mmatrix
Well-known member
Selling a pair (2) of Vintage McCurdy AT284 mic preamp cards. Tested, working and sounding really good (I have Neve, API, Quad Eight, etc. to A/B against). They are ALL DISCRETE (NO IC CHIPS) with a FET input stage. These cards are AT286 cards (output cards) where the FET preamp stage was completed and an input transformer was added (they are the same card as the AT284 preamp card, but were stamped AT286 because only the output stage was filled at the factory). The input transformer is from an old mic preamp card, but I am not sure what the make is for these transformers. They look like they can be early Beyer, Sennheiser or something of the like. They have a nice high step up for the FET input. The cards come with the correct 10 pin edge connectors and parts layout illustration. They also come with TWO (2) schematics - the original and a copy of the original with the changes that were done.
The changes that were done were to extend the bandwidth and control the extremely high gain of these preamp cards. One change that was done was a decrease in the value of some capacitors so there is less high end rolloff. There is also one capacitor that was eliminated as well so now these preamp cards have a full bandwidth that goes to 20KHz. These cards were originally designed for broadcast, so the bandwidth was decreased to 15KHz by using high end filtering. This filtering was decreased to extend this bandwidth. The other change was a decrease in one of the output resistors, so as to control the extremely high gain of these cards. I used a 1K linear gain adjustment pot instead of the 5K pot (that is what is called for by spec). These cards have a ton of gain and are great with ribbon mics. All other parts on the cards are to spec.
I have a few of these in my studio (that I am definitely keeping) and am selling a few extra ones that I have. You need an XLR input jack, an XLR output jack (Yes, they have electronically balanced outputs), a gain pot and a 48VDC power supply (they run on 48VDC). If you are racking them up, I would also suggest a -20db (or -10db) input pad if you are using really hot mics or micing loud sound sources.
These are really cool preamps to have in your arsenal. Email with any questions. $125 per card or $225 for the pair (2).
The changes that were done were to extend the bandwidth and control the extremely high gain of these preamp cards. One change that was done was a decrease in the value of some capacitors so there is less high end rolloff. There is also one capacitor that was eliminated as well so now these preamp cards have a full bandwidth that goes to 20KHz. These cards were originally designed for broadcast, so the bandwidth was decreased to 15KHz by using high end filtering. This filtering was decreased to extend this bandwidth. The other change was a decrease in one of the output resistors, so as to control the extremely high gain of these cards. I used a 1K linear gain adjustment pot instead of the 5K pot (that is what is called for by spec). These cards have a ton of gain and are great with ribbon mics. All other parts on the cards are to spec.
I have a few of these in my studio (that I am definitely keeping) and am selling a few extra ones that I have. You need an XLR input jack, an XLR output jack (Yes, they have electronically balanced outputs), a gain pot and a 48VDC power supply (they run on 48VDC). If you are racking them up, I would also suggest a -20db (or -10db) input pad if you are using really hot mics or micing loud sound sources.
These are really cool preamps to have in your arsenal. Email with any questions. $125 per card or $225 for the pair (2).
