Audio Transformers for a DIY Project

[jimmyfun]

Hi there,
i wonder if anyone of you know where to find two transformers for a diy project with this spec:

the first is a step-down audio input transformers



turn ratio:  2:1
dc resistance: 200Ω/ 100Ω (50Ω+50Ω)
dc impedance: unknown

the second is something like an auto-transformer or a OT with multiple tap / extra winding on the primary



turn ratio: 0.5 (2:1)
dc impedance: 140Ω CT primary/ 35Ω secondary
dc resistance 2Ω-2.5Ω primary/ unknown secondary


Cheers
Jimmy

[kingswayguitar]

welcome to the forum jimmyfun!

[GibsonGM]

One supplier:  http://www.hammondmfg.com/index.htm

You might try to go thru Tubesandmore.com   or Mojo musical supply, though...manufacturers tend to be pricey...

Good luck!

[teemuk]

i wonder if anyone of you know where to find two transformers for a diy project with this spec:

These look like they might belong to an old transformer coupled transistor radio.



So try cannibalising a bunch of old transformer coupled transistor radios.  

[jimmyfun]

Ok thanks.
From the diagram and data sheet i know that the input transformer turn ratio is 2:1 with a DC resistance of 200/50 (50 +50) and the output transformer has a dc impedance of 140ohm CT / 35ohm (2:1 turn ratio from my calculations) with a dc resistance on multi tap primary of 2-2.5 and nothing on the secondary side! Can you explain the peculiarity of this output transformer? why the speaker is plugged in two taps on primary?

[tubegeek]

Schematic? Hard to know without the rest of the circuit.

[PRR]

Audio transformers "must" have a Power specification.

And usually Frequency Response goal.

The two parts you show *suggest* a 1960s push-pull transistor power amp. But 3V 0.1 Watts or 24V 5 Watts or 60V 50 Watts?

Power transformers are the classic fake-audio transformers. The 2:1 part auto-transformer is logically any CT winding. Figure your audio voltage, triple it, find a winding. But the text-spec does not fit that diagram.

The other... if that goes to transistor bases and IF you can find a 120:6VCT:6VCT transformer, it may work. But that is 10 or 12 leads, and most transformers today are 8 pins max.

[jimmyfun]

Thanks PPR!
9V - 1 WATT
Yes it is a a '60s pp transistor based amp similar to mullard circuit where the driver transformer primary is connected to the drive transistor collector and to the ground with secondary to the bases of the output transistors. Output Transformer primary is connected to the output transistor by collectors (the 2 ohms windings), then the speaker is connected through two resistor from the bases to the remain taps on primary (2.5 ohm), Ct to the ground.
The secondary, instead of a speaker load, is connected to the negative cap then to the ground.