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Problem Rolling the OP AMPS in the RP533

Posted: Tue Apr 30, 2013 7:51 am
by kp4xb
Hello Voodoo audio brothers. Yesterday I rolled out the old OP AMPs on the RP533 and the RP562. I installed a AD823AN on them. The RP562 is ok but the RP533 is acting weird. Now the RP533 is without signal randomly. When that happens, I crank up and down the Output level on the RP533 and it fix the problem for minutes but suddenly stop again. When is without signal, there is a high pitch hum. That was for the first 15 minutes of trying. Then, from there I start to speak about a 15-30 minutes consecutively and the problem was less and less but is still there. What could cause this problem? Defective AD823AN? Do I have to perform the burning time of 50 hours to correct this problem?

Thanks for all the help you could bring.

KP4CA (ex KP4XB)

Posted: Thu May 02, 2013 12:59 am
by Voodoo Guru
Howdy Carlos,

Yea, it sounds like a bad op amp, which is rare. Put the original op amp back in, or if you have another AD823, swap it out. If the original op amps are destroyed or thrown away and you don't have any spares, take the ones out of the RP562 and swap them to see if the problem shifts over to the RP562.

The AD823 are usually pretty robust, but we have had one or two bad ones over the years. You do have to follow correct static preventative guidelines while handling them, and be sure you install them in the correct orientation, IE lining up the dots and also that the pins are seated correctly into the sockets, sometimes they can bend weird.

One other thing is you have to be careful where you buy them from. Counterfeit IC problems are getting more common these days, especially with high dollar audio IC's. Just beware of ebay and other places that offer the "too good to be true" deals and stick with the trusted major suppliers.

Good Luck,

Posted: Thu May 02, 2013 5:59 am
by kp4xb
Hi Guru:

I think that it is. Sadly I bought them from Ebay and I think that they are the counterfeit one because of the price. 10 for $17.50... I didn't know that detail when I bought them. Could you recommend me a good supplier here in the US? Been not the originals, I think that they are going to give me more problems in the near future...

Thanks, I really appreciate your help.


Posted: Thu May 02, 2013 6:24 am
by Voodoo Guru
Howdy Carlos,
Yea, the counterfeit issue is getting pretty rampant, especially from China.
We don't buy any component parts from China, especially IC's. You must be sure the supplier your getting from has a good reputation.

We've had excellent luck from either Digi-Key or Newark for small quantities. Have also had good luck with Verical for bulk orders, but only have made a few with them so far.

Take Care,

Posted: Thu May 02, 2013 8:15 pm
by kp4xb
Hello Guru:

Excellent. I placed an order with Newark just a couple of minutes ago. I'm convinced that I bought a counterfeit OP AMP from China on Ebay and that cause my problem. Next week is going to be here the new ones. Thanks for the recommendation.

73 from



Posted: Sat May 04, 2013 10:20 am
by ECC82
Unbelievable, didn't know that they counterfeit those as well. Luckily bought them at DigiKey. Thanks for bringing the counterfeit issue on the board, warning for us all.

Posted: Tue May 14, 2013 2:50 pm
by kp4xb
Thanks Guru for your help. Definitively was a counterfeit OP AMP. The new OP AMP arrived from Newark and this one are very different. Here is a picture of them. The one on top is the counterfeit and the one in the bottom is the original. The imprint information in the original OP AMP is dark gray. In the counterfeit is light gray. Also the dot mark in the original is smaller than the fake one. The RP-533 is now without issues and sounds very good. Also I change it on the RP-562 because it was starting to give me problem. Now both Bellaris are happy and me too...:-)


I'm posting this to beware other about this issue. Thanks again Guru and I hope to hear you on the bands soon.


KP4CA :D :D :D :D

Posted: Thu May 16, 2013 12:02 pm
by ECC82
tnx and compliments for the sharp detailed photo.

Edit: in 2015 the photo is no longer available :cry:

Posted: Thu May 16, 2013 3:23 pm
by Voodoo Guru
Terrific Carlos,
We're glad it worked out for you!!

It's anything for a buck these days, No semiconductors are bought other from reputable dealers here, there is just too much of a chance getting the bad ones.

Take Care,