Rotel RB-991 Power Amp Upgrade

Almost any Hi-Fi component can be upgraded to higher performance using our techniques and components. The two things go together – the know-how and the right component. Over the last 30 years, we have developed our knowledge of where the biggest problems lie and how to overcome them to unleash better performance from a given piece of equipment.


Released in 1998 and weighing in at over 15kgs and delivering 200 watts per channel, the RB-991 punched well above its sub $1000 price tag. Rotel’s design philosophy has always been about sourcing high quality parts from specialty manufacturers. Circuit topology designed to minimize signal paths and to keep each channel's signal path identical and finally, critical evaluation i.e. lots of listening to determine the subtle sonic attributes of different parts or circuit layouts and optimise them!




How is this design philosophy implemented in the RB-991? The power supply is based on a 1.2kVA multiple-secondary toroidal transformer. Each channel's power supply is separate, with individual rectifier arrays and banks of slit-foil capacitors. According to Rotel, 20 output devices (10 per channel) are employed to maximize stability and reliability under extended high-output conditions. The dual-differential input with constant-current source feeds a class-A voltage-amplifier stage, which leads in turn leading to the triple Darlington output section. The circuit employs Black Gate and Wima capacitors and Roederstein metal-film and Vishay military-grade resistors.

Phew! Quite a lot to get our teeth into then! Our upgrades build on the strengths of the amplifier. Everything you love about the sound remains – it just gets so much better.


There is a significant amount of internal wiring that we upgrade. Over 5m of high purity Kimber copper TCX (awg 15) wire is used. Almost all the entire power supply and signal circuits are re-wired.






16 component upgrades/changes are made across the power supply and signal amplification section. Because the RB-991 is made with audio grade caps in the first place, we didn't feel there was a need to change too many of these components instead choosing to focus on other areas. One key upgrade we make, is the addition of four additional Kimber caps delivering a smoother more natural sound.





We've used Russ's favoured audio grade Panasonic capacitors which give a smooth and detailed sound. The amplifier is completely disassembled to gain access to key areas of upgrade and given a general clean and health check too! Post upgrade, the unit is then soak tested for 24 hours.



To clean up and give the power supply input an upgrade. Firstly a Silencer™ mains filter is fitted and then a substantial upgrade is made by replacing all 6 internal fuses with our SuperFuses.






If you don't have exactly the same model as listed above, but a very similar unit, then it's highly likely that the same or similar upgrades will apply. But we can't guarantee that until we have the unit here for inspection. Get in touch and let us know what you have.




Equipment upgrades are proving hugely popular. During peak times there may be a wait of several weeks before we can carry out the upgrade. So before we get your equipment here, it must be booked in so we can ensure a speedy turnaround of the upgrade. Once you have placed your order, we will contact you to arrange a suitable week and getting the equipment here.

In Person
For those of you who are local enough or if you fancy a trip to the lakes, you can drop off your equipment personally and then collect it when it’s complete or we can ship it back to you.

By Courier
We can arrange a courier collection of your equipment for an additional cost. We currently use UPS.
To make things easier, we can offer several collection options.

1. We can arrange a specific day for the courier to call and collect your equipment. Someone will need to be available all day at the collection address as we’re unable to arrange a time slot for collections.

2. Dropping off at a UPS Access Point. UPS use a network of local shops to deliver and collect parcels from and to. We can either post you a collection label or email you the label (you will need to print the label at home/work). Securely box up your equipment, affix the collection label to the outside of the box and take it to your preferred Access Point where you will be issued a receipt. UPS Access Points can be found here (link opens in a new window), simply enter you postcode to find your nearest one.

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Please note this is just an upgrade modification, it does not include the Rotel amplifier.