Embedded Files
Another in my series of older projects that I haven't yet documented. This was the addition of a custom tape head preamp to an Otari MX-55 back in 2014. Below is an ad introducing the MX-55 from 1988 followed by a magazine cover also from 1988.
This shows the MX-55 on its rolling stand. This particular unit was manufactured in 1996.
A closeup of the meter bridge and level controls.
The top of the meter bridge opens up to reveal audio PCBs for each channel.
Those audio sections will be replaced with a separate preamp in this modification.
The rear of the MX-55 opens by folding down to expose the supply and take-up motors near the top and the power supply/transport contol PCB (at the bottom).
While in here, the electrolytic caps on this board were all replaced.
This shows the MX-55 transport with the front cover removed. There's a single heavy cast aluminum chassis that serves as a mounting base for all the transport parts. This is a big step up from the MX-5050 which uses a simple aluminum plate.
The first step in adding a new tape head preamp was to replace the cables coming from the playback head with new low capacitance cable, circled here, which will feed the new tape head preamp.
The panel circled here is the new tape head preamp electronics.
The only two controls are for power and to select NAB or IEC equalization.
This shows the inside of the new tape head preamp. Power transformer and regulated power supply to the left, audio PCBs for each channel on the right. NAB/IEC EQ is selected by the front panel switch, and there are separate frequency response trimmers on the PCB for both NAB and IEC equilizations.
Another view of the tape head preamp mounted in the Otari. The white cables feed the audio outout to the VU meters.
Audio output is via RCAs on the bottom in this photo, and inputs are the cables we attached earlier to the playback head (the silver RCAs on the lower right).
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