[Michael G.]

So.., I'm thinking about putting a 4 pin XLR on the Senn cable, and connecting directly to stereo amp speaker terminals using a K-1000 cable. Has anyone done this (successfully)?

 

[Hirsch]

Without some sort of attenuation, you're risking the headphone, as a power amp will fry it. You'd need some sort of attenutor after the power amp. A simple attenuator cable designed by Joe Grado ties the + lead of the headphone to a 2 ohm 10 watt resistor that goes to ground, and a 20 ohm 10 watt resistor that goes to the + signal out of the amp (the ground lead from the headphone goes straight to ground). If the amp accepts a dual banana plug, that provides enough support to hold the resistors in place (you need two of these cables, one for each channel). You can use a 1/4 inch jack at the headphone end of the attenuator cable (tying both attenuating cables together at the headphone jack) and would not have to modify the Sennheiser cable at all. I recently built one of these for a friend, and it works very nicely.

 

[Michael G.]

Quote:

Originally Posted by Hirsch Without some sort of attenuation, you're risking the headphone, as a power amp will fry it. You'd need some sort of attenutor after the power amp. A simple attenuator cable designed by Joe Grado ties the + lead of the headphone to a 2 ohm 10 watt resistor that goes to ground, and a 20 ohm 10 watt resistor that goes to the + signal out of the amp (the ground lead from the headphone goes straight to ground). If the amp accepts a dual banana plug, that provides enough support to hold the resistors in place (you need two of these cables, one for each channel). You can use a 1/4 inch jack at the headphone end of the attenuator cable (tying both attenuating cables together at the headphone jack) and would not have to modify the Sennheiser cable at all. I recently built one of these for a friend, and it works very nicely.

Thanks, Hirsch. That was sorta along the lines I was thinking...

 

[Canman]

Quote:

Originally Posted by Hirsch Without some sort of attenuation, you're risking the headphone, as a power amp will fry it. You'd need some sort of attenutor after the power amp. A simple attenuator cable designed by Joe Grado ties the + lead of the headphone to a 2 ohm 10 watt resistor that goes to ground, and a 20 ohm 10 watt resistor that goes to the + signal out of the amp (the ground lead from the headphone goes straight to ground). If the amp accepts a dual banana plug, that provides enough support to hold the resistors in place (you need two of these cables, one for each channel). You can use a 1/4 inch jack at the headphone end of the attenuator cable (tying both attenuating cables together at the headphone jack) and would not have to modify the Sennheiser cable at all. I recently built one of these for a friend, and it works very nicely.

I fried two different speaker amps while connecting an HD-600 with the Joe Grado amp cable. This may have something to do with different impedance since the cable was designed for 40 ohm phones (HP-1000).

 

[Hirsch]

Quote:

Originally Posted by Canman I fried two different speaker amps while connecting an HD-600 with the Joe Grado amp cable. This may have something to do with different impedance since the cable was designed for 40 ohm phones (HP-1000).

Ouch! I'm not sure what that would happen, though. The impedance seen by the amp is going to be slightly lower than the impedance of the two resistors, which are connected serially from + to ground. That's a maximum impedance of 22 ohms seen by the amp. Paralleling a 300 ohm headphone instead of a 40 ohm headphone with the 2 ohm resistor will result in reduced current to the headphone, but why would it blow an amp? I'm not sure why that would fry anything. Note that this is a polar cable. The 20 ohm resistor must be on the + side of the connection, or there won't be any resistor at all between the + output of the amp and the headphone, which could lead to something blowing somewhere. However, even if you blew the headphone and created a dead short, there would still be 20 ohms across the output of the amp, which should keep it from blowing. Wait a minute. If one side only was connected with reverse polarity, you'd have a straight line from the + signal on one side to ground (the grounds meet at the jack), which would almost guarantee blowing the amp, regardless of headphone impedance.

In any case, an Antique Sound Labs UHC Signature might be what's needed. It's an outboard transformer for connecting headphones to a power amp. Another possibility would be the AudioValve Impedanzer, but I don't know how well that would work with anything but the RKV.

 

[Michael G.]

Quote:

Originally Posted by Hirsch In any case, an Antique Sound Labs UHC Signature might be what's needed. It's an outboard transformer for connecting headphones to a power amp. Another possibility would be the AudioValve Impedanzer, but I don't know how well that would work with anything but the RKV.

Actually, I do own the UHC Signature device, and while I have found it to be pretty transparent passive interface, I am interested in comparing it to the hookup sceme now under discussion. Maybe after my new HD-600's arrive I'll make a comment on the results...