bajaman wrote:but IMHO it´s a cheap and poor concept which doesn´t produce any result what cannot be achieved also with VCA´s.
Tell that to Dave Gilmour and Pete Townshend
They pulled their VCA based compressors from their boards and are CURRENTLY using the Demeter Compulator in their touring Pete Cornish built pedal boards.
Sorry, but I don´t intend to teach lemmings not to follow his neighbour, and it doesn´t matter if ones name is David or Pete.
But why I should be so stubid to do it for myself.
Seriously though, I was trying to build a 9v pedal to mimic the sound and response characteristics of the famous Teletronix LA2A broadcast limiter,
Seriously... the Demeter Compulator and your concept have the same amount in common with a LA2A like a FuzzFace with a Tubescreamer - both of the last distort and both "compress".
One of the "secret recipes" of the LA-2A is the use of an electroluminescent light device with a special characteristic (and not the LDR).... without including that behaviour you are far away from an LA-2A.
So please let´s talk about a "feed-forward opto-compressor-concept" and not the LA-2A... that would be blasphemy in the ears of hardcore-studio-guys.
and it uses optocouplers and senses the input signal BEFORE the voltage gain recovery amplifier
This concept is called "feed-forward" compressor and also made with VCA´s:
http://rupertneve.com/products/portico-5043/
and very well knon since the mid-70´s:
http://www.aes.org/e-lib/browse.cfm?elib=2252
I for myself designed one with 2 OTA´s in parallel as variable resistors in the feedback loop of an op-amp in 1981.
- in this respect it operates far differently than any VCA feedback AGC based design that I am aware of on today's market.
If you are not aware of it, doesn´t mean that it doesn´t exist since more than 30 years.
Compare a 1khz square wave fed into a VCA based device such as the BOSS CS2 and you will be horrified at what comes out of the output socket.
As I wrote above:
The sh*tty "Dynacomp & Clones" concept is not all and everything in the VCA-compressor-world.... And I don´t intend to discuss about the behaviour of the worst example. Noone is using this sh*t - and paying horror prices for it - except of guitarists.
If the Attack and Release times are correctly adjusted on a (non-dynacomp)(feedback)VCA-based compressor/limiter we can compare it without any problems.
Now build my pedal - it should not take you very long - and compare the response, and you will see why I am so enthusiastic about this project.
bajaman
Yes, it will sound new and good.... (espacially for the guys who only know dynacomp-(clones).... and it´s ok to be enthusiastic - but please stay on the technical floor...
As you can read in long discussions about lamps/ldr´s for the univibe the response of both have an influence on the tone.... Did you ever have a look on the response curves of an LDR ? they have a very long recovery-time.....
If they wouldn´t, Demeter and your circuit would be a ringmoduator instead of a compressor due to the lack of a smoothing-cap in the side-chain. For this reason you only have two knobs instead of three...
:
You can´t adjust the recovery (release) time....
analogguru
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Every (bootweak)-pedal has a purpose....
...it might be a door stop or a hammer, but every (bootweak)-pedal has a purpose.
There´s a sucker born every minute - and too many of them end up in the bootweak pedal biz.