bottlenecker
Poster Extraordinaire
Wasn't there a dano/silvertone with a seperate OT for each of it's two speakers?
Thought Experiment: two output transformers in parallel
- Thread starter Peegoo
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Wasn't there a dano/silvertone with a seperate OT for each of it's two speakers?
Norman Crowhurst wrote a few articles about twin-coupled amplifiers that cover most of the questions that might arise.
Of course, this is more of a hi-fi approach, resembling an ultra-linear output, but still an interesting possibility for using two OT's in parallel.
Of course, this is more of a hi-fi approach, resembling an ultra-linear output, but still an interesting possibility for using two OT's in parallel.
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Things to do with two OT's. I drew up a few combinations, but never got around to finishing all the possibilities, so some of the bits are just standing there, but here it is anyway, maybe I will carry on one day... but maybe not.
As your thread is titled, they are just "thought experiments".
The PDF contains some maths to accompany the diagram.
edit... i just see I did do some more combinations... but as I say, unfinished, and a question mark is also there for some later consideration.
As your thread is titled, they are just "thought experiments".
The PDF contains some maths to accompany the diagram.
edit... i just see I did do some more combinations... but as I say, unfinished, and a question mark is also there for some later consideration.
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This is also a novel idea, adding a centre speaker from two stereo speakers.
No series primary and parallel secondary with an 8 ohm speaker?
I didn't realize quite how many possibilities there would end up being, and I certainly don't claim to have run through them all, or maybe even to have envisaged the full scope of what's possible.
The sheet has several drawings of unconnected transformers, both with and without centre taps, and/or with dual output impedances..... feel free to complete a few combinations that I did not get around to, and see if you can get a series primary and parallel secondary with an 8 ohm speaker.
philosofriend
Tele-Afflicted
I agree with Ten Over's analysis. If each OT goes to its own separate 8 ohm speaker, the primaries wired in parallel should load the power tubes about the same as one OT feeding a 4 ohm load. This seems a reasonable experiment.
Connecting the secondaries of two OTs together in parallel might be ok, but if you got them out of phase you would be in a heap of trouble. Each secondary winding would be looking to be loaded down by a speaker. Instead each secondary would see the other one as an active current sucking negative impedance. If the two were perfectly out of phase, there would be no output to the speaker, but huge currents would be rushing between the two secondaries. This would cause the load seen by the power tubes to go very low, probably overheating the tubes and/or OT primaries.
We guitar tinkerers know how to hook two pickups up out of phase and get an odd thin sound, what you hear in that case is the difference between the two signals. If the two pickups somehow had identical signals, wiring them out of phase would give no output.
You could verify correctly phasing two OTs with both primaries and secondaries in phase by feeding the combo a very low level AC test signal, like from a signal generator (with no power amp). The source should not have enough power capability to burn up a transformer. One way of connecting the secondaries together should give an AC voltage while the wrong phase should give close to zero volts.
Connecting the secondaries of two OTs together in parallel might be ok, but if you got them out of phase you would be in a heap of trouble. Each secondary winding would be looking to be loaded down by a speaker. Instead each secondary would see the other one as an active current sucking negative impedance. If the two were perfectly out of phase, there would be no output to the speaker, but huge currents would be rushing between the two secondaries. This would cause the load seen by the power tubes to go very low, probably overheating the tubes and/or OT primaries.
We guitar tinkerers know how to hook two pickups up out of phase and get an odd thin sound, what you hear in that case is the difference between the two signals. If the two pickups somehow had identical signals, wiring them out of phase would give no output.
You could verify correctly phasing two OTs with both primaries and secondaries in phase by feeding the combo a very low level AC test signal, like from a signal generator (with no power amp). The source should not have enough power capability to burn up a transformer. One way of connecting the secondaries together should give an AC voltage while the wrong phase should give close to zero volts.
Another article I found somewhere, with a slightly different dual SE topology.
You should define which PP/CT connect as double the OTs must have a "core cap" (SE OT) to prevent core saturation. Also which normal PP OT function when connect as double.
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