PWM in deluxe Electric Mistress??

[StephenGiles]

I quote from another board

And the LM324 section makes me think of the oscillator you find in the Deluxe Mistress (pulse width modulation?

What the.............?

[oskar]

You can safely say that is wrong. On the Electric mistress there is a 4013 sitting in between the LFO and the delaychip. The 4013 divides the LFO frequency by two and by doing this it becomes a 50/50 dutycycle squarewave.

[StephenGiles]

But see this - under The Comparator section - could well be PWM, in which case MXR Envelope Filter #3 on my desk first thing Monday morning!!

http://www.freescale.com/files/sensors/doc/app_note/AN1518.pdf

[oskar]

I don't get the OP in front of the 4013 completely but I think it works like this. When the output is low the 47p cap is discharged through the diode from the inverting input. This is a VCO I think. The LFO sets the trippoint of the comparator and by doing this modulates the frequency... no PWM, it wouldn't make sense... ( to me that is...  )

[StephenGiles]

I don't get the OP in front of the 4013 completely but I think it works like this. When the output is low the 47p cap is discharged through the diode from the inverting input. This is a VCO I think. The LFO sets the trippoint of the comparator and by doing this modulates the frequency... no PWM, it wouldn't make sense... ( to me that is...  )

Thanks for your thoughts, I can sleep tonight now!!

[Thomeeque]

I don't get the OP in front of the 4013 completely but I think it works like this. When the output is low the 47p cap is discharged through the diode from the inverting input. This is a VCO I think. The LFO sets the trippoint of the comparator and by doing this modulates the frequency... no PWM, it wouldn't make sense... ( to me that is...  )

I've tried to emulate this comparator section in LTSpice, unfortunately it did nothing (probably wrong LM311 model) - but my believe is it's VCO as well, it cannot be nothing else IMO..

[oskar]

Yeah, I think I grasp it now completely.
I'm refering to the factory schematic dated 3-dec-2002, new sensory corporation.
C19 is charged with a constant current through Q2. When it reaches the LFO amplitude the comparator goes low and discharges C19 through D4. This way you get a very narrow spike as output from the VCO so you need to divide the frequency to get a proper squarewave because the delaychip won't have it no other way.

[Thomeeque]

Yeah, I think I grasp it now completely.
I'm refering to the factory schematic dated 3-dec-2002, new sensory corporation.
C19 is charged with a constant current through Q2. When it reaches the LFO amplitude the comparator goes low and discharges C19 through D4. This way you get a very narrow spike as output from the VCO so you need to divide the frequency to get a proper squarewave because the delaychip won't have it no other way.

Wow, it makes perfect sense, hat's off!

[StephenGiles]

Yeah, I think I grasp it now completely.
I'm refering to the factory schematic dated 3-dec-2002, new sensory corporation.
C19 is charged with a constant current through Q2. When it reaches the LFO amplitude the comparator goes low and discharges C19 through D4. This way you get a very narrow spike as output from the VCO so you need to divide the frequency to get a proper squarewave because the delaychip won't have it no other way.

Wow, it makes perfect sense, hat's off!

But the LFO is moving all the time surely?

[oskar]

But the LFO is moving all the time surely?

Yes. What is the filter matrix thing?   

[StephenGiles]

But the LFO is moving all the time surely?

Yes. What is the filter matrix thing?   

That's just an EH marketing jargon name from the 1970s I think.

[oskar]

No. Nice try though, thinking out of the box. It's some kind of fixed delayrate. If you sweep it manually you should end up with flanging too.
I'ld try it but some bastardo stole my mistress   

[StephenGiles]

No. Nice try though, thinking out of the box. It's some kind of fixed delayrate. If you sweep it manually you should end up with flanging too.
I'ld try it but some bastardo stole my mistress  

Oh yes it is, agreed a fixed delay rate which is varied by the Range pot from memory, but the name was marketing jargon - from a 1980s EH designer.