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In Reply to: RE: UTC output transformers LS-63 posted by Tre' on April 15, 2015 at 14:09:39
when the large signal (power response)is -3db the phase angle of the composite load impedance will be 45 degrees.
But keep in mind that the -3db is at 20 hz, 10 hz or 6 hz. How much program material do you have that dip down that low?
What would be the distortion from your speakers at the stated half power at these low frequencies?
MSL
Builder of MagneQuest & Peerless transformers since 1989
Follow Ups:
"It does not matter if your speaker does not go down to 31.25 Hz or not. If you are sending low frequency information to the amplifier, the amplifier will make the plate voltage move. If the plate voltage moves, the tube must spend bias current to charge and discharge the primary inductance as well as the actual primary load impedance. If the plate voltage or current "clips" because of low frequency plate excursions, [all] the sound will suffer."
I already bi-amp at 200Hz. My mid speaker doesn't play very well below 200Hz. After reading VS's article I placed a cap (a high pass filter) in series with the input to the SET amp. The sound, all the sound, got much better.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
you were saying your prefer solid state amps for low end duties...
but what strikes me is that many solid state amps have the functional characteristic of delivering less power as the secondary's load impedance increases...
how many times do you see Sand State M10,000 delivers X number of watts into four ohms but only half of X into eight ohms...
just goes to show that after a 100 years of tubes and sixty plus years of sand... we've still not achieved technical nirvana.
But things can sound damn, damn good and I still enjoy listening to music.
MSL
Builder of MagneQuest & Peerless transformers since 1989
"how many times do you see Sand State M10,000 delivers X number of watts into four ohms but only half of X into eight ohms..."
Mikey, that's just Ohm's Law. A solid state amp is a voltage source, and it's maximum output swing is strictly limited by the power supply. Apply an identical voltage to two resistors, and the larger value resistor draws less current. Less current - for the same voltage - dissipates less power in the load.
--------------------------
Buy Chinese. Bury freedom.
with its multi-tap secondary applies more voltage to the larger load...:)
The other side of that SS example is that when the load is halved power doubles( assuming its PS can deliver the current ). So, n Kw into 8R leaves you with 2n into 4R, and 4n into 2r...and of course n/2 into 2R.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
".......I still enjoy listening to music."
So do I.
From the old TV commercial, "Nothing's perfect Ma'am"
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Tre.
I largely agree with you as regards taking steps to exclude frequencies that an amp is not designed nor capable of handling well.
I remember back in the eighties Frank Van Alstine designed such an input for his ST-70 mods... to my ears the amp sounded better with the filter than without. But that may not have been due to power handling issues either alone or in concert with other performance issues...
I just read about a week ago... his newly produced ST-70 offerings still use an input filter... and if I recall correctly the -3db points are 5 hz and 50khz.
But in terms of low freq cutoff point for the large signal model... the -3db frequencies demonstrated are pretty darn low...
again... what source material is going to have recorded data at these frequencies?
Seems like we are chasing ghosts a bit here...
MSL
Builder of MagneQuest & Peerless transformers since 1989
"Seems like we are chasing ghosts a bit here..."That could be but limiting the LF of my SET made a huge subjective improvement.
I think VS answers why in the section of his article "How does the low frequency load line affect the high frequencies?"
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 04/15/15
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