Cambridge Audio Azur 640R (7.1 Speaker Amplifier)

Introduction

From the mid 2000s, this 15kg (33lbs) behemoth is a 7.1 surround sound speaker amplifier, able to power each of the seven speaker channels at 100 watts rms (into 8Ω), or just two channels at 120 watts rms each, with a maximum power draw of 1400 watts. This is the most powerful amplifier (for the price) I could find second-hand on eBay, and has other features including, HDMI switching, capabilities for multi-room connections, and so much more that I don't even really understand, let alone know how to use.

Ports, Buttons & Knobs

Before disassembly, lets just take a look at the physical features of the device. Starting from the front, it features a blue-tinted Vacuum Fluorescent Display (VFD) - which I didn't even realise until cleaning it as the display lens was entirely stained with dust - as well as a series of buttons for: power, inputs, AM/FM tuner, digital sound processing, and speaker modes. There's a mute button next to the volume knob; a 6.35mm headphone port; and a set of audio/video ports for "Video 3" hidden by a plastic cover. All of this is mounted to a thick metal plate that alone doesn't weigh an insignificant amount.

Looking around the back, there are two banks of ports, with a vent in-between. The left side has all the connections to the inputs - Video 1 & 2, Aux, DVD etc - along with its 4 HDMI ports for switching, a serial port, and some antenna ports for the inbuilt tuner. The right side features all speaker connections, component ports, as well as the multi-room ports.

Disassembly & Cleaning

PCB Arrangement

Given its age and vented top, a fair amount of dust has accumulated inside (as well as a concerning amount of wall plaster...), and removing the top cover gives a brilliant view of how all of this works. On the left side is where the power comes in - the large capacitors, some relays, and the giant (and heavy) toroidal transformer. The Main PCB is flat along the bottom of the case, and is basically the size of the case. Three vertical boards connect to this through a many a series of pin headers and screws to secure them in - the inner two are "Power Amplifier 1 & 2" PCBs and are full of resistors, capacitors, transistors, and some diodes; and the rightmost one is the "Decoder PCB". This board features the microcontroller that controls the device, with an on-board power supply for AC to DC conversion (directly connected to the transformer). It features circuitry for digital to analogue converters for all channels, as well as some logic related and some sound processing ICs. In addition, this board then has connections to the tuner, display, and video boards.

Before cleaning, the internals looked like this:

And after cleaning, it looks a bit better. At the top back, under the plastic sheet, reveals yet another large PCB - the Video board. Here is the display management for the aforementioned HDMI switching, as well as whatever is required for all the digital coaxial, composite, s-video, and optical S/PDIF TOSLINK connectors to function.

Underneath this, you will find that all rear connectors are nested at the back, on a series of perpendicular sub-boards connected to other sub-boards. It's rather interesting how they have utilised the internal space of the amplifier, and I can only really show it through many images once the entire device is mostly disassembled.

Looking inside, the central rectangle is a massive metal heatsink, with a 90mm fan, that directly connects to the heatsinks of the power transistors (2SA1943) that are rated for 150 watts each.

On the right side, With the Decoder ahd Video PCB removed, the following can be seen: Power Amplifier PCB 2; the Main PCB at the bottom; the connectors for the Decoder PCB; the PCBs for Optical and Co-axial outputs; the places where the HDMI, Antenna and Video PCBs go; and the RS232 connector for serial, shown below.

The left side has the multiroom ports on a horizontal sub-board, and the speaker outputs below are on a vertical board directly behind the speaker protect relays, but this was hard to show.

Case Assembly

To get to this point, you may have noticed the side panels being removed. These are connected to the top, bottom, and slot in with the front and back panels. They need to be removed before the front assembly, and are shown below - they have a nice zig-zag pattern in them.

Removing them reveals the side view of the unit, and allowing me access to the power circuitry to inspect the relays and surrounding components (more on this later).

The base of the unit holds most of it together, and mainly has screw points for the Main PCB. You don't really want to remove the back panel as so much more needs to come out and it doesn't serve much purpose. From underneath, it looks like this, with two of the plastic feet missing (that are now just sharp screws scraping across my floor).

With all the PCBs and non of the panels, this is what it looks like:

But lets take a closer look at everything inside...

PCBs

The Decoder board is the star of the show, with all the interesting electronics - and there's plenty of it. The large Cirrus Logic IC in the middle (CS494003-CQ) is a "Multi-Standard Audio Decoder and Programmable Digital Signal Processor". Then to the right, you will find a CS42526-CQ which is a 6-channel CODEC with S/PDIF Receiver. Above this one is a 28L SOIC package which I believe to be a CS43122 122dB 24-Bit 192kHz DAC. In addition, there is an EON EN29LV040A 4Mb CMOS Flash module supporting a SyncMOS SM5964C40J 8-bit microcontroller. And, on the right end of the image, is a BD3817KS providing 7-channel volume control.

I'm yet to test the functionality of the video, HDMI, and coaxial boards/ports, and the seller also said they hadn't tested them. Whilst they could be useful, I haven't got around to setting up HDMI or reprogramming the display. Either way, one thing I noticed when disassembling, on the Video PCB, was a very odd surface-mount inductor. There are a number of darker patches (like burn marks) around this board, but what jumped out at me (literally) was the way this inductor was soldered. The only reason I can think of to explain this is that something got too hot and melted the solder, but that wouldn't explain the localised effect.

The power amplifer boards, I find kind of amusing - they just contain mostly passive components, nicely arranged, with headers to connect to the mainboards. There's not much more than that - they're all through-hole components, which I don't quite understand why, but it's probably cost related.

There are many more boards, and a lovely exploded diagram can be found in the service manual, but I don't want to bore you with my ramblings, so lets move on.

Front Display Assembly

The last part to look at in detail is the front display module. By the time I got around to disassembling this, the light had gone outside, so please excuse the orange kitchen lighting.

This piece is rather heavy; everything is mounted to a thick metal sheet that makes the front of the device. The construction is also rather interesting - on the other side it has perpendicular rails with screw holes, which allow it to be connected to the side pieces of the chassis and creates the structure of the box. But within these rails, it has a thin inner frame of which the PCB mounts to, the buttons sit on and the volume potentiometer screws into. This is shown below and I'm not quite sure why this was done. As far as I can tell, it mostly just offset the PCB from the front plate, which is was probably necessary for the screen.

Regarding the "Video 3" connectors which are hidden under a removable cover, there is an addition piece that clips into the front frame that forms the back wall of these ports. There is also a display lens (that was absolutely filthy) which is glued to the front.

Side note: it is also apparent the volume potentiometer has been bonked at some point (probably in shipping), and has warped the inner frame - this metal is meant to be flat and perpendicular:

As mentioned, the Display PCB is mounted to the inner frame of this, which is where the VFD is featured in all of its glory. This board is unsurprisingly quite empty as it is just a series of buttons and the display. The potentiometer is on the small rectangular board to the right, and is connected to the Display PCB, then the Display PCB connects to the Main Board PCB, via a 5-pin connector. The phones output has its own 4-pin connector to the Main Board PCB, and the Video 3 connectors go via a long slim PCB which eventually connects back to the Decoder PCB. This whole assembly was a pain to get apart...

...but at least it achieved something - cleaning the display lens. They aren't quite comparable but here are images from before and after. It was notably brighter after, and looks significantly better.

Power & Relays

I paid surprisingly little for this - as stated later - and whilst it works, it has a hissy fit every time it turns on. In the power section at the back left corner, a bank of 4 relays sit together quietly and patiently waiting for power - and once they receive it they make it known to the whole room. Louder than I would casually listen to music at, the relays constantly click for a variable amount of time. Although normally for more than 20 seconds, it can occasionally be a few minutes at most. Once it stops, everything works perfectly... except the one time it just stopped outputting sound...

Either way, these are the speaker protect relays, and given its age, its a fairly normal point of (partial) failure. According to the internet, the clicking typically isn't caused by defective relays but something wrong with the surrounding circuitry, particularly blown capacitors. I've tried to investigate this but I see no issues with anything nearby, and looking at the service manual, there isn't even much connected in proximity - however it seems some signals are being transported from the opposite corner of the amplifier. The reason for the relays tripping, would be because the speaker protect signal is being activated, that's its purpose, so there could be an issue with grounding or decoupling as some stray DC voltage could, in theory, cause problems. A more recent dive in to the service manual, reveals the importance of the Decoder PCB and "Protect 1" and "Protect 2" signals directly connecting to the main microcontroller.

I am yet to diagnose the actual issue and further prevent this issue. The one time it did just stop working was fixed by power cycling the amplifier. I would assume something more serious did happen that time. If you have more experience or knowledge on this topic, please contact me :).

Closing Thoughts

You've made it to the end, so now you get to know the grand sum that I coughed up for this amplifier. I spent a total of £27.19, including postage. It didn't come with a remote, makes horrific sounds when turning on, and is missing two feet, but it certainly powers speakers. I'll have to see if I ever get around to fixing the relay issue, but I think I got a decent deal on this one regardless. It's probably worth its weight in metal alone...