Rotel Amp mods, are there any??

[giskard]

I am looking for mods for my aging RA980BX. I changed the U bridges with silver coaxal wire and decent plugs and now has a far more palpable sound to listen to but I feel there should be more lurking inside.

- Has anyone tried using Vishay resistors in the pre amp section?
- would black gates for small caps be an upgrade?
- Should I take care of the smoothing caps?

I am not very technical and it makes a bit harder because I don't have schematics or anything. Does anyone know a site for schematics?

Last question, would changing the bias in the output section change the sound dramatically and is it potentially dangerous
for the amp. (I live in an area with a very bad power grid, and I mean bad as in huge swings, constant static and blow outs.)

Well enjoy the music.

Giskard

[mpopovics]

Cheapest and fast modifications are:
- upgarde the ps diodes with shottky diodes
- upgrade filter caps near opamps (yes, BG is good...)
- change opamps (OPA627 or similar)
- change output binding posts for better quality -> connect with good quality wires

Regards,

[Al Raj]

Hi,

I wish to mod my RB991 power amp. I appreciate your valuable suggestions.

rgds
Raj

[giskard]

Sorry, can't help you out here, I have many problems attaining knowledge for my amp. Can't even get a schematic for it . Well the message above was at least very helpful, thanks for the info.

enjoy the music
giskard

[Vidalgo]

Hi,
in my opinion, most of Rotel's amplifiers has well-balanced design. Regular tweaks aren't lead to significant improvements (and easy to get something wrong).
I have RA971Mk2. Only one mod really help to me. This is lowering gain at input stage. With typical CD output level and medium-sensitivity speakers, there is situation when for comfortable listening volume knob must be in positions close to beginning. At middle position - just overloading. After some research found: signal goes through mech.selector and volume control to input amp.stage, based on OPA2604 with gain about 6.
So, need to change feedback resistors for lowering gain, now I live with gain 2.

[audiotux]

Hallo Al Raj ,
you can use better binding posts , RCAs.better power cable and inside better
coupling caps BG NX and better emitter-resistors and soft recovery diodes !

Greetings from Germany

Jürgen

[hienrich]

in my opinion, most of Rotel's amplifiers has well-balanced design. Regular tweaks aren't lead to significant improvements (and easy to get something wrong).

I also think so

I have here with me two cloned one (RB991 and RB1090), they actually
sound solid and crispy, so I think nothing is to be modified with this
amps

rgds,

hienrich

[Al Raj]

Hi, audiotux & hienrich,

Greetings to you from India.

Thanks for the feed back. I found 991 was somewhat on brighter side (in 2ch stereo) but powerfull especially in the bottom end. It's excellent for HT applications. IMO found not that satisfactory for pure 2ch stereo. Anyway listening tastes are different from person to person & I'm not supposed to commnet much on that :-).

I wish to carry out some minimum tweaks as suggested by audiotux. audiotux my sincere thanks to you for this.

rgds
Raj

[giskard]

Hi;

I've read your responses and they are all very helpfull; the 971 MK2 is a nice balanced little amp which I would not try to tamper with either, unfortunately the 970 and 980 integrated amps are a bit different in that especially the 980 is very harsh and pinchy on top, the U bridges are not so good and I have a feeling that a change of resistors in the preamp (this should only be a few in the signal path) would do wonders in opening the top end a bit.
Diodes, opamps are all great ideas to tinker with. Upgrading internal wiring is good, what wire do you use??


The biggest problem I have right now is the schematics so I know the values.

Well thanks for the input.


enjoy your music and don't strip your soul

Giskard

[metalman]

FYI, if you contact Rotel, they sell copies of their service manuals in the US for $20 each.