Positive Ground Circuit Redesign??
- Thread starter Bio77
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giovanni
Well-known member
Oof that looks really annoying to do! It’s definitely possible technically, even keeping the same components, but I have never done anything like it. One good starting point may be this article: http://www.muzique.com/lab/fuzzface.htm
Bio77
Well-known member
Cool, thank you! This looks like what I assumed and switching is strait forward. I was worried there was something else I wasn't aware of.
I wonder why they chose this configuration? The two transistors are PNP, maybe this is easier or just regular practice in the 70s.
Anyway, I’m planning to breadboard some sections and see if it can be switched. Plan to do the LFO and clock section.
Bio77
Well-known member
Thanks for taking a look! I'd be worried about heterodyning with a charge pump. LectricFX used charge pumps in a lot of their early versions of flangers and have since updated them to 18V. There were tons of troubleshooting threads back in the day on Mad Bean
Bio77
Well-known member
Hey Scruffie! Post from you, just made my day. I'll bug you in a few days
Cheers!
bean
Legume Liaison
I think maybe you'd need to fiddle with the bias voltage to pin13 of the TDA1022? I'm not sure though.
There's some non-centered (≠4.5v) vrefs as well
Bio77
Well-known member
I'm planning to swap out the TDA1022. Just ordered some SSI2100 delay chips. Running across them was the inspiration for getting back into this.
If you flip the resistor chain, pin 13 gets 1V(ish).
It's just -9V because of the TDA1022 datasheet.
I did say not far off; I worked it out properly last time I looked at it.
Do you know how to make the clock circuitry compatible with a 5V chip?
Bio77
Well-known member
No. I thought the 512 stages would be easier to fit the clock to, I hadn't considered the voltage change.
You'll also have to contend with how the mixing is done here... the TDA1022 has a lot of signal loss, so the mixing resistor (albeit partially determined by trimming) is of smaller value than the dry to compensate.
Unfortunately for you, said mixing is part of the output low pass filter and by changing that value (so you don't end up with too much wet signal) you'll change the
Plus the extra input gain might not agree with the SSI's available input swing.
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I'll tell you what, I'll reimagine the audio path for you to suit the new chip, you don't need the 4049 any more and may as well just use a different oscillator (anything that runs on 5V happily should be fine) and then the LFO is, well it's just an LFO driving an LED.
If you build just the original LFO & 4007 clock section on a breadboard, you can, assuming a decent LDR, get a good idea of what clock range you should be aiming for.
If you build just the original LFO & 4007 clock section on a breadboard, you can, assuming a decent LDR, get a good idea of what clock range you should be aiming for.
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Yes the schematic is wrong, what's all the +1, +2 business about though?
So (excuse the quick shoddy drawing) you want the attached.
Don't worry about testing it at +9V or +5V, looking at the SSI datasheet this morning, it doesn't have an internal divider akin to the Reticon chips as I assumed, just an inverter so it'll need a cleaner clock than the 4007 can provide... just find out the clock frequency the original gives and then a MN3102/CD4047 or the like can be shoved in its place.
Also while looking at the datasheet this morning I saw the specs on the SSI aren't as good as I'd hoped they might be for a new chip... it's going to be a bit of a balancing act between noise and distortion in this circuit.
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Bio77
Well-known member
It is a screen shot from a lecture I found, not sure about the 1s and 2s.
That's a bummer. In that case, would two 3009s be a better choice?
With all the flangers you have designed, have you found the clock to have a minimal impact on the sound? I wouldn't have guessed that. For example, the Small Clone and Boss choruses sound so different, one has the CMOS clock and the other the 3102. Is it only about the frequency and sweep or does the quality/shape of the clock signal have an impact on the sound?
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