This kit contains all components necessary to build a RED-25 opamp. This is without a doubt the simplest discrete opamp kit available on the market today. All the heavy lifting is done for you, courtesy of the pre-mounted SMT components.
The RED-25 is Whistle Rock Audio's version of the sought-after Huntington era AP2520 from API.
Although a mostly SMT discrete opamp may seem unorthodox, you can be assured that all the components in the RED-25 have been carefully selected with a no-compromise approach. Throughout the prototyping stage, no less than three different manufacturers of equivalent SMT transistors were evaluated. It goes without saying that only the very best were chosen for the RED-25. In fact, performance measurements of the opamp show that the RED-25 is on par with its through-hole counterpart.
All surface-mount resistors are Susumu thin-film resistors and all capacitors are Murata C0G/NP0 types for the lowest noise and distortion achievable.
The RED-25 sounds large and impressive. The low-end alone is worth making it a part of your tone arsenal.
FEATURES:
- Supply voltage: +/-12 to +/-18V
- Matched input transistors
- Quiescent current draw: +/-30mA @ +/-16V
- Dimensions (LxW): 1.1"x1.1"
- Height: 0.95" from the tip of pins to top of output transistors / 0.625 from lowest solder joint to top of output transistors
- Gold finished pins
- Standard 990 / 2520 footprint
- High current output
- Carefully selected quality components throughout
Customer Reviews
This was my first time employing a discrete op amp in a design and also my first experience with DIYRE so I wasn't sure what to expect. In the past, I've used 5532s and the like for my designs. The RED25's transition into clipping is so cool and full of vibe! I'm using it in this design as the mic preamp gain stage after the input transormer, and it immediately made the design sound like a vintage console. With a pad on the output of the RED25, you can easily drive it into heavy saturation/clipping and get some truly insane sounds. Combining it with a subminiature 6021 tube-driven, passive baxandall EQ (see attached photo) sealed the deal. While it may be a bit spendy for a single op amp, I'm fully convinced that the sonic result is worth the price. Plus, it's super easy to put together. My only complaint is that I wish the kit had an option to include the mating sockets for the mounting pins so one doesn't have to commit the mount with solder in case it needs to be swapped for any reason.
This is listed as a beginner project. And I think they should say it's a beginner project if you know how to solder well. And it helps if you have a magnifying glass. These solder points are very small, and I do believe it takes some technique to make good joints when they are this small and this close together. Also having a fine point iron. It turned out well, and sounds great.
This design is not API compatible as the website advertising them would have you believe. Buyers beware.
I built a pair of these in 15-20 minutes. I tested them out in some Capi VP26’s and they sounded great. More hifi sounding than the CA-0252’s I normally have in them. But the Red-25’s will ultimately end up in a pair of VP25’s that will be arriving shortly for kick drum duties mostly.
Super simple to put together and a great op-amp - whether you're using for an output option on one of DIYRE's kits or as a replacement for a 2520 somewhere else!
