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2015-08-16 by Stephen Richards
Hi Ken and all, One of my CGS48 VCO's has suddenly started completely loosing control of pitch. Every output is displaying the same behaviour. The pitch is wavering like a mosquito and occasionally jumps or drops dramatically in pitch. Supply voltage is fine , chips seem fine. I
2015-08-08 by Stephen Richards
Range CCW to MIX INV jack with a 1K as per diagram then to CCW pad, just to be sure ? From: "Ken Stone otherunicorn@... [cgs_synth]" To: cgs_synth@yahoogroups.com Sent: Saturday, August 8, 2015 1:16 PM Subject: Re: [cgs_synth] CGS13 V2.2 Gated Comparator - Range pot wiring. Look
2015-08-08 by Stephen Richards
Thanks Ken From: "Ken Stone otherunicorn@... [cgs_synth]" To: cgs_synth@yahoogroups.com Sent: Saturday, August 8, 2015 1:16 PM Subject: Re: [cgs_synth] CGS13 V2.2 Gated Comparator - Range pot wiring. Look at the symbols on the PCB. The little CCW arrow goes to the CCW end of the
2015-08-08 by Ken Stone
Look at the symbols on the PCB. The little CCW arrow goes to the CCW end of the pot. The triangle goes to the wiper. The CW end goes nowhere (or is shorted to the wiper). On Sat, Aug 8, 2015 at 12:18 PM, Stephen Richards okayjustalittle@... [cgs_synth] cgs_synth@yahoogroups.com >
2015-08-08 by Stephen Richards
I decided to check up on myself and have a poke under the hood of my SWAMP panel. The range pot wiring is vexing me... Because i am using the CGS 31 V1.2 Digital Noise Mixer section instead of a CGS04 ; i need to confirm a few wiring things. I'm a bit confused about which diagram
2015-08-06 by Ken Stone
Good stuff :) On Thu, Aug 6, 2015 at 8:29 PM, Paul Bower paul@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: Yup it was me using the wrong pad as ground - all working fine and the NAND/AND module is now sat next to the XOR/OR that I completed around 13 years ago Gratuitous ph
2015-08-06 by Paul Bower
Yup it was me using the wrong pad as ground - all working fine and the NAND/AND module is now sat next to the XOR/OR that I completed around 13 years ago Gratuitous photos maybe in a few days :-) Cheers Paul On 4 Aug 2015, at 21:49, Paul Bower paul@... [cgs_synth] cgs_synth@yahoo
2015-08-04 by Paul Bower
Sage advice :-) I checked the pins on the 4093 even though I ‘knew’ they would be fine - hey presto I think I figured it out I originally used the MTA156 connector for one board and for the second board used the auxiliary pins to piggyback the two (I didn’t do this on my other mo
2015-08-03 by Ken Stone
In that case, check it is getting the correct voltage to its power pins first :) On Tue, Aug 4, 2015 at 12:15 AM, Paul Bower paul@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: I was afraid you would say that - i got into the habit of soldering ICs direct to boards I’ll pop i
2015-08-03 by Paul Bower
I was afraid you would say that - i got into the habit of soldering ICs direct to boards I’ll pop in a replacement chip (maybe with an holder this time) On 3 Aug 2015, at 15:06, Ken Stone otherunicorn@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: Swap the two CMOS chips betw
2015-08-03 by Ken Stone
Swap the two CMOS chips between your units, and see if the fault follows the chip, or says with the board. On Mon, Aug 3, 2015 at 11:23 PM, Paul Bower paul@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: I thought you were all ignoring me, then I realised my Yahoo settings wer
2015-08-03 by Paul Bower
I thought you were all ignoring me, then I realised my Yahoo settings weren’t correct and the Yahoo notices were going to spam :-) Anyways… I’m still plugging away at this one, and got a little DSO Nano so I can actually measure things reasonably properly I separated out the two
2015-07-30 by neilbaldwin70
Interesting. My problem one will produce the oscillation with no input. On 30 Jul 2015, at 03:03, Richard Brewster pugix@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: I think I've solved my problem. The input level was too high. I put a pot between the VCO output I am using
2015-07-30 by Richard Brewster
I think I've solved my problem. The input level was too high. I put a pot between the VCO output I am using and the input to the gain cell. Lowering the input level made the parasitic oscillation disappear. Richard On 7/29/15 7:37 PM, neil.a.Baldwin@... [cgs_synth] wrote: Exactly
2015-07-29 by neilbaldwin70
Exactly what I'm getting Richard though oddly only in one of two I'm using on the same build. A solution to this would be an enormous relief: this has spent about 3 solid days on my bench and I don't seem to be able to do anything to alleviate the noise. On 29 Jul 2015, at 19:48,
2015-07-29 by Richard Brewster
I just built six of these for two Serge VCFQ modules. I am getting approximately unity gain with the test circuit with a 5K6 to ground on the CV input and the CV pot disconnected. My problem is a high frequency parasitic oscillation on a portion of the negative excursion of the o
2015-07-27 by Stevie Richards
Thanks Dmitri Yes, I found a thread on EM shortly after posting this yesterday that had just that. On 28 Jul 2015, at 1:11 am, "Dmitri SFC dankedout415@... [cgs_synth]" cgs_synth@yahoogroups.com > wrote: most people just make a buffer on small perf board with an opamp
2015-07-27 by Dmitri SFC
most people just make a buffer on small perf board with an opamp
2015-07-26 by Stephen Richards
Hi Ken and all I'm a massive fan of the CGS48 VCO but i would really like to get the level of the SINE and SINE/SAW outputs up to the same levels as the SAW and PULSE outputs. Have any of you done this with success ? Would it be a matter of changing resistors ? Or is some sort of
2015-07-24 by Neil Baldwin
And a short video with audio. You can see/hear as I increase the gain from 0 up to (nearly) max and back down again. https://www.dropbox.com/s/xs82ic593zgkb6z/IMG_1798.MOV?dl=0 On 24 July 2015 at 16:15, Neil Baldwin neil.a.baldwin@... > wrote: I hooked up the scope again and this
2015-07-24 by Neil Baldwin
I hooked up the scope again and this time turned up the gain to max. The interference is a square-ish wave that decreases in pitch as you increase the gain (and vice versa). Seems to kick in at the crossover point between -ve and +gain https://www.dropbox.com/s/2yl7gzxkobxey67/IM
2015-07-24 by Neil Baldwin
Thanks for the tip. Unfortunately it has little to no effect. I've practically rebuilt that cell from scratch now, even matched the other transistor pair. I'm wondering if it's being adversely affected by other circuits around it though the fact that I've got two identical gain c
2015-07-23 by ghpicard
It looks like an HF oscillation. You could try enhancing the decoupling of the power supply input. Ceramic 10nF capacitors between the power legs of the ICs (+ and -) and ground can help. They must be soldered directly on the pins to avoid spurious inductance. Also, try not to ro
2015-07-22 by Ken Stone
Sorry, I have no idea what's causing that. Maybe read up on Blackmer cells. On Thu, Jul 23, 2015 at 4:24 AM, Neil Baldwin neil.a.Baldwin@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: Thanks Ken. On one of the gain cells, the output breaks up quicker than the other. I matched
2015-07-22 by Neil Baldwin
Thanks Ken. On one of the gain cells, the output breaks up quicker than the other. I matched the NPNs as suggested but it doesn't make any difference. If I turn the gain pot up, at a certain point (just past midway if it matters) suddenly there is an inaudible load on the output.
2015-07-22 by Richard Brewster
I had a couple of these bi-color LED left over from another project. http://www.digikey.com/product-search/en/optoelectronics/panel-indicators-pilot-lights/524928?k=67-1187-ND The LED driver circuit was similar to the one driving those in the other project. This is how I guessed
2015-07-22 by Dmitri SFC
Blue or red on a bi polar LED will be far brighter than than yellow or green so I end up putting different value Resistors behind both LED legs. If its blue up to 30k , Then a far lower value like 10r behind yellow or green. --
2015-07-21 by Ken Stone
It depends on the LED you select. Try some of the the LEDs with various resistors on the correct voltage before you decide. On Wed, Jul 22, 2015 at 4:18 AM, Richard Brewster pugix@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: What resistors are people using for RLED for the
2015-07-21 by Richard Brewster
What resistors are people using for RLED for the LED driver that Ken added to the SSG? The assembly notes don't mention it. I am thinking that 1K might work fine. Thanks, Richard Brewster http://pugix.com
2015-07-20 by Richard Brewster
Thanks, Ken! On 7/20/15 6:51 PM, Ken Stone otherunicorn@... [cgs_synth] wrote: Follow what is on the PCB. It appears I did a cut-and-paste from the Neg slew parts list, then forgot to finish editing it. 100n is the correct value for the integrator caps. Thanks for pointing out th
2015-07-20 by Ken Stone
Follow what is on the PCB. It appears I did a cut-and-paste from the Neg slew parts list, then forgot to finish editing it. 100n is the correct value for the integrator caps. Thanks for pointing out the error. Ken On Tue, Jul 21, 2015 at 8:04 AM, Richard Brewster pugix@... [cgs_s
2015-07-20 by Ken Stone
To decrease the available gain, reduce the value of the CV pull-down, or reduce the value of the feedback resistor between pins 5 and 6 of the cell. Ken On Tue, Jul 21, 2015 at 1:12 AM, Neil Baldwin neil.a.Baldwin@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: Getting somewhe
2015-07-20 by Richard Brewster
I'm building a Dual Positive Slew and find that the capacitor list doesn't match the PC board. There are two 0.1uf bypass caps on the board (both on +V), but 4 called out. Also there are 4 100n mylar caps listed, but only 2 on the board. Moreover, there are two 330n caps listed.
2015-07-20 by Neil Baldwin
Getting somewhere now, cheers Ken. Incidentally, if you wanted to decrease the amount of available gain, would it just be a relatively simple mod? On 20 July 2015 at 11:44, Ken Stone otherunicorn@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: Leave the 10n there, and add a co
2015-07-20 by Ken Stone
Leave the 10n there, and add a couple 100n on the main board (it's stripboard, isn't it?) Adding a 100k trimmer wired b/w the rails via 100k (or greater) to the CV input will let you trim it to unity. It seems to vary a little, dependent on the transistors used. On Mon, Jul 20, 2
2015-07-20 by Neil Baldwin
So try swapping out the two 10n caps for something else? Also I've notice that with the CV disconnected and, for example, a 5V sine wave connected to the input, the gain at the output stage is massive. Should you see unity gain with no CV applied? On 20 July 2015 at 10:47, Ken St
2015-07-20 by Ken Stone
You probably need more decoupling on the power pins to the cells. These cells have huge gain. On Mon, Jul 20, 2015 at 7:00 PM, Neil Baldwin neil.a.Baldwin@... [cgs_synth] cgs_synth@yahoogroups.com > wrote: Thanks Ken With +/- 12V voltage to the CV voltage divider part I'm seeing
2015-07-20 by Neil Baldwin
Thanks Ken With +/- 12V voltage to the CV voltage divider part I'm seeing about -0.6 to +0.6 V at the CV pin which is correct. However, with no input signal to Input, turning up the gain pot eventually results in horrendous feedback-type output. Neil On 19 July 2015 at 11:34, Ken
2015-07-19 by Ken Stone
4.7 instead of 5 pf can be ignored. 100n instead of 220n will cut your bass response. It is ESSENTIAL that there be a pulldown resistor on the CV input e.g.: a 100k to 5k6 voltage divider is needed between your CV and the gain cells CV input. On Sun, Jul 19, 2015 at 8:16 PM, neil
2015-07-19 by neilbaldwin70
http://www.cgs.synth.net/modules/cgs108_vca.html I've built a couple of these to add CV amps to an existing project but am having trouble getting them to behave. Some things to note: - they're running off 15V so I'm wondering if there are some resistor changes required? - I had t
2015-07-19 by scottwest8
Woo-hoo...Logic prevails! That's what i get for mixing schematics between the non-inverting buffers of the cgs33EUR and those of the UNI33. Thanks, I'll tie-in my non-inverted inputs backwards.
2015-07-18 by cg_synth
As long as you are happy with having to plug a signal into each input to get a response, no, you don't need any switched connection on the jacks. As that is how a NAND works, you should be fine. The only possible reason to use a switched jack to positive (via a 1k resistor) would
2015-07-18 by unrecordings
Hello all About 12 years ago I built a wonderful Quad OR/Quad XOR module, and started a Quad AND/Quad NAND. Well finally last night I got around to finishing it. I think I've misinterpreted the build notes somewhere along the line - do I need to tie the NC inputs to +15v for the
2015-07-17 by cg_synth
You are forgetting that the input buffer stage also inverts.
2015-07-17 by scottwest8
Anyone want to give me a reality check…in the schematic for the UNI33 matrix mixer, the "A" bus (non-inverted, since it goes through both inverting stages) is grounded in unipolar mode, while the B bus (inverted, since it goes through only one inverting stage) is not. This means
2015-07-10 by Ken Stone
Look for a construction error. No idea specifically what, but swapped wires, solder dags between pads, overenthusiastic soldering lifting pads on the circuit board, which can be a problem on single sided PCBs. Wrong parts (PNP instead of NPN etc). Missing links. On Fri, Jul 10, 2
2015-07-10 by jorgen.vandeburgt
So still not perfect. One quart has a very limited rise. It oscillates until I reach about the 20% mark of the rise button. After that it stops abruptly. The other quarts work fine, this is the only one that has this. I've measured the pot and it's working fine and outputting 0 -
2015-07-05 by Richard Brewster
Great suggestion, Ken! I swapped the 100K and 47K resistors that you referred to on the CV path. Now the gain is 1.125 at +5V into a 100K on the CV input. That's just right. I'll use a 300K for the resistor to the initial gain pot. Thanks for the help. Richard Brewster http://pug
2015-07-05 by Ken Stone
I'd try changing the 47k between pins 1 and 2 of the TL072 in the CV path, and/or the 100k between that and the PNP. You may also be able to reduce the 47ks in the matched pair, as well as increasing the 130k's. Or use transistors with more gain in the CV circuit. Ken On Sun, Jul
2015-07-04 by Richard Brewster
The gain with +5V into the 100K CV input resistor is about 0.2, rising to 0.6 at +15V on the CV input, a lot less than unity. I tried substituting a 22K for the 100k going from pin 1 of the input summing TL072 to the base of the matched transistor pair (with 220 ohm resistor to g