Among other implementations, I've known the Altec 15095A transformer as a 1:10 MC SUT for decades. On the other hand, the 6AH4GT came a very close second to the triode-connected 6F6 + Hashimoto HL20K6 line transformer in my main stereo rig.
!!!WARNING!!!
The voltages in the following schematic are potentially lethal! Build at your own risk!
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| I've used both a capacitor input (CLC) and choke input (LC) type power supply. Each has a distinct sound and I leave it up to the DIYer to decide what suits their taste. |
The Altec 15095A is wired as a 15kΩ:600Ω step down transformer. It's not designed to take any current at all; don't even try, or you'll burn the hair-thin copper windings. A Vitamin Q 1µf/300V paper in oil coupling capacitor blocks direct current from the plate of the 6AH4GT triode.
This triode has an amplification factor of 8 and a plate resistance of 1780Ω. With a plate resistor that's 2.8 times (5k/4W) its plate resistance, the 15kΩ Altec 15095A presents an easy load.
For another approach to configuring a 15095A as a 600Ω line output, please check out the Altec 1566 mic preamp schematic.
As shown above, with 1V rms input, output = 0.94V rms. Therefore, gain is less than unity. I solved the gain issue with the additional benefit of a solid 600Ω broadcast studio standard buffer for my variable EQ monaural phono preamp + other line level sources.
The square waves translate to a frequency response of 30-15,000 Hz +/- 0.5dB or 20-30,000 Hz +/- 1 dB into a 600Ω load. Not bad for a circuit that dispenses with musically detracting global negative feedback. Since I don't monitor seismic activity, nor do I intend to annoy bats, this bandwidth is ideal for my musical needs.😉
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