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Old 13th November 2014, 04:06 PM   #1
cspirou is offline cspirou  France
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Default Differences in headphones and speaker amps

Are there differences in the way speaker amps and headphones amps are designed besides intended power output?

In other words if I connected my headphones to the speaker terminals, is there any particular reason why this would sound bad or would be bad for the amp?
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Old 13th November 2014, 04:16 PM   #2
Mooly is offline Mooly  United Kingdom
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You would probably find a typical power amp connected directly to headphones would produce a lot of audible noise (hiss/hum). One reason for this is that a power amp might have a voltage gain of 20 to 40 or more, a headphone amp is usually little more than a line level buffer stage with at most a gain of say five, often less.
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Old 13th November 2014, 04:18 PM   #3
rayma is offline rayma  United States
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Originally Posted by cspirou View Post
Are there differences in the way speaker amps and headphones amps are designed besides intended power output?
In other words if I connected my headphones to the speaker terminals, is there any particular reason why this would sound bad or would be bad for the amp?
Should work fine, but there could be more noise or hum audible from the speaker amplifier. You could try a series resistor in each channel around 100 Ohms,
check the manufacturer's literature.
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Old 13th November 2014, 04:29 PM   #4
00940 is offline 00940  Belgium
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This works even better than a simple resistor in serie.
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Old 13th November 2014, 04:35 PM   #5
rayma is offline rayma  United States
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This works even better than a simple resistor in serie.
Yes, this has a good damping factor for the phones drivers.
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Old 13th November 2014, 04:46 PM   #6
cspirou is offline cspirou  France
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Originally Posted by Mooly View Post
You would probably find a typical power amp connected directly to headphones would produce a lot of audible noise (hiss/hum). One reason for this is that a power amp might have a voltage gain of 20 to 40 or more, a headphone amp is usually little more than a line level buffer stage with at most a gain of say five, often less.
Would this mean that low powered tube amps would be viable for headphone use? Or even low powered SS amps like the First Watt amps by Nelson Pass?
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Old 13th November 2014, 04:55 PM   #7
rayma is offline rayma  United States
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Originally Posted by cspirou View Post
Would this mean that low powered tube amps would be viable for headphone use? Or even low powered SS amps like the First Watt amps by Nelson Pass?
Yes, the Pass amps would be good, especially ones with low gain. You may have some hum from some tube amps with phones.
Some amplifiers, both tube and ss, will require 4 wire balanced conections to phones, with no common ground.
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Old 13th November 2014, 06:11 PM   #8
cspirou is offline cspirou  France
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Originally Posted by rayma View Post
Should work fine, but there could be more noise or hum audible from the speaker amplifier. You could try a series resistor in each channel around 100 Ohms,
check the manufacturer's literature.
Wouldn't that increase the output impedance to 200 ohms and cause a lot of distortion?
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Old 13th November 2014, 06:35 PM   #9
rayma is offline rayma  United States
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Originally Posted by cspirou View Post
Wouldn't that increase the output impedance to 200 ohms and cause a lot of distortion?
I'd go without series resistors, but it's pretty common to use them.
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Old 13th November 2014, 06:42 PM   #10
Mooly is offline Mooly  United Kingdom
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Originally Posted by cspirou View Post
Would this mean that low powered tube amps would be viable for headphone use? Or even low powered SS amps like the First Watt amps by Nelson Pass?
Hmmm... if the basic noise/hum level was low then a possibly yes.

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Originally Posted by rayma View Post
Yes, the Pass amps would be good, especially ones with low gain. You may have some hum from some tube amps with phones.
Some amplifiers, both tube and ss, will require 4 wire balanced conections to phones, with no common ground.
This is exactly how I see it too. Low gain is key and the hum... well if you can detect any hum/hiss/noise with your ear up to the speaker then imagine how that will be with headphones directly coupled to the amp output.

All things are possible... it just might not be as straightforward as you think.
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