pretty nice textures
Greetings.

Yes, I think that is referred to as 'Width' in R.G.'s schematic. Mark Hammer had suggested a resistor in series with the 1M pot, I was going to have to experiment with that, so thank you for confirming it, I'll do it your way!

[frequencycentral]

Perf populated, now I'm waiting for the FETs to arrive, that's what the four six pin SIL sockets are for. I decided to use a BC212 PNP instead of the BC557 I listed on my layouts, as it's hfe is very close to the 2n4125 used in the original P90.

I think this is the best perf work that I've ever done:

[frank_p]

   
Master Perfer 

[foxfire]

it makes me dizzy just looking at it. well done, know make me one...

[frequencycentral]

Just finished testing my build. I can confirm that the perf layout is now officially VERIFIED! Cool! Therefore, the PCB layout should also be verified, as all I did to that was copy the perf layout and replace the jumpers with traces. I can also confirm that this circuit works well with LM324, which I did have some misgivings about due to their preference for single supply rail operation, but they work just fine.

I ordered and tested thirty 2n5489 FETs, and was lucky enough to find three pretty well matched sets, with Vgs of ~1.8v, ~2.3v and ~2.5v. Having said that, I also tried some unmatched 2n5457 left over from my four stage P45 build, and it still sounded pretty good once the bias was tweaked in.

I still have to do some tweaking of the range of the Bias and Width pots. For the Bias I used a 100K pot with a 47K resistor in series at either end, I need to remove the resistor between the pot and ground, and increase the other end to 100k to put the centre bias central on the pot. I also need to reduce the 430K resistor I put in series between the Bias pot and the Width pot.

If anyone wants them, I've got two spare well matched sets of eight 2n5489, or four sets of four if you just want to build a 4 stage stock phase 90. PM me.

[frequencycentral]

Here's my circuit board with the pots mounted on a seperate piece of perf, makes it very easy to test/mod:





Here's the pot board layout too, it may help to explain the resistor values I'm changing to get the Bias pot and the Width pot working right:

[frequencycentral]

After playing about with the resistors I placed either side of the Bias pot, I'm coming to the conclusion that I should maybe change out the 5.1v zener for a higher voltage zener, as the 'centre' bias is still pretty close to ground. The Tonepad P90 project file mentions something about this for subbing in different types of FETs. The matched set I'm using has a Vgs of 1.8v, I suspect that lower than this would be easier to bias with the 5.1v zener. My vref is ~3v at the moment, I'm wondering if I use a different zener to get the vref up to ~5v I'll get the centre bias close to the centre of the Bias pot. The alternative is increasing the value of R3 on my pot board (I've already reduced R2 to 0K), but it seems to be a diminishing returns situation. Any thoughts anyone? It would be great if R.G. could chip in here.

[frequencycentral]

I searched and found a P45 (with univibe mods) thread where JC Maillet suggested putting one or two 1n4148 in series with the zener to raise the vref and centralise the bias on the Bias pot, so I'll try that.