The UHER power supply mic connector provision (power coming for the internal batteries) can be used to power an electron tube 7.5V anode voltage pre preamplifier.
Example an ECC82 (12AX7) double triode electron tube (Pleiades V0 series). Each half can be used for each channel. The anodes operate greatly with 7.5V by biasing from plate to grid with a 4 Megohm electron accelerating resistor. The heaters can be in series and underheated to 7 volts instead of 12V. This will make the electron tube further low noise, perhaps at the limit of nature. A similar underheating technique is used on possibly the best microphone ever on the planet, favorite by Madonna, Sinatra, Beatles etc, the Neumann U47 with the internal VF14 tube underheated for low noise and high resolution.
Or 2 EF183 electron tubes can be used connected as triodes, example the Pleiades V4.
Example mics are Sony F-96, Beyer M55 H N, Sennheiser MD421 HN, MD441, Electro-Voice RE15, RE16, Shure Unidyne III.
[Why an electron tube or JFET front end amplifier?
They are high impedance giving an open sound with big midrange and extended high frequency perception.
Low Z direct connection to transistor sounds nice but the sound seems restricted.
The electron tube drives the transistor input stage with a big low noise signal. This increases subjective loudness, signal to noise ratio. The singer or actor can sing or speak at a very comfortable natural unforced voice and the magnetic tape modulation can be deep.
So far this has been tried on Marzntz MD430, Sony TC-D5M, Sanyo MR-410 with great results, big and natural sound quality and almost complete absence of hiss. The limiting factor being usually the recording environment acoustic noise level.
A problem is possibility of transient clipping of the following stages.
It is hoped this will be absent on Uher running at 7.5ios.
Such a simple front end stage is present on condencer or electret mics next to the capsule.
So why not also give world class studio moving coil microphones the treat they deserve? Less expensive mics can sound amazing too as we know from discography. For example Sade, Bono U2 using the SM58 on studio vocals or Stevie Nicks Fleetwood Mac using the more expensive MD421 or MD441.]
Input transformers can be used for stepup and low noise and for compensating the proximity effect and electromagnetically damping pop and wind noise. Ribbon microphones can be used too.
Some of the above mics have high impedance versions as they have the input transformer inside them. This further simplifies things. And all one then needs is an ECC82 and 1 or 2 resistors and capacitors for top quality studio sound.
Another option is using a JFET prepreamp like electret condenser microphones do. An example is the K117 JFET, Pleiades K117 prepreamp.
Also many microphones can be connected to the input transformers in series - parallel combinations. This may produce direct to stereo or mono recordings of unparalleled noise performance and sound quality, punch and loudness.
Reference:
On preserving the transconductance of electron tubes at anode potential as low as less than 6 volts - euroelectron blogspot
Tubes vs Transistors, is there an audible difference? - Russel O. Hamm - JAES
Shelley Yakus - Production Viewpoint - interviewed by Robbert Carr - Vintage King Audio
https://vintageking.com/media/article-archives/pdf/shelly-yakus.pdf
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