Joined: 07 Aug 2006
|Posted: Tue May 02, 2017 10:58 am Post subject: newly built Gates SA-39B 'tribute' compressor/limiter
|A modern variation on the Gates SA-39 limiter, built recently by David Pendrill of the UK (DaveP on GroupDIY), and tweaked a bit by myself. I'm acting as his sales agent, as I have it here in the US.
This is a completely hand-built tube audio limiter with point to point construction using modern parts. DaveP even cut all the metalwork himself! A fantastic looking build in my opinion, with a nice smaller 3RU footprint.
I have owned, restored, and modified about ten of the original, and this sounds like it fits in the 'family of sounds' those units provide. It’s currently taking a test drive at Mitch Easter’s place Fidelitorium, and his immediate quote was it’s “killer”, followed by “I liked the SA 39 on "personal" vocals, acoustic guitars, upright bass, percussion instruments, things like that. Sometimes it was good on electric guitars, you know, it could be good on anything, sometimes it just didn't add anything, but it never sounded bad. It wouldn't be the thing to use for super slammin' things, in the modern sense, but it does great 60s "glue" on drums, or as a compressed channel to mix in with the straight drums. I'm surprised it's so much like the old one in terms of when it gets furry!”
It has expanded attack, release, and threshold controls not available on an original which give a much wider color and control palate.
It uses a 600 ohm T attenuator on the input, more like the early Gates SA-39's, and a six step output attenuator with 6 dB steps.
The threshold control runs both above and below the original,
allowing you to overload the amplifier stage more greatly, or get a much softer/smushier sound with low thresholds.
The release goes fast enough to get into distortion territory as well, several steps faster than an original.
If you run lower threshold, slower attack, and moderate release, it begins to behave more like a Sta-Level type compressor.
The noise floor is very low, as good as any real SA-39 I've ever measured.
It differs from the original circuit in a few ways, having a different type output tube that provides a bit less overall power, and a different approach to the regulated tube power supply section. This tube regulated PSU provides regulated DC to the entire amp, where the original only supplies regulated DC to the earlier stages. The tube filaments are all DC as well.
Here's a link to discussion about the build.
$1995 plus shipping and insurance
ElectroMagnetic Radiation Recorders
Tape Op issue 73