[BUILD] SEM VCF

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Kampfzwerg
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Post by Kampfzwerg » Thu May 16, 2019 11:15 am

Yeah found it RAL1015 it was.

:tu:

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Flareless
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Post by Flareless » Thu May 16, 2019 12:01 pm

@ Kampfzwerg - Thanks!! I'll check it out.
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keninverse
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Post by keninverse » Thu May 16, 2019 1:22 pm

tufraniuh@yahoo.com wrote: So I was fantastically lucky to have two defective SEM modules from different manufacturers not only sounding the same, but also noisy the same.
No reason to continue to be snarky. Some of the other posters asked you to at least share a pictures but at this point you so far came onto the board complaining about a build and we don't have any idea of how it's built. Is the wring short? Is the PCB free of flux? What's your power supply look like? Do you have an oscilloscope? Did you trace the circuit and find out where the noise is appearing? Are the OTAs known, good OTAs? What type of FET are you using? Steps can be taken to mitigate noise but you don't seem to be sharing much so that's it from me

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Post by tufraniuh@yahoo.com » Thu May 16, 2019 1:40 pm

Nevermind that didn't work at all
Last edited by tufraniuh@yahoo.com on Fri Jun 07, 2019 2:25 am, edited 1 time in total.

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keninverse
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Post by keninverse » Thu May 16, 2019 2:03 pm

tufraniuh@yahoo.com wrote: Maybe you wanted to say the modular is not for me? Or even music is not for me?
By this you confirm that the noise is present and it would be better for me not to try to fix it, because it is impossible, or as you say "vintage circuit just isn't going to perform to you"
Google helped me "ca3080 noisy"
:picard:

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Post by Lemmy » Mon Nov 18, 2019 5:50 pm

Is this PCB available in the UK or EU?

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Post by Lemmy » Wed Nov 20, 2019 7:09 am

Or:
1. Can I order from Synthcube to the UK?
2. Would the God's Box Humpback filter be a good substitute?

Edit: Or the Erica Synths Multimode VCF? https://www.thonk.co.uk/shop/erica-mult ... l-diy-kit/

Any recommendations welcome...

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Cedrik Ha
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Re: [BUILD] SEM VCF

Post by Cedrik Ha » Thu Jan 16, 2020 10:50 am

I build the SEM VCF for my MU System and got massive problems regarding 50Hz hum most likely caused by a ground issue or something else. I already reworked my cable management here in the studio to get rid of potential ground loops but that didn't fix the problem. I tested the module with two different power sources (Rigol DP832 PSU and the power-one PSU of my System) and also used the input of a mobile speaker that is not connected to ground to hear if the hum is still present and so it was. I picked up the signal from the low pass output with nothing plugged into the inputs, cutoff fully opened and resonance to 0.

Maybe someone else can confirm a similar behavior of his module.

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Re: [BUILD] SEM VCF

Post by LED-man » Thu Jan 16, 2020 11:38 am

Same issue by a customer from me.
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emmaker
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Re: [BUILD] SEM VCF

Post by emmaker » Thu Jan 16, 2020 8:04 pm

Providing all the options, fixes and panel wiring have been done correctly.

Get out the ohm meter and check all the grounding on the board and front panel.
Make sure all the op-amp inputs are OK, if left open they may pick up the AC.

OTAs are very sensitive to the control current (Iabc). If the current limit is exceeded they will be destroyed so that might be something to check.

Good luck.
Jay S.

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emmaker
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Re: [BUILD] SEM VCF

Post by emmaker » Fri Jan 17, 2020 4:57 pm

Another trick that came to mind is just start touching the PCB pushing on parts while the filter is running.

The resistance and capacitance from your finger and pressure may change the sound. If so that may give you a clue where the problem is.

If there is an open connection the pressure may close the circuit and it may work. The resistance/capacitance may be enough to get things to make a different noise.

Again good luck.
Jay S.

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synthcube
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Re: [BUILD] SEM VCF

Post by synthcube » Tue Apr 14, 2020 10:45 am

greetings all
with gratitude to moogah, we are happy to report we have a new run of PCBS for the SEM VCF-- with necessary corrections for the trace fix and the transistor silkscreen orientation issue-- now fixed

the pcb is 100% compatible with the eurorack panel and barcode panel pcb, and also used for our Frac and dotcom/MU panel versions-- BOM remains the same---

link to moogah sem vcf on synthCube

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Re: [BUILD] SEM VCF

Post by Cablebasher » Mon Sep 14, 2020 6:25 am

Hey guys

What jacks fit the panel PCB?

My PJ301BM fit but the panel holes are too big for them.

Any ideas?

Thanks.

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