Put your EFM synth kit corrections here, thanks!

Dave Kendall · Posted: Tue Sep 11, 2007 1:47 pm Post subject:

Ask away - there's a wealth of experience here, including quite a few guys who came here (and many of them stayed) when EFM went periodically down......
Do check Fonik's site first though, the collection of stuff there is a pretty good record of what we can find of the last few years, and shows what was going on, and, if anyone's got anything that 's not here or on the fonik site, speak up! there's at least one circuit ( the 9V version of the VCF6C for example, that got lost......)

EFM stuff can be made to work just fine, but be prepared for some odd PCB trace faults, and other weird shit. I got pissed off originally, then loved it, as I realised it was teaching me how to trace circuits and debug them. But don't expect the boards to be as trouble free as the boards that guys here are making. The guys here are seriously hard core, and you just have to follow the threads to see how feedback is making it all even better.

This Forum is a rather rare and wonderful thing that we are part of.
Very Happy

mosc

fonik

Dragon's Lair · Posted: Mon Sep 24, 2007 12:11 am Post subject:

It looks like everyone is on there own now, I just logged into the EFM site, and to all intents and purposes, it's gone, all that's there now is a blog with nothing on it. So it looks like Tom has abandoned his customers yet again, it's a good thing this forum exists, or we would all be screwed.

prophei · Posted: Mon Sep 24, 2007 12:18 am Post subject:

elektro80 · Posted: Mon Sep 24, 2007 12:55 am Post subject:

Tom is a member here as well. And he has responded to some issues.
He has seen some hard times recently. Don´t´go too hard on him.

fonik · Posted: Mon Sep 24, 2007 2:47 am Post subject:

...and the EFM site is not totaly dead. tom installed a blog/discussion forum for the synth-diy list member gino wong, a place to discuss the VCF6.

Dave Kendall · Posted: Mon Sep 24, 2007 3:56 am Post subject:

prophei · Posted: Mon Sep 24, 2007 6:55 am Post subject:

Dave Kendall

This page
was just flagged up in the synth diy list in case anyone here missed it.
IIRC, Harry Bissell from sdiy recommended 220uF for C9.

There's an empty area in the top left corner of the pcb if anyone wants to add a non-inverting summer for the CV inputs. You could just about get a TL072 + a few resistors in there.
Now, where's my pcb drill..........

cheers,

Dave

machvingtsun · Joined: Jul 07, 2007 Posts: 11 Location: Galway

Personally I like the look of the blog and Tom did give me help so hes not such a bad guy, havent tried posting to the blog yet though.

mosc · Posted: Mon Sep 24, 2007 3:33 pm Post subject:

If someone who talks to him feels like it, you can offer him a dedicated forum here. Then he won't have to maintain any software. Let him know people can upload images and audio here.

elektro80 · Posted: Mon Sep 24, 2007 3:34 pm Post subject:

I sent him such a message yesterday. Shocked

mosc · Posted: Mon Sep 24, 2007 3:35 pm Post subject:

prophei · Posted: Mon Sep 24, 2007 3:47 pm Post subject:

that is a great idea. i hope he accepts!

raisinbag · Joined: Dec 28, 2011 Posts: 5 Location: Uranus

Hey, old topic, hope it is still alive. Does anyone have the original docs for the VCF2e? I have a PCB I found kicking around and want to build it up. I found the doc with the Mods on fonitronik site. Just was curious if there is anymore info out there before I start to build. Thanks

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

raisinbag · Joined: Dec 28, 2011 Posts: 5 Location: Uranus

fonik · Posted: Thu Dec 29, 2011 7:30 am Post subject:

got it. hope, this is the right one?

VCF2e org

raisinbag · Joined: Dec 28, 2011 Posts: 5 Location: Uranus

keninverse · Joined: May 28, 2011 Posts: 15 Location: houston

I finally finished my bassace that's been sitting on my shelf for quite some time. I had several issues with my build but with the help of the venerable Dave Brown I was able to get this thing working. I'd like to publicly thank him for all his help. Totally cool dude to help out.

1) First all the pots are wired backwards in the schematic in terms of conventional pin orientations. Most of my pots were wired up backwards for this reason...I can't believed I overlooked this.
2) The cut off pot on the filter has one side tied to V- and the other to V+ on the board. One side of the pot needs to be tied to ground instead of V+.
3) There are several instances where the BOM conflicts with the values listed on the schematic. As with all EFM diy GO WITH THE SCHEMATIC. I should have heeded this warning from the beginning. A few problems off the top of my head are the voltage dividers at the slide and accent CV inputs.
4) The kludges listed in the build docs are correct
5) Finally 0.1uF slide discharge cap (C11?) needed to be increased to 1uF
6) EG had problems with a wrong value resistor making up the R67/R68 divider. I think this was listed incorrectly in the BOM but may have been my mistake but I can't remember.
If I were just building this board I would rewrite the entire BOM based on the schematic. Hope this helps someone out there with a 7 year old project.

vladosh · Posted: Tue Jan 10, 2012 11:22 am Post subject:

Finished a SEM type filter recently from the wildcat schematics - it's the third vcf there .. so posting just cause i like the vcf a lot .. and strangely i don't get crazy resonance as Fonik said somewhere it just sounds good to me ,but speaking at the chat room folks (very grateful !) there advised me to put 10K resistor between the expo converter and the LM13700 so i did and later saw in other schematics of the same filter EFM had that 10K resistor .. so for anyone in a need of a simple and good sounding multimode vcf here's a layout with that 10K resistor http://www.flickr.com/photos/62167965@N08/6674259633/in/photostream