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In Reply to: RE: Best type of amp for low impedance/high sensitivity headphones? posted by nyrocker on March 04, 2014 at 06:43:21
Wow, I couldn't agree less with that suggestion!
Padding down the input does not change the sound character whatsoever. In fact, if one implemented a stepped attenuator, this could simply be done in the design of the control itself.
If you start putting series resistors at the output, you change the output impedance of the headphone amp, which changes the damping and distortion performance. You will absolutely hear this, it's not hard to measure, and it's very tedious to implement this and get it right. What's worse is that when you plug in a different set of headphones, you'll have to start all over. Frankly, this can make a Frankenstein mess with low resale value.
I've linked a page below that runs down how to adjust the range of a level control.
Also, if you have a transformer coupled headphone amp, you will generally have different impedance taps, and using the lowest impedance tap will reduce the sensitivity of the amplifier.
Follow Ups:
Thanks for the link. I've tried Rothwell 20db RCA attenuators, using them at the input. Is what you're suggesting a lot different from these?
http://www.rothwellaudioproducts.co.uk/html/attenuators.html
I would say that they helped a fair amount with the volume knob but also affected the sound. In an A/B comparison I preferred not using them. I'll read through your suggestion. But is there a different amp alternative that would avoid this modification?
That is the general idea, but you would get ideal performance by knowing the impedance that you're starting with (of the existing level control), then selecting your pair of resistors appropriately.
In order for an in-line RCA attenuator to work reliably, the resistors used will generally be lower values so that the following control impedance is less of a variable. This can result in some degradation (IMO).
If I had to guess, this pad would present an 11K load to your source, as opposed to your level control, which would likely be 47K-250K. (The manufacturer doesn't explicitly state impedance, but they do mention compatibility)
If you're getting an amp custom-made, just asked for a stepped attenuator whose range is 20dB below normal. If you already have an amp, you could just build such an attenuator and replace the existing level controls.
Thanks again CB! (I'd love to know the story on your handle :)
I will discuss this with Goldpoint and see what works best.
Best of luck on your search! Sometimes it's tough to avoid the audio hypochondria.
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