CA-0252 Capi vintage API 2520 rev.A

This is the new CA-0252 DOA. CAPI’s own take on the 2520 style opamp.
This design is based on an original early 70’s vintage 2520 that they back-engineered all the way to the point that they concluded they needed to get some of the transistors custom made to get as close as possible to the original….. So they did!

This Discrete Operational Amplifier is not the same circuit as the gar2520. Gary’s version is 9 transistors with a resistive current source for the input transistor long-tailed pair. The CA-0252 is a 10 transistor circuit with a transistor current source for the long-tailed pair.

” The CA-0252 DOA is pretty unique. Such a version has never been realized before as far as I know. I am being as faithful as possible to the exact type of parts used in the early 1970’s OG 2520s. I know this because I was gifted an unpotted 2520 from a friend a few years before we moved to Nashville. My friend got this amp from a trade show in the early 1970’s. I looked at it a few times and thought “no way”. After it living in a drawer of parts for years, I pulled it out in the fall of 2019 and jumped into the deep end. Interestingly, when the same friend saw on social media that I was finally working on it, he sent me 2 more unpotted amps and a few never populated PCBs. That said I had plenty of OG data to pull from!

Input transistors
The OG input transistor pair were BC414Cs. In researching these parts, I found BC237C to be the recommended replacement. So, due to supply issues, we chose to use BC237Cs for these. To our ears they were closer to the OG than the commonly used BC550C etc.

Interstage NPNs
The OG was TIS98 for these 3 transistors. We have been using Fairchild TIS97s for our BT50s so decided to stick with them for this situation. Since TIS97s are long out of print and very hard to find, we had them custom made by a US manufacturer. Its actually amazing that can still be done!

Interstage PNPs
The OG was 2N5087 for these 3 transistors. I was able to procure a mother-load of NOS National Semiconductor 2N5087s so that is what we are using. They definitely sound different than the more recent Fairchild or ON Semi stock.

Output Transistors
The OG output transistor pair were metal can TO-39s, specifically BC141-16 and BC161-16. These are unobtainium and have been for years. We tried the Multicomp version and found them lifeless so we had them custom manufactured like the TIS97s. They are outstanding parts and a very big part of the tone. ” J.Steiger

The CA-0252 only come with the longer terminal pins so there is no issue in a 2500 that may have other components under the opamp footprint. These longer pins impose no issues when used in a situation with no components under the amp. Just leave them long. If you have an old school situation where the amps are soldered directly to the PCB, just solder them in and cut the pins off.

Some of the applications the CA-0252-DIY DOA can be used for:
• Microphone Preamplifiers
• Line or Booster Amplifiers
• Lossless Combining Amplifiers
• Balanced Transformerless Amplifiers
• Equalizers and Compressors

Additional features and specs:
• Industry standard 2520 footprint for plug-in or PC mount connections
• Low noise, high power output
• Low distortion
• Minimum load impedance is 75 ohms for full output voltage
• Power supply voltage is bi-polar +/- 12 VDC to +/- 20 VDC

Fully built to perfection in Canada with a 1 year warranty.
Assembled with Kester solder.
These can be also build to order.