Classic card is going to be the latest stock card for HM901. Basically it is the original stock card (or the 2nd stock, before they switch to power card) found on HM801, they tweak it a bit for the HM901.
HM-901
Classic card is going to be the latest stock card for HM901. Basically it is the original stock card (or the 2nd stock, before they switch to power card) found on HM801, they tweak it a bit for the HM901.
LarsHP
Headphoneus Supremus
What's the output impedance of that amp card (for HM-901)?
For the stock AD8397 card, less than 1 ohm. Same for the Classic card and the balanced card. You don't need to worry about output impedance on the HM901 as Hifiman is keeping the output impedance very low this time.
LarsHP
Headphoneus Supremus
Nice. I just asked because you said the discrete amp / Classic amp card was basically the Standard amp from the HM-801 which had 18 Ohms output impedance.
Yes, the Classic card (which isn't fully discrete btw, but opamp + transistors buffer) is similar in topology to the old stock card on HM801. They just did it the way I have mod'ed my HM801 stock card by removing the 18 ohm resistors on the output.
Theodore
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Maybe mine since I ordered the Sony....but I doubt it
Excuse me,but which is this Sony?
Theodore
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Thank you very much.
jedie
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Mimouille
Headphoneus Supremus
Well as soon as Price Japan sends it...so early December...but if I receive it after the 12th I will be in France for a month so you will have impressions from others first...
chardy52
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Hello, Considering buying HM-901 but a bit confused about amp cards. Any help would be greatly appreciated. I primarily use Heir Audio 5.0 iems and Shure 535s. I'm basically looking for a recommendation on which amp card I should use. I have read there are volume issues with using the balanced card with iems. High impedance vs low impedance and how it relates to my iems is also confusing to me. Im just not sure what would be my best options for the HM-901. I'm currently using a Cowan J3 + Heir Audio Rendition amp. Looking for a more compact solution to great sound. Thank You so much for any advice you can give.
If you are limited to mostly IEM, there is an IEM card though.
LarsHP
Headphoneus Supremus
The output impedance is less than 1Ohm from both the Balanced and IEM amp cards (and maybe all the other HM-901 cards too). This means your headphones will sound as intended (no change in frequency response).
If you only plan using HM-901 with IEMs and don't want to get balanced cables for these, I would suggest getting the IEM amp card. If the Classic (the "new standard") amp card is available now - then this could also be one to consider. However, practically noone here has heard it (except user jamato8):
http://www.head-fi.org/t/656138/hifiman-hm-901-a-review-in-progress-factory-visit-pg-18-imgs-pg-19-fw-dsd-1-082/1575#post_9984465
http://www.head-fi.org/t/656138/hifiman-hm-901-a-review-in-progress-factory-visit-pg-18-imgs-pg-19-fw-dsd-1-082/1575#post_9986361
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