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WIGGLING 'LITE' IN GUEST MODE

ETI/Maplin Transient Generator
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Author ETI/Maplin Transient Generator
fitzgreyve
"It's an envelope generator Jim, but not as we know it".

This is something I've been wanting to build in euro for a while, but didn't want the complexity of the original circuit from the ETI/Maplin 5600/3800 synths. This is a "re-imagining" of the circuit but PIC based, using modified code from the Electric Druid LOOPENV (http://electricdruid.net). Used with permission. (Thanks Tom!)

It looks like a simple ASR envelope generator, but has fully variable start, hold and final levels (i.e. slopes can go up or down), initial delay, and optional fixed hold duration. Add to that lin or exp slopes, a "retrigger" mode (that fully mirrors the original circuit action), and CV control of time and output level (carried over from the original LOOPENV).

0-5volt (optionally 0-8volt) "ENV" (envelope) output, and +/- 5volt "LFO" output.

The ETI transient controls had a range of 5mS to 5 seconds. In this module they all have a range of 1mS to 10 seconds in four decades, i.e. 1 -10mS, 10-100mS, 100-1000mS, and 1-10 seconds

The attached build doc contains a full description.

Only two ICs, and no adjustments.



PCBs are GBP 8
Panels (10hp) will be GBP 15
Programmed and tested PICs GBP 3.

(I also have "BETA" PCBs available which need one link wire adding - if you are happy with one of these, I'll reduce the PCB price to GBP 5)

Some PCBs available now, Panels and more PCBs will be ordered once I get an idea of numbers.

As this is derived from ED's open source code, the source code and hex files are attached for you to programme your own or modify futher.
These are released under the same CC BY-NC-SA 4.0 licence - i.e. no commercial use please.
woodster
One for me please, very cool to see it come to fruition thumbs up
Zaibach
Very interested in this! One full set for me, please!
Sideshow
Cool that somebody adapts the ETI-circuits for modern modular SlayerBadger!
And I must say that the envelope of the 5600s is pretty awesome, lots of fun smile
whoop_john
As someone who built both a an ETI 4600 and a 5600s back in the day, I can confirm that this is a great transient generator and can be set to play 3 note arpeggios because the start, hold and end levels can be set. The original had a system where a quick tap would trigger the loop mode and a longer one wouldn't. I am assuming this emulation does the same thing.
whoop_john
I also forgot to say many thanks for your brilliant hard work. Much appreciated.
sammy123
Cool Mark. I'll take a set.
whoop_john
Did you find that you didn't need the usual caps on the analog input pins between the input and ground, to reduce jitter?
Zaibach
Found a small error in the BOM: listed are two 14-pin ic sockets, I think it's supposed to be one 14pin and a 20pin socket. Looking forward to building this!
fitzgreyve
whoop_john wrote:
The original had a system where a quick tap would trigger the loop mode and a longer one wouldn't. I am assuming this emulation does the same thing.

As far as I could figure from the circuit (and from distant memory), the "quick tap" would definately start it looping, but the "long tap" appeared to actually be that it would not loop if the gate was still high when it hit the loop end point - that's what I've coded and it works rather well.

whoop_john wrote:
Did you find that you didn't need the usual caps on the analog input pins between the input and ground, to reduce jitter?

Not experience any problems, and have been playing with it with various software versions for several months now.
fitzgreyve
Zaibach wrote:
Found a small error in the BOM: listed are two 14-pin ic sockets, I think it's supposed to be one 14pin and a 20pin socket. Looking forward to building this!


thanks, my mistake - now fixed.
m0d01
I'll take 1 of each (pcb, panel, pic)

PPP me!
Ayab
Please reserve a full set for me too.

I really like the idea of a different set of controls for hopefully encouraging me to use different envelopes. Probably take a while to be able to predict what it does!!

Will pm
Larrea
I'd like a full set as well--PCB, panel, PIC please.

Thanks!
fitzgreyve
I make that 5 sets so far - a couple more and it will be viable to get panels made up.
latigid on
PCB+Panel please smile
whoop_john
Ayab wrote:
Please reserve a full set for me too.

I really like the idea of a different set of controls for hopefully encouraging me to use different envelopes. Probably take a while to be able to predict what it does!!

I don't think it is going to change your life. An ADSR has a sustain level, with a start and end level that is zero. This affair allows the start and end to not be zero, so if you are using it as an envelope with a VCA, then you will simply have some sound coming through at the beginning and end which you probably didn't want unless sustained drones are your thing.

So this unit comes into its own when used with filters and pitch - as I said before - it can do cute three note arpeggios, which can be triggered or not as you play, once you have mastered it.

Inverse envelopes can be easily set up which might have some mileage in stereo panning effects and so forth.

Out of all the ETI synth modules, I always thought this module was the strongest, although I really liked the VCAs too - they doubled up as ring modulators when AC coupled by means of a switch. Relatively simple to build also. Perhaps I should do a PCB for this?
Larrea
whoop_john wrote:
Out of all the ETI synth modules, I always thought this module was the strongest, although I really liked the VCAs too - they doubled up as ring modulators when AC coupled by means of a switch. Relatively simple to build also. Perhaps I should do a PCB for this?


Sounds like this would be an intriguing pair.

I'm interested.
whoop_john
Larrea wrote:
Sounds like this would be an intriguing pair. I'm interested.

The ETI VCA uses an MC1496 and there are various VCAs and ring modulators around that are based on this IC. As far as I know the ETI version is the only one that does both jobs in one.
whoop_john
I was looking at the filter output stage of this Transient and comparing it with the one you used in the 110M-ish LFO. They are the same, except R2 in the Transient is 12k whereas its equivalent in the LFO, R20, is 33k. Is the 12k here correct? If so, why?
latigid on
Of course, the non-zero off state isn't good for typical note on-off, but as said if could be cool for drones.

One of my favourite aspects of the Sherman Filterbank is that its sustain stage can go below zero. This way you can get awesome "low-pass gate" type of sounds. I hope something similar can be done here?
spotta
I'ld like to grab a set please, sounds interesting. Happy to have one of the boards that needs a small fix.
ArboriaAuralist
Count me in for a full set, please.

I love the ETI stuff, so also consider me interested in the VCA.
fitzgreyve
whoop_john wrote:
I was looking at the filter output stage of this Transient and comparing it with the one you used in the 110M-ish LFO. They are the same, except R2 in the Transient is 12k whereas its equivalent in the LFO, R20, is 33k. Is the 12k here correct? If so, why?


THe lfo has a chebyshev filter, this one is bessel.
(I am quoting electric druids datasheets).

If anyone wants to try and see if there is any difference in practice:
for bessel, R2=12k, R4=33K
for chebyshev R2=33k, R4=47k

on the lfo I reverted to the chebyshev as I though I was getting some ripple on the square wave.
whoop_john
fitzgreyve wrote:
THe lfo has a chebyshev filter, this one is bessel.
(I am quoting electric druids datasheets).

If anyone wants to try and see if there is any difference in practice:
for bessel, R2=12k, R4=12k
for chebyshev R2=33k, R4=47k

Your PDF for the Transient currently states R4=33k, not R4=12k as you say above.
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