I have owned this 33609 since new in 1988 Its in excellent condition a few rack scuffs as can be seen but remarkable condition for its age.

Its identical circuitry to the "Metal Knob" models , apparently the metal knobs became unobtainable

and were replaced with the ones you see here.

A "Neve 33609 ISS 12" refers to a specific model of the Neve 33609 stereo compressor/limiter, signifying an early production version with the "ISS 12" serial number indicating its vintage status and likely featuring the original circuit design by Geoff Tanner at Neve, known for its classic "2254" feedback compression circuitry, hand-wired transformers, and a warm, smooth compression character highly sought after in professional audio applications like mixing and mastering.  Key points about the Neve 33609 ISS 12:

* Classic Stereo Compressor: This model is considered a classic stereo compressor, renowned for its smooth and transparent compression with a unique sonic character often described as "warm". 

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* Hand-wired Neve Transformers: Utilizes high-quality, hand-wired Neve transformers which contribute significantly to the sound quality. 

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* 2254 Feedback Compression: Employs the same feedback compression circuit found in the legendary Neve 2254 compressor, providing a familiar and desirable compression behavior. 

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* Vintage Design: "ISS 12" indicates an early production run of the 33609, potentially with slightly different circuitry compared to later versions. 

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* Applications: Ideally suited for use on stereo busses, drum mixes, vocals, and other stereo sources where a smooth and musical compression is desired.