If I wanted to add a 120ohm output jack to my PPA...

[HiGHFLYiN9]

Is this what it would look like?

Thanks!

 

[amb]

Yep, but use 120 ohms resistors instead of 120K ohms.

The question is, why would you want such a thing? Those resistors are typically used to prevent lo-Z cans from loading the output of opamps (or other low-current output stages) excessively. The PPA has an output buffer and will happily drive a lo-Z can directly without them. The resistors would only introduce voltage loss, decrease damping factor and cause frequency response aberrations (due to non-linear impedance of the headphones themselves).

 

[HiGHFLYiN9]

Thanks AMB, i thought it might be nice to have a second output for different impedance cans (kinda like Dodd Audio has three different outputs) but I guess this aproach wouldn't work eh. Any other suggestions?

 

[MisterX]

It's not that it won't work it is just that there are a few downsides to adding the resistors

Try some ultra low Z cans with your amp and see if you have any need for that type of a solution.

 

[HiGHFLYiN9]

Yeah the low-Z cans work just fine, it's just that the stepped attenuator spends most of the time in the 9 o'clock position when I'd prefer it in the 12 for more control. It's not something I'd have to do I was just thinking about a possible solution for more pot play with low Z cans w/o switching the gain as it's right where I want it for higher impedance cans.

 

[Sovkiller]

Quote:

Originally Posted by highflyin9 Yeah the low-Z cans work just fine, it's just that the stepped attenuator spends most of the time in the 9 o'clock position when I'd prefer it in the 12 for more control. It's not something I'd have to do I was just thinking about a possible solution for more pot play with low Z cans w/o switching the gain as it's right where I want it for higher impedance cans.

Why not lowering the gain of the amp...

 

[Sycraft]

Well I would most recommend to just not worry about it. I mean unless your high impedance headphones are maxing the volume control (which on a PPA means you either set your gain too low or your source sucks) what's the worry? Just turn it down for lower impedance jobs. It's no different than lower/higher level sources. For normal sources, I set my mixer to -30dB, for DVD-A sources with good dynamic range, I set it to 0dB.

If you really must have variance, varying the gain is probably the way to go. You can get switches that deal with 3 independant circuts at a number of different positions. Then install different resistors to change the gain. Or just use varsistors if you want and do it like a mixer.

 

[HiGHFLYiN9]

Thanks for all the info, I probably won't worry about it, just a curiousity I wanted to run by a few people

 

[setmenu]

Some headphones can benefit from a bit of added source impedance,
the Beyer DT931 is often preferred with around this value to tame a
sometimes rather bright presentation.
Another example is the ETY ER4p, this phone with an added 75 Ohm source
resistor becomes the 'S' .
Perhaps if space allows, it would be a good idea to try a dual pot or
switched attenuator instead of a single value resistor.


Setmenu