A Multiband GSSL !

[Cardinen]

Hi all,

For some time I had this crazy idea in mind,  inspired by this thread https://groupdiy.com/index.php?topic=70580.0

The idea was to make a multiband compressor with 3 Gssl and a simple 6dB/Oct crossover with variable frequency.

I used some old gssl pcb (rev.7) with a few mods:

- THAT 1246/1646 for in-out
- Relay True Bypass  and Mute
- Adapted Attack and Release time for each band
-  Make up gain 5dB with 0.5dB steps
- Ratio 1,5:1 added
- LedBar meter reduction
- Sidechain link between compressors (still to be done)

The crossover is based on single pole R-C filters with 2 buffers at input and output for each band, the frequency is changed by the resistor values;  At the moment i have only set a fixed position at 100hz for the low and 5khz for test purpose.
I've used super matched pairs of Styroflex and Polypropylene caps for the filters.

I admit that at the beginning i was a little skeptical about this project, as a mastering engineer i was afraid of phase issues or flat response of the crossover, i have to say that when I listened to it the first time all the fears passed 

I'm very happy with the result, the unit is very clean and the crossover is imperceptible with no gain reduction or make up gain,
in the past I have happened to work with the Maselc Mla-3, and i have to say the workflow is very similar.

It took me several months of work to complete it, it was a fun but also frustrating project at times ... but hey! this is DIY!  8)

 

[Cardinen]

Inside photo

 

[Cardinen]

Inside photo 2

 

[Rocinante]

This is great but it feels like you would want more control over narrower bands. Still I am certain it would be a great tool.

 

[Gold]

Looks great. I’m glad to hear that style crossover is transparent.

 

[Rob Flinn]

Looks great.  Did you not think of adding the turbo boards ? With my single band version I find myself never using it much out of turbo mode.

 

[Cardinen]

This is great but it feels like you would want more control over narrower bands. Still I am certain it would be a great tool.

Yes bands could be narrower but i find it very useful this way for tame an harsh hi-hat or stop an uncontrolled sub, it’s a great tool.
Wide bands give me good feeling about transparency

Looks great. I’m glad to hear that style crossover is transparent.

Thanks Gold 

Looks great.  Did you not think of adding the turbo boards ? With my single band version I find myself never using much out of turbo mode.

It was not planned to add turbo boards on this but will see in the future...

 

[petermontg]

Congrats C, Long may it serve you.

 

[Script]

What are you using for summing amp?

 

[Cardinen]

What are you using for summing amp?

Nothing so special, just an inverting configuration OPA based (opa2134)

Congrats C, Long may it serve you.

Thank you! 

 

[Gold]

This is great but it feels like you would want more control over narrower bands. Still I am certain it would be a great tool.

A 6dB/oct filter is the only order that will do a perfect mathematical sum. Steep filters won’t . For a narrow frequency band you would need steep filters.

For frequency dependent compression of a narrow band I think a dynamic EQ would be a better choice. That way you can dial in what you want without using steep filters.

 

[Script]

Nothing so special, just an inverting configuration OPA based (opa2134)

Thanks. Well, that is more special than a TL07X for summing duties.

 

[mjrippe]

That is fantastic!  I love the layout and the use of different color LED bar meters for each band.  If I was still recording I would lust after one of these.