Resonant Lopass Gate PCB's (New Batch 4/29/12)

knob_alchemist · Joined: Mar 03, 2012 Posts: 11 Location: Italy, Südtirol

Ok finished, one unit , works fine Very Happy

....now I need a good panel for it....suggestions or a FPD panel for eurorack to share???

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Thanks!!!!

knob_alchemist · Joined: Mar 03, 2012 Posts: 11 Location: Italy, Südtirol

PS:: it's normal that in BOTH and FILTER mode there's a little hum? In VCA mode there isn't....

fonik · Posted: Mon Apr 23, 2012 10:53 pm Post subject:

knob_alchemist · Joined: Mar 03, 2012 Posts: 11 Location: Italy, Südtirol

No change touching the wiring...no one with this hum?

knob_alchemist · Joined: Mar 03, 2012 Posts: 11 Location: Italy, Südtirol

It seems that the hum is the signal of the VCO (more audible whe the VCO is at high range freq) in the LPG...I tried to set the trimmer but no change in the hum.... Rolling Eyes

djthomaswhite · Joined: Nov 22, 2007 Posts: 140 Location: Orange, CA

Hello builders and analog tweakers,

I am making some of the Resonant Lopass Gate (RLPG) circuit boards available again. I need to replace some that we're sadly lost in the shipments for the last batch and to replace my personal board stock for my own projects. I have received interest for additional boards recently so I will be taking orders to include extra boards in this replacement order.

If you want boards, please PayPal $15 per board to djthomaswhite@yahoo.com with "RLPG Order" in the subject line and I'll note your order. This cost per board includes shipping (global) via USPS. I always replace any boards lost in shipping, hence this order.

This board is the latest revision, but I will fix the IC ground issue in the mixer section thereby eliminating the need for the kludge to fix the board. Board orders are being accepted from now until May 13th with the new board order being placed on Monday the 14th. Boards take 2 weeks to arrive so orders won't start shipping until the week of May 28th. I know this delays delivery, but I order boards to demand and this method has worked well in the past.

I hope you find the news that I am making this limited run of Resonant Lopass Gate boards available to be good news. This project is a fun one and people from beginners to experts have enjoyed it. Please contact me with any questions or feedback directly at djthomaswhite@yahoo.com

Thank you,

Thomas White
Natural Rhythm Music
http://www.naturalrhythmmusic.com/lopass.html

Toller · Joined: Jun 04, 2012 Posts: 1 Location: Germany

Hi,

I seem to have the same problem as knob_alchemist (see 2 posts above): the original signal is bleeding through (quietly, yet audible), even when the offset is all the way down and no cv fed in. Especially noticeable in both and filter mode.
Something wrong with the wiring / some kind of crosstalk maybe? Or is this normal?

knob_alchemist · Joined: Mar 03, 2012 Posts: 11 Location: Italy, Südtirol

Hi I've see your post and your PM... Your Problem is exactly the same of mine....Maybe is normal and depend from the VCOs??
I've not resolved the Problem, but is not a tragedy, I use a mixer to attenuate the signal of VCO (I use 2 A-110 in FM) and the bleeding is very quiet...
Suggestions? Maybe is normal?

numbertalk · Posted: Wed Jun 06, 2012 3:44 pm Post subject:

Possibly related to the vactrol? If I'm understanding your issue I think this is normal for a vactrol, that it doesn't really turn all the way "off", if you know what I mean.

Starspawn · Joined: Jun 14, 2013 Posts: 85 Location: Oslo

Any left of the last run or a new one planned soon?

Mongo1 · Joined: Aug 11, 2011 Posts: 411 Location: Raleigh NC

I think SynthCube.com has some...

Gary

peng · Posted: Thu Dec 05, 2013 7:33 am Post subject:

My main question is this:

What is the "Deep" switch for?

I have read that it is for very large CV voltages.
But I don't get it.
What does it do to large CV voltages?
Anything that an input attenuator couldn't?
This version of the module has CV input attenuators so does that make the deep switch useless?
It practice, it seems to be.

If you have ever engaged this switch please explain why.

(I tried to post to Muff's but that forum is SNAFU lately...again)

muziekzen · Posted: Tue Jul 29, 2014 4:14 am Post subject: Unstable Lopass gate

Hello everyone,

I have built 2 Lopass gates and one of them is very unstable. The offset frequency randomly changes (without any CV modulation) and it happens in all modes (VCA, VCF and both).

I attached an audio file of the issue.

I wonder if anyone has had a similar problem.

Thank you!

g

LOPASS Gate filter problem (Snippet).mp3

Description:

Download

Filename:

LOPASS Gate filter problem (Snippet).mp3

Filesize:

753.06 KB

Downloaded:

1707 Time(s)

loydb · Joined: Feb 04, 2010 Posts: 393 Location: Providence, RI

I'm looking for a good Euro FP for either 2 or 4 of these babies. Anyone?

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

4x
http://synthcube.com/cart/forums.html?route=product/product&filter_name=lpg&product_id=224

2x (out of stock right now)
http://synthcube.com/cart/forums.html?route=product/product&filter_name=lpg&product_id=223

loydb · Joined: Feb 04, 2010 Posts: 393 Location: Providence, RI

Thanks! Ordered one, plus a panel for my Tabula Rasa while I was at it!

loydb · Joined: Feb 04, 2010 Posts: 393 Location: Providence, RI

Has anyone wired up one of the quad Euro panels? A wiring diagram would rock...

Thanks!

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

The four LPG's are simply wired individually according to the schematics. You will however need a simple mixer to mix the 4 outputs. This can be done with an op-amp like a TL072 and 7 resistors.

- use a 3PDT on-off-on switches for the VCA/VCF/VCA+VCF modes

- use 2 CV inputs: one directly in and the other with an attenuator

- cutoff and resonance pots are wired using the same orientation as the pot markings on the PCB

- re. mixer: use this, but ignore the red portion:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

http://www.cgs.synth.net/modules/cgs04_mix.html

loydb · Joined: Feb 04, 2010 Posts: 393 Location: Providence, RI

Thanks!

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

Re. mixing 4 LPG's: also consider using a simpler solution of 4x 10k resistors if you don't mind a signal level drop - which may not be an issue if you're mixing 4 loud-ish signals.

Connect one end of the resistor to the normalization pin of each of the LPG's audio output jacks, then connect all four other ends together at the main mix output jack.

loydb · Joined: Feb 04, 2010 Posts: 393 Location: Providence, RI

Thanks! I will probably do the full-on mixer, it should be small. I'm also drilling the panel to add the 'Deep' switch to each board.

Ayab · Joined: Oct 27, 2015 Posts: 181 Location: London, UK

Firstly thank you Thomas for this excellent project.

I noticed on someone's build (forget which) that the 1k resistors were white? Just realised must be heat shrink? Extra shielding?

Btw i really like the look of the acrylic panel by knob_alchemist. Does anyone know method of adding simple but uniform annotation to the (back in reverse would make hand painting a bit tricky but I could use a stencil - but v.time consuming).

I am really enjoying slowly comprehending some of this fascinating area (the surface!) which was a mystery only recently. I hope to maybe be of help to some beginners in the future. Sorry about the long post effect of reading the Open letter post - and yes I do have a day off today Laughing

AKMacAddict · Joined: Jul 20, 2013 Posts: 1 Location: Anchorage, Alaska

intercorni · Joined: Jun 04, 2007 Posts: 69 Location: hamburg

Does anyone have the problem that the resonance starts too early?
At about one third of the way I'm already in the self-oscillation Sad

Then the signal stops completely.
I use a linear potentiometer for the resonance.
And i try the mod from https://modularsynthesis.com/nrm/lopass/lopass.htm
But it is the same.
Maybe is a antilog pot better?

intercorni · Joined: Jun 04, 2007 Posts: 69 Location: hamburg

The trimm-pot TP1 does nothing - any suggestions?
The Offset-Pot works fine.