sr1200
Well-known member
Didnt abechap do the PIE (pye) clone and use a chip for the "chopper"? Yep, its sitting next to me and sounds great. why not borrow that section from him?
sr1200 said:Didnt abechap do the PIE (pye) clone and use a chip for the "chopper"? Yep, its sitting next to me and sounds great. why not borrow that section from him?
ruffrecords said:sr1200 said:Didnt abechap do the PIE (pye) clone and use a chip for the "chopper"? Yep, its sitting next to me and sounds great. why not borrow that section from him?
I checked out the schematic on his web site and I did not see a chip for the chopper; just a transistor as in the original
Ian
jasonallenh said:Getting into some murky water here, but SKnote has a PWM compressor as well. I have one. Ask away. I think the PWM is 500kHz?
MicDaddy said:I think PIC18 will do 1MHz PWM with some sacrifice of resolution?
Chris_V said:Still possible.
I have not check for other manufacturer but from microchip, you can found in the PIC24 or dsPIC33E line high speed PWM with claim to have 7ns resolution. This means that at 10 bits you still have a PWM frequency of 130kHz.
DSPIC33EP32MC202 is at 2€30 at Mouser, so it is still cheap ...
ruffrecords said:jasonallenh said:Getting into some murky water here, but SKnote has a PWM compressor as well. I have one. Ask away. I think the PWM is 500kHz?
Have you had the lid off? What chips does it use?
Cheers
Ian
ruffrecords said:jasonallenh said:Have you had the lid off? What chips does it use?
Cheers
Ian
I actually found the previously mentioned TL5001CP as well. Other than that, just a bunch of the standard TL07- opamps
I just pulled it out and checked. It has one of these:
http://www.vishay.com/docs/70054/dg444.pdf
I'd be interested to know what you think.....................
jasonallenh said:ruffrecords said:jasonallenh said:Have you had the lid off? What chips does it use?
Cheers
Ian
I actually found the previously mentioned TL5001CP as well. Other than that, just a bunch of the standard TL07- opamps
I just pulled it out and checked. It has one of these:
http://www.vishay.com/docs/70054/dg444.pdf
I'd be interested to know what you think.....................
DG444/5 are well known and respected audio switches. Perfect for this job. Were there any other (none audio) chips near them?
Cheers
Ian
ruffrecords said:It just occured to me there may be a fundamental problem using PWM in a micro. Assuming we want 8 bit resolution in our PWM signal, this means the clock feeding the PWM counter needs to be 256 times the the required PWM frequency. Thismeans even if we want a PWM frequency as low as 100KHz, we need a clcok of 25MHz.
Cheers
Ian
usekgb said:I use an Atmega328P to generate a 200kHz PWM signal at 50% duty cycle to drive an analog delay line. It can go faster, but 100kHz is the maximum frequency of the BL3208a chips that I used (each chip see fs/2 with original polarity and inverted polarity). The microcontroller generates any frequency that I need between 26kHz and 200kHz, depending on the delay setting, or the tempo tapped in. So, this is well within the ability of a microcontroller.
I have been investigating the use of a microcontroller for a PWM based guitar compressor for some time. I think the biggest limitation will be attack time, due to the time it takes the micro to do the a/d conversion and process the signal.
ruffrecords said:getting a hi enough frequency is not to hard. The problem is being able to alter the pulse width to the necessary resolution. If you want say a resolution better than 0.5% then you need 8 bits. This means the internal oscillator in the micro driving the PWM modules needs to be 256 times the PWM frequency. So if the PWM frequency is 100KHz, the oscillator needs to be 25.6MHz.
Cheers
Ian
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