1964 AMPEG B-12XY

This is a very strange and rare amp made by Ampeg from the early to late 1960’s. It has possibly the oddest tube lineup I have ever seen in a guitar amp; 7027, 7199, 6SL7, 6SN7, 6D10, 7591, and 5AR4 type tubes are all used in this amp along with very unique circuit engineering. This amp sports both reverb and vibrato effects which are both tube driven. The reverb is nothing like a traditional Fender/Marshall/Vox design, it actually is it’s own separate tube amplifier with it’s very own power tube, output transformer, volume control, and speaker jack. The amp originally came with a separate 2x4” “satellite” speaker cab that could be placed anywhere in the room along with the main combo producing a 3-dimensional wet/dry mix that sounds amazing. The vibrato is also different from the standard amplitude modulation Tremolo used by most amp manufacturer’s. This is a frequency/phase modulation vibrato whose design was heavily borrowed from Wurlitzer Organs. It has much in common with the 1960’s Vox AC30 Vibrato Effect, and sounds more like a phaser and pitch vibrato combined. The other design choice that makes this amp special is it’s use of a 2-way crossover system in the combo speaker cab that utilizes a 12” Jensen guitar speaker along with a Jensen high frequency horn/driver. All and all a very cool amp that is completely hand-wired and makes a great studio option. Nothing sounds like it.

The amp came in having had a basic cap job/re-tube done but not all of it was done right and the cap job was already 15+ years old. The reverb did not work, the vibrato was weak, and there was heat damage to many resistors. Also the satellite speaker cab was missing and the combo speaker cab had been modded to have a second horn placed over the port - this was then hooked up to the reverb speaker jack. I have no idea who would do something like that, since running the reverb through a high frequency horn made it sound like it was coming out of a metal trash can. It needed a ton of work and may have had the most components replaced in any single job I have done. It needed all new filter/signal caps, power/misc. resistors, speaker jack, speaker cable, new handle, cleaning, and a re-pop of the reverb speaker cab.

The amp was fully restored and efforts from previous repairs undone and corrected. An almost complete cap job was done excluding the CE brand 40/40/40/40uf 525v electrolytic cap can, which was kept from a previous repair - all associated parts and wiring to it were redone however. The chassis mounted “fire-cracker” cap was replaced with two MOD brand 70uf 350v units and two 220k 2 Watt Metal Oxide Resistors in a balanced series topology. The rest of the electrolytics were replaced with upgraded voltage and temperature rated MOD/Vishay brand units. All of the paper/foil signal caps were replaced with upgraded voltage rated Mallory/Vishay brand polyester film capacitors. The carbon comp and wire-wound power resistors were replaced with upgraded 2 Watt Metal Oxide, 5 Watt Wire-Wound, and 10 Watt Wire-Wound type resistors respectively. 5 Watt Wire-Wound resistors were used for the plates of the Tremolo section for the same reasons as above - reliability, heat damage and drift. New 2 Watt Metal Oxide and 2 Watt Metal Film type resistors were installed in the bias circuits and some cathode positions - this was done due to heat damage. The higher wattage resistors mean better reliability and a lower noise floor. A new 4 pin XLR speaker cable was installed due to the original having been worn out. The death cap was deleted, rendering the polarity switch non-functional.

A new 2x4" satellite cab was made custom by Fliptops out of Buffalo, NY.

All of the original tubes tested good and were left in place. The tube lineup was: V1-V2 = RCA 7027A Matched Pair, V3= Soviet 7199, V4 = Sovetk 6SL7, V5 = Soviet 6SN7, V6 = RCA 6SN7, V7-V8 = GE 6D10, V9 = Sylvania 7591, V10 = Sovtek 5AR4. The Fixed Bias for the RCA 7027A’s was set to %46 Class AB Plate Dissipation with a B+ of 498VDC. The broken handle on the filp-top lid was replaced with a Blue Faux Leather Ampeg style handle. The tube sockets were all treated with De-Oxit to remove/prevent corrosion. The pots were sprayed out and the amp was cleaned inside and out. This was a complicated job, but the amp came out with an incredible tone that is hard to describe due to its originality. This is one of the only Ampeg B-12XY’s out there that has actually had every single thing restored properly and is ready to survive for the next 60 years. The customer is going to use this in an active recording studio environment, which is perfect for this piece.