[BUILD] God's Box 'Humpback' - 8hp Eurorack Multimode VCF

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diode_destroyer
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Post by diode_destroyer » Sat Nov 25, 2017 1:38 pm

Also, looks like the full kits are back in stock at Thonk now...

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JAO
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Post by JAO » Sat Nov 25, 2017 1:42 pm

diode_destroyer wrote:Also, looks like the full kits are back in stock at Thonk now...
Indeed. CA3080AE back in production, also being sold by thonk separately.

AntonWoldhek
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Post by AntonWoldhek » Thu Dec 14, 2017 5:05 pm

So i ordered the pcb/panel option and the rare part (the CA3060 and the silver mica caps). Unfortunatly the pcb/panel option didnt link up to the matched transistor's which are also required.

If i didnt use matched 2N3906's, what problems would i likely get?

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keninverse
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Post by keninverse » Thu Dec 14, 2017 5:56 pm

It looks like these are just used in the control input so it just won't track 1v/oct very well. Just buy a tape of transistors and you will probably be ok if the transistors are next to each other on the tape. Or you can use a fritz transistor matcher and match them yourself or you can pick up a ssm2220

AntonWoldhek
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Post by AntonWoldhek » Wed Jan 03, 2018 7:45 am

Thanks Ken!

Anybody got a suggestion for equivalent of the 2N3819? I normally buy from TME.eu or Tayda but it seems only mouser has this mosfet.
https://nl.mouser.com/productdetail/cen ... 6jNH1TQ%3D

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JAO
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Post by JAO » Wed Jan 03, 2018 9:18 am

AntonWoldhek wrote:Anybody got a suggestion for equivalent of the 2N3819?
That one is conveniently available on ebay.
Or see here for suitable replacements.

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Post by AntonWoldhek » Wed Jan 03, 2018 10:51 am

Thanks JAO!

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mantid
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Post by mantid » Thu Feb 22, 2018 10:27 pm

Hi,

I built this today and so far so good.

Would anyone be able to clarify: CV1 and CV2 are multiple inputs (each with their own attenuators) to adjust the same thing (cutoff)?

I would love a "user manual" if there is one. I watched the divkid video and the module is largely self-explanatory, but if there is a doc I am overlooking, would love to know about it.

Thanks!

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Post by AntonWoldhek » Fri Feb 23, 2018 4:08 am

Dont have it at hand but i was under the impression CV2 was for Resonance.

[edit] looking at the schematic I think you are correct.

Ms304671
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Capacitors

Post by Ms304671 » Fri Feb 23, 2018 11:45 am

Hi all,

Firstly my apologies for the incoming noob question.

The buid doc asks for 1 x 1nF 102k and 12 x 10nF 103. I know these have 10% tolerances. My question is can i substitute these for the capacitors i have available in my parts box which are 102J & 103J (5%)?

I think/ hope the answer is yes, would save me another mouser order, just looking for some clarification from a more experienced builder.

Thanks in advance!

:help:

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autodafe
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Post by autodafe » Sun Mar 11, 2018 6:47 am

I built one from PCB+Panel

I ended up creating a short between -12 and GND on the power header pins...

I think I shorted for just a couple of seconds, nothing was powering uo so I quickly turned it off...

The filter now does nothing. Only some cracking noise when resonance is full open.

Could the 2 second short have fired the ICs? or other components I will need to replace?

Also, is the value of the trimmer really important? I had another trimmer lying around and I used this...

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Post by zorglub76 » Fri Mar 30, 2018 3:29 pm

Anyone knows what are RX1, RX2, second RX2, RX3 and second RX3? These are empty pads (test points?) on the board.

I've built my second Humpback. The first one works great, but I'm having problems with the second one and don't really know how to debug it.

At RX1 I measure -11.34V on both modules
At RX2 (close to RX1) I measure -0.062V on good, and +4.865 on bad one
At second RX2 and RX3 that are close one to the other, I measure 0V on both modules
At the second RX3 (at the bottom of the board) I measure 0.266V on the good and 10.79V on the bad one.

I've turned all the pots on the module to 0 (counter clockwise) and disconnected all patch cables when measuring the voltages.

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JAO
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Post by JAO » Sun May 06, 2018 9:19 am

A question about the old panasonic 0.33uF lacquer coated metal film capacitor.

Can this be substituted with the potted box type?

I've done mods before where the old style were integral to the sound, but I'm finding them difficult to source.

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Post by infovore » Sun May 06, 2018 10:38 am

mantid wrote:Hi,

I built this today and so far so good.

Would anyone be able to clarify: CV1 and CV2 are multiple inputs (each with their own attenuators) to adjust the same thing (cutoff)?

I would love a "user manual" if there is one. I watched the divkid video and the module is largely self-explanatory, but if there is a doc I am overlooking, would love to know about it.

Thanks!
Correct. CV1 and CV2 are two attenuated CV inputs for cutoff (there's no CV for resonance). If you put the attenuator full to the right, the CV signal will be applied in full, and added to the position of the main cutoff knob. It allows you to mix two different CV signals at different quantities.

I'm not quite sure what else you'd need a manual for. Input goes into input, level is attenuated by the INPUT knob before it hits the filter; CV1+CV2 have attenuators and add to the CUTOFF knob; RESONANCE is RESONANCE. All four outputs along the bottom operate simultaneously: Lowpass, Hipass, Bandpass, Notch. There's a jumper on the back to determine how much the resonance scale goes up to; it's possibly to put some seriously heavy distortion on in the higher setting.

And... that is it. It's a filter. It's a fun one.

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mantid
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Post by mantid » Sun May 06, 2018 2:29 pm

I just like more info than less. I've figured out all the apparent function via trial and error at this point and do love this filter. The two CV inputs for Cutoff is a fun approach, although I wouldn't have minded one for resonance.

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JAO
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Post by JAO » Sun May 06, 2018 6:01 pm

JAO wrote:A question about the old panasonic 0.33uF lacquer coated metal film capacitor.

Can this be substituted with the potted box type?

I've done mods before where the old style were integral to the sound, but I'm finding them difficult to source.
Does anyone use generic green in place of old red panasonic?

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infovore
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Post by infovore » Mon May 07, 2018 12:01 pm

mantid wrote:I just like more info than less. I've figured out all the apparent function via trial and error at this point and do love this filter. The two CV inputs for Cutoff is a fun approach, although I wouldn't have minded one for resonance.
One for resonance is more complex - or rather, it requires adding a VCA to the circuit, not just wiring a jack and a pot together. The resonance pot is basically just an attenuator how much feedback gets fed back into the filter. So to control that with voltage you need a VCA.

(This is one of the things in the circuit design of MI Ripples - the VCA chip ends up serving two purposes - one VCA is used to allow for CV control of Resonance, and the other becomes the output-VCA on the LP4>VCA output, controlled by GAIN. I always wonder which need for the VCA came first).

ScientificDreamz
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Post by ScientificDreamz » Sat May 26, 2018 8:03 am

Would this be suitable as a first build? :)

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Post by Catflap » Sun May 27, 2018 4:23 am

ScientificDreamz wrote:Would this be suitable as a first build? :)
Yes, It was my first build. Nothing in the build that is overly complicated. Just take your time and try not to rush when the finish line is in sight.

magnesi
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Hiss from filter

Post by magnesi » Mon May 28, 2018 5:50 am

Hi, I'm getting a lot of hiss from my Humpback especially in low pass mode. Is this normal or does anyone think I need to replace something?

I love the sound of the filter otherwise.

Solved: So...I'm new to this whole modular stuff and was using the filter at the end of my chain (after microbrute or Monologue). This I realise now is recipe for noise especially on vintage design filters.

Since then I've built my rack uo to a full basic modular synth i.e. Oscillators, filter, LFO, EG and VCA. The noise has completely disappeared now. One good reason I guess to have the VCA at the end of the chain?

Yep!... I'm still learning

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mantid
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Post by mantid » Sat Jun 09, 2018 1:37 pm

Thanks for the follow-up!

I'm still really loving this filter - and such a fun, simple build.

danfastlikeflan
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Post by danfastlikeflan » Tue Jun 19, 2018 12:46 pm

Anyone know what the trim pot does? I haven’t seen any word on what it does
Thanks

magnesi
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Post by magnesi » Tue Jun 19, 2018 1:11 pm

danfastlikeflan wrote:Anyone know what the trim pot does? I haven’t seen any word on what it does
Thanks
I'd like to know the answer too. I can't seem to hear it making any difference on my one.

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Post by Thonk Support » Tue Jun 19, 2018 1:19 pm

Basically the trimmer adds a very small offset to the centre frequency, in reality it probably should have been designed out of the final board as it's not very useful, it turned out the tolerances of the final BOM kind of made it not necessary. So essentially, don't worry about it.
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AS of October 2020 this account which used to go by the name of Monobass is now manned by various staff at Thonk.

magnesi
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Post by magnesi » Tue Jun 19, 2018 1:38 pm

Monobass wrote:Basically the trimmer adds a very small offset to the centre frequency, in reality it probably should have been designed out of the final board as it's not very useful, it turned out the tolerances of the final BOM kind of made it not necessary. So essentially, don't worry about it.
Thanks Monobass. So if I've turned it in several directions (mine doesn't seem to have a stop point in either direction) should I need to recalibrate anything? I've twisted it quite a few turns. Not quite sure what you mean by "centre frequency".

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