Phase 90 (PEZ 90, Tonepad)

[WelshWonder]

Hi all,

I just finished the Phase 90 off Tonepad. I got the matched FET's (2N5952) and off my own back, I checked the datasheets for them to see which pin was 'G'. It seems that the layout on the tonepad site (http://www.tonepad.com/getFile.asp?id=42) is incorrect and the orientation of the 2N5952's are back to front. Is it me or is the tonepad layout wrong? Here's a link to the datasheet ----> http://www.ortodoxism.ro/datasheets/fairchild/2N5952.pdf

By the way, the pedal works well, although the effect is fairly suttle, not really in your face. I tweaked the trimpot to taste and the only part I had to substitute (for now) was the 500k reverse log pot, instead I am using a 470k log.

[Shed_FX]

Hi,

You are correct the layout is incorrect and should be the otherway around (For the fiarchild fet). It depends upon the brand and type of Fet you used. I plumped for BF245A which i could get hold of. These were matched too and got a good phase effect. The 470k pot should work ok but you could try messing with a 30k resistor to bias it towards the far end of the sweep, if you will use it at more at those speeds (Does that make sense?  ). I used a 470k pot too and has worked fine the real clincher is adjusting the trim pot.

So:

1. Check the fets are correctly orientated one last time.
2. Adjust the trim pot whilst playing through the effect.
3. Try placing a 30k resistor in series with the 470k

Hope that helps. Oh and don't forget to post some pictures of the finished article on the Pictures! thread.

[WelshWonder]

Thanks Shed for your reply. I was wondering how to wire a resistor to a potentiometer to increase the pots capacity e.g. going from 100k to 570l via a 470k resistor. Not something I'll do for this project but for my TS808 project, problem is that I got a 100k pot that needs to be 500k...

[WelshWonder]

Anyone got any suggestions on how to do the above?

[Shed_FX]

With the Tube Screamer use a 470K pot for the drive. Then if you want you can change the characteristic of the control slightly by placing a 30k in parallel. The SD-1 uses a 1M pot in its place so you can experiment around with the value. However using a 100k and adding resistors to bring it up to 500k will just give you a very limited control in that case. Think of it as the sweep of 100k with give you a 5th of the change in drive as the 470k (roughly). If you are just starting out use as close as you can get as stated in the schematics. But as we are both over in the UK we can only get standard parts like 470k 47k and 22k rather than the american equivalents. The problem is that for different situations the difference in the pot value with have a different effect. For a volume control at the end of a circuit, it does not necessarily need to be the exact value as it is simply a voltage divider. Just play about and you'll get the hang of deciding what to replace with what.

Cheers

[simetric]

I've built one of these recently with the same layout and have problems too. I built one last year and i remember i had to turn the fets 180º. But in this one if i turn the fets have no efect, so i left them as the layout and then it works, but not as well as the other. i think it's problem of the fets, so i'll try with other sets.
But the stranger thig is that as i use different supplies i have to adjust again the trimmer.  Isn't it crazy?
Sounds different with different batteries or p supplies.
Can you help me???
thanks