The DAP 310

The Dorrough Discriminate Audio Processor Model 310 revolutionized radio processing. After its release in 1973, about 9,000 units were sold. AM and FM radio enjoyed a new fidelity that it had never seen before.

The DAP inspired a lot of radio engineers and technicians to test their favorite modifications. The crossover points were changed. The peak limiter was disabled. The release times on the compressor cards were decreased. The list goes on. A lot of people learned more about audio from working with their DAPs than they did from any other single piece of equipment. Along the way, Mike and Kay Dorrough gave generously of their time and their spare parts keeping owners and operators happy.

Not all of the replacement parts necessary to keep DAPs alive are still available. However, unless the printed circuit boards or meters are damaged, almost all DAPs can be brought back to life and returned to service. Internet broadcasters have started buying up DAPs and having them restored. They work extremely well for that application, and they sound great.

It would be impossible to identify all of the modifications that have been made to DAPs over the years. Some of them are Dorrough-sanctioned, many of them are not. The fact of the matter is, if a DAP is restored to its original condition with very few modifications, it can be a wonderful sounding piece of equipment.

There have been lots of copycats and claimed improvements by competitors over the years, but there has been only one DAP. There is no question that Mike Dorrough is the father of multiband audio processing. This website is dedicated to this piece of history that thankfully will just not go away. Hopefully you will find content here that will help you maintain your DAP or at least to reminisce about the good old days.

Now, click on “RECENT POSTS” for even more DAP love.

Mike Phillips


  1. Do you rebuild DAPs? I have one in nice shape I would like to use in the air chain of a small AM radio station.

  2. When using 2 for stereo is it necessary or optional to use the interconnect? Dual mono should be ok, right?

    • Yes, they will work without the stereo interconnect, but not having the two channels track each other can cause some weird “ping pong” stereo effects with music. The cable is easy to make. Why would you not want to use one?

  3. I would, It was just a curiosity as I could find no clarified documentation. Unfortunately I have to return the so called “matched pair” of 310’s from ebay. No limiter cards, cut wires and heavy damage from undersized shipping box. Yup, they were matched alright. So now it’s a moot point until I find another 310 or two. 🙁

    • Did you get the ones that have the DIN stereo interconnect replaced with an XLR jack? Do you mean NO limiter cards (6) or no PEAK limiter cards (2)? A lot of people removed the peak limiter cards when they used the DAP with another processor after it in the chain, but I always preferred them stock (except for the power supply modification.) Good luck finding a matched pair. Even pairs that were previously matched have aged differently. You can get them pretty close to matching so long as the JFETs are the originals and are of the same vintage.

  4. How’d you make out with the ebay guy and the pair of damaged 310’s, any luck?

  5. Asking the admin of the group.. I had your email but lost it.. I had 2 banged up ones that got sent back.. and its about that and.. I obtained something else.. fire me an email

  6. We properly repair, rebuild and calibrate broadcast audio equipment at our facility in Rhinebeck, NY

    • I’m not aware of one. If someone has or does one, I’m happy for them to post the link here. It’s a good idea.

  7. Do you or anyone have a DAP 310 for sale in any condition or know of one? I’m hoping to locate one that is reasonably priced which at least has the meter lights working. I’m hoping to display it in a broadcast museum. Please advise and thank you.

    • One just showed up on eBay. However, proceed with caution. There are several visible problems. It has to be completely overhauled as it has the original capacitors. The faceplate is bent. The main VU meter is not original. There are not enough pictures to determine whether it has been butchered with modifications. The cards appear to be plugged in at an angle, although it could be the picture and not the unit.

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