My finds continue.
A friend of mine had given me some studio flash power packs that had received pretty bad water damage. He also had some flash units that developed faults. So, I parted out the power packs and used the capacitors and rectifiers to fix the flash units. However, I also removed these transformers and for fun tested them for frequency response. To my total surprise they tested incredibly well. I also had some power transformers that I had removed from professional Tascam and Aiwa tape recorders over 10 years ago. I thought, hmm, how about them? The result is below.
The transformers were driven from an unbalanced 600 ohm source. Secondary was loaded with 4k7 resistor and drove into a balanced load (OP275). Tests were not surgical. So, there is a bit of give and take in the numbers quoted.
These are the transformers removed from the flash power packs. They have core sizes of 65mm x 50mm x 20mm. They have 6 independent taps giving good practical turn ratios. They measured 15Hz -19kHz flat.
[ATTACH=full]112405[/ATTACH]
This one came from I think Tascam 112R. It has two independent centre tap secondaries with normally with 15.8 - 0 -15.8 and a single tap at 8V. I used one of the centre tap secondaries and it gave almost 7:1 turns ratio. 15Hz -20kHz flat. Between 30kHz and 65 kHz there is a slight rise in amplitude with about 1dB hump, and starts to roll of at 65kHz.
[ATTACH=full]112406[/ATTACH]
This one came from Tascam 133. It has one independent centre tap secondary and one single 8V. I tried the center tap secondary and it gave about 8:1 turns ratio. It is 50Hz - 15kHz flat. Slight drop between 50Hz and 20Hz. From 15kHz the response starts to climb up and there is 1dB rise in amplitude at 28kHz. From 28kHz starts to climb steep and there is 5dB rise at 55kHz and then rapid roll-off.
[ATTACH=full]112407[/ATTACH]
Now this came from an Aiwa cassette deck. Actually there were two of them one with additional secondaries. They were externally mounted to the rear panel. At the time I thought it sounded like an audiophile hype but it really surprised me. This thing gave 10Hz - 60kHz flat. There is a negligible rise from 60kHz and at 110kHz there is about 0.6dB increase in amplitude. The amplitude response starts to climb and there is 3dB rise at 160kHz then rapid roll-of. However, I would not get too excited about the frequency figures after 60kHz as the fly leads are bundled together at termination and the capacitances between them are taking effect, hence possible cross talk.
[ATTACH=full]112408[/ATTACH]
I have no idea what you make of these but I was really surprised. I have a number of these transformers but I am not counting my chickens yet as I would also like to test them subjectively. At the same time they made the transition from power transformer shelf to audio transformer shelf..
