Harmon Kardon HD-970 modded, a world beater? - Page 13 - diyAudio
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Old 15th May 2010, 05:44 PM   #121
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Originally Posted by georgehifi View Post
Rafal hi, the only simple mod without going beserk like I did would be to change the SMD OP275 I/V opamps for something better, I would suggest SMD AD825's but these are singles and the OP275's are dual so you would have to find a 2 x single smd to single dual smd converter board, this would be the place to look.

Cimarron Technology, Inc.

Single-to-Dual Op-Amp Adapter - SO8 to SO8 version (p/n 031101A)

Cheers George
Thanks, did you heard how so-modified 970 is playing? How it will change sound characteristics of HD970 and is it worth to do this upgrade?
cheers
Rafal
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Old 15th May 2010, 09:30 PM   #122
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From my experience with these two opamps as output opamps the differences are that the OP275 are a bit slow and tubey sounding, where the AD825 has slam and is very fast and detailed yet still sweet, but in the I/V stage ???????
I/V opamps should have good settling times and be quick and the AD825 is better than the OP275 in this regard, as well as having a good sound.
Cheers George
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Old 16th May 2010, 09:29 AM   #123
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1. What changes beside the opamp change can have the greatest impact on sound quality HD970? Can you name/list them ?

2. What do you think about YouTube - Visual Sound: Myth Buster #2: Op Amps ?

cheers
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Old 16th May 2010, 12:00 PM   #124
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ad1955 evaluation board ad1955eb.pdf

Cheers George
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Old 16th May 2010, 05:48 PM   #125
Ola is offline Ola
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Old 16th May 2010, 08:06 PM   #126
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Talking more mods

Besides the op amps?......well from my experience, I would say put in a good clock ( Burson or LC Audio ) and also replace at least the op-amp supplies with newclassD regulators...they are superb.
good luck
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