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 Forum index » DIY Hardware and Software » fonik's place
PS3100 Resonator PCBs
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fonik



Joined: Jun 07, 2006
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PostPosted: Mon Mar 19, 2007 1:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Etaoin wrote:
By the way, is the "wet" output supposed to be lower gain than the "dry" output?
I need to have to mix output at about 90% and up to even hear the filtered signal.

i actually didn't care much about that. but i observe the same here (and don't forget i just tried to be close to the originial schematic).
looking at the schematic i'd said: R6/R13 seem to work as voltage dividers (or am i wrong here?). maybe you should try to increase R13 to the a value close to R6. i think i will try it tonight...

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bugbrand



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PostPosted: Mon Mar 19, 2007 4:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Got mine! Thanks Matthias!

Surely you can raise the value of R11 to amplify the filtered signal a bit if the wet output is lower than the dry?

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etaoin



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PostPosted: Mon Mar 19, 2007 5:04 am    Post subject: Reply with quote  Mark this post and the followings unread

That's what I was about to try. Question remains: why is it lower? Or is it also lower in a real PS3100?

The real PS has a 1k / 27 ohm divider at the filter input, so one would expect the signal to be even lower on that. Or does the PS have some gain in the filters? Could the difference between the vactrol and the original HTV cause the difference in gain?
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fonik



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PostPosted: Mon Mar 19, 2007 1:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
Etaoin wrote:
By the way, is the "wet" output supposed to be lower gain than the "dry" output?
I need to have to mix output at about 90% and up to even hear the filtered signal.

i actually didn't care much about that. but i observe the same here (and don't forget i just tried to be close to the original schematic).
looking at the schematic i'd said: R6/R13 seem to work as voltage dividers (or am i wrong here?). maybe you should try to increase R13 to the a value close to R6. i think i will try it tonight...

oh, that's really funny: i just hooked up the PS3100 board and guess what? the dry output has lower gain than the wet! and therefor it's obvious why i didn't cared about it: i want the wet and not the dry output, hehe.
so i ended up with a 2.7k for R11 to lower the gain of the wet audio path!
don't ask me, what's going on here...
and here is a sample. i'm turning the mix pot from dry to wet to dry:
PS3100mix(520kb)

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funkyfarm



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PostPosted: Wed Mar 21, 2007 11:18 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi !


You know what ? (yes ..."I'm happy"...vactrols in one hand, waiting for the pcbs to come, but)
I have few questions !

1. RESONANCE

I’ve read that Q is fixed at 5
yusson wrote:
No, it's the frequencies of the three cells that are under CV, the resonance of these filters is fixed (and is around Q=5).


Is there a way to tweak this Q factor ?
Or this is no use ?

And what is that « strange » resonance control !? Wink

http://homepage2.nifty.com/rjb/images/diy_resonator01big.JPG


2. TRIMMING

The three 100k trimmers (tied to -15V) set the potentiometer range ? what the procedure ?

3. LED Display

How do the LED behave ? displaying frequency value ? overload detector ? or it just blings along with positive excursion of the lfo ?

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funkyfarm



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PostPosted: Wed Mar 21, 2007 11:36 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:

so i ended up with a 2.7k for R11 to lower the gain of the wet audio path!
don't ask me, what's going on here...



Are you still at 10V PP at the output ?
The overall gain is still more or less 1 ?

no way to "boost" the dry signal ?
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fonik



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PostPosted: Wed Mar 21, 2007 11:46 am    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
I’ve read that Q is fixed at 5
yusson wrote:
No, it's the frequencies of the three cells that are under CV, the resonance of these filters is fixed (and is around Q=5).

Is there a way to tweak this Q factor ?
Or this is no use ?
And what is that « strange » resonance control !? Wink
http://homepage2.nifty.com/rjb/images/diy_resonator01big.JPG

don't know about that. i am sure yves knows more about that!

Quote:
The three 100k trimmers (tied to -15V) set the potentiometer range ? what the procedure ?

i used them to have 0V at the summing node (base of BC550) when no CV applied and freq pot set to zero.

Quote:
How do the LED behave ? displaying frequency value ? overload detector ? or it just blings along with positive excursion of the lfo ?

they reflect whats going on inside the cell. they are in parallel to the LEDs of the vactrols, so they give you an idea how much current is going through them (comes in very handy when connecting different CV sources to the resonators).

i am sure someone else with better skills than me is able to explain in more detail.

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numbernone



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PostPosted: Wed Mar 21, 2007 1:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just got the boards today...lovely work.

And boy am I glad that I have a pile of other projects to finish before I think about starting these. Plenty of time for the many much smarter than I folks to perfect them!!!


3 cheers for Mattias!!!!
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fonik



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PostPosted: Wed Mar 21, 2007 1:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
(...)http://homepage2.nifty.com/rjb/images/diy_resonator01big.JPG(...)

definetely OT: when i take a look at radio junk box' site i see a lot of strange symbol (and they are not japanese): squares, &, $ and what not. wrong settings of my browser?

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fonik



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PostPosted: Wed Mar 21, 2007 1:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
funkyfarm wrote:
And what is that « strange » resonance control !? Wink
http://homepage2.nifty.com/rjb/images/diy_resonator01big.JPG

don't know about that. i am sure yves knows more about that!

ha! took a look at RJBs original schematic: it's nothing but the wet/dry mixing pot...

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sonicwarrior



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PostPosted: Wed Mar 21, 2007 1:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Got mine today.

Wow, they're small! Smile
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sneakthief



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PostPosted: Wed Mar 21, 2007 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

oh fonik beat me to the answer about the RJB resonance knob.

sonicwarrior - small but big-sounding Smile

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funkyfarm



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PostPosted: Wed Mar 21, 2007 3:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

For sure, I’m so stupid ! LEDs display “the sweep” of each BPF frequency ! That rocks !

fonik wrote:
ha! took a look at RJBs original schematic: it's nothing but the wet/dry mixing pot...


Yep ! MIX control is a STEREO logarithmic potentiometer followed by another simple inverting mixer (the two cursors are blended)
Log curves may affect the mix around center position (“no-hole-in-the-middle-style” ?!)
Maybe this could also prevent gain loss ? Wink


Unlike the peak emphasis at cutoff frequency of a classic 4pole LPF, I guess the amount of “RESONANCE” should be listen here more as the amount of the “effect” from these resonant filters…

PS : I note that output signal is out-of-phase in RadioJunk design (with the added dry/wet mixer), another inverter buffer could be missing...

http://homepage2.nifty.com/rjb/pdf/rjb_diy_synthe_701a_resonator_schem_revA.pdf
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funkyfarm



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PostPosted: Wed Mar 21, 2007 4:01 pm    Post subject:
Subject description: Q factor ?
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Is it simple math to find the Q factor (that’s correct ?), the bandwidth of this bandpass filter ?
I guess it could be “read” with some noise on a software spectrum analyser…
but, maybe this part of the secret ?

http://homepage2.nifty.com/rjb/diy_synthe12.htm

http://homepage2.nifty.com/rjb/pdf/rjb_diy_synthe_701a_resonator_schem_revA.pdf


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bugbrand



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PostPosted: Wed Mar 21, 2007 4:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've populated one of the boards I got, but want to add some bits & try some things...

I quite like having at least two inputs into such a module, so I'm going to add a little simple mixer (making sure it keeps things in-phase) and I'll put on an extra channel that I'm going to try with a feedback path out of the pure wet path (ie taking another 100r resistor from the output of U3 (pin7)) --- this may have good resonance effects perhaps? (or am I barking again)?
'cos I'm also going to add a hardwired inverted output of the LFO (ie so one resonator can sweep up while another sweeps down) I'll have another free inverter and could try inverted or non-inverted feedback... who knows which may or may not work - hopefully I can report back tomorrow - hell yeah, I'm keen to get this going!

I'll certainly do such things as measuring the PtoP at output... (and report back if no-one has already done so)

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Scott Stites
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PostPosted: Wed Mar 21, 2007 5:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
ha! took a look at RJBs original schematic: it's nothing but the wet/dry mixing pot...


If I'm not mistaken, 'Resonance' was the original label for that control on the PS3100.

Quote:
I'm also going to add a hardwired inverted output of the LFO (ie so one resonator can sweep up while another sweeps down)


Ad Aspera Per Kitchen Sink! This greatly expands the resonator's pallette. As I've mentioned before in this thread, having a master LFO level control feeding three bipolar attenuators is working very, very well for my triple SVVC. This allows you to not only select which filters will be modulated inversely, but also allows you to modulate each filter with varying intensity from the same LFO. Anyway, just one inverter will work wonders, too. Listening to a fast sweep with all LFO signals at the same phase, then inverting just one of them is like night and day.

The feedback stuff sounds interesting, too - I never tried that, being as there were three filters to feed back to, and I was lazy (though nowadays I'd probably try a simple triple Vactrol VCA configuration). In any event, I think that if you get it working, it will be awesome. With the original resonator, I very rarely, if ever, deviated from the wettest mix I could get. Being able to increase the resonance of the filters themselves might just rocket it into new territory.

One thing I do recall doing with the original Korg circuit was isolating a single filter and feeding a signal just through it - as it turns out, these filters sound quite funky on their own. Might make an economical way to have your cake and eat it, too, with a BugBrand suitcase synth - you could use it as a resonator or as three separate filters for three separate sources (or both simultaneously).

Cheers,
Scott
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andrewF



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PostPosted: Wed Mar 21, 2007 6:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
funkyfarm wrote:
(...)http://homepage2.nifty.com/rjb/images/diy_resonator01big.JPG(...)

definetely OT: when i take a look at radio junk box' site i see a lot of strange symbol (and they are not japanese): squares, &, $ and what not. wrong settings of my browser?


depends on your browser, but click on VIEW - character encoding- then you may have to mess around....i use mozilla and have it set to Auto detect - Japanese. It may work if you set it to Unicode too.
Then you have to be able to read Nihon-go! or a quick visit to babel-fish might help.
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etaoin



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PostPosted: Wed Mar 21, 2007 10:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I'm going to try with a feedback path out of the pure wet path (ie taking another 100r resistor from the output of U3 (pin7)) --- this may have good resonance effects perhaps?


Doesn't it need the path from the output, through the dry/wet/resonance pot back to the input to even do resonance?
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terjewinther



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PostPosted: Thu Mar 22, 2007 6:03 am    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
LEDs display “the sweep” of each BPF frequency ! That rocks !

I am looking at the schematics and the PCB that I got (it all looks great, BTW), and think I get it, but with some limitation into electronic know-how I need to ask:
Does this mean that it is best to use a bi-color LED to show both positive and negative values?
Terje Winther
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funkyfarm



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PostPosted: Thu Mar 22, 2007 9:21 am    Post subject: Reply with quote  Mark this post and the followings unread

terjewinther wrote:
funkyfarm wrote:
LEDs display “the sweep” of each BPF frequency


Does this mean that it is best to use a bi-color LED to show both positive and negative values?


No, I don't think it.
This LED indicates "how much current is going through" the vactrol...indeed it represents the "R" value, which sets the frequency of the filter.

No light means minimum cutoff frequency (20Hz ?) while a full shining LED shows you reach the higher freq setting...
When it starts shining, you have an upward freq shifting, when it dimes, the sweep is from a high point to a lower one.


(R elements are part of one dual vactrol)


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terjewinther



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PostPosted: Thu Mar 22, 2007 4:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
terjewinther wrote:
funkyfarm wrote:
LEDs display “the sweep” of each BPF frequency

Does this mean that it is best to use a bi-color LED to show both positive and negative values?

No, I don't think it.
This LED indicates "how much current is going through" the vactrol...indeed it represents the "R" value, which sets the frequency of the filter.
No light means minimum cutoff frequency (20Hz ?) while a full shining LED shows you reach the higher freq setting...
When it starts shining, you have an upward freq shifting, when it dimes, the sweep is from a high point to a lower one.


Great. Thanks a lot.

tw.
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bugbrand



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PostPosted: Thu Mar 22, 2007 4:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok, some updates..

First off - wow, I had so much fun playing with this module, even with it unfinished. Really really great sounds and it'll be even better when its not just a circuit board with pots'n'stuff flying off it & mounted in a rack. I haven't tried the CV inputs or LFO yet even..

Ok, things:

First off - the blend knob - this really didn't work out well - there seemed to be a great output drop at either end and other wierd-ness - ie bad.

So next I tried with a dual-gang pot - take dry level down as you're taking up the wet volume. This didn't work well either - think I need a buffer amp after. So, for now I left this and just took the pure wet output and mixed externally the dry signal in a mixer before output. I'm thinking now that I'll have a 2 channel (non-inverting) mix on the output with independent mix levels for dry & wet. By the way, I also replace R11 with a 47k trimmer pot to adjust the wet signal strength - I didn't measure what value I'd ajusted it to yet and probably will tweak it somewhat 'cos the output obviously depends on what is going in and also the resonators...

On to the feedback path -- this can certainly be very good though I got a load of shrieking noises too! I'd made a 3 channel input mixer to precede the module - 2 standard audio inputs (DC coupled) and then a 3rd input with option for AC or DC coupling. This 3rd channel I then wired up from the wet output (through another 100r resistor from U3 pin7) --- I also wired in a switch and opamp inverter so that I could quickly invert the feedback signal.

Positive feedback 1st - this obviously emphasises the resonators and can quite easily lead to big shreek feedback, mainly when two resonators are close together (or harmonically related). But! When it is tweaked subtly it can add a great deal to the sound. I really should have recorded some things.... oops.!.

Negative feedback was much more subtle - I'm guessing this is making more of a notch filter arrangement, canceling the resonator frequencies? It is quite different in sound from no feedback or positive feedback.

So, the real problem is how to control the feedback path and avoid the big sounds in the positive mode - actually, if indeed there was a 2channel output mixer (dry / wet independent levels) then you'd make some good sounds from full-level dry and low level of feedbacking resonators.

Hmm, opto-compressor on the feedback path?


Another little note - R16, 19, 22 -> I figured these should probably be 2k (or 2k2) for 12v supply.?.

.... Oh, a bit more on the output levels - dry vs wet levels.
I think the input buffer amp does indeed put out an un-attenuated signal and the signal drop is coming from the blend arrangement. Is there a passive way to do a decent blend or do we need opamps?

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etaoin



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PostPosted: Thu Mar 22, 2007 11:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:

So next I tried with a dual-gang pot - take dry level down as you're taking up the wet volume. This didn't work well either - think I need a buffer amp after.


You'll end up with the RJB design... That has the dual gang pot and buffer opamp.
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funkyfarm



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PostPosted: Fri Mar 23, 2007 12:15 am    Post subject:
Subject description: another buffer ?
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Etaoin wrote:

You'll end up with the RJB design... That has the dual gang pot and buffer opamp.


RJB design which output signal is out-of-phase ? Cool
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etaoin



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PostPosted: Fri Mar 23, 2007 12:22 am    Post subject:
Subject description: another buffer ?
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Quote:
RJB design which output signal is out-of-phase ?


Don't know about that. I just meant that that also uses a dual pot and additional opamp. I didn't claim it was better than the original.
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