Overview

The Presonus model M80 is an eight channel microphone preamplifier designed for live and recording studio use and employs transformer balanced input circuitry. Presonus also makes the model MP20 which is basically a two channel version of the M80.

Not long ago on the newsgroup called rec.audio.pro, ( RAP for short ), a discussion about the Presonus M80 and MP20 got a lot of attention because it was brought out that while the original design and production run of these two mic pres used the famous and highly regarded Jensen transformers in the input stage, Presonus had switched to another brand of transformer around the beginning of the year 2000. This was quickly verified by several owners of M80's and MP20's and also the people at both Presonus and Jensen. Mixed opinions and emotions developed as people wondered if their newer units would sound better with the originally specified and advertised Jensen transformers while others with the original units wondered if they we missing out on some new benefit that the current transformers might offer. People with older and newer units who had been completely happy with the sound they were getting before the RAP discussion were suddenly unsure if their mic pres sounded good or not.

Due to this situation I ended up communicating with Rick Naqvi and Jim Odom of Presonus and Bill Whitlock of Jensen Transformers. Both companies were very helpful, friendly and informative and seemed genuinely interested in the satisfaction of their customers and showed a great deal of pride and confidence in their products. They both made generous offers to assist me in doing a comparison test between the two different transformers and since I talked with Presonus first I accepted their offer. I was very pleased, impressed and humbled by the high quality of support both companies provided and my sincere thanks goes out to them!

Below are three links that will take you to the various stages of my comparison experience. The first is 'The Transformer Swap' and will explain what I had to do to change out two of the transformers in my M80. The second link is 'The Listening Tests' and will allow you to make up your mind which transformer you prefer on a variety of sound sources. The third is a short discussion of what my conclusions and opinions are about the tests.

You will be reminded again several times throughout this site but please keep in mind that these tests are in no way scientific or controlled and that any opinions you develop from the materials here ( especially when reading my opinions ) are VERY subjective and the margin for error is fairly wide. Use this site as a reference or starting point but it will be best if you do your own comparisons with equipment in your own studio.

I sincerely hope that you will find this site interesting, if not useful, and I'm open to any comments or suggestions you might be willing to share.

Best of luck!

John L Rice