Quote:
Originally Posted by Michael_Joly  The quick answer is no - no changes are required.
But your question is a good one and deserves a more nuanced answer. Despite the fact the power supply used for the Nady TCM-1050 and Apex 460 provides a clean and stable source of current to the microphone some DIY'ers have experimented with changes to this power supply.
But to back up a second...
...the purpose of a tube microphone power supply is to provide high voltage DC to the plate, low voltage to the heater, bias voltage to the capsule and tube operating point bias. The 1050 / 460 power supply does all this and does it with adequate stability and low AC ripple (hum). In fact the 460 and 1050 have a lower hum level than one well-known $1000 tube mic I've heard. So why have DIY'ers experimented with these power supplies?
Perhaps it is because voltage and current parameters can be manipulated for effect. Probably the most well known manipulation of a tube parameter is the "starved plate" voltage reduction that causes a tube to produce distortion at a lower signal level than would occur if the tube was operating at or near full plate voltage. Similarly; tube heater voltage, tube bias point and capsule bias voltage can all be manipulated for effect. Some DIY'ers claim to prefer certain voltage and current settings that provide them with a specific combination of subjective qualities (S/N, sensitivity, compression onset, capsule diaphragm "stiffness" etc.). While it is technically possible to install variable controls for the basic tube operating parameters doing so would open a Pandora's box of experimentation. Now for the DIY'er perhaps that is the goal - ultimate flexibility and control.
However, I've made a decision to leave the 460 / 1050 as designed because it works well according to the basic criteria I mentioned above. And, as I've said before, I'm striving to be known for a certain midrange-focused, sibilance-free top end "sound" that are the hallmarks of a broadly useful microphone. I am less interested in special application microphones or microphones that have been manipulated in some way (power supply mods or other) for effect or to please one set of ears. |
Hi Michael
I find these power supplies for these microphones to be less than par for a
top shelf microphone. They work for the mic and circuit they were designed for.
The capacitors are not quite the same standard as the Nichicon, Panasonic, Rubycon and Elna counter parts.
The quality of wire that is used in these supplies are average and not the best for a high end microphone.
I find that re-building the power supply with good capacitors, Teflon Silver coated Copper stranded wire makes a big difference in the performance of the microphone. Increasing the values of these components and adding by-pass capacitors decreases the ripple in the current and allows transients to flow quickly through the capacitor and the capacitor recovery time is less.
In custom builds I have also changed the transformer out with a Hammond and used high end Mills wirewound resistors for additional noise reduction. The power supply was dead quiet and the mic sounded amazing.
Reducing the voltage in the power supply does not necessarily result in a starved plate design. The 12xx7 tube variety can handle a wide range of voltages from more than 300vdc max to 45vdc on the lower end with out being a "starved plate." The typical C12 type circuit has any where from 55 to 75vdc and that depends on the bias scheme. I typically reduce the B+ voltage from 140 to around 120vdc to the mic. I have not heard of anyone reducing the plate voltage to where it is indeed starved.
I also modify the power supply to provide negative bias to the grid. This makes the mic a true fixed bias microphone. This gives the mic a much richer tone.
The bottom line is:
Everything matters