Squeexebox revisited

March 26 2010
(Also see my first article from a year ago)

After succesful installation of my System Asioka at home, I was very happy with the sound, especially that the squeezebox duet bettered all my previous CD transports.
Two weeks later, an upgrade bug bit me again so I liooked for easy ways to improve the Squeezebox.

Good product as it is, its achilles heel  is power supply. So I decided to take a good look at it first.

The wall wart which is supplied is DEFINITELY not a transformer based supply. It is a cheap impulse supply and it looks suspicious already.

First -I looked at  the input 9 V DC as supplied:

My photo above may be bad, but you can see what  is going on. The raw supply is ultra noisy. It contains a whole spectrum of spikes, some of them almost  0,3 V deep.

Above - the same factory supply after I fitted some oscons on the main Squeezebox PCB.  The impulses got about 10 x smaller.

So I decided to build a PSU consisting of a 10 VA transformer for 9 VAC, a C-REG-C-L-C-L-C  construction. It produces rock solid DC without any funny stuff going on.
Here is the result (loaded with SQB, not idling.)

As you can see, it is as flat as flat goes.  For me - it is flat enough.

Finally I kept both solutions: oscons in PCB and good PSU.
I have built a box made of veneered MDF to accomodate the SQB and the new power supply. Since SQB needs to communicate in WIFI - I could not use a metal box. MDF is transparent for wifi.

Above: the main power input capacitor - it is inadequate both in size as well as quality (ESR).
I decided not to replage but to keep it and ADD a better oscon  in parallel.

Here is how I soldered the incoming 9VDC - instead of using a wobbly and noisy plug - I hardwired the SQB to the PSU.

Arrows poin to the pos and neg points for adding a  bigger cap. Make sure it is a low ESR type and bigger than 200 uF. I would like to warn you about using the typical low ESR caps like teapo - because these are usually only good for 6,3 V circuits, not 9.

The yellow-blue pair of wires is power supply.  NOTHING gets removed here.

Above: the output RCA jacks are snipped and floated.
Red circle shows a critical point where a good cap will feed the voltage regulator which feeds the DAC chip. (a mod unnecessary if you use SQB as a transport only.)

The hardwired supply of the DC is ready to work - I have burned a hole in the box using the tip of my soldering iron.

The better (High-End ) power supply for the Squeezebox Duet as a Transport (plus the  Lampizator output stage).

Above: a test drive of the SQB and the power supply box. All works OK.

Above - the beautifully veneered box and SQB before installation inside.

Above - all is finished. SQB is inside the new home.
K is the SQB PCB
H is high voltage anode supply for tubes
E is the transformer for lampizator
D is an array of caps for heater supply of the tubes (rectified but unregulated).
F is the SQB sdupply first cap - 30 000 uF / 16 V
C is the SQB dedicated transformer - 9 VAC by 1 A by 10 VA
B is the lampizator - using two 6H6P in SRPP mode.
A is a pair of military PIO capacitors for tube output decoupling.

C is the main capacitor for SQB supply.
B is the pair of Roedestein caps after the 9 V regulator
A is the regulator 7809
J is the radiator
D is a fast cap 2,2 nF for bypass of electrolytes.
H is the second pair of Roedesteins
K is the earth bar
E and F are chokes between capacitors
(remember - the PSU is a noise free - C-REG-CLCLC)
G is an output oscon.

Above - the regulator from 9V to 5V for the DAC is now invisible under the two blue oscons.
The cubic oscon is an SMD type, 10 uF / 10V  installed AFTER the regulator. The cyllindrical one is 220/10 installed BEFORE the regulator.  It is soldered in place of these two holes in the PCB .

Improving the SP/DIF output of the Squeezebox Duet Transport.

Last mod concerns the SPDIF output. I did not trust the tiny SMD parts so I installed directly from the chip - the 220 nF cap (Vishay MKP (marked D) and C is the series 200 Oh,m resistor and  B is the parallel 75 Ohm resistor (soldered to the GND - the frame of the RCA socket.
I secured the cap by a blob of Soudal superfix glue.

The sounding of the upgraded Squeezebox Duet.

The result: the is definitely a better sleep and pride of achievement. Via a transport SPDIF -  I can detect beter sound quality but the magnitude of change is small. I think that the scene is deeper and low bass is deeper too.

The lampized Wolfson DAC chip is another story. It is not a Sabre killer, but it is a very decent dac. I could live with it. It is clear, dynamic, with great bass, I mean - it is so good that Iwould not use an external dac at all if I was not so crazy about DACS.

Overall, as a transport only, the Squeezebox reading my HDD server - sounds better than any transport I ever had. It even beats the modified CEC. The sound is fresh, spectacular, fast, powerful - you name it. There is something very right about that sound, Almost as if jitter was non existent issue.

It has been now 3 weeks  I havent touched a CD disc. I only use a HDD. I am afraid - there is no going back.