OPA637AP in Rotel RCD-02

ckng · 10th December 2006, 04:25 AM

Hi,

Has anyone tried replacing the Op-Amps in the Rotel RCD-02 with OPA637AP? I tried using 4 of them on browndog adaptors on my RCD-02 and I get quite a bit of static noise on the output. Are they oscillating or something?

I also tried the new National Semiconductor LM4562 and they worked fine, without the noise. The OPA637APs worked well on my DIY headphone amp so they are working fine.

Did a search here and on Google and cannot find anything specific to OPA637 and RCD-02, so any help would be appreciated. Thanks!

Regards
CK

analog_sa · 10th December 2006, 10:45 AM

What is the gain?

poynton · 10th December 2006, 11:35 AM

Quote:

Originally posted by ckng
Hi,

Has anyone tried replacing the Op-Amps in the Rotel RCD-02 with OPA637AP? I tried using 4 of them on browndog adaptors on my RCD-02 and I get quite a bit of static noise on the output. Are they oscillating or something?

I also tried the new National Semiconductor LM4562 and they worked fine, without the noise. The OPA637APs worked well on my DIY headphone amp so they are working fine.

Did a search here and on Google and cannot find anything specific to OPA637 and RCD-02, so any help would be appreciated. Thanks!

Regards
CK

OPA637AP are not unity gain stable and must operate in conditions where the gain is greater than 5.

It is likely that they are oscillating.

Use the LM4562s. They are by far superior to either the OPA627 or OPA637.

Andy

tubenut · 10th December 2006, 02:45 PM

Op amp rolling in a headphone amp the other day discoverd that the OPA604 I was using has 2 offset adjust pins, in the design i plugged em in to one of these normally not connected pins ended up strapped to -Vs... Funny stuff happened. Can not remenmer but does 627/637 not have the same offset adjustment?

JM2C

G

KHashmi316 · 11th December 2006, 03:39 AM

Quote:

Originally posted by poynton

OPA637AP are not unity gain stable and must operate in conditions where the gain is greater than 5.

It is likely that they are oscillating.

Use the LM4562s. They are by far superior to either the OPA627 or OPA637.

I recently Brown Dog'd a pair of 637s, replacing the stock 4558s in my Toshiba SD-3990. Not getting static noise" ckng noted and, overall, the sound quality has improved. But I did lose some "focus" and imaging. See this headwize thread for more info:

http://headwize.com/ubb/showpage.php...d=1197&fpage=2

Ruach · 11th December 2006, 04:09 AM

I think that your 637s are oscillating.

You should use 627 instead

ckng · 11th December 2006, 03:12 PM

Thanks guys. I'll just run the LM4562s in it for some time and see how it goes over time.

Regards
CK

10th December 2006, 04:25 AM	#1
ckng diyAudio Member Join Date: Jan 2006 Location: Singapore	OPA637AP in Rotel RCD-02 Hi, Has anyone tried replacing the Op-Amps in the Rotel RCD-02 with OPA637AP? I tried using 4 of them on browndog adaptors on my RCD-02 and I get quite a bit of static noise on the output. Are they oscillating or something? I also tried the new National Semiconductor LM4562 and they worked fine, without the noise. The OPA637APs worked well on my DIY headphone amp so they are working fine. Did a search here and on Google and cannot find anything specific to OPA637 and RCD-02, so any help would be appreciated. Thanks! Regards CK

10th December 2006, 02:45 PM	#4
tubenut diyAudio Member Join Date: Nov 2002 Location: South Africa, Jhb	Op amp rolling in a headphone amp the other day discoverd that the OPA604 I was using has 2 offset adjust pins, in the design i plugged em in to one of these normally not connected pins ended up strapped to -Vs... Funny stuff happened. Can not remenmer but does 627/637 not have the same offset adjustment? JM2C G __________________ Guillaume Croak Audio Exploration

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10th December 2006, 10:45 AM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	What is the gain?

11th December 2006, 04:09 AM	#6
Ruach diyAudio Member Join Date: May 2003 Location: Singapore	I think that your 637s are oscillating. You should use 627 instead

11th December 2006, 03:12 PM	#7
ckng diyAudio Member Join Date: Jan 2006 Location: Singapore	Thanks guys. I'll just run the LM4562s in it for some time and see how it goes over time. Regards CK

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