I built a 6 in, 4 out speaker switch for my amps. Uses nixies to tell you how it's set, too. The power button is now red instead of blue, and the FUF relays were replaced with Phoenix Contact. I had one amp that would oscillate at 860kHz with no speaker connected, but strapping 100R/5W across the speaker outputs sorted that. Yes, the interleaved PTs as OPT can pass 860kHz.
True (probably); but you can put speakers in series and short-out the one(s) you do not want to hear. The momentary double-impedance "should not" be a strain. For just two speakers in a harsh environment (music stage), toggle switches can found that are a lot more robust than affordable rotaries and slides.
Here's an example of reverse diode protection from plates to ground.
https://el34world.com/charts/Schematics/files/Marshall/Marshall_2001_375w.pdf
Should go well with kodabmx 2KW relay box.
https://el34world.com/charts/Schematics/files/Marshall/Marshall_2001_375w.pdf
Should go well with kodabmx 2KW relay box.
Not a bad idea if you aren't using sweep tubes that can handle the back EMF without arcing...
I wouldn't use 1N4007x2 though. I'd probably use a diode for a microwave oven.
I wouldn't use 1N4007x2 though. I'd probably use a diode for a microwave oven.
Its not the tubes but the transformers. And not the first time you go WANG! into no load, but a gradual breakdown of insulation with repeated abuse.
Running your tube amplifier at low amplitudes without load is not usually problematic, but if cranked beyond clipping where the output stage can cut-off, then that stored magnetic field needs to go somewhere and it will find the weakest breakdown spot. I've seen this happening as sparking between the tube pins, where the OPT had obviously a sufficient amount of insulation to withstand this test.
With a tube OPT the highest voltages are between separate layers. Not so using those power toroids. I would take extra precautions about overvoltage due to flyback pulses.
If I run one of my 6550 monoblocks with no load I can hear it pretty good too. I can hear it just as well if not better running fully loaded (into a dummy load). That one has the protection diodes which have been fully tested. And ive heard noise (music) coming from the dummy load itself.
If I run one of my 6550 monoblocks with no load I can hear it pretty good too. I can hear it just as well if not better running fully loaded (into a dummy load). That one has the protection diodes which have been fully tested. And ive heard noise (music) coming from the dummy load itself.
Excellent it is just a small arc in the OPT producing the sound.
The protection diodes keep the plate voltage between 0V and 2*HT. With no load if a tube conducts heavily then as the plate voltage goes to zero there is nowhere for the current now in the primary to go and so the voltage keeps on going below zero. Therefore on the other plate above 2*HT until something gives. With the diodes in the voltage cannot go below zero so there is now a path for the current in the transformer to collapse.
The protection diodes keep the plate voltage between 0V and 2*HT. With no load if a tube conducts heavily then as the plate voltage goes to zero there is nowhere for the current now in the primary to go and so the voltage keeps on going below zero. Therefore on the other plate above 2*HT until something gives. With the diodes in the voltage cannot go below zero so there is now a path for the current in the transformer to collapse.
That's a thing, and very real for LARGE utility transformers. But I think what we hear in our little irons is more the electrostatic forces between windings. The wires move slightly, even if shellacked. (BTW: "Magnetostriction" is the preferred spelling. And no, a browser spell-chucker still does not know the word.) There is also electrostriction straining the dielectric.
Ya that's the word LOL
From Wiki:
From Wiki:
Transformers
In transformers magnetic noise and vibrations are generated by several phenomena depending on the load case which include Lorentz force on the windings,[12] Maxwell forces in the joints of the laminations, and magnetostriction inside the laminated core.I installed 10w/100 ohm resistors on the 4ohm outputs......I believe I DO NOT need to install same on the 8ohm outputs??? Please advise....
