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Post by Ithilstone on Nov 13, 2015 12:02:12 GMT
Hi there,
Can somebody here can help me? And explain in plane English how to measure headphone cable capacitance??? or maybe someone here already know what is capacitance of HE-6s standard cable ( new ver. balck )
Cheers
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solderdude
Administrator
measureutternutter
Posts: 4,882
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Post by solderdude on Nov 13, 2015 16:54:56 GMT
The cable capacitance is of no issue with the HE-6
The 50 Ohm impedance load of the headphone is a 'heavier' load on the output stage and resonances caused by total inductance of the headphone circuit and the cable capacitance will be damped sufficiently by the lopw (highly resistive) load the HE6 provides.
With high impedance headphones (say 250 Ohm and higher) cable capacitance could possibly 'upset' the feedback loop of certain not well designed amplifiers. Usually amplifiers should not even have problems with 1nF loads.
You need either a capacitance meter (and measure an open cable between the wires) or you can use a high resistor value (say 10k Ohm) and measure the -3dB roll-off point using a scope and tone generator. Possibly you may even need 100k Ohm for this.
Even when the cable capacitance is 1nF and the output R of the amplifier = 120 Ohm the -3dB point of that RC flter is >1MHz This means nop influence (<0.1dB and 1 degree phase shift) below 100kHz.
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Post by Ithilstone on Nov 14, 2015 11:27:10 GMT
Hi solderdude, Thanx for info but capacitance of that cable is important to me and it is because my amp is only conditionally stable and if I want to connect them to speaker taps I need to be sure that cable is below 200 pf/m other wise I will risk sending my amp into oscillation - and it is not a poor design - it is purposefully build like that. "You need either a capacitance meter (and measure an open cable between the wires) or you can use a high resistor value (say 10k Ohm) and measure the -3dB roll-off point using a scope and tone generator. Possibly you may even need 100k Ohm for this." So I could buy this goo.gl/XMDvMy - but what do you mean by "and measure an open cable between the wires" - would that be wrong to just connect both ends of the cable to meter ?
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solderdude
Administrator
measureutternutter
Posts: 4,882
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Post by solderdude on Nov 14, 2015 13:51:57 GMT
Yep that's a meter that'll do it.
You will have to disconnect the cable from the meter and then measure it. Measure between S and T and R and T as well as from R to T connections.
Still, if you want to connect it to a speaker amp then simply use a 10 Ohm resistor in series with the output. In this case the cable capacitance is of no concern any more. Even with 100nF cable capacitance the 10 Ohm resistor will turn the load in a boucherot filter. As the HE6 is purely resistive as a load the output impedance is of no relevance. Als damping factor isn't affected as the load the 'membrane sees' goes from 50 Ohm to 60 Ohm.
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Post by Ithilstone on Nov 14, 2015 22:18:17 GMT
That's great - and thank you very much for all the information.
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