Some pics of my modded Rotel RCD-991 - diyAudio
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Old 25th February 2005, 01:49 PM   #1
av98m is offline av98m  Singapore
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Default Some pics of my modded Rotel RCD-991

Just wanted to share...over 50 electrolytic caps were replaced, including 18 of the 22 Blackgates F that came stock with the player. Opamps were also upgraded from OPA2604s and NE5532s to OPA627BPs. Replacement caps include Elna Cerafines(4), Elna RJHs(8), Sanyo Oscons(14) and Panasonic FCs(27, I think). There are only 6 stock electrolytic caps left on the player.


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Old 25th February 2005, 02:02 PM   #2
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Any comments on the sound improvement?
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Old 25th February 2005, 03:13 PM   #3
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Why are u pulling out Blackgates and putting in Elna and other caps, people usually do it the other way around.
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Old 26th February 2005, 12:42 AM   #4
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Hi av98m,

How does it sound? What has changed?

Regards,
Extreme_Boky
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Old 26th February 2005, 08:10 AM   #5
av98m is offline av98m  Singapore
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Hi guys. There was a small but very noticable improvement in bass,dynamics, speed, transparency and soundstage, but without becoming more harsh or sibilant. Those who prefer a warmer and more laid back presentation may not like the changes brought about by the mods. I'm thinking the blackgates somehow gave a slight veil to the presentation. None of the blackgates removed were directly in the signal path, all were supplying power and we opted to replace them with ultra low-impedance caps, in the case of the caps supplying power to the DAC chips sanyo oscons were used. I forgot to mention that the opa627 opamps were biased into class A as well (the class a modules are not visible because they are mounted underneath the pcb)

All mods done by a friend, in stages, we spent lots of time talking and poring over datasheets.
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Old 15th August 2006, 02:35 AM   #6
dtm1962 is offline dtm1962  Canada
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Default RCD 991 Mods

How did approach biasing the 627's into Class A.
I have a 971 that I replaced the 2604's with 627B as well.

I did add 6-7 OSCONs as well as 8 or so Pany FC as well changing all 9 PS diodes to Schottkys as well as adding .068uF between pin + & - pins of the OPA627's.

Let me know.

Thanks,

Dan
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Old 15th August 2006, 04:06 PM   #7
adhoc is offline adhoc  Australia
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That's slightly odd - if you wanted a less 'laid back' sound, why did you put in OP627s?

I would recommend that you try the OPA2107 if you want something with the bass of the OPA627 with a little more energy. Other alternatives could be the AD8620 (on adaptor), AD746, AD823 or AD712.
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Old 23rd April 2010, 09:31 PM   #8
arupg is offline arupg  Latvia
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I have a friend's 991 and am planning to better the analog sound by opamp rolling. 627 is certainly the most fav opamp as I love the sound off them. Apart from the OPA 2604 that the Rotel 991 uses (1 per ch), there are 2 more NE5534 in there AFTER the I/V. Are they also to go in fav of 627?

Attached a schematic.

Suggestions and recommendations will be most appreciated.

Thanks in advance!
Attached Files
File Type: pdf SERVICE MANUAL RCD-991 12.pdf (182.2 KB, 69 views)
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Old 24th April 2010, 05:45 PM   #9
Mooly is offline Mooly  United Kingdom
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Default For anyone blindly swapping :)

Just in case any one thinks of blindly swapping an NE5532 or OPA2604 for an OPA627 (yes I see you used adapters) then your going to be in for a shock... the OPA is a single device, the other are duals.

It's interesting reading listening impressions on opamps in CD players. Must admit I do like the OPA604/2604 particularly as an IV convertor on a TDA1305 DAC. Far more musical than the NE5534.
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Old 24th April 2010, 06:19 PM   #10
arupg is offline arupg  Latvia
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@ Mooly :

Yes, am aware the 627s are single hence for 2604 will require a browndog adapter with 2 x 627s mounted for every 2604.

But in the positions where the 5534 are which are single OPAs, was just wondering if it would be beneficial going the 627 there. Inputs will be welcomed.

Cheers!!
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