1966 Ampeg B-15N

The amp that many people associate with James Jamerson and Motown, the B-15 is an all time favorite low powered tube bass amp that is perfect for recording. This one came in with an all original tube set, and was almost completely original electronically. The symptoms included humming, crackling/popping, and lack of treble response. There was also physical damage to the wooden chassis tray, and one of the four shock-mounts was broken and needed a replacement.

The amp was given a full cap job including the electrolytic cap can, the chassis mounted “fire-cracker” cap, board mounted electrolytic’s, and all the paper/oil signal caps. Brands used included CE, F+T, Sprague Atom, and Mallory. The carbon comp power resistors were replaced with upgraded 2 Watt Metal Oxide type resistors. A new 220k 1 Watt plate resistor was installed on the first gain stage due to noise - the higher wattage resistor means better reliability and a lower noise floor. A new 3 prong power cord was installed for safety reasons and modern electrical code. The death cap was deleted, rendering the polarity switch non-functional.

All of the original Ampeg/Sylvania branded tubes tested good and were left in place. The tube lineup was: V1-V3 = SYLVANIA 6SL7, V4-V5 = SYLVANIA 6L6GC Matched Pair, V6 = SYLVANIA 5AR4. The Fixed Bias for the grey-plate SYLVANIA 6L6GC’s was set to a factory spec correct %52 Class AB Plate Dissipation with a B+ of 460VDC. The broken part of the wood head tray (one of the side rails) was carefully taken apart and glued (Titebond 3) back into place, then clamped with bar clamps for 48 hours. The broken shock-mount was replaced with a custom made version from Fliptops.net - the Ampeg specialty site in New York. The amp was cleaned, and all the hardware was tightened. A great sounding amp for guitar or bass.