From the consigner:
A Custom combo amp mod/build inspired by the 1964 Vibroverb, the rare model made iconic by Stevie Ray Vaughn. All parts new except for t he reused amp chassis and original '69 Bandmaster circuit board, power, and reverb transformers.
My pandemic hobby was building amps and i have too many now :(
This one started as a '69 silver-face Bandmaster Reverb head. The circuit design of this '69 Bandmaster did not change much from the '64 black-face Vibroverb. It was simple removal of some unnecessary filter/biasing parts of the output section that I can only guess were added over time to increase manufacturing yield (?). These unnecessary parts have been removed. Only a couple of other resistor values needed adjusting and voila! it matches the AB763 Vibroverb schematic from '64.
I believe the original power transformer is the same model used in '64 black-face amps that had the 2 6L6 power tube output section like the Vibroverb (date code on the power transformer is March 1969) and with GZ34 rectifier tube the DC voltages are in range of a '64 Vibroverb, some of the highest ever of any black-face amp. You can also see that most all of the original chocolate-drop and blue Mallory coupling caps along with carbon comp resistors are still there for vintage tone. A filter cap-job was performed as the filter caps in the doghouse were definitely going bad. Additionally all the preamp cathode bypass caps in the preamp stages were also replaced with new caps, but not original in-circuit coupling caps.
On the the mods and new upgrades:
-The output transformer was upgraded to Mercury Magnetics SRV over-sized 50W model, a new Mercury Magnetics choke also installed.
-A multi-tap speaker impedance selector added
-Reverb and Tremolo were added to the normal channel, a mod which also puts the the channels in phase (can jumper together if desired like a Fender tweed or Marshall amp.)
-The tremolo circuit was modified to slow the pulse rate.
-The tone circuit of the normal channel was adjusted to emphasize mids, useful as a lead channel, or just having the option of a channel voiced a bit differently than stock mid-scooped Fender vibrato channel.
-Raw switch (tone circuit bypass) installed on Normal channel.
-Bypassable Effects loop added w/return volume control (Mojotone active FX loop)
-Adjustable power tube bias pot with additional filter cap on bias voltage output
-Switchable fixed or cathode bias for output section. Fixed would be the '64 Vibroverb circuit.
-New, properly grounded power cord installed with legacy "death cap" removed
-New reverb tank and cabling installed.
-Cabinet is new Mojotone pine cabinet
The FX loop mod is particularly useful for this amp. Besides being a great option to insert FX such as delays and reverbs, the return volume control becomes a useful master volume option. This amp is VERY LOUD. Adjusting the pre-amp volume controls can be very touchy and you might prefer pre-amp tone at a higher setting or maybe you are using both channels and want to control volume of both with one knob. Even if not using effects, you can short the send/return and use the FX return volume as a master volume control. Additionally when you trim the FX return level like this, the overall noise floor of the amp goes down accordingly and reduces hiss at lower volumes when you don't need all of the 40w of output.
A Custom combo amp mod/build inspired by the 1964 Vibroverb, the rare model made iconic by Stevie Ray Vaughn. All parts new except for t he reused amp chassis and original '69 Bandmaster circuit board, power, and reverb transformers.
My pandemic hobby was building amps and i have too many now :(
This one started as a '69 silver-face Bandmaster Reverb head. The circuit design of this '69 Bandmaster did not change much from the '64 black-face Vibroverb. It was simple removal of some unnecessary filter/biasing parts of the output section that I can only guess were added over time to increase manufacturing yield (?). These unnecessary parts have been removed. Only a couple of other resistor values needed adjusting and voila! it matches the AB763 Vibroverb schematic from '64.
I believe the original power transformer is the same model used in '64 black-face amps that had the 2 6L6 power tube output section like the Vibroverb (date code on the power transformer is March 1969) and with GZ34 rectifier tube the DC voltages are in range of a '64 Vibroverb, some of the highest ever of any black-face amp. You can also see that most all of the original chocolate-drop and blue Mallory coupling caps along with carbon comp resistors are still there for vintage tone. A filter cap-job was performed as the filter caps in the doghouse were definitely going bad. Additionally all the preamp cathode bypass caps in the preamp stages were also replaced with new caps, but not original in-circuit coupling caps.
On the the mods and new upgrades:
-The output transformer was upgraded to Mercury Magnetics SRV over-sized 50W model, a new Mercury Magnetics choke also installed.
-A multi-tap speaker impedance selector added
-Reverb and Tremolo were added to the normal channel, a mod which also puts the the channels in phase (can jumper together if desired like a Fender tweed or Marshall amp.)
-The tremolo circuit was modified to slow the pulse rate.
-The tone circuit of the normal channel was adjusted to emphasize mids, useful as a lead channel, or just having the option of a channel voiced a bit differently than stock mid-scooped Fender vibrato channel.
-Raw switch (tone circuit bypass) installed on Normal channel.
-Bypassable Effects loop added w/return volume control (Mojotone active FX loop)
-Adjustable power tube bias pot with additional filter cap on bias voltage output
-Switchable fixed or cathode bias for output section. Fixed would be the '64 Vibroverb circuit.
-New, properly grounded power cord installed with legacy "death cap" removed
-New reverb tank and cabling installed.
-Cabinet is new Mojotone pine cabinet
The FX loop mod is particularly useful for this amp. Besides being a great option to insert FX such as delays and reverbs, the return volume control becomes a useful master volume option. This amp is VERY LOUD. Adjusting the pre-amp volume controls can be very touchy and you might prefer pre-amp tone at a higher setting or maybe you are using both channels and want to control volume of both with one knob. Even if not using effects, you can short the send/return and use the FX return volume as a master volume control. Additionally when you trim the FX return level like this, the overall noise floor of the amp goes down accordingly and reduces hiss at lower volumes when you don't need all of the 40w of output.
This item is sold As-Described
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| Listed | a year ago |
| Condition | Excellent (Used) Excellent items are almost entirely free from blemishes and other visual defects and have been played or used with the utmost care.learn more |
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