Aikido circuit question

jayme · 14th September 2007, 09:02 PM

Don't the 1M safety resistors on the output stage form a voltage divider, and inject half of the B+ noise into the output coupling capacitor?

DougL · 14th September 2007, 09:22 PM

It would if you pull the first tube.

Otherwise the Rp of the lower triode + Cathode Resistor of the lower triode will "swamp" the 1 Meg Resistor.

Think Zout vs. 1 meg voltage divider.

Doug

I was looking at the other tube. Same principal applies to the output.

zigzagflux · 14th September 2007, 09:22 PM

I would say yes and no.

The noise is injected into the output, at 1/2 the magnitude of ripple, and at a 500K source impedance.

The musical content, however, is also injected into the output, at a much higher signal level, and a much lower source impedance.

The end result is that at the source impedances involved, the injected noise is benign to nonexistent.

jayme · 14th September 2007, 09:31 PM

So...given a "noisy" CLCLC PSU with some B+ fluctuation due to poor wall power, the likelihood that the Low Frequency B+ noise is being injected into the outputs at this point is very low, correct?

14th September 2007, 09:02 PM	#1
jayme diyAudio Member Join Date: Sep 2005	Aikido circuit question Don't the 1M safety resistors on the output stage form a voltage divider, and inject half of the B+ noise into the output coupling capacitor?

14th September 2007, 09:22 PM	#2
DougL diyAudio Member Join Date: Feb 2004 Location: Wheaton IL. Blog Entries: 25	It would if you pull the first tube. Otherwise the Rp of the lower triode + Cathode Resistor of the lower triode will "swamp" the 1 Meg Resistor. Think Zout vs. 1 meg voltage divider. Doug I was looking at the other tube. Same principal applies to the output. __________________ Scienta sine ars nihil est - Science without Art is nothing. (Implies the converse as well) Mater tua criceta fuit, et pater tuo redoluit bacarum sambucus

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14th September 2007, 09:22 PM	#3
zigzagflux diyAudio Member Join Date: Oct 2006	I would say yes and no. The noise is injected into the output, at 1/2 the magnitude of ripple, and at a 500K source impedance. The musical content, however, is also injected into the output, at a much higher signal level, and a much lower source impedance. The end result is that at the source impedances involved, the injected noise is benign to nonexistent.

14th September 2007, 09:31 PM	#4
jayme diyAudio Member Join Date: Sep 2005	So...given a "noisy" CLCLC PSU with some B+ fluctuation due to poor wall power, the likelihood that the Low Frequency B+ noise is being injected into the outputs at this point is very low, correct?

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