Seventh Circle Audio

I understand the other three:
N72 - Neve 1272
J99 - Jensen 990 TwinServo
A12 - API 312

but what's the C33?

The C33 is only a SPICE simulation at this point, but it's my implementation of a circuit that's been popular in some hi-fi circles for many years. The most renowned designer I'm aware of who uses the topology is John Curl, hence the "C" in C33.

Basically, it's a complementary, symmetrical, differential, cascoded JFET front end, followed by a bipolar gain stage, with a complementary pair of MOSFETs at the output. Everything is biased class A. Distortion is inherently low due to the strict complementary arrangement, but that also means very few even-order distortion products. It'll be direct coupled (after the input transformer, probably a Lundahl, with OT optional) and should be very clean, but with that subtle JFET character.

How can you comment on the speed of the C33 in comparison to the other three SCA designs? the A12 and N72 are certainly not the fastes, and I don;t know about the J99 but if one is looking for something like the Buzz MA 2.2 which has an incredibly high (much higher than we need) slew rate which of theses models (incl c33) would fit best.

My interests is for percussions, acoustic guitar and mandolin especially. A fast mic like the AKG451b and a fast pre like the Buzz make for ultra realistic instrument tracks. What would be the best combo with your products (assuming we all want to use nothing but SCA from now on )

Shane