These discrete opamps are hand built in Chicago at Process Haus with a digital Weller iron and Kester solder. Soldering is tight and neat and the PCBs are fully cleaned. Opamps are burned in and tested with a scope, and spectrally measured in Spectra Foo and/or Izotope RX. We also make and have listings for other OpAmps such as GAR 2520, GAR1731, and 990 types.
The CA-0252 fits in the standard API 2520 foot print that is used in mic pres, Eqs and compressors. You can use this to replace API 2520 that are dead, or as an upgrade.
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To explain the design on sonic difference between the CAPI CA-0242 and the API 2520, I have pasted in Jeff from CAPI's description below:
The CA-0252-DIY is not the same circuit as the gar2520. Gary's version (the CAR 2520) is 9 transistors with a resistive current source for the input transistor long-tailed pair. The CA-0252-DIY is a 10 transistor circuit with a transistor current source for the long-tailed pair. You can see by comparing the BOM's that they differ in many other ways as well.
The CA-0252-DIY is a pretty unique kit of parts. 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.
The CA-0252-DIY only ships with the longer terminal pins so there is no issue in a 2500 etc 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
Includes all top quality parts and components
Product Photos: All photos of the product are original photos taken in-house of units built at Process Haus.
Warranty: Parts and labor are covered for one year for component level failure due to normal operational use.
Shipping: We ship OpAmps in a USPS flat rate small box. In 2023 thats over $9, but we cap it at that and eat the balance. If you order more than one, its only an extra dollar for shipping each additional OpAmp in the same box (the dollar covers the extra insurance). If you think you need more than one OpAmp, you can can save a bit combining on one order for shipping. Also, different OpAmps we sell can be combined to save on shipping.