EL34 Push Pull weirdness - Page 4

Sch3mat1c · 11th December 2004, 06:23 AM

Y'mean a zobel? For HF crud? Depends on where it is. I'd make it around a quarter of the output stage power if you have it on the OPT. More if you want to be testing HF response at any reasonable power level for any length of time!

Fragman, the problem with chasing down motorboating is, because it's inside a loop, every point in the chain (including the effect it has on the PSU, which IMHO is the cause, phase shift oscillator style as I mentioned previously) shows the signal.

Tim

waner · 11th December 2004, 08:38 AM

Hello

What is a zobel (I`m not that good on english)?

The wattage for the anti ringing resistor is 1W

Mattias

Sch3mat1c · 11th December 2004, 07:17 PM

A zobel network is a resistor in series with a capacitor. Its function is to dampen with the resistor when the frequency is above what the capacitor allows. At low frequencies, the reactance of the capacitor is large and the resistor has no effect. At middle frequencies, the resistance and reactance are about equal to the impedance of the circuit and it begins to damp the system, without causing undue phase shift as a plain capacitor would. At high freuquencies the reactance is small and disappears, applying the resistor directly to the circuit, damping it fully.

Tim

11th December 2004, 06:23 AM	#31
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Y'mean a zobel? For HF crud? Depends on where it is. I'd make it around a quarter of the output stage power if you have it on the OPT. More if you want to be testing HF response at any reasonable power level for any length of time! Fragman, the problem with chasing down motorboating is, because it's inside a loop, every point in the chain (including the effect it has on the PSU, which IMHO is the cause, phase shift oscillator style as I mentioned previously) shows the signal. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

11th December 2004, 07:17 PM	#33
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	A zobel network is a resistor in series with a capacitor. Its function is to dampen with the resistor when the frequency is above what the capacitor allows. At low frequencies, the reactance of the capacitor is large and the resistor has no effect. At middle frequencies, the resistance and reactance are about equal to the impedance of the circuit and it begins to damp the system, without causing undue phase shift as a plain capacitor would. At high freuquencies the reactance is small and disappears, applying the resistor directly to the circuit, damping it fully. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

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11th December 2004, 08:38 AM	#32
waner diyAudio Member Join Date: Dec 2004 Location: gothenburg	Hello What is a zobel (I`m not that good on english)? The wattage for the anti ringing resistor is 1W Mattias

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