Barton 2LFO SH -- anyone built a Frac version?

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gnombient
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Barton 2LFO SH -- anyone built a Frac version?

Post by gnombient » Tue Feb 14, 2017 3:19 pm

Getting back into modular after a few years away... I'd like to add LFOs for my modest little Frac system, and recently saw this: http://www.bartonmusicalcircuits.com/2LFO/

I know Blacet makes a fine LFO, but my space is limited and I'm wondering if this may be more bang for my buck.

Does anyone have experience with this module (in any format?) Anyone who has built a Frac version have any tips to share about components or general build? Is this a fool's errand?

Rob_C
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Post by Rob_C » Tue Feb 14, 2017 7:11 pm

Go for it! You can build the 2LFOSH for either 12 volts or 15 volts (bipolar), as stated in the instructions. There is no pre-made Frac panel available, but you can order a blank panel from PAIA or Blacet and drill the holes for the potentiometers and 3.5mm jacks. The circuit board will mount at a 90 degree angle with 4/40 L brackets.

Link ->PAIA single wide Frac blank panel

Mr Barton sells inexpensive blank Euro panels for his modules, with all holes drilled (but no labels, you have to add your own). If you request, he will leave off the Euro mounting slots, and you can drill your own Frac mounting holes. Keep in mind this Euro panel will be about 1/4" short of a Frac panel, and is not the standard width of Frac panels (1.5", 3.0" etc). But it is a quick and dirty way of mounting the module.

gnombient
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Post by gnombient » Tue Feb 14, 2017 7:33 pm

Thanks for the encouragement Rob!

My question regarding components stems from the documentation's note for +/-15V builders (quoted here, emphasis mine):
The parts values presented in the schematic are for a +/-12V system. When building for +/-15V a few of the components associated with the schmitt trigger need to be replaced. These values are untested, you may need to experiment with different values to get the performance you want. The 220K in it's feedback path should be increased to a 330K. The 2.7K/2.2K voltage divider should be replaced with a 2.2K/1K voltage divider, and the 100K resistor between the pot's wiper and the integrator should be increased to 150K.
I can follow instructions and handle a soldering iron well enough to build Blacet kits, but don't have much in the way of the theoretical electronics knowledge that would help me to make a confident determination regarding component values and performance... My instinct is to use the suggested substitutions and not worry about it, but I thought I'd ask around first to see if anyone else had other thoughts.

EDIT to add: I conveniently already have a Paia panel that I can use for this project, so at this point it's a matter of ordering the components and making/finding time to work!

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nikmis
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Post by nikmis » Wed Feb 15, 2017 10:44 am

I built the BMC 013 random resonator, BMC 015 vca mixer, and the BMC 009 UWQ all in frac format, +/-15. They work fine. That doesn't really answer any questions but I just wanted to contribute

gnombient
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Post by gnombient » Wed Feb 15, 2017 7:08 pm

nikmis wrote:I built the BMC 013 random resonator, BMC 015 vca mixer, and the BMC 009 UWQ all in frac format, +/-15. They work fine. That doesn't really answer any questions but I just wanted to contribute
Good to hear that your Frac builds went well. When you built those modules, did you have to do anything with alternate component values to compensate for the voltage change?

gnombient
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Post by gnombient » Thu Feb 23, 2017 5:07 pm

Quick follow-up... Reconsidering my Frac approach (see my separate post), so Barton is on hold... :oops: Thanks for the input anyway!

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Spivkurl
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Post by Spivkurl » Tue May 08, 2018 5:55 am

This is the first module I added to the partial frac system that I just picked up from a fellow wiggler.

I already had the board stuffed and tested at +/- 15v, and sitting waiting for a home. I used the recommended component values for this supply voltage without trouble. I also just used the euro style panel, since the rails are wood on this case. Worked out just fine, and adds a ton of capability to the setup!

The frac system had only one true LFO, which was shared with the phaser, so it definitely need more CV sources. Can't think of a better option beyond revisiting my old LFO/SH design from way back.

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