LM13700 1 volt/octave temperature stable VCO ?

[frequencycentral]

I just love the LM13700!

I've used it for VCOs and VCLFOs in my mini sound effects synth where stability/tracking isnt an issue. I've also designed a tube tremolo which uses a 13700 as the LFO, there's a stompswitch to select between two speed controls, with a slew limiter so the transition between the two speeds is gradual. I'm just finishing up a multimode envelope follower for guitar using a 13700 as a HP/BP/LP VCF.

My work with the 13700 has been based on its data sheet, and grafting Roland 100m front ends for the CV inputs where needed. All of the above are applications where stability/tracking isnt an issue.

My DIY modular is built around Oberheim SEM VCOs, SEM and Moog Prodigy VCFs, Roland 100m VCAs, EGs, S/H, Noise. It started out as an expansion of my original Roland 100m, hence its mostly Roland clone stuff.

What I'm wondering is there a temperature stable 1 volt/octave LM13700 VCO design/schematic with a decent waveform set, sync etc. Anyone know of one? I guess I have an urge to build a mini modular using 13700 for everything - VCOs. VCFs, VCAs and RM. Or is it just not a suitable device for precision applications? Then again CA3080 filters seem to track pretty well, so why shouldn't LM13700 VCOs do the same? Is such an animal doesn't exist should I design one? Any hints, tips or advice?

Thanks!

[Scott Stites]

Thomas Henry's 21st Century Synth book (the one you can get from Magic Smoke) has a great LM13700 VCO in it.

[frequencycentral]

[andrewF]

haven't tried it -


the full article is here -
http://www.jiisuki.net/reports/howto-build-analog-synth.pdf
(schematics in the appendix)

[frijitz]

The two discussed here work very well:

http://electro-music.com/forum/topic-19841.html&postorder=asc



Ian

[bubblechamber]

i've built a very stable 13700 VCO using the design off the data sheet(which is remarkably close to Thomas Henry's) and adding a variation of Thomas Henry's expo converter, but just about any expo converter that's meant for a 3080 based VCO will work. i'd breadboard the VCO and on a separate breadboard build a couple of expo converters and see which one you like the best. i went through 5 or 6 before i found one that i really liked.

[ryktnk]

hello

I agree with Mr bubblechamber, the VCO in the Technotes
works very well.

I used the TH VCO1 expo converter with a THAT 320 Dual PNP
http://www.thatcorp.com/300-series_Matched_Transistor_Array_ICs.html

Tracking is great - about 7-8 octaves.

More accurate than a Roland 100m VCO !

-ryk

[jano2358]

sorry but you web site SUCKS!!! it's hurt my eyes!

[blue hell]

[frequencycentral]

[blue hell]