Seventh Circle Audio Preamp Kits – The A12 Preamp (similar to API 312/512)

It’s about time that I wrote about Tim Ryan’s Seventh Circle Audio preamp kits. There is a lot of good info from posts over at Gearslutz, and Tim’s site does an excellent job of providing assembly info, tips, and some of the best build instructions I’ve seen. I’ve built close to sixteen of these preamps in three different types so far: the A12, the N72, and the J99. Not to keep anyone in suspense, but they’re all amazing. The A12 is the focus of this review.

For those who haven’t built an SCA kit yet, you get a new, clean circuit board and all of the necessary components in neatly packaged bags with a bill of materials (BoM) and a schematic. You can download the build instructions at the website. There’s a forum with a lot of support, but Tim’s resources online are just about all you’d ever need not only for these projects, but most any general electronics project.

Plus, the kits are an even better value even if you don’t consider yourself a soldering genius: if you screw the whole thing up royally, you’ve still got the option to send it back to him and he’ll fix it! This mic preamp insurance is a fixed-rate godsend when something goes wrong.

The SCA A12 was the first preamp type that I built. I had an API 3124 to compare it with. I never fell in love with the API 3124. Perhaps I had been predisposed to the Great River MP2-NVs in the rack, or the Chandler TG2 preamps I usually use for overdubs. Either way, the API wasn’t bad, but it wasn’t my first choice for around low end sound. I liked the midrange, but it didn’t have the low end character that I was looking for.

The SCA A12 is an easy build.  It uses an input and output transformer from Cinemag (see the latest Monkbam writeup on Cinemag transformers and the great customer service). Now, there are different output transformer choices – instead of a steel core, you can also choose ones with a high or low content nickel core. From the man himself: “We’re now stocking (Cinemag) CMOQ-2L low-nickel and CMOQ-2H high-nickel output transformers for the A12. These parts give lower distortion and less “color” than the standard steel transformers for more variations in tone.” I’ll focus on the A12 with a steel core output transformer that is pretty darn close the original API output transformer in sound.

In about 3 to 4 hours from start to finish, I can build a single A12. There are no surprises and if you build more than one, you quickly learn the layout of the board. However, it’s advised that you measure the resistance of each and every resistor you put in the board. On one previous unrelated project, I went too fast. When there’s a hundred resistors, good luck finding the one you either misplaced or placed with the wrong value. It pays to go methodically and slowly through the build. The few extra minutes you spend  will help insure you against ripping parts out later on.

I used the SC25 op amp, but you can use others too, like ones from API, John Hardy, Forsell, Old School Audio, etc. Once you adjust the voltage for the particular op amp you are using, it’s done. Just install it in the chassis and hook it up the power supply. So, the sound?

To my ears, the A12 is much more preferable on just about any source than the API 3124. I never used the 3124 for vocals, but I find myself using the A12s on vocals a lot now. They have a great low end that fits perfectly with their aggressive midrange. I think this was why I never got married to the 3124 – the midrange was there, but I didn’t feel that the low end was quite in line with what I wanted to hear. That problem doesn’t exist with the SCA A12 preamp at all. I love this thing! It kills on drums, especially. Compared to the Great River (a completely different design), the A12’s low end holds up nicely and both preamps sound excellent.

Michael Wagener had some nice things to say about the SCA preamps too in response to a question on “Yes, loved ’em. I have 4 original APIs (one is serial number 009) and the SCA sounded almost identical, if anything a little tighter in the low end, which is a good thing.”

Also, Michael’s thoughts four years down the road: “For what it’s worth, I have been using a bunch of N72s for more than 4 years now (as well as A12s and C84s). They are on every record I’ve done since I bought them, and it’s not like I don’t have any other mic pres to choose from. I don’t know if the N72 sounds anything like a Neve and I really don’t care, but they are dam good mic pres and worth every penny, which can’t always be said for the old gear. I did a lot of comparisons with “real” Neves and a bunch of “clones”, and in every shootout I liked the newer stuff better.”

The controls are simple on the A12: there is a Grayhill (same switch used on the Great River) gain control switch which selects gain in steps of 5dB. There is an output control which can attenuate the signal up to 6 dB, allowing you to drive the preamp a bit harder before hitting tape or your A/D converter. The only other two switches are for 48V phantom power and a phase reversal switch.

For the money, you absolutely cannot beat the Seventh Circle Audio kits for a given preamp. Actually, I’d go even further and say that there’s very few preamps if any that can beat these. Everything in this range is super expensive and has a slightly different character – not worse or better. This A12 is the preamp that helped me realize what quality products SCA offers. After building 8 of these, it also spurred me on to the N72, which will be reviewed next.

6 Responses to “Seventh Circle Audio Preamp Kits – The A12 Preamp (similar to API 312/512)”
  1. Ron says:

    Did you try the A12B? they are supposed to be the sample but with a more efficient amp implementation

    • Ron says:

      meant the same SCA A12 = A12B……fixed op amp…

      • monkbam says:

        Hey Ron,

        I have not tried them yet. It’s been a few years since I was able to test these preamps out and since then, Seventh Circle has expanded the options available. Tim Ryan (owner) is a great resource and always open to answering questions. I would check with him for specific details. If you get an answer, come back here and follow up for future readers!

      • Ron says:

        Thank you for digging into it! as per the electronics, the A12b is leaner than the A12 so as an engineer he probably simplified the design making it actually less expensive in parts but of the same sound then I see the price the same. Still looking into whether anybody has tried them… will probably have better luck to get an answer from him in detail. If I do I will get with it.!

Check out what others are saying...
  1. […] by monkbam on August 26, 2010 · 1 Comment  Now that we’ve reviewed the A12 preamp, the N72 is a natural next choice. It is a circuit that is Neve-esque, having a tame top end but a […]

  2. […] When I started to research the SCA J99 preamps, I found far less information than I had for the SCA A12 or the SCA N72 preamps. I think that most people who first buy the Seventh Circle Audio gear end up […]

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