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WIGGLING 'LITE' IN GUEST MODE

ETI/Maplin Transient Generator
MUFF WIGGLER Forum Index -> Music Tech DIY  
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.
4floorsofwhores
I'd love a full set cheers
fitzgreyve
whoop_john wrote:
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.

Sorry, my typo in the posting - for Bessel R2=12K, R4=33K

**I will be placing an order for panels on Friday 19th. If anyone else is interested, let me know before then. **
Ayab
Hi whoop_john
Yes, I was getting over excited by the unusual naming of the panel controls. Being impetuous is just one of my bad habits! But I do also like the idea of arpeggios - thanks for clarifying. I'd be up for the Maplin VCA too.

How different VCA's sound depending on design and choice of components is certainly interesting - and how they overdrive.

Fitzgreye
I made a paypal payment for a set but it has just been refunded. Whats the deal? *EDIT* Sorry, just seen the note with the paypal refund stating that you are waiting until panels arrive before taking orders. That's two cases of my assumption problem in one thread!!

Have a good weekend folks.
fitzgreyve
I'm ordering panels and PCBs based on the responses above.

I'll let you all know as soon as I have these in stock.
ArboriaAuralist
w00t
KSS
whoop_john wrote:
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.

PAIA 4710
fitzgreyve
Panels are now in and looking good.

I've now mailed everyone who expressed an interest so far.

Reminder that I also have limited "BETA" PCBs available which need one link wire adding (see build doc) - if you are happy with one of these, I'll reduce the price by GBP 3. Let me know if you want one of these when you order/pay - First come, first served on these.
ArboriaAuralist
Panel & PCB have arrived and look great! applause
Swyndger
Hello!

I discovered this just now, and I hope, it's not to late.
Would be very interested in PCB, Panel and PIC. I would take a BETA PCB if the others are sold out smile
fitzgreyve
Swyndger wrote:
Hello!

I discovered this just now, and I hope, it's not to late.
Would be very interested in PCB, Panel and PIC. I would take a BETA PCB if the others are sold out smile


PM'ed
latigid on
Mine came in the post yesterday. Many thanks!
fitzgreyve
latigid on wrote:
Mine came in the post yesterday. Many thanks!


post here (or PM) if any problems or questions.
woodster
What's the score with LED orientation, just wondering which is anode on the pcb ?
Larrea
Mine arrived two days ago; looks good.

Thanks!
fitzgreyve
woodster wrote:
What's the score with LED orientation, just wondering which is anode on the pcb ?


the anodes are all toward the top of the PCB if it was installed in the rack (i.e. the left side of the PCB picture in the build doc).
woodster
Ahh, this thing is really amazing, some of the most wonky shapes and such dynamic interplay between the controls. Then I added some simple LFO shapes into the 2 CV's and all hell truly broke loose, it was a good moment.
This is fun!
whoop_john
I am confused by something in the manual where it states:

- TIME CV …if a jack is inserted in TIME CV, the Time control acts as an attenuator.

Surely the above relates to the LEVEL CV, not the TIME CV, or am I missing something?
fitzgreyve
woodster wrote:
Then I added some simple LFO shapes into the 2 CV's and all hell truly broke loose, it was a good moment.
This is fun!


For even more weirdness, possibly try feeding back the module output into one of the CV inputs (this is something I found on my 100m LFO module, where feeding the +ve or -ve output into the rate CV input will bend the waveform into non-linear shapes). Unfortunately the Transient CV's will only take 0-5V (you can't have everything!) so some external CV mixing might be needed for maximum flexibility.


whoop_john wrote:
I am confused by something in the manual where it states:

- TIME CV …if a jack is inserted in TIME CV, the Time control acts as an attenuator.

Surely the above relates to the LEVEL CV, not the TIME CV, or am I missing something?


the time CV input connects to VR8 (the "time" pot) via J1, both of which are normalled to 5V.

The Level CV input (J2) is also normalled to 5V, but doesn't have an associated pot.
whoop_john
whoop_john wrote:
I am confused by something in the manual where it states:

- TIME CV …if a jack is inserted in TIME CV, the Time control acts as an attenuator.

fitzgreyve wrote:
the time CV input connects to VR8 (the "time" pot) via J1, both of which are normalled to 5V.

The Level CV input (J2) is also normalled to 5V, but doesn't have an associated pot.

I normally associate the word attenuate with an amplitude adjustment, such as would be used to adjust the Level CV. But your manual relates the word attenuate to the Time CV. You may be using the term attenuate to refer to timespan rather than amplitude, or it may be a mistake in the manual. I was just asking for clarification.
fitzgreyve
attenuates the incoming CV.
whoop_john
fitzgreyve wrote:
attenuates the incoming CV.


Gotcha now smile
cjnuk3
Hi, late to the party as usual! Are the pcbs, panel and PIC still available please? I'm happy with a beta pcb.

Many thanks.
fitzgreyve
cjnuk3 wrote:
Hi, late to the party as usual! Are the pcbs, panel and PIC still available please? I'm happy with a beta pcb.

Many thanks.


PM'ed
5600synth
whoop_john wrote:
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.

Interesting thread, a bit late, but some thoughts (built my 5600 in 1979).

The problem with using the original 5600 Transient 'A' Retrigger for 3-note arpeggios was that it forces the final note to have a slope (it uses a dual gang 2M2 pot for separate delay/slope).

I neatly replaced Retrigger switch SW3 sub-min toggle A (two position) with a sub-min toggle F (3 position). In the third position it shorts the slope track of VR1 (pins 1 & 3) so you can have repeating 3-note arpeggios with or without a final slope.

BTW I was never happy with the action of the Transients, the A/B/C stage switching action sometimes seemed a bit fuzzy and not distinct. I solved the problem by inserting 1K5 resistors before the IC6/1 and IC6/2 gate inputs.

Another problem I found was in the Envelope Generator, too often you got annoying clicks if prematurely chopping off previous note. Unlike other envelope designs I have seen, a new note forces the level back to zero before starting new envelope, rather than pick up the level from wherever the last note ended. Solution was to insert a switch to isolate R1 from IC5 pin 2 (which conveniently is via a PCB wire link).
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