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previous: steve I realize that purpose built headph... -- 2/14/2001 7:16 AM

Re: power amp as headphone amp

2/14/2001 4:53 PM
Doc	Re: power amp as headphone amp Headphones draw only milliwatts of power. Because of this, it is not necessary to match the optimum load impedance to the output stage. You can connect 600 ohm headphones directly to the 16ohm tap. You can parallel 4 sets of phones if you like. It's best to include a series resistor, usually from 100 up to 250 ohms, between the output transformer tap and each headphone signal lead (one resistor per channel) to limit the peak current into the headphone drivers. You can make up a small metal junction box with four paralleled open circuit stereo headphone jacks, a pair of series protection resistors, with a pair of lamp cord lengths exiting the box and terminating in forked lugs for attachment to the Left & Right speaker terminal screws on the Stereo 70. The EL34 output tubes will still operate, but at a much higher load impedance. Since you are not trying to extract any signifigant power, there is no stress on the tubes. It is not necessary to use resistor networks to fool the tube into actually seeing 16 ohm loads. A shunt loading resistor is not necessary. Doc

2/14/2001 4:53 PM

Doc

Re: power amp as headphone amp

Headphones draw only milliwatts of power. Because of this, it is not necessary to match the optimum load impedance to the output stage. You can connect 600 ohm headphones directly to the 16ohm tap. You can parallel 4 sets of phones if you like. It's best to include a series resistor, usually from 100 up to 250 ohms, between the output transformer tap and each headphone signal lead (one resistor per channel) to limit the peak current into the headphone drivers.

You can make up a small metal junction box with four paralleled open circuit stereo headphone jacks, a pair of series protection resistors, with a pair of lamp cord lengths exiting the box and terminating in forked lugs for attachment to the Left & Right speaker terminal screws on the Stereo 70.

The EL34 output tubes will still operate, but at a much higher load impedance. Since you are not trying to extract any signifigant power, there is no stress on the tubes. It is not necessary to use resistor networks to fool the tube into actually seeing 16 ohm loads. A shunt loading resistor is not necessary.

Doc

Replies:

K B Not to break-up the awesome tube id... -- 2/14/2001 9:16 PM