Circuitbenders Forum

Circuitbenders Forum => Circuitbending discussion => Synths & Samplers => Topic started by: wax+wire on July 30, 2015, 11:59:49 AM

Title: alternatives to LTC1799 - clocks with CV in
Post by: wax+wire on July 30, 2015, 11:59:49 AM: does anyone use things other than an LTC1799 as a replacement clock for their keyboards (casios in particular)? i'm keen to add a lfo input to create a vibrato effect on my pitch, but from what i gather an LTC doesn't take control voltage input. while i've done it with LDR/vactrol setups in series with the resistor setting the frequency, it isn't really ideal.

Has anyone used 74HCT4046 or a similar chip as an alternative clock source for a crystal in a casio type keyboard?
Title: Re: alternatives to LTC1799 - clocks with CV in
Post by: g8tr1522 on February 20, 2017, 07:35:18 PM: I'm also looking for an alternative oscillator. Something that can go higher than 33MHz.

But for the CV in, if you're using this clock replacement circuit :
http://www.getlofi.com/wp-content/uploads/2008/10/2_LTC_Instructions.jpg (http://www.getlofi.com/wp-content/uploads/2008/10/2_LTC_Instructions.jpg)
Then you would just replace the pot with some sort of transistor circuit that would behave like a voltage-controlled resistor. I'd give more details, but I'm still learning transistors myself. You could use a BJT or MOSFET though.
Title: Re: alternatives to LTC1799 - clocks with CV in
Post by: g8tr1522 on February 20, 2017, 07:40:07 PM: According to this stack exchange post: http://electronics.stackexchange.com/questions/158281/why-are-mosfets-better-than-bjts-in-application-of-voltage-controlled-resistor (http://electronics.stackexchange.com/questions/158281/why-are-mosfets-better-than-bjts-in-application-of-voltage-controlled-resistor)
JFETs are best for implementing voltage controlled resistors (VCRs).

Here's a Vishay paper on using JFETs as VCRs.
http://www.vishay.com/docs/70598/70598.pdf (http://www.vishay.com/docs/70598/70598.pdf)
Title: Re: alternatives to LTC1799 - clocks with CV in
Post by: Circuitbenders on February 22, 2017, 10:30:14 PM: Quote from: g8tr1522 on February 20, 2017, 07:35:18 PM
I'm also looking for an alternative oscillator. Something that can go higher than 33MHz.

linear do another LTC that runs at higher frequencies. Its on the linear site, but i can't remember what it is.
Title: Re: alternatives to LTC1799 - clocks with CV in
Post by: davelybob on March 10, 2017, 06:39:57 PM: Quote from: Circuitbenders on February 22, 2017, 10:30:14 PM
Quote from: g8tr1522 on February 20, 2017, 07:35:18 PM
I'm also looking for an alternative oscillator. Something that can go higher than 33MHz.

linear do another LTC that runs at higher frequencies. Its on the linear site, but i can't remember what it is.

LTC6905. 17 MHz to 170 MHz, the 1799 is 1 KHz to 33 MHz. Figured that one out with Getlofi, I use his 1799s since I'm stateside. Put a 1799 in a little toddler-friendly mp3 player, guess I fucked up the original crystal so I couldn't make it switchable, so I'm stuck with it playing the songs slow all the time, and since USB is clocked at 48MHz, I can't swap out the files either. He was going to do up a couple on his boards for me, but that was like probably a year ago now, I should really touch base with him, the ball is probably in my court.

As far as CV on an LTC1799, the vtl5c3 I've got rigged up to my re-clocked Yamaha REX-50 is lots of fun with a sequencer. The response time I'm sure isn't what a lot of people would hope, hella glide on that, but it can still do some wacky shit.