Listening to music in your own home requires a signal amp connected to a source, making Hi-Fi stereo amplifiers the equipment of choice for the discerning music fan.
Whilst for some time now such devices have been eclipsed at most manufacturers by their home cinema equivalents, certain Hi-Fi focused brands have continues to make them in modest quantities - in particular at French constructor BC Acoustique, whose well-constructed products always receive a warm reception.
Such is the case with the EX 332D amp which, for a fairly reasonable price, has a power of 2 x 120W/8Ω (which can go up to 2 x 200W/4Ω) with an integrated S/PDIF-compatible DAC (24-bit/192kHz on the coaxial input), four inputs with one in symmetrical mode and the possibility of an optional additional module (phono pre-amp or USB DAC).
Add to this intelligent design and an acute attention to detail, and this device has enough to grab the attention of HiFi enthusiasts.
Presentation
With its facade in silver or black brushed anodised aluminium and the precise arrangement of its controls, the BC Acoustique EX 332D means business (which our arms also noticed - the amp is pretty weighty!).
There's an actual "off" switch located on the base of the device to the right, which allows you to fully turn it off - not just standby - without having to crawl around looking for the plug socket. There is also a standby/on button to the right of the headphone Jack. A Gain button allows for levels up to 10dB, which offers more fine-tuning. The button marked "Direct" can bypass the bass and treble settings, which have retractable dials in order to preserve the purity of the signal.
The volume dial is located in the centre of the front panel; there is also the input selection button and the LED remote control signal receiver.
Connectivity
The connectivity of the EX 332D amp goes for quality over quantity; it is not plentiful, but it is well-designed. The user can choose between three Cinch inputs, one stereo input (symmetrical on XLR) and two S/PDIF inputs, one coaxial and one optical, the cap of the latter being connected to the base by a thin nylon wire to prevent loss.
The Line 3 has an AV Bypass option which means the amp can be used without using the amplification function, which the Option input acts as an ordinary input, but this is disactivated when the optional module is used (we used the DAC EX DAC-UB-3X, which you can see in the photo below).
The EX 332D has two Pre outputs, one in asymmetrical mode and the other in symmetrical mode, as well as two unfiltered Sub outputs. This means that the subwoofer used will need its own low-pass filter, which is normally always the case in Cinch connection.
The terminals for the speakers are protected models, and the amp can be used in mono bridged mode for optimum power, thanks to a small switch activating the necessary internal changes.
Realisation
The weight of this 2 x 120W amp reminds you that to generate serious watts, you need a hefty power supply that starts with a transformer ratio. With a power of 700VA, the EX 332D is dealing with some pretty high values, and can generate enough energy to allow each amplification stage to deliver 200W at 4Ω!
The transformer is a carefully-constructed traditional model - we noticed that the coils are varnished and have a copper foil belt to help prevent radiation leaks, while its attachment to the housing base is made by four threaded rods blocked by solid cap nuts (nice attention to detail).
The power amp supply uses a finned radiator to cool the diode bridge and two transistors which serve to regulate the power feeds. The filtering of the power stages is assured by six Nover "Audio Grade" capacitors of 10,000μF/63V, whilst four Rubycon 1200 μF/63V capacitors filter the regulated power supplies.
A second circuit located under this power supply hosts the standby supply, and includes its own transformer as well as various power supplies needed for the rest of the electronics (pre-amp, control circuit, integrated S/PDIF DAC, switching relay) that use LM7805, LM7812 and LM7912 regulators. You can also see some of the optional DAC which is connected to this power feed by two wire tapes.
To get to the rest of the electronics, located in two compartments isolated from the central section dealing with power and amplification, we had to carefully deconstruct the back panel to find the input and output circuits and that of the integrated S/PDIF DAC, as well as the front panel to access the pre-amp circuit with its motorised volume potentiometer by Alps and the circuit for the buttons and the electronic management, which you can see below, and which is equipped with an Atmel Atmega48/V micro-controller.
Below you can see the card containing the pre-amp and the control of the bass an treble, which are performed by fixtures with New Japan Radio Company (JRC) NJM5532 operational amplifiers. There are also Nichicon Gold plastic layer electrochemical condensers.
In the compartment along the back face are the connectors for the inputs and outputs along with their electronics and the S/PDIF inputs.
The interface concerning the S/PDIF inputs is on a Cirrus Logic CS8416 circuit (24-bit/192kHz) and the digital-to-analogue conversion is performed by a Burr-Browm PCM1793 chip (also 24-bit/192kHz). The signals are then treated by an active filter built around a NJM5532 operational amplifier made by JRC.
Below you can see the input switching relays and the symmetrical outputs on XLR plugs with their balancing circuits which use two NJM5532 operational amps, as well as the pre and sub outpits, which deliver a signal which corresponds to the sum of the signals from the left and right tracks.
Each amplification channel uses its own circuit mounted on a finned radiator firmly attached to the bottom of the casing, and the power stages consist of Toshiba 2SA1943 and 2SC520 push-pull dual complementary transistors, each supporting a considerable current of 15 amps and 150W power.
The optional EX DAC-UB-3X DAC
The USB DAC looks much like any other standalone DAC in black anodised aluminium casing, except its connectivity is specifically tailored to connect to the EX 332D amp, with special feeds particularly for its analogue functions.
It is available both with and without an S/PDIF input on a bayonet connector. At the USB input, it is compatible with digital audio signals up to 24-bit/192kHz and DSD64 and DSD128 in native mode including conversion, which is rare enough to make note of. It's also compatible with Android or iOS mobile devices via an adapter cable.
It can be integrated to any EX 332D (or in fact one of the preceding BC Acoustique amp models, including the EX312 - EX322 - 322D - EX332D - EX362D - EX888 - EX322.1 - EX888.1) and a video installation guide is available on the product page on BC Acoustique's website.
Its conception is also similar to that of a standalone DAC and its USB interface uses a powerful XMOS 8U processor capable of dealing with digital audio signals up to 32-bit/394kHz and DSD.
The S/PDIF interface is handled by a Cirrus Logic CS8422 circuit (24-bit/192kHz) and the digital-to-analogue conversion is performed by a Cirrus Logic CS4398 circuit. A 74HC157 circuit send the I2S signals from the USB or CS8422 towards the CS4398.
The digital-to-analogue converter is a Cirrus Logic CS4398 which decodes the PCM signals, or DSD in native mode; these are not converted to PCM signals as is the case most of the time, the DSD compatibility stopping at the input of the conversion chip.
For this, the DAC control software developed by BC Acoustique configures the CS4398 in Direct DSD mode when reading DSD signals so that they are directly sent to the output filter, bypassing other stages, as was the original aim for such signals (but which rarely happens).
After the conversion, the signals pass through an active filter implemented around a NJM5532 operational amplifier before reaching the amplifier.
Listening
Having opted for the optional USB DAC in direct mode, we began with the thunderous In The Hall of The Mountain King from Grieg's Peer Gynt, performed by the Berliner Philharmoniker led by Jeffrey Tate. The EX 332D doesn't struggle to build some power to deliver the forceful burst of the timpani at the end of the piece, yet it manages subtlety and finesse in the interplay between the xylophone and the triangle during the Dance of the Mountain King's Daughter before building up to an explosive ending.
In Solvejg's Song, the restitution is delicate with the voice is exactly where it should be, supported by a singing orchestra punctuated by pizzicati in the lower strings which are reproduced with sufficient broadness.
What is nice with this amp is that whilst powerful it's not crude, instantly reacting to the demands of the music. It's like a good motor which can drive with agility whilst being able to quickly react to the smallest stimuli whilst accelerating.
With the Vespri per l'Assunzione di Maria Vergine by Vivaldi performed by the Concerto Italiano and led by Rinaldo Alessandrini, you can really appreciate the rapid response of this amp which reproduces the attacks of the bows on the strings with great liveliness, whilst the soprano is crisp with playful edge in the treble, which is also noticeable in the brass of the Allegro from Dixit Dominus.
The restitution is likewise lively and punchy in the song Papaoutai from Stromae's album Racine carée, with solid basslines that allow the vocals to really shine and remain perfectly defined, even when the volume is turned up.
The results are similar using the internal DAC with an S/PDIF input, where the restitution also produces great sound quality.
For the restitution of DSD files, we used an orthodynamic headset connected to the headphone output, allowing us to be totally immersed in the music.
With the few files that we listened to, the sound quality was superb - and the headphone output was clearly pretty good as well.
In conclusion, the BC Acoustique EX 332D is a very cleverly-designed device, with good realisation and musical performance. If you want to go more advanced with your music files, the integration of the EX DAC-UB-3X would be the ideal solution for this device.
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Original article by PHILIPPE DAUSSIN Translation by RACHEL HARPOLE