MAC - Micro Auto Compressor

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chrisp
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MAC - Micro Auto Compressor

Post by chrisp »

This deserves its own thread.

I've been taking a little look at the pic Joe posted, and I'd like to know if I'm the right track ....

(1) its an opto compressor with program sensitive attack and decay
(2) you WILL need a DINGO to run it, as the actual VCA and bypass relay switch sit on that board.
Chris P
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Joe Malone
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Post by Joe Malone »

(1) its an opto compressor with program sensitive attack and decay
Yes just think solid state LA2A or LA3A. Attack and release are set by the opto cell type.
(2) you WILL need a DINGO to run it, as the actual VCA and bypass relay switch sit on that board.
Yes you will need a Dingo for the audio path as the MAC PCB is only the sidechain PCB. The bypass relay is on the Dingo as well but you do NOT need the VCA on the dingo as this is a opto compressor. The opto cells sit on the MAC PCB. Makeup gain is provided by the dingo output opamp.

The MAC can be easily added to a Dual 99v kit at the fader/trim control point as that runs on +/-24v rails. Trying to work out if it can run with a BAD kit as it is or I will do a 48v rail version PCB that will.
Joe :-)
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jensenmann
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Post by jensenmann »

Joe, is there an option to include the DIngo VCA section into the signal chain with the Opto? I´m thinking of a box à la squash-it-to-hell with both Opto and VCA characteristics. Having the possibility to catch transients and then tastefully compress it with an opto is what I pretty often do with 1176 and LA2A. This combination 4x in a tiny 1HE box would be killer
Jens

edred
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Post by edred »

Joe, do you have a rough idea of price? Ballpark will do.

Thanks.

skipwave
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Post by skipwave »

Hi Joe,

How close to the Forsell opto sidechain is your comp? Looks like you went with a fullwave rectifier, and only two opamp stages (one 2604). One inverting and one non, each driving a fullwave bridge into the vactrol LEDs?

I was just figuring out how to integrate the Forsell opto with a BabyAnimal mic pre. I'm making a small box for traveling with an mbox mini. I had settled on using the LDR as the shunt R in a U-pad on the output.

Details of the Forsell here: http://www.diyfactory.com/projects/fors ... /ffosc.htm


Thanks!

Brian

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Joe Malone
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Post by Joe Malone »

Joe, is there an option to include the DIngo VCA section into the signal chain with the Opto? I´m thinking of a box à la squash-it-to-hell with both Opto and VCA characteristics. Having the possibility to catch transients and then tastefully compress it with an opto is what I pretty often do with 1176 and LA2A. This combination 4x in a tiny 1HE box would be killer
No the VCA is for a separate compressor project. Cannot be used at the same time as the OPTO on the dINgO.
Joe, do you have a rough idea of price? Ballpark will do.
MAC kit price will be $80AUD. Parts list here http://www.jlmaudio.com/MAC%20Parts%20Kit.txt
And the Mac Link kit $20AUD. Parts list here http://www.jlmaudio.com/MAC%20Link%20Parts%20Kit.txt
How close to the Forsell opto sidechain is your comp? Looks like you went with a fullwave rectifier, and only two opamp stages (one 2604). One inverting and one non, each driving a fullwave bridge into the vactrol LEDs?
No we had an opto comp similar to the Forsell in the works but once the Forsell version came out I decided there was no reason to go down the same track. So went off on a different tangent and experimented with lots of simple opto comps configurations with the aim to be minimum controls for a easy to use tracking compressor along the lines of a LA2A and LA3A which has ended up good enough to be able to use on stereo buss as well with the small MAC link PCB.
I was just figuring out how to integrate the Forsell opto with a BabyAnimal mic pre. I'm making a small box for traveling with an mbox mini. I had settled on using the LDR as the shunt R in a U-pad on the output.
The ideal for that is the BAD as it has 2 amp stages and would work perfectly. But you can do it in the BA by cutting one track and adding the compression element between the secondary of the input transformer and the +in of the opamp like Manley do in there voxbox.

Circuit for the MAC here http://www.jlmaudio.com/MACSCH.pdf
Joe :-)
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haima
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Post by haima »

might want to re-export the schem pdf - it seems to be blank... at least it is for me!

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Joe Malone
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Post by Joe Malone »

It works fine but you need the latest PDF reader.
Joe :-)
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haima
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Post by haima »

you are right... i opened it in GIMP and it was all there!

i guess the "preview" (the simple viewer) in Mac Os 10.4 doesn't read your latest pdf type! i always use preview to read your pdfs so i assumed it must have been a dud.

h

skipwave
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Post by skipwave »

Oh, of course! No need for an inverting amp with a full wave bridge. The second bridge is for the meter. Neat!

I do have a BAD pcb. Maybe the opto will get sandwiched between its stages. 8)

chrisp
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Post by chrisp »

Joe Malone wrote:Attack and release are set by the opto cell type
For those playing along at home, attack is about 3.5 ms, release is about 500 ms for the VTL5C2.

A few more questions when you've got a moment:

(1) The opamps on the DINGO board - I assume they exhibit the same sonic character as they do in BA kits? So far a snappy clean sound you'd look at maybe the hybrids, or for a more textured sound the 99V?

(2) The MAC board includes a path to pin 6 of the IDC connector, which on the DINGO is the cv feed to the 2181 VCA - I assume this actually does nothing as the 2181 isn't fitted.

(3) What's the DINGO/MAC power consumption?

(4) The "Reduction" pot - this is a threshold control right? With the slope determined by the ratio pot?

Thanks
Chris P
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Joe Malone
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Post by Joe Malone »

1) The opamps on the DINGO board - I assume they exhibit the same sonic character as they do in BA kits? So far a snappy clean sound you'd look at maybe the hybrids, or for a more textured sound the 99V?
Yes JLM99v is fat and silky, Hybrid is tight and fast with silky tops in class A, OPA2604A fast and tight. If you lower the +/-rails to 18v you can use NE5532A as well. When using a Dual opamp like OPA2604A or NE5532A the dingo is electronically balanced out while the JLM99v and Hybrid are quasi-balanced out like the BA kits with no output transformer (Audio out on pin 2 only, pin 3 for noise pickup only). But the JLM111DC output transformer can wire into the side of the dingo PCB to give true balanced out for these.
(2) The MAC board includes a path to pin 6 of the IDC connector, which on the DINGO is the cv feed to the 2181 VCA - I assume this actually does nothing as the 2181 isn't fitted.
Pin 6 is used in the MAC configuration for comp link function and when the ribbon cable from dingo to MAC also continues to MAC link PCB the link function requires no extra wiring.

Image
Image
(3) What's the DINGO/MAC power consumption?
Totally depends on the opamps used. But an AC/DC power supply can run about 8 dingoes with MAC comps in any configuration. The 3 power wires to each dingo are the only normal wiring that is needed to them.
4) The "Reduction" pot - this is a threshold control right?
Yes just like a LA2A.
With the slope determined by the ratio pot?
The Ratio is normally a 3 position toggle but a 10k rev log pot can be used instead of the switch if fully adjustable ratio is needed.
Joe :-)
JLM Audio
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MikoKensington
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Post by MikoKensington »

It looks like I'll need to have a fundraiser sale, soon.

Sylvain
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Post by Sylvain »

Whoa!!!, :)

Does that all fit in a one U rack case... more specifically the meters ?

Syl

MikoKensington
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Post by MikoKensington »

What are the specifics on the meter requirements? Does this need a true VU? I ask because I have some dead sexy 0-1mA DC meters that I'd love to use somewhere. :wink:

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