Harmon Kardon HD-970 modded, a world beater?

[niewiem]

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

 

[georgehifi]

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

 

[niewiem]

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

 

[georgehifi]

http://www.diyaudio.com/forums/digi...valuation-board-ad1955eb-pdf.html#post1297336

Cheers George

 

[Ola]

For I/V - LM 6172

 

[Chilli6565]

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

 

[CasperG]

help needed with HD970

I want to upgrade my HD970 by replacing the OP275's with AD825's. And since I live in Holland where Tentlabs also is based I plan to add a XO2.2 clock with XO power supply too.

Does anyone (George perhaps?) has a schematic how to add these correct in the HD970?

Thanks in advance, Casper

 

[CasperG]

extra info

I just found the oscillator in the schematics and added this as a jpeg.

I think I must remove the oscillator itself and L2, C53 and C55 when I add the Tentabs XO2.2 clock and connect the output to the Pin 5 location on the circuit board (and no other connections to the circuit board are made). The XO2.2 will then be fed by the XO power module. Am I correct?

Thanks, Casper

 

[Ola]

Use LM67xx series opamps, a lot better.