Technical Service Bulletin

June 16, 2023

Rotel Bluetooth 5.1 aptX™ HD Module 

The latest Apple iOS version (including OS V15.7.2) may cause the APPLE MUSIC app to stop playing audio when manually jumping between tracks in a playlist.  The Bluetooth connection is maintained but there is no audio output and no playback information (sample frequency and/or bit rate) displayed.  A hard power cycle of the unit remedies this issue. 

Earlier versions of iOS do not appear to have the same issue.  Other iOS Apps (i.e. iTunes, Spotify, Tidal, etc.) are NOT affected by this use case.

If this is reported, please contact Rotel at sales@rotelglobal.com to order a new Bluetooth 5.1 module (Rotel Part Number: 093E-BTM0002-D-1) with updated firmware V1.04 (or newer) that resolves this iOS compatibility issue.  

Note: All new delivered spare parts will be programmed by new firmware V1.04 (or newer) before package and shipment from now on, either of below two methods can help to identify this change.

   

   

Bluetooth module replacement requires removal of the top cover and replacing the Bluetooth module in the socket (no special tools or soldering is required) as shown below.

Affected unit models include: A12MKII, A11 Tribute, A11MKII, A14MKII, RC-1590MKII, RA-1592MKII, RA-1572MKII, RC-1572MKII, RA-6000

Release Type

A12MKII

A11 Tribute

A14MKII

RA-1572MKII

RA-1592MKII

RC-1572MKII

RC-1590MKII

RA-6000

A11MKII

Release Notes

 

PDF file download please click below:

Technical Service Bulletin - Rotel Bluetooth 5.1 aptX™ HD Module

You can find a knowledgebase for Roon and answers to FAQs at https://help.roonlabs.com/portal/en/home.

There is also an article with information on how to contact Roon Technical Support at https://help.roonlabs.com/portal/en/kb/articles/faq-how-to-contact-roon-technical-support.

Yes - if your Rotel product has a back panel input labeled "PC-USB", you can simply connect your computer to this USB input using a standard USB cable. The computer should then recognize the Rotel system as an audio device and you can then play music from your computer through your Rotel system. Do note that you may need to select the speaker as the primary output device for the computer.

• For windows users this can be done by Navigating to Start -> Control Panel -> Sound and Audio devices -> Playback.

• Mac OS X users should navigate to System Preferences -> Sound -> Output.

If you have a Rotel product that does not have a PC-USB input, if your computer has analog or digital audio outputs you could connect your computer to a Rotel receiver or surround processor using one of the analog or digital inputs as you would connect any other source component such as a DVD player or CD player.

Or, for even better sound quality, add a USB DAC to your system such as the RDD-1580. The RDD-1580 features a rear panel PC-USB connection that can be used to connect your computer to the system for high quality audio playback. The DAC would then connect to your Rotel system using the analog output of the DAC into an analog input in the system.

A Class D amp works by taking the analog input signal and creating a PWM (pulse width modulation) replica of it-essentially a train of pulses, which correspond to the amplitude and frequency of the input signal. In its most basic form, a comparator circuit is used to match the input signal with the PWM signal. The PWM signal is then amplified by an output stage operating in switch mode, which is to say there are two states, on or off, at very high speed, corresponding to the PWM pulses. A linear amplifier's output stages, by comparison, see a continuous waveform and, to avoid distortion, are on for more than half the waveform (Class A/B) or for the complete waveform (Class A), thus greatly reducing efficiency and generating heat.

The amplified PWM waveform is low pass filtered to recover the audio waveform and eliminate spurious ultrasonic noise before outputting it to the speakers. This process seems digital but is in fact analog in nature. The signal is not "digitized", i.e., assigned a numerical value; the PWM pulse train is an "analog" of the input audio signal. What distinguishes Rotel Class D amps from other designs on the market are innovations in the area of generating a highly accurate PWM signal (COM, which stands for Controlled Oscillation Modulation) and in the feedback circuits (MECC, Multivariable Enhanced Cascade Control) to provide a stable filter characteristic in spite of variable loudspeaker impedances. In simple terms, this means that our Class D amps offer full bandwidth performance at very low distortion in "real world" applications-just like our linear amps, but with the benefits of being smaller, cooler and much more energy efficient.

Why aren't there more Class D amps on the market? For starters, creating stable, full bandwidth Class D circuits while controlling RF/EMI byproducts isn't easy. Few companies have the technological know-how to do it. It also requires extensive use of Surface Mount Devices (SMDs), again putting it out of technological grasp of most audio manufacturers. We have invested with a technology partner to realize these designs.

Here's another key detail that often causes confusion. The Switch Mode Power Supply (SMPS) is not what makes these "switching" amplifiers. As just described, the amplification stage is a high speed switching circuit and what defines this design as Class D. A Class D amp could, in fact, use a conventional power supply; and a linear amp could use a SMPS. A traditional power supply stores large amounts of energy, but wastes "excess" energy not demanded by the load in the process. An SMPS matches output to real-time requirements, supplying only the power required by the load, as a result operating very efficiently. The analogy is a water tank (linear supply), which is always being refilled and spills over if demand is insufficient; compared to an endless series of buckets (SMPS), which can be slowed down or sped up as required. The SMPS in our Class D amps reflects the fact that the Class D amplification circuit does not require the massive energy storage of a linear power amp, so the more efficient/compact SMPS is a better choice.

To sum up, our Class D designs offer:

1. Excellent audio performance, testified to by numerous critical reviews and awards. Rotel Class D designs are the most advanced in the world.
2. High energy efficiency (90%+, compared to 50-60% for Class A/B amps). In our increasingly "green" world, this is an important point.
3. Compact size relative to power output.
4. Cool running as little energy is wasted as heat.
5. Low output impedance translates to high damping factor, or control over the loudspeaker.
6. Low impedance load tolerant.