Help explaining VC Bugcrusher?

[Shorty]

Hey there! I'm interested in building a sample rate reducer type effect i.e. the Bugcrusher-> http://www.bugbrand.co.uk/pages/sounddevices.htm (scroll down for bugcrusher)

I've looked at the simple schematic with only a sample rate knob-> http://www.bugbrand.co.uk/pages/sounddevices.htm
and I can get my head around building that, however i think it would be really cool to be able to control the sample rate with some kind of LFO (i.e. rate sweeps up and down). Is this the same kind of idea? -> http://www.bugbrand.co.uk/images/circuits/vc_rate_reducer.jpg
that's apparently the same circuit, only voltage controlled. What does that mean? where do CV1 and CV2 connect to in that schematic and what do those 10k linear pots do/control?

Thanks a bunch for anyone willing to explain.

[frequencycentral]

This might be useful: http://electro-music.com/forum/topic-11369.html

[Shorty]

Yes! Thankyou, that was helpful. So the LM13700 is a voltage controlled resistor?
Meaning that if the voltage into that chip had a sweep, the sample rate would sweep?
That does make sense, but I don't understand how the bit of the circuit above that (TL071 etc) controls voltage?
Wait, is the TL071 oscillating which changes voltage?

If so, I'm still hazy on where to connext CV1 and CV2 and what they do, as well as what the pots control? (I cant read that little font)

[Shorty]

Gargh, now more confused...looked up LM13700 datasheet, and it is a 'Dual Operational Transconductance Amplifier'
a.k.a weapon of mass confusion, I am now lost again.
And unfortunately I have to go study for my english exam tomorrow morning, so this mystery will have to wait until tomorrow afternoon.

p.s. if someone solves it for me between now and then I will be eternally grateful! 

[Shorty]

looked up LM13700 datasheet, and it is a 'Dual Operational Transconductance Amplifier

Scrap that, I had another look at the datasheet and there is a voltage controlled resistor application in there.
What's more, comparing it to the bugcrusher schematic, it is the same application! Yay, I know what's happening there now.

But. I know that by varying voltage to pins 1+16 of the LM13700, the resistance across pins 5+7 to 10+12 is varied.
How does the Opamp/transistor circuit feeding pin 1+16 change voltage?
And most importantly, what do I connect CV1 and CV2 to?? Haha.
I've ordered samples of the AD781, so I can breadboard this up once I get them, but I'm still stuck on that issue.
Anyone at aaaaaall wanna tell me? I'll be your friend?

Just for reference we're still talking about this schematic http://www.bugbrand.co.uk/images/circuits/vc_rate_reducer.jpg

[frequencycentral]

I'm still hazy on where to connext CV1 and CV2 and what they do, as well as what the pots control? (I cant read that little font)

These are control voltage inputs, that circuit has been put together in a 'modular' way. You can connect various other circuits to the CV inputs, such as LFOs, Sample and Hold, Envelope Generators etc - whatever you input there will influence the sample rate.

The LM13700 is your friend, a very useful device - at least it's my friend. With The VC Bugcrusher you are more into modular synth territory than guitar pedal territory.