The Bassman, Bandmaster, Super & Pro
The Bandmaster, Super, Pro and Bassman amps in the Tweed lineup start the higher power end of the 50's Fender lineup.
There are several variations of amps that share almost virtually identical circuits as the Bandmaster. The Super and the Pro are basically the same amp with different output transformers and speaker configurations. Frankly, I build a lot of Bandmasters as heads and supply them with multiple load output transformers. The circuit snuggles in between the Deluxe and the Bassman. It uses the more powerful 6L6 or 5881 power tubes, a 5U4 Rectifier for more voltage and 3 preamp tubes for more tone control options and gain.
The Bandmaster and its cousins feature Fixed bias for the power tubes. Bias is set and can be tailored to the power tubes via a resistor set and negative voltage from a power supply tap and the use of a diode. This marks a change for the Tweed amps and gives the higher powered amps a firmer bass response, more clean headroom and great overdriven tone. These amps are about 25-30 watts.
The Bassman drives the power tubes at higher voltages still and uses the beefy power supply capacitors that required Leo to move them to the top side of the amp in what is called the "doghouse" on the chassis. This became the common location for the higher powered amps in all the Tweed, Brownface and Blackface amps to come. Leo was all about saving money and it was cheaper to use individual capacitors and mount them on top rather than the multi cap can style units of the day. The result of this extra power supply filtering was big strong bass response- these guys sound like a piano with almost a reverb like clean tone. The Bassman amp is about 40-45 watts.
Here are some examples I have built. They range in price from $700 for a reproduction Bandmaster chassis ready for a combo or head cabinet up to $1500+ for a full Tweed Bassman with 4 speaker cabinet.
Here is the outside view of a 5E7 Tweed Bandmaster. Power, Output transformers and a choke that reinforces the power supply and removes ripple from the circuit. It has the 4 inputs, 2 Volume controls of the Deluxe but adds a Bass and Treble tone control and a Presence control to help add a brighter or darker character to the amp.
Here is a look at the tube side of the Bandmaster. Big bottle 5U4 rectifier and 6l6 or 5881 power tubes as well as 3 preamp tubes. This amp has two output jacks with 4 or 8 ohm taps.
Internal shot looking down the bigger power supply capacitors. Note the elevated heater windings and cloth wiring for interconnects to the eyelet board and the tube sockets. It takes me a long time to get this just right but makes a nice quiet amp.
Here is an 5F6a Bassman just finished without its knobs yet. The Bassman has 2 volume controls, 4 inputs, treble, middle and bass controls and presence. The Tweed Bassman became the model that Marshall copied to produce their JTM amps of the 60's. It's actually the model for many amps to come and is considered one of the greatest Blues and Rock amps ever made. Real 50's Bassman amps in original and good condition are worth many thousands of dollars.
Note the big output transformer. Its part of the secret to its huge sound and bass response.
Here is a look inside. The small black diode and the smaller capacitors in the foreground are the bias circuit for the amp.
Here is a closeup of wiring detail to the volume and tone pots
There are several variations of amps that share almost virtually identical circuits as the Bandmaster. The Super and the Pro are basically the same amp with different output transformers and speaker configurations. Frankly, I build a lot of Bandmasters as heads and supply them with multiple load output transformers. The circuit snuggles in between the Deluxe and the Bassman. It uses the more powerful 6L6 or 5881 power tubes, a 5U4 Rectifier for more voltage and 3 preamp tubes for more tone control options and gain.
The Bandmaster and its cousins feature Fixed bias for the power tubes. Bias is set and can be tailored to the power tubes via a resistor set and negative voltage from a power supply tap and the use of a diode. This marks a change for the Tweed amps and gives the higher powered amps a firmer bass response, more clean headroom and great overdriven tone. These amps are about 25-30 watts.
The Bassman drives the power tubes at higher voltages still and uses the beefy power supply capacitors that required Leo to move them to the top side of the amp in what is called the "doghouse" on the chassis. This became the common location for the higher powered amps in all the Tweed, Brownface and Blackface amps to come. Leo was all about saving money and it was cheaper to use individual capacitors and mount them on top rather than the multi cap can style units of the day. The result of this extra power supply filtering was big strong bass response- these guys sound like a piano with almost a reverb like clean tone. The Bassman amp is about 40-45 watts.
Here are some examples I have built. They range in price from $700 for a reproduction Bandmaster chassis ready for a combo or head cabinet up to $1500+ for a full Tweed Bassman with 4 speaker cabinet.
Here is the outside view of a 5E7 Tweed Bandmaster. Power, Output transformers and a choke that reinforces the power supply and removes ripple from the circuit. It has the 4 inputs, 2 Volume controls of the Deluxe but adds a Bass and Treble tone control and a Presence control to help add a brighter or darker character to the amp.
Here is a look at the tube side of the Bandmaster. Big bottle 5U4 rectifier and 6l6 or 5881 power tubes as well as 3 preamp tubes. This amp has two output jacks with 4 or 8 ohm taps.
Internal shot looking down the bigger power supply capacitors. Note the elevated heater windings and cloth wiring for interconnects to the eyelet board and the tube sockets. It takes me a long time to get this just right but makes a nice quiet amp.
Here is an 5F6a Bassman just finished without its knobs yet. The Bassman has 2 volume controls, 4 inputs, treble, middle and bass controls and presence. The Tweed Bassman became the model that Marshall copied to produce their JTM amps of the 60's. It's actually the model for many amps to come and is considered one of the greatest Blues and Rock amps ever made. Real 50's Bassman amps in original and good condition are worth many thousands of dollars.
Note the big output transformer. Its part of the secret to its huge sound and bass response.
Here is a look inside. The small black diode and the smaller capacitors in the foreground are the bias circuit for the amp.
Here is a closeup of wiring detail to the volume and tone pots