1930s Universal 1089 Double-button Carbon Microphone Input Transformer - NOS and TESTED!

Fully tested NOS/mint condition 1930s Universal 1089 Double-button carbon mic input transformer. As featured in the very first "Type 30" I built for a very high-end customer - which is still in active use - check out the YouTube sound example of that preamp to get an idea of how this could sound!

Since modern mics are essentially an evolution of carbon mic tech, the 200 ohm input impedance spec is also perfect for virtually ALL vintage & modern mics: condenser, dynamic, ribbon, etc. that are in the 150-350 ohm output impedance range.

This particular unit seems to match manufacturer specs and measures closely to my other 1089. The build quality is unsurpassed - in my experience, the build quality and reliability is equal and beyond vintage 30s/40s/50s Thordarson, which I consider to be another top-of-the-line brand during the era. The amazing chrome art-deco case puts this over the top though - its the nicest carbon mic transformer I've ever worked with. Only selling to focus on building my miniaturized PlateMic plate reverbs - and I'm willing to sell my most valuable/prized/rare parts to make that happen (please see the mint&working condenser mic capsules also for sale).

Transformer Testing Data (Using Fluke 87V for DCR and BK Precision 879B for rough impedance tests):

Primary DCR winding 1 to CT=13.8ohms / 2 to CT=12.8ohms / 1 to 2 = 26.5ohms

Primary Z @ 1khz test freq. winding 1 to CT=118.4ohms / 2 to CT=118.55ohms / 1 to 2 = 447.3ohms

Primary L @ 100hz test freq. winding 1 to CT=66.7mH / 2 to CT=68.1mH / 1 to 2 = 276mH

NOTE: All primary tests w/manufacturer spec'd 100k ohm total secondary load across windings 1+2.

Secondary DCR winding 1 to CT=3.0k / 2 to CT=3.2k / 1 to 2 = 6.3k

Secondary Z @ 1khz test freq. winding 1 to CT=34.3k / 2 to CT=34.9k / 1 to 2 = 132.3k

Secondary L @ 100hz test freq. winding 1 to CT=23.4H / 2 to CT=23.7H / 1 to 2 = 94.9H

NOTE: All secondary tests w/manufacturer spec'd 400 ohm total secondary load across windings 1+2.

Turn ratio test using BK Precision 879B, O-scope, and no additional loading:

582.2mV AC rms @ primary = 9.13VACrms secondary for 1:15.68 turns ratio / 245.92 impedance ratio

These test line-up very closely with the manufacture spec of 1:15.8 turns ratio / 1:250 impedance ratio.

Manufacturer specs from 1933 Universal Microphone Co. Catalog:

"In chrome plated case. A two-button microphone input transformer having an exceptionally flat frequency characteristic ranging from well below 40 cycles to over 10,000 cycles. Has center-tapped primary, 200 ohms to each side and the secondary impedance is in the order of 100,000 ohms. Secondary matches impedance of all standard types of amplifier tubes and is center tapped which allows its use on either straight or push-pull amplifiers. Primary matches all standard types of two-button carbon microphones. Net weight 2 1/4 lbs. Size 2-3/4" x 3-1/4" by 3-1/2".

Please note: No refunds on vintage items - please do your research before you purchase!

Thanks for looking!

-Richard, CVPA