Gristleizer |
In this project, Chris (stobiepole) and I have put together PCB and vero layouts for the legendary Gristleizer by Roy Gwinn and popularized by Chris Carter and the Throbbing Gristle. We have verified both and have found no ticking problems in our builds from the LFO. We are planning to use this as a starting point into some new territory with this kind of noise maker.
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Chris said:
You could replace the trimpots (except for the bias) with external pots for even more wacky sounds.
Using the MAX1044 power circuit makes biasing the Gristleizer much easier - you should be able to leave the trim pot set at the mid-point.
Future plans for this one include adding a CV input, so that an external LFO can be used to drive the filter.
Posted 24.08.2007 at 6:27 pm
Audioguy said:
wow this one looks cool. I dont suppose you would have a part number for the rotary knob????
Posted 28.08.2007 at 8:59 am
gaussmarkov said:
Futurlec.com and digikey.com both have some relatively cheap 3-pole 4-position rotary switches. I’ve never seen 2-pole switches except with more positions so I would just leave the third pole unused.
Posted 28.08.2007 at 11:41 am
certain_ant said:
I’m building one of these on protoboard.
Your connections to SW2 B1 and B4 are
swapped on the layout. I’ve used schottkies instead of the Ge diodes - no problems. From IC1 pin 6 I have another
transistor rigged as a follower with a LED plus load in its collector to +9V and its emitter grounded. 6k8 between its base and IC1 pin 6. This gives a flashing indication of the rate. Crude but maybe useful.
I’m going to use this thing in a modular synth so I’ve got +/- 12V. I’ve used three terminal regulators to get the 9V rails. Maybe not needed. Perhaps you can just increase R7, R8 a bit?
Posted 15.09.2007 at 6:08 am
certain_ant said:
Oh and another point. C7 is a bit low isn’t it. With R19, you get a time constant of 4.7ms => 200Hz. I’d
increase it to 1uF since non polarized 1uF aren’t that expensive or enormous any more. Is there anything to be gained at the top end by using better op-amps for IC4 and IC5?
Posted 15.09.2007 at 6:20 am
certain_ant said:
And another. Chris said “replace the trimpots (except for the bias) with external pots”. If you look at Chris Carter’s note at http://www.throbbing-gristle.com/gristleizer/
the ‘bias’ is the one trimpot he does bring out on the case. Haven’t tried it myself yet.
Posted 15.09.2007 at 6:28 am
gaussmarkov said:
Hey certain_ant! Thanks for all the useful comments. I will fix that hook up error.
Honestly, i don’t understand the circuit well enough to know whether changing R7/R8 is enough to account for increasing the supply to +/- 12V.
Regarding C7, that’s not an unusual choice for guitar effects but I can see that you might want to increase it. And while you are messing with the input, you might want to increase the input impedance as well. For electric guitars, 47K is pretty low.
As far as IC4/IC5 go, I think you would hear the difference upgrading those op amps. Whether it’s preferred or not is probably going to be a matter of taste.
The LED indicator and trimpot thoughts are money. Thanks again!
Posted 15.09.2007 at 7:45 am
gaussmarkov said:
The hook ups to SW2 have been fixed. Thanks again to certain_ant!
Posted 16.09.2007 at 1:28 pm
certain_ant said:
Thanks for the prompt response!
Looking at the datasheet, TR1 2n3906 will take 40V collector-emitter and max 200mA collector, so I don’t think it will blow up even if you took the rails to +/-15V. Tr2 might hit a problem though. I read its datasheet and didn’t understand what the limits were! Maybe I’m better off with the three-terminal regulators.
Regarding IC4 input, you could take R19 to 470k - which would give your high impedance and my low freq response. However, I seem to remember that 741s get upset if the input resistors are greater than the feedback resistor. So maybe consider replacing IC1 with something more recent rigged as a low-noise, high impedance x10 buffer.
However, as you say its a matter of taste and this unit obviously isn’t meant to give ‘hifi’ reproduction anyway.
Posted 17.09.2007 at 4:38 am
gaussmarkov said:
Hi again!
I would say that TR2 can be any JFET you like. So that should not stand in the way.
And, because you mention it, it now occurs to me that I have frequently seen the 741 with a 1M bias resistor. I am willing to bet that increasing R19 to 1M, along with increasing R21 to 1M and R20 to 100K, will be just fine. And, as you say, there is nothing lost in making an upgrade either.
Cheers!
Posted 17.09.2007 at 4:51 pm
certain_ant said:
Ok. I can confirm that it runs off +/- 12 V just as well as the original +/- 9V without damage. Looking at the envelope waveforms it produces, there isn’t much difference between the rising triangle, the falling triangle and the equilateral triangle. Listening with synth modules as input, they sound pretty similar too, except maybe at the lowest LFO frequencies. Are others finding that? If true, you might as well drop the rotary switch and have only the square and equilateral positions swiched by a 2-pole-2-way toggle. It would save a bit of cash. Yes, having the bias brought out as a control is good, but none of the other presets do anything interesting enough to the sound to be worth bringing out to knobs.
Posted 17.10.2007 at 11:55 am
gaussmarkov said:
Thanks for the build report. Maybe Chris will pipe in about his build. He does not have an oscilloscope, but his ears should be enough.
Posted 18.10.2007 at 12:18 pm
Roy said:
The design is very much a product of the seventies. Modern opamps would undoubtedly be better. Ditto diodes - any old diode is fine. Clicks, if you get them, will be a layout issue. The momentary current discharging the integrator cap is large and you should be careful where it goes.
Rising ramp, falling ramp and triangle should all sound very different. If they don’t, something is wrong.
The input impedance is way too low - an error in the design. It should be at least 1M for a magnetic pickup. Modern opamps help here.
Roy Gwinn
Posted 25.10.2007 at 11:44 am
gigelmargel said:
hello,
i build one, but i can’t obtain 0V at the output of IC3 using the offset trimpot…also i have some problems using the bias trimpot…it sound very distorsed on some settings…on the 3 position of the 4 pole switch i have a big volume drop…can anyone help me with some certain tensions to verify my build?
best regards!
Posted 26.12.2007 at 1:36 pm
gaussmarkov said:
I see that you have gone to Aron’s forum for help. Perfect!
Posted 29.12.2007 at 9:01 am