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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Mon Mar 19, 2007 1:07 am Post subject:
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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... _________________
cheers,
matthias
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Big Boss at fonitronik
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Mon Mar 19, 2007 5:04 am Post subject:
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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
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Mon Mar 19, 2007 1:57 pm Post subject:
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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) _________________
cheers,
matthias
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Big Boss at fonitronik
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
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Posted: Wed Mar 21, 2007 11:18 am Post subject:
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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).
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Is there a way to tweak this Q factor ?
Or this is no use ?
And what is that « strange » resonance control !?
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
Joined: Jan 21, 2007 Posts: 583 Location: France
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Posted: Wed Mar 21, 2007 11:36 am Post subject:
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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
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Wed Mar 21, 2007 11:46 am Post subject:
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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).
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Is there a way to tweak this Q factor ?
Or this is no use ?
And what is that « strange » resonance control !?
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. _________________
cheers,
matthias
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Big Boss at fonitronik
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numbernone
Joined: Aug 16, 2006 Posts: 477 Location: new york city
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Posted: Wed Mar 21, 2007 1:20 pm Post subject:
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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
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Wed Mar 21, 2007 1:34 pm Post subject:
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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? _________________
cheers,
matthias
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Big Boss at fonitronik
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fonik
Joined: Jun 07, 2006 Posts: 3950 Location: Germany
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Posted: Wed Mar 21, 2007 1:42 pm Post subject:
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fonik wrote: |
don't know about that. i am sure yves knows more about that!
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ha! took a look at RJBs original schematic: it's nothing but the wet/dry mixing pot... _________________
cheers,
matthias
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Big Boss at fonitronik
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sonicwarrior
Joined: Dec 22, 2005 Posts: 266 Location: Cologne, Germany
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Posted: Wed Mar 21, 2007 1:48 pm Post subject:
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Got mine today.
Wow, they're small! |
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sneakthief
Joined: Jul 24, 2006 Posts: 569 Location: Berlin
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Posted: Wed Mar 21, 2007 1:56 pm Post subject:
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oh fonik beat me to the answer about the RJB resonance knob.
sonicwarrior - small but big-sounding _________________ Sneak-Thief - raw electrofunk |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
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Posted: Wed Mar 21, 2007 3:04 pm Post subject:
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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 ?
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
Joined: Jan 21, 2007 Posts: 583 Location: France
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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Posted: Wed Mar 21, 2007 4:39 pm Post subject:
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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) _________________ http://www.bugbrand.co.uk
http://www.bugbrand.blogspot.com |
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Scott Stites
Janitor
Joined: Dec 23, 2005 Posts: 4127 Location: Mount Hope, KS USA
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Posted: Wed Mar 21, 2007 5:38 pm Post subject:
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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
Joined: Dec 29, 2006 Posts: 1176 Location: australia
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Posted: Wed Mar 21, 2007 6:03 pm Post subject:
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fonik wrote: |
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
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Wed Mar 21, 2007 10:48 pm Post subject:
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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
Joined: Aug 31, 2004 Posts: 65 Location: Nesodden, Norway
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Posted: Thu Mar 22, 2007 6:03 am Post subject:
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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
Joined: Jan 21, 2007 Posts: 583 Location: France
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terjewinther
Joined: Aug 31, 2004 Posts: 65 Location: Nesodden, Norway
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Posted: Thu Mar 22, 2007 4:07 pm Post subject:
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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?
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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.
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Great. Thanks a lot.
tw. |
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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Posted: Thu Mar 22, 2007 4:11 pm Post subject:
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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? _________________ http://www.bugbrand.co.uk
http://www.bugbrand.blogspot.com |
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: Thu Mar 22, 2007 11:25 pm Post subject:
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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.
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You'll end up with the RJB design... That has the dual gang pot and buffer opamp. |
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funkyfarm
Joined: Jan 21, 2007 Posts: 583 Location: France
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Posted: 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 ? |
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etaoin
Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL
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Posted: 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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