Audio Transformers - Help

gingertube · 15th July 2009, 04:33 AM

I have acquired a pair of THOM and SMITH Ltd. (Sydney Australia) Audio Transformers Part No MT. 03.540.2

According to the info plate on these trannies
Primary is 7500 Ohm Impedance (510 Ohm DCR)
Secondary #1 is 70,000 Ohm Impedance (2850 Ohms DCR)
Secondary #2 is centre tapped 1100 Ohms Impedance (60 Ohms DCR).

Physical size is 70 x 65 x 50 mm

Anyone hazzard a guess as to what these trannies were originally used for?

I'm intending to use them as phase splitters. Secondary #1 to diffamp driver grids and the centre tapped 2nd secondary for a bit of feedback in the diff driver cathodes (Centre tap to a current source). Does that sound feasible to you guys?

Cheers,
Ian

Wavebourn · 15th July 2009, 04:49 AM

Sounds reasonable, but may be it is made to drive an output toob?

Hearinspace · 15th July 2009, 05:27 AM

Thom & Smith made radios. There's a good chance your transformer was used in one. If you really want to know more about the transformer itself I'd hook up with the vintage radio collector world.
There are a number of vintage radio sites in Oz . Here's one. Look for a guy named Steve (Stephen) Savell. He has travelled all over the country documenting radio collections and if he can't help you put a finger on it he probably knows who can.

Geek · 15th July 2009, 09:09 AM

Those impedances almost appear to be 2-way radio transformers...

70,000 ohms would be the microphone..
1100 ohms the headphones...
The primary would be switched between the anode (receive) and grid (transmit).

Just a guess from working with ancient AM TX's

Cheers!

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15th July 2009, 04:33 AM	#1
gingertube diyAudio Member Join Date: Oct 2004 Location: Adelaide South Oz	Audio Transformers - Help I have acquired a pair of THOM and SMITH Ltd. (Sydney Australia) Audio Transformers Part No MT. 03.540.2 According to the info plate on these trannies Primary is 7500 Ohm Impedance (510 Ohm DCR) Secondary #1 is 70,000 Ohm Impedance (2850 Ohms DCR) Secondary #2 is centre tapped 1100 Ohms Impedance (60 Ohms DCR). Physical size is 70 x 65 x 50 mm Anyone hazzard a guess as to what these trannies were originally used for? I'm intending to use them as phase splitters. Secondary #1 to diffamp driver grids and the centre tapped 2nd secondary for a bit of feedback in the diff driver cathodes (Centre tap to a current source). Does that sound feasible to you guys? Cheers, Ian

15th July 2009, 04:49 AM	#2
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	Sounds reasonable, but may be it is made to drive an output toob? __________________ The devil is not so terrible as his mathematical model! Wavebourn: We Create Creativity!

15th July 2009, 05:27 AM	#3
Hearinspace diyAudio Member Join Date: Jun 2008	Thom & Smith made radios. There's a good chance your transformer was used in one. If you really want to know more about the transformer itself I'd hook up with the vintage radio collector world. There are a number of vintage radio sites in Oz . Here's one. Look for a guy named Steve (Stephen) Savell. He has travelled all over the country documenting radio collections and if he can't help you put a finger on it he probably knows who can.

15th July 2009, 09:09 AM	#4
Geek diyAudio Member Join Date: Sep 2004	Those impedances almost appear to be 2-way radio transformers... 70,000 ohms would be the microphone.. 1100 ohms the headphones... The primary would be switched between the anode (receive) and grid (transmit). Just a guess from working with ancient AM TX's Cheers!

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