Reviving the SEX

[Maxwell_E]

I recently purchased a nice used pair of HD600's and realized it's been too damn long since my SEX was a part of my main system. I have the old 1.0 with C4S so the headphone jack doesn't short. As of now, I just unhook the hot lead to my speakers (banana plugs) when I wanna listen to my headphones, but I'm getting tired of that and have an irrational fear of wearing out the connector. I realized I could either A) put a DPST or DPDT mini toggle in the line between the jack and the binding posts to switch the speakers or, B) clip the 120 ohm resistors and rewire the jack so that it functions just as it's supposed to and cut signal when a plug is inserted. Or I could C) just deal with unplugging the speakers once in a while and keep a mechanical contact out of the circuit. Thoughts anyone?

Sub-question. How critical are these resistors wired to the jack? I remember in the manual it said something about a certain industry listening standard, but I don't see these in the SEX 2.1 page.

Edit: I accidentally a word

 

[Paul Joppa]

The 120 ohm resistance is an old standard, still (I believe) active as an IEC standard - but badly obsoleted pretty much ever since the Walkman, and certainly now in the days of the iPod. The resistor does two things:

1) it equalizes the power into phones of widely varying impedance. Modern low impedance, high sensitivity phones designed to work on less than a volt have a low impedance, and draw excessive power without the resistor. This causes the noise floor to be audible and requires the gain control to be turned way down, which traditional studio phones with high impedance need the level control turned way up.

2) it decreases the damping factor for low impedance phones. Low impedance phones that are designed for low-voltage sources (iPods etc) are often intolerant of this, resulting in a bloated an unnatural bass response. Presumably there are some low-impedance phones that are well damped internally and do not need a high damping factor, but it's certainly not all of them.

The resistor disappeared with the new version because we could no longer get a headphone jack from any source that would allow its use and still disconnect the speakers.

I am not at all happy with the situation, but there's not much I can do, either.

 

[Maxwell_E]

Ok, so knowing that the 120 ohm resistor needs to stay, would you suggest a mini toggle to switch the speakers or just pulling the plug each time?

 

[Paul Joppa]

At this point I have no universal remedy good for all headphones. Therefor, it depends on the impedance and sensitivity of your headphones, and possibly on whether they are among the ones that are not happy with the 120 ohm resistance.

 

[Maxwell_E]

My headphones now are Sennheiser HD600's and HD280's. I'll be using the SEX with just the 600's or the speakers. At 300 ohms I'm understanding that the benefits of the 120 ohm resistors are lost on these high-impedance phones. I have no plans of getting any new headphones after looking at my bank statement.

 

[Paul Joppa]

My headphones now are Sennheiser HD600's and HD280's. I'll be using the SEX with just the 600's or the speakers. At 300 ohms I'm understanding that the benefits of the 120 ohm resistors are lost on these high-impedance phones. I have no plans of getting any new headphones after looking at my bank statement.

OK, then just get rid of the 120 ohm resistor and wire the jack so it cuts out the speakers. I don't recall what exactly was the original jack, but if it's not suitable just get the new one or anyghing similar and wire it like the current version 2.1 amp.

I'm not up to speed but probably someone here has a recommendation for a good switching jack, if you want to get fancy.

 

[Paul Birkeland]

I'm not up to speed but probably someone here has a recommendation for a good switching jack, if you want to get fancy.

I think we use the best one