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Impedance matching in amps and cans

post #1 of 5
1/30/09 at 8:36pm
Thread Starter 
Being new to the website and I am already contemplating a headphone amp! I purchased a pair of 701's and they sound very good new, if it's true they sound better with a long break-in, I can't wait to hear how much better they will sound. I am used to listening to a product before making a purchase. How much should I worry about the high out impedance of the ASL in OTL mode (one of the reasons to buy this amp) with the AKG 701? The difference is not small but almost 10x the impedance of the 701's (62 vs 600). I am not usually a numbers guy, but will there be enough oomph in OTL mode? I am not locked into an OTL amp but I do want tubes. Other choices were Cayin (any noise issues), Woo WA6 or 6SE, and a used SP mpx3. Any other amps please free to mention. Thanks.
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post #2 of 5
2/3/09 at 10:52am
Thread Starter 
Thread closed for lack of response or interest.
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post #3 of 5
2/3/09 at 11:54am
You should try posting in the amps forum.
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post #4 of 5
2/3/09 at 2:21pm
Quote:
Originally Posted by drjjpdc View Post
Being new to the website and I am already contemplating a headphone amp! I purchased a pair of 701's and they sound very good new, if it's true they sound better with a long break-in, I can't wait to hear how much better they will sound. I am used to listening to a product before making a purchase. How much should I worry about the high out impedance of the ASL in OTL mode (one of the reasons to buy this amp) with the AKG 701? The difference is not small but almost 10x the impedance of the 701's (62 vs 600). I am not usually a numbers guy, but will there be enough oomph in OTL mode? I am not locked into an OTL amp but I do want tubes. Other choices were Cayin (any noise issues), Woo WA6 or 6SE, and a used SP mpx3. Any other amps please free to mention. Thanks.
600 ohm output impedance to 62 ohm load impedance is a massive mismatch. Not only are just 10% of the amp's theoretical power usable, the high serial impedance also generates a frequency-response distortion in the shape of the headphone's impedance curve.

I agree that the K 701 sounds nice with tubes, but my then EMP had troubles with heavy low-bass attacks. (Note that the K 701, although low impedance, has a rather low sensitivity.) I've been told by a friend that the Earmax Silver Edition is an ideal match, but that's another price level. I guess a transformer-based tube amp (isn't the MG Head switchable?) is the way to go for you -- or a hybrid or a solid-state amp (such as the Corda Symphony).
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post #5 of 5
2/3/09 at 7:05pm
Thread Starter 
Thank you JaZZ. That's exactly the kind of advice I was looking for.
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