Befaco Even VCO

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CliffordMilk
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Befaco Even VCO

Post by CliffordMilk » Mon Sep 21, 2015 1:07 pm

I'm looking for an audio demo of the 'even' output from this module. Could someone out there point me in the right direction please?

thermionicjunky
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Post by thermionicjunky » Mon Sep 21, 2015 1:30 pm

Not the Befaco, but the same waveform from the Bergfotron Advanced VCO (with some phaser/VCF processing):

http://hem.bredband.net/bersyn/Ljud/Flutron.mp3

http://hem.bredband.net/bersyn/Ljud/Even,phaser.mp3

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CliffordMilk
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Post by CliffordMilk » Mon Sep 21, 2015 2:16 pm

Interesting - thanks.

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Richie Witch
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Post by Richie Witch » Tue Sep 22, 2015 9:24 am

I have a kit for one arriving today. Once I get the thing built, I'll try to post some audio samples.

Anything in particular you want to hear?

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Post by tallhouserecordingco » Tue Sep 22, 2015 3:35 pm

I'm interested in this module too - looking at ordering a kit myself. I've never built a DIY synth kit, but I've done several guitar pedals and a tube amp.
Richie, in addition to some audio samples, I'd be interested in your thoughts on the build.
Many thanks in advance!

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Jumbuktu
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Post by Jumbuktu » Tue Sep 22, 2015 10:49 pm

I am interested in the kit. However, the 'Even' output looks like just another waveform. It would be interesting if there was some sort of CV control over the harmonic mix, but this doesn't seem to be provided.

The octave switch is a big plus, especially if this VCO is tracks as accurately as claimed.

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chapelier fou
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Post by chapelier fou » Wed Sep 23, 2015 3:39 am

The octave switch isn't cv controlled, is it ?

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CliffordMilk
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Post by CliffordMilk » Thu Sep 24, 2015 1:46 am

Thanks. I was wondering what a sweep of the 'even' harmonics would sound like.

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mbartkow
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Post by mbartkow » Thu Sep 24, 2015 3:13 am

Mix a sinusoid with a sawtooth one octave higher, and presto - you have your even harmonic waveform. I believe this is how the waveform is actually derived in Befaco VCO.

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Post by thermionicjunky » Thu Sep 24, 2015 9:19 am

mbartkow wrote:Mix a sinusoid with a sawtooth one octave higher, and presto - you have your even harmonic waveform. I believe this is how the waveform is actually derived in Befaco VCO.
Yes, specifically a double-frequency saw derived from the same VCO core mixed with a sine with the proportion of 1:1.27.

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Zanna83
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Post by Zanna83 » Fri Sep 25, 2015 3:00 am

I'm very interested in this module! I'm considering to realize a set of 4 for polyphonic pourposes.

Anyone who got the chance to try it ?

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Richie Witch
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Post by Richie Witch » Mon Sep 28, 2015 8:51 am

Spent some time this weekend working on the kit, so here are some first impressions:

The kit is nicely organized. It comes with step-by-step instructions, organized by "bag". So you start by opening "Bag A" of the main board and follow the sequence given in the instructions.

The PCB is dense! In order to fit between components, the type on the board identifying the part labels is the tiniest I've seen, and in a couple of cases, the writing is defaced by the layout of the holes in the board. For example, R1 and R4 are unreadable. I had to reference the schematic to determine which location matched which resistor. I had some trouble distinguishing between 5' and 6's, and 8's and 0's because of the extremely small lettering, but usually worked it out by process of elimination.

There are a couple of surface-mounted component, and thankfully, they are pre-installed on the board. That was a big relief on a board this tightly designed.

The quality of the board and the components seems really good. So as long as you've got a good magnifier and have decent skills reading schematics, it's not a difficult build.

I would consider this an "intermediate" kit.

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Zanna83
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Post by Zanna83 » Mon Sep 28, 2015 9:49 am

@Richie Witch :

Thank you for your review of the assembling phase. From your description it seems to me that i should be able to put together this module! :party:

However, before puchasing it i would like to read some impressions regarding its sound. For example i still don't understand if it's triangle core or sawtooth core!

Maybe it would be interesting to compare with other VCOs in the same price range. For example VCOb, Dixie II, Pittsburgh...

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phonodyne
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Post by phonodyne » Sun Oct 18, 2015 5:21 am

I'd also be keen to hear thoughts on the sound of it or, even better, hear some demos. It looks like a nice kit.
thermionicjunky wrote:
mbartkow wrote:Mix a sinusoid with a sawtooth one octave higher, and presto - you have your even harmonic waveform. I believe this is how the waveform is actually derived in Befaco VCO.
Yes, specifically a double-frequency saw derived from the same VCO core mixed with a sine with the proportion of 1:1.27.
So is it a sawtooth core, then? I can't seem to find that info anywhere in the Befaco product details.

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mbartkow
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Post by mbartkow » Sun Oct 18, 2015 6:13 am

Based on the schematics, it's a classic saw core design, however a BJT is used to discharge the capacitor (instead of a commonly used JFET), which may have impact on the sharpness of the edge of sawtooth, hence it will impact the timbre slightly. This may also yield a small spike in the triangle waveform which will sound a little buzzy. These are only speculations based on personal experience with similar circuits, I don't have the actual module.

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Randy
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Post by Randy » Sun Oct 18, 2015 9:52 am

mbartkow is correct about the triangle.



Randy

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phonodyne
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Post by phonodyne » Sun Nov 08, 2015 8:17 am

Thanks for the additional info and video. I'm considering building a pair of these. There aren't too many audio examples or opinions floating about yet, though.

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Post by Footkerchief » Thu Nov 26, 2015 9:49 pm

Any other opinions on this module? Size, price, and feature set all look good, but would need verification of the tracking, and audio demos.

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Post by Footkerchief » Sat Nov 28, 2015 12:20 pm

Surely someone has some opinions on this module?

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jensu
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Post by jensu » Sat Nov 28, 2015 12:41 pm

I'm onto this aswell. Would be gret to get DivKid to make a series on the befaco modules. Even VCO and Rampage at least.

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Post by insula » Mon Nov 30, 2015 5:56 am

jensu wrote:I'm onto this aswell. Would be gret to get DivKid to make a series on the befaco modules. Even VCO and Rampage at least.
i have both modules, i'm going to try this week to make a demo-, let see how goes. :omg:

besides the rampage module is a really cool and flexible complex evnvelope generator. :nana:

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jensu
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Post by jensu » Mon Nov 30, 2015 7:28 am

insula wrote:
jensu wrote:I'm onto this aswell. Would be gret to get DivKid to make a series on the befaco modules. Even VCO and Rampage at least.
i have both modules, i'm going to try this week to make a demo-, let see how goes. :omg:

besides the rampage module is a really cool and flexible complex evnvelope generator. :nana:
That would be really nice. The rampage seems like a bit of a no-brainer.

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bonjourmyfriends
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Post by bonjourmyfriends » Thu Feb 04, 2016 3:30 am

Could someone with this kit tell me the values for the pots for Fine Tune and Pulse Width?

I had PCBs printed, and I've got every part ready to order except the two pots - the values are not included anywhere on the schematic or instructions, although it does say that they're this type (PDF Datasheet).

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galingong
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Post by galingong » Thu Feb 04, 2016 4:16 am

bonjourmyfriends wrote:Could someone with this kit tell me the values for the pots for Fine Tune and Pulse Width?

I had PCBs printed, and I've got every part ready to order except the two pots - the values are not included anywhere on the schematic or instructions, although it does say that they're this type (PDF Datasheet).
I have found nothing regarding those values, even in the CAD files.

Although I can make suggestions based on the circuit. Both of them are voltage dividers. Since the PW knob is connected to +12V and -12V you should be ok with a 100k linear.
The value of the Fine knob defines the range. On the front panel it says +7 and -7 (I guess that's a perfect fifth, 1 Octave total range). If you want to go for that, the pot value should be 10k linear.

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galingong
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Post by galingong » Thu Feb 04, 2016 4:44 am

I'd also like to ask something - what is component T_P_1 for? It's supposed to be a single pinhead on the control board, but I couldn't find it's counterpart on the main board, nor have I figured out it's purpose.

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