After working on and listening to Albert Talley's 1954 Bassman (serial #0035), model 5D6 I had decided to build eleven of these. The dual 5Y3 rectifier in the 5D6 Bassman was only made for a very short period. The later 5D6A and 5E6 used dual 5U4GB rectifier tubes.
The Bassman was designed for the first mass-production electric bass, the Fender Precision Bass. It was introduced in 1952 and discontinued in 1983. Up to until 1954, the Bassman amps had only 1 speaker (circuit 5B6), but it was the four 10" speaker combination (officially introduced in 1955 as model 5D6-A) that came to be the greatest and most sought after amplifiers in history. The first 4x10 Bassman amplifiers started with a batch of prototypes in November and December 1954, model 5D6. No schematic for the 5D6 circuit have ever been found, and only 5 of these early examples have been found to have survived. The earliest serial number known to still exist is 0013, but 0032, 0075, 0077, and 0780 are also known to exist. These rare few are known to sound better than the revered 1959 5F6-A circuit, and are fetching prices in excess of $15000 USD
Features for our amp:
-Free D2F custom fit cover
-Mallory 150 caps -Sprague Atom filtering caps -F&T bias cap
-JJ power tubes and 12AX7 tubes -Electro Harmonix 12AY7 tubes -JJ 5U4GB RECTIFIER!!!!
-Mercury Magnetics for all transformers and chokes
-carbon comp resistors (except the 2 watt power -resistors, Metal oxide)
-Carling switches -Switchcraft jacks and plugs
-CTS pots and 1 Alpha pot
-Jensen P10R speakers with bells for the lower 2 speakers
-finger jointed pine cabinet with lacquer finish
-2000 degree rated heat shield tape for the area behind the power tubes (old amps used asbestos)
-Vintage cloth covered wire
No devices, circuit board or tube sockets are mounted with sheet metal screws! The circuit board is mounted to the 6/32" x 1/4" stainless steel standoffs which are mounted to the chassis with a 6/32" locking nut with plastic insert. Tube sockets are mounted with stainless steel 4-40" screws and lock nuts. Transformers are mounted with 8/32" screws and lock nuts. There are a few modern day adds to the amp for safety, efficiency. The 6.3 volt heater circuit is fused at 6.3 amps and the +5 VAC is fused at 12amps. There is an in-rush current limiter on the 120 VAC line that helps protect the amp as it first comes on.
Channel 1 normal, channel #2 is bright. Two inputs per channel. . Input 1 goes to parallel 12AY7 triodes via a switching jack on input # 2. When input #2 is used it is a single triode input, inputl #1 is then grounded unless plugged into. When both #1 and the #2 input are used each goes to a single 12AY7 triode section.
Controls: **Volume** **Volume bright channel" **Treble** ** Bass** ** Presence**
The original was a 2-hole chassis, two channels, with 1 jack per channel. The one I am building is schematically the same but with a second channel and a single 5U4GB rectifier. The bias is also adjustable. Dark Brown chicken head knobs and an amber jewel dress it up a bit, too!
Power output: Approximately 38 watts RMS into a 2 ohm load
Cabinet dimensions: 23 1/2"(W) x 22 5/8"(H) x 10 1/2"(D)
Covering: Brown Stripe Coated Tweed, Oxblood w/ Stripe Grill Cloth
Hardware: Large Brown leather Handle, Chrome Glides...
Tubes: 1 5U4GB Rectifier tube Power: 2 x 6L6GC JJ Telsa Preamp: 3 x 12AY7
(EH tubes) and 1 x ECC83/12AX7 (JJ Telsa)
Speakers: 4 x Jensen P10R with bell covers on lower 2 speakers
Fox Vintage Amp
5U4GB, 2 x6L6GC power
Dual triode inputs
No longer available