Ibanez 301 Flanger at 9V. It works! Question.

[Morocotopo]

Hi guys, yesterday I was repairing/rehousing a DIY Ibanez 301 flanger, one of my first builds,  the out mixer IC never worked well, turned out to be a missing trace in the copper. Here´s the files:

http://www.tonepad.com/getFile.asp?id=49
http://www.tonepad.com/getFile.asp?id=52

I made it originally with a charge pump, because it needs 18V, so as to be able to use it in the pedalboard. But that brought with it heterodyning, that needed a bank of 8 100uF caps to ground in the power line to quiet it, not very elegant, takes out too much space ... a mess. I seemed to recall someone in the forum saying that it could possibly run at 9V, so I looked at the schem. The 18V are converted to 12V to power the thing. Not very efficient... So I thought, well from 9V to 12V that´s not so much difference... So, I removed the 12V regulator and fed it with 9V to the power trace. Guess what? It works!
No discernible headroom difference, no apparent added noise, sounds good. So, there you have it, you don´t have to mess with extra transformers to use it.
Now, I have a question: Is there any part of the schem that should be changed/updated to run at 9V? My guess is not, but maybe it´s not running optimally with the lowered voltage and could be optimized to it. Oscillator speed / amplitude, clock frequency...

Well, if you have any suggestions they are welcome.

Cheers!

[Fender3D]

That's right, it runs at 12V stock.
You'll need to rebias it when running at 9V, and you can't reach the same modulation depth 'cause the lower voltage driving the clock...

PS
this is the 2nd thread about power supply I'm in...
why don't you people supply your pedal with 15-18Vcc then regulate it as needed?
most pedals (expecially when diy) work better with higher supply...

[Morocotopo]

Fender, thanks for responding. Could you elaborate a bit more on the changes needed? If you´re talking about resetting the trimpot, I did it of course.

[Fender3D]

Yep, rebiasing it's just a matter of retrimming (just as biasing it's a matter of trimming doh  )
The modulation depth is more "intriguing":
You should measure the clock at its minimum and its maximum @ 18 (12) Vcc, then try and reaching the same values.
Maybe playing with R149/R148 will be enough, maybe you'll never get the same max/min ratio...
If you manage to get an higher max/min ratio than 18V stock, then it's party time 

[Morocotopo]

Thanks Fender. Today I had time to test this. Tried it at 9V and at 12V, and sure enough the clock frequency is slower at 9V (lower "pitched" sweep). I fired up the oscilloscope and the clock freq at 9V was about half. I calculated (very bluntly) about 200KHz at 12V and 100KHz at 9v. So I started reading the MN3101 datasheet, to see how to mod the clock freq. Eventually I got the same speed by replacing R141 with a 22K, R140 with a 220R and C123 for a 56pF one, so if you want to make this work at 9V, replace those parts and voilá!
I tuned it by ear, and I can´t hear any difference now, except by maybe a tiiiiiiiiny bit less of width in the sweep, but nothing too dramatic, but that might just be the trimpot fiddling. Looking at other schems that use the MN3101/MN3007 combo or the low voltage ones, all that use 9v power (Boss CE2, etc.) have the equivalent to C123 at 47p. I guess the 301 has a 180p to compensate for the higher voltage.
Well, that´s all folks, hopefully someone else will try this. It´s a nice little flanger, worth the build and more so when you don´t need special power arrangements!