Ampex 601 and a Pair of 602 Reel to Reel Tube Amplifiers

Ampex 601 and 2x Ampex 602:

I just got a fantastic score of fleabay yesterday. It was a lot of three Ampex reel to reel tube amplifiers. One is a 601 unit and the other two are 602 units. The 602 pair both have their stock input and output transformers installed in place, but the 601 is missing its plug-in input transformer. I really like both of these units. The 601 has a tube rectified power supply for high voltage and will have an artificially center tapped AC source for the 6.3v heaters. Nothing wrong with AC heaters is you do them right to cancel out the hum. The 602 has a power supply is completely different from the 601. It uses a solid state rectified voltage doubler circuit for high voltage and a solid state rectified DC for the heaters. I usually tune it to be slightly cold at around 6 volts. The sounds of the two units are slightly different despite having identical audio circuits. Because of the tube PSU the 601 has a softer edge and feels silkier overall. The 602 with its solid state PSU has slightly more gain + headroom and is tighter overall. It is a little more aggressive and gives up the softer edges of the 601. It is an interesting trade-off and I like to have both on hand for the different sounds. I have used them interchangeably on just about any source and it really just comes down to personal taste.

My plans are to make each unit a two channel microphone preamp with XLR microphone and 1/4" DI inputs as well as dual outputs: one will be transformer balanced on an XLR jack and the other will be impedance balanced on a 1/4" TRS jack. One of the 602 units will get the stock input and output transformers from both 602s while the other 602 and the 601 will get Jensen input and output transformers throughout. All three will be put up for sale to raise funds for the station. If you are interested please inquire for pricing and availability.