Conception pédagogique d'un compresseur pour pas cher du tout...

The attack circuitry of all my optical compressors operate by making high surge currents available through the LED; initially, with the older Joemeek circuits, this worked to overcome the very slow response time of the light-dependent resistors (the light cells). Nowadays, this is less important as I use a much faster reacting cell.
The very early compressors used a little transistor array as the current drive, and in the earliest SC2 (the ones with a bevelled edge front panel) the power supply was only just capable of driving the required high currents, so the later compressors did sound just a little tighter because of an improved attack response.
The release circuitry was always a 'compound' circuit responding quickly to transients, and more slowly to steady sounds ( this system is usually called 'auto' by other manufacturers). This arrangement never changed on the SC2 through all the variants, except on very late SC2.2 models where I think I shortened the release times generally.
One of the 'secrets' of the SC2 sound was a little trick that I still use, to make the compressor release time actually shorten just before compression releases completely. This makes for a very odd looking release curve, but is great for compressing drums.
So, to answer the question directly, yes, the old V1.05 still had a slightly 'soggy' power supply and is probably the most collectable SC2 nowadays. The later ones had a slightly 'tighter' sound due to the attack curve being more controlled.
As a matter of interest, the new P38EX has settings that can duplicate the early SC2, but without the image shift that the early compressors were prone to suffer from.
Ted Fletcher

Posts: 402
Joined: Tue Feb 12, 2008 2:06 pm

Ah! So the problem is over-compression on one side..... That is always caused by one of the opto resistors being more sensitive than the other, it can be an 'ageing ' problem.
Under the lightproof box there are two light cells (type ORP12) and a pair of LEDs. Physically moving the light cells will give different compression results.

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