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The stock Receiver is purchased at a bargain price, and the cost of every single component counted to make the product competitive; and a great achievement it is. With such keen pricing, the circuitry is designed with the bare minimum, but adequate to deliver good performance nevertheless. The entire unit contains only 3, 2 of which are for output coupling the signal from the Wolfson WM8501 DAC. Decoupling for the power supplies are all low value surface mount capacitors (SMD), aside from the input bypass capacitor. The WM8501 DAC can operate off a single +5V regulator, and this is precisely what we find inside the Duet, a SMD 7805 for the DAC’s digital & analogue supply with minimal bypassing. The DAC itself uses two X7R type capacitors for decoupling the digital & analogue supplies. The DAC’s output is designed so it can be directly capacitor coupled at the output and a pair of 10µF SMD electrolytic are fitted for this purpose. For the digital circuits all capacitor decoupling is SMD are careful thought has been given to the placement of the DSP chips.

Space inside is limited so the upgrades have been carefully thought out to optimise the unit as cost effectively as possible. The upgrades we complete are divided into two categories, ‘digital’ for those wishing to improve the digital output to an external DAC, and ‘full player’ for optimising the internal DAC and regulated power supply for using the RCA outputs.

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Full Player Upgrade

Starting with the DC input we install a Bybee Slipstream Quantum Purifier to reduce noise on the incoming power supply rail. The DC input rail is bypassed with a general purpose capacitor, this is upgraded to a Sanyo OS-CON SP type. OS-CON capacitors are characterised by lower ESR and ability to handle higher ripple current than their wet electrolytic counterparts.  Low ESR is so important in electronics because the lower the ESR the faster the capacitor can discharge. This is a great benefit because it means the capacitors can respond faster to current transitions. We then replace the generic 7805 regulation for the DAC with the Super-regulator 3. This is a discretely designed regulator that uses 23 high performance components on a 4-layer PCB to achieve similar size to the 78xx series. The Super-regulator 3 rejects noise at the input, the regulation circuit is in a ‘closed loop’ and the resulting DC output noise is fast, extremely low in noise and highly stable ensuring the optimum supplies to the DAC and associated circuitry on 5.0V power lines. We next add a bulk electrolytic OS-CON capacitor for bypassing the regulator output, a 1206 size capacitor is fitted as stock so the addition of the OS-CON reduces noise. The WM8501 datasheet recommends bulk 10µF capacitors close to the DAC’s digital & analogue PSU pins as possible, the stock unit comes equipped with on a 0.1 µF SMD type only so we add 10µF OS-CON at the supply pins to reduce noise at the input supply of the DAC. The finishing brush strokes are made by installing Sontech SFRT-AL resonance control. This is a specially designed visco-elastic material which removes vibrations across a wide bandwidth ensuring the sensitive components inside the Receiver are free from noise.

Digital Only Upgrade

Starting with the DC input we install a Bybee Slipstream Quantum Purifier to reduce noise on the incoming power supply rail. The DC input rail is bypassed with a general purpose capacitor, this is upgraded to a Sanyo OS-CON SP type. OS-CON capacitors are characterised by lower ESR and ability to handle higher ripple current than their wet electrolytic counterparts.  Low ESR is so important in electronics because the lower the ESR the faster the capacitor can discharge. This is a great benefit because it means the capacitors can respond faster to current transitions. The digital upgrades continue with improvements to the local decoupling for the clock & DSP circuitry, the stock unit uses only surface mount capacitor to decouple the data processing and logic chips so we add OS-CON decoupling to lower noise and improve transient response. For the digital output itself it is back to the Bybee filters where we add a Slipstream Quantum purifier at the digital output to improve the quality of the digital signal. The finishing brush strokes are made by installing Sontech SFRT-AL resonance control. This is a specially designed visco-elastic material which removes vibrations across a wide bandwidth ensuring the sensitive components inside the Receiver are free from noise.

The level-2 digital upgrade takes the Bybee concept a step further where we add a Slipstream purifier to the DC input. Hook the Duet receiver up after adding the Bybee purifier here and it takes seconds to realise the range of improvements from this modification. The reduction is grain and noise is immediately apparent, backgrounds are notably quieter. There is also a marked increase is detail, dynamics, and low frequency depth. Music is cleaner sounding with less blurring, digital edginess. We then replace the low cost chassis mount RCA phono with a WBT NextGen cu phono and terminate with 6N OCC wire. The NextGen is a state-of-the-art connector that ensures the highest level of signal integrity between player & DAC.

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The TeddyDuet replaces the wall-wart power supply for your Squeezebox Receiver for a major upgrade is sound quality. Read more here >>>

Superclock 4 Clock Upgrade

The Receiver like the Squeezebox Classic, has a Pierce’ type oscillator based on a 74HCU04 inverter chip. This type of oscillator is simple and easy to implement but also very noisy, jittery. We highly recommend upgrading the factory clock to Superclock 4. The audible benefits are are not subtle. Bass is cleaner, tighter. The sound-stage has improved dimensionality with better focus of instruments and vocals. You will hear more detail, improved tonal qualities.

Installing the Superclock 4 inside the Receiver does not require the removal of the wireless card. Both wireless and Ethernet capability is unaffected.

Sound Quality

The stock Receiver already achieves a high standard via its analogue outputs (RCA), but compared to a good entry level CD player the sound quality has a metallic tinge, too much bite and can sound thinner and washed out compared to CD. There is no question of detail & clarity, it has that aplenty but the tonality does lack a sense of warmth and naturalness compared to Red Book CD.

Hook up the upgraded Receiver and your immediate impression is that of a more relaxed and accomplished sound. Background noises are reduced and tones gain depth and warmth giving the music a greater body and solidity. Stereo separation and focus is also better, where previously you heard a ’mass of sound’, the upgraded Receiver made better sense of the music, now vocals were more firmly placed in the mix, instruments having better spatial qualities.

Switch to the digital output in to an external DAC and the improvements in sound are clearly manifest. Similarly to the analogue outputs, here we find a marked reduction is noise in favour of a more open, cleaner and sweeter sound. Detailing is also better, you are able to hear sounds that were previously buried in the mix, the music being more relaxed, less grainy, less strident.