Re: Pearl Microphone Labs

Has anyone heard one of these mics?  The XFY54 is one of those low voltage sub-miniature pentode tubes with 1.25 vdc direct heated filament and 67.5 volts anode, intended for battery operation.  The tube appears triode connected in the schematic.  No output transformer in the mic, medium impedance output coupled off the anode to a transformer in the power supply.  Noisy?  Prone to hum, RFI, etc.?

Appears that mic could be run off a single flashlight battery for heater and seven 9 volt batteries in series for the anode...

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/Jakob E.

I usually see that one spec'ed for 22.5V anode voltage and 10mA heater, e.g.: https://www.vintageradio.nl/Buizen/xfy54.htm

..all well within phantom power reach..

/Jakob E.

documents:

https://groupdiy.com/index.php?topic=75851.0

Exactly like the Altec lipstick mics, and the Royer DIY tube mic plan. 

I'd never heard of that tube type before, or even that naming convention.  The tube would run off phantom, but you'd give up the higher capsule bias of the dedicated supply.  The 4M7 bias resistor looks low at a glance, but I'm possibly looking at that wrong. 


There's a FET version, EC/EK-71.  Probably the same transformer in the PSU. 

Check the Milab historical, there's a DC-20/21 that is the direct descendent, same form factor and quick release clip.