Ham Sandwich
Headphoneus Supremus
- Joined
- May 22, 2006
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The 1/8 rule seems to be more of a design exercise on paper to figure out a good ratio that covers a wide variety of situations, including low ohm headphones. In practical use with highish ohm headphones the ratio can be less, with ratios of 1/2 or so being a starting point.
Some modern headphone amps have a high output impedance. Especially OTL (Output TransformerLess) tube amps. Here's an example of one that has an output impedance of 120 ohms, Bottlehead Crack. They recommend headphones with an impedance of 200 ohms or more be used with it. So that's around the 1/2 ratio mark.
With your NAD I'd think a 250 ohm Beyer or possibly a 600 ohm Beyer would work fine. Or a 300 ohm Sennheiser (like the HD600 or HD650) would work fine. There's other highish ohm headphones out there as well.
If I was looking for a dedicated headphone amp that would be compatible with a wide variety of headphones I'd want an amp with a very low output impedance. I don't know why Beyer went with 100 ohms for their amp. They do make 600 ohm headphones so maybe that's part of the reason. It does limit the suitability of the amp if you happen to have any low impedance headphones in your collection.
Some modern headphone amps have a high output impedance. Especially OTL (Output TransformerLess) tube amps. Here's an example of one that has an output impedance of 120 ohms, Bottlehead Crack. They recommend headphones with an impedance of 200 ohms or more be used with it. So that's around the 1/2 ratio mark.
With your NAD I'd think a 250 ohm Beyer or possibly a 600 ohm Beyer would work fine. Or a 300 ohm Sennheiser (like the HD600 or HD650) would work fine. There's other highish ohm headphones out there as well.
If I was looking for a dedicated headphone amp that would be compatible with a wide variety of headphones I'd want an amp with a very low output impedance. I don't know why Beyer went with 100 ohms for their amp. They do make 600 ohm headphones so maybe that's part of the reason. It does limit the suitability of the amp if you happen to have any low impedance headphones in your collection.