SqueezeBox Duett : a sympatic caps tip

[Eldam]

@Voxonline,

Good news for britains : hifficollective

try one of these two BG N 33uF/16 vor BGN NX 47 uf/6 V:

black gate N type capacitor listing page

Nichicon FP cap aluminium can are on Mouser.
Nx HiQ22uF6.3V5 x 7radial wire£3.16CAP-9485N33uF16V6.3 x 11radial wire£4.23CAP-9324Nx HiQ22uF6.3V5 x 7radial wire£3.16CAP-9485N33uF16V6.3 x 11radial wire£4.23CAP-9324

 

[voxxonline]

As I remember hfcollective just list them but caps out of stock

 

[GaryB]

Do you use a FP cap (red mark for negative) ? did you try without the MLCC (don't like it...). The blue nichicon polymer sound awful here in my system, but same value with FP or SEPC are far better than the blue nichicon polymer.

I used a single 220uf FP cap with 10uf MLCC bypass. I didn't try it without the bypass.

Here are the other changes that I already made to the Duet. Mostly I followed the recommendations for adding electrolytic caps to various regulators along the lines of what's shown on the Lampizator site.

1) 470uf FP capacitor at the input
2) 100uf std electrolytics on the regulator just by the input, to the left of the WLAN card
3) 220uf blue Nichicon caps to the 5V supply near the location marked C22 on the circuit board
4) 220uf blue Nichicon cap for the 74HC04 that drives the SPDIF output

Different from the Lampizator site, I added a Newava SS22083 transformer for the SPDIF. Below is a circuit diagram showing how I wired it up.
---Gary

 

[Eldam]

Did you found some shematic about the Duet ? Which type of powersuplly do you use ? Shunt, linear, the original one ?

The trafo replace a cap or is just added as noise stoper ?

With my raindrop Hui DAC there was a trafo at the input od the CS8814 SPIDF input chip. As written by lampizator removing this bad trafo did a great improvement.

But if i look at your shematic it means than I have no DC stoper between the spidf output of the Duet and the spidf input of my DAC... and my futur SUBBU DAC (because I remove the 100 nf MKT cap for more details). Maybe for myselfit will be more carefull to repopulate the pcb with the dc bloker cap in the SUBBu before the WM8804 spidf receiver...

Near the C22 is for the DAC chip only according to me, not sure it has influence on the xilink?

For the 220 input cap, my test with the original PS and // caps change the sound but were not an improvement. Think it woulg be better to remove the original cap (didn't found the datasheet of it... G serie ???) but too afraid to remove the fragile trace of the pcb if removing the smd cap... How much measure the 4 tantal caps (C120,C134...) after the electrolytic C4 220 uf ? they would "waste" any new polymer cap before them...

Maybe for critica position SEPC or FP caps would be better than "blue Nichicon Polymer"... each time I used the blue i come back to FP or purple SEPC polymer...

Do you know the use of J8 holes ???

 

[GaryB]

Did you find some schematic about the Duet ? Which type of power supply do you use ? Shunt, linear, the original one?

I don't have a schematic for the Duet.
My experience with power supplies for the my various squeezeboxes has been that the stock switching power supplies inject a lot of noise back into the power line and can degrade the sound of other components in one's system. I've had good luck either replacing the switching supply with a good linear supply or using a good line filter with the switching supply. For my Duet, I use the original switching supply and a DIY line filter using a common mode choke and some caps.

The trafo replaces a cap or is just added as noise stopper ?

The benefit of the transformer is mainly as a noise blocker. It's useful to separate the ground of the digital source from the DAC ground.

. . . if i look at your schematic it means than I have no DC stopper between the spidf output of the Duet and the spidf input of my DAC... and my future SUBBU DAC (because I remove the 100 nf MKT cap for more details).

You will still need a DC blocker at the DAC input, so you'd need to put one in the V3 Subbu DAC if you don't have one now. I like slightly bigger than 100nf caps for this applications and typically use a few uf MKS.

Maybe for critical position SEPC or FP caps would be better than "blue Nichicon Polymer"... each time I used the blue i come back to FP or purple SEPC polymer...

Do you know the use of J8 holes ???

Sorry I haven't experimented a lot with different types of polymer caps in my Duet. I just kept adding caps until it sounded "good". And I don't know the connection for the J8 vias.


---Gary

 

[Eldam]

Thanks Gary,

I try again a linear PS. Maybe my supplier of electricity or environment are better than your about the genuine SB PS...

I assume than your try with one or two FP cap for spidf added nothing or few ?

i have excellent MKC stacked multilayer, i will try it as DC blocker for SPIDF signal...

 

[GaryB]

I try again a linear PS. Maybe my supplier of electricity or environment are better than your about the genuine SB PS...

Eldam,
It could very be true that the quality of the power in Europe is better than in the US. But my comments were not about the quality of the power from the local supplier. It was about the Squeezebox power supply adding noise into the house wiring which then makes your preamp or power amp sound worse. That's why I said that a powerline filter between the AC outlet and the switching power supply is very helpful. I like this combination even better than a linear supply and it's what I'm now using.

I assume than your try with one or two FP cap for spidf added nothing or few ?

I haven't done more experiments because of other commitments. I don't think there was much improvement by adding the FP cap but audio memory can be wrong. I'll go into the Duet and disconnect the FP cap and listen again. That type of switch can help determine if something good happened. Do you miss it when it's gone or don't you notice? I'll report back later.
---Gary

 

[Eldam]

But what I said is maybe than my wall outlet PS is good enough not to need PS filter in relation to the stock Duet PS...

It is well know that numeric need the most cleaned powersupply. I have to try that way. The better is to have two line from the wall only for the hifi : one for the amp the other for the pre and the rest of the chain...

I try again with or wiyhout this duet caps combination. Well, no doubt, i conform my first post.

Well I know that discovery is not universal, maybe this particular combination solve specific problems in my listening environement ?! The new setup plays much better in my listening room ?! Less reflexion and peak energy at boring listening distance ? I don't know and don't want to go with false theory or bad understanding about this setup !

If somebody have the SB Duet and a rare BlackGate N (i maid a mistake : i have a N bipolar type not a polarized NX) and a SEPC : just try to tell me if it's bad or not, better or not !

in my home it works, and I like to think there is less difference between two home environments than between two setups. Sure it's a mix.

So I gave this particular setup and hope it helps something or somebody say it doesn't help for futur progress in understanding the little SqueeseBox Duet gem.

 

[Bud Barnez]

Yes, you can wire directly from the Duet to the Subbu V3 DAC. Just remove the SPDIF RCA connector and use a good 75 ohm coax to make the connection. I like RG174, a 75 ohm miniature coax cable but any 75 ohm cable would be OK. In my Duet, I also added an SPDIF transformer since I think it's a good idea to isolate grounds between the digital source and the DAC. I used a Newava S22083, digikey # 470-1003-ND. I also increase the size of the blocking cap feeding the SPDIF transformer.

---Gary

Gary,

Thanks for your suggestions and posting schematic. I've ordered some PE-65612NL pulse transformers to install.

In the schematic you posted, is all the circuitry after the 74HC04 components you added or is some on the board as standard? Did you tap SPDIF from pin 2 on 74HC04?

Also what about "the origin of SPDIF" as Lampizator describes, from pin 3 on Xilinx chip? Do you recommend taking SPDIF from the 74HC04 as better?

Thanks.

 

[Bud Barnez]

Caps in power supply

I tried measuring the power supply with and without some added caps in the 9V input and at the 5V C22 position.

I used 180uF OS-CONs in both positions. Here are pictures of the results.

I'm no expert, so possible I was measuring wrong, but settings on scope were 5mV per division and 0.5mS.

I'm not sure how these pictures will appear but this is the order I uploaded them in:

1. 9V input from original SB Duet power supply (1)
2. 9V input from original SB Duet power supply but with 180uF OS-CON (7)
3. 5V at C22 original SB Duet power supply, no caps added (4)
4. 5V at C22 original SB Duet power supply with 180uF OS-CON at C22 (8)

Looks to me like adding capacitor at input degrades the power - comments welcome!

 

[Bud Barnez]

Alternative power supply

I then tried a power transformer from a ZX Sinclair. This is supposed to supply 9V though it measures about 14V unloaded.

I then swapped the 1000uF capacitor in the ZX supply for a nicer Panasonic and changed the diodes for soft switch. I was really impressed with the change in performance - I never thought it would make much difference but see evidence below (maybe the capacitor in it is so old it wasn't performing as it should).

The standard ZX power supply wax reasonably good to used the maximum resolution on my antiquated scope (5mV per div) with 5x magnification.

1. SB Duet power supply for comparison
2. ZX Sinclair power supply
3. ZX Sinclair power supply with 5x magnification
4. ZX Sinclair power supply with new cap and diodes with 5x magnification

I then added a linear regulator and the result was even better.

 

[Bud Barnez]

So what's the the effect?

I will be using the SPDIF output so not concerned with analogue.

Here is the SPDIF wave form before and after power supply modifications.

Before is the raw SD SPDIF as it comes out of the box. After is with OSCONS added to the Duet board and using the ZX Power supply and low noise regulator.

It looks to me like the power supply modifications have made the waveform much sharper but the level is reduced significantly. Measurements were taken from the RCA jack on the back of the box.

Scope setting 0.1V per div @ 0.2us ("zoomed" at 5mV/div)

1. Original Duet SPDIF output
2. SPDIF after above modifications
3. Zooming in on edge wave form (after modifications, I didn't get the equivalent picture pre mod)

Edit: I notice that the settings are not quite equal in the before and after. the variable magnification on the volts/div dial are different. I thought this may account for the difference in apparent level but actually it makes it more pronounced as the after picture is effectively zoomed in more. Also AC coupling and DC coupling settings are different too, though I just compared these and seems to have no impact on the measured waveform here. Although the amplitude varies there is a pronounced difference in the wave form.

Should I be worried about a reduced output voltage though?

 

[GaryB]

I've ordered some PE-65612NL pulse transformers to install.

I don't have any experience with this particular transformer. It's got relatively high inductance (2.5mH) vs. the Newava transformer that I used which has 225uH inductance. Other DIYers have characterized the Newava with high end measurement equipment and shown it works well in this application. So you're on your own here - no guarantees on how well this transformer will work. But definitely go ahead and try it out and tell us how it works.

In the schematic you posted, is all the circuitry after the 74HC04 components you added or is some on the board as standard? Did you tap SPDIF from pin 2 on 74HC04?

Also what about "the origin of SPDIF" as Lampizator describes, from pin 3 on Xilinx chip? Do you recommend taking SPDIF from the 74HC04 as better?

Thanks.

I disagree with Lampizator on taking the SPDIF from the Xilinx chip. The 74HC04 is used as a buffer and should work fine. I don't have an unmodified Duet to tell you all the part numbers any more but I've attached a diagram showing roughly how the SPDIF in the Duet is wired up. You should be able to trace this out and see where the components are located. From the pictures on the Lampizator site, the 0.1uf cap is located just above pin 1 of the 74HC04 and Ra is a 368 ohm resistor right next to the cap. Rb is calculated so that Ra in parallel with Rb gives an impedance of 75 ohms. So Rb should be about 95 ohms. If you want to reuse parts on the Duet then remove the output inductor and Rb. Hook up the transformer primary between Ra and ground. Put a resistor of the same value as Rb across the secondary of the transformer and hook to the output of the transformer to the output jack.

---Gary

 

[Eldam]

Looks to me like adding capacitor at input degrades the power - comments welcome!

Hi Bud,

thanks for sharing and measurements,

I have no scope but my ears confirmed that with some experiments like :
orginal PS and one with Linear Technologie regulator and Panasonic FC caps;

with and without added caps at C4 (input cap). each time I prefer the genuine PS. Adding cap at C22 is better when embeded DAC was used (analogic chinch output).

But I will try linear power supply when having time...

Why ! You sacrifice the first Personal Computer PS ! Piece of collection 😉

May you can measure at SB input but after the Self at L20 (just behind the SB plug) because here this self coil makes a Pi filter after C4 and before the brown smd tantal caps...

 

[Bud Barnez]

It's got relatively high inductance (2.5mH) vs. the Newava transformer that I used which has 225uH inductance. Other DIYers have characterized the Newava with high end measurement equipment and shown it works well in this application. So you're on your own here - no guarantees on how well this transformer will work. But definitely go ahead and try it out and tell us how it works.
---Gary

Ok, maybe I should have pursued a Newava but the Pulse transformer was easier for me to get. I will give it a go once I get hold of them. It is described as being for digital audio so hope it isn't too shabby.

I disagree with Lampizator on taking the SPDIF from the Xilinx chip. The 74HC04 is used as a buffer and should work fine. ---Gary

Thanks for clarifying. I will try connecting in the same way as your previous schematic.

On the subject of the additional caps for the power supply, do you know what the regulator on the wi-fi card is for? Is this used for anything important on the main board, or is it just related to the wi-fi? I will use Ethernet so wondering if it is worth any attention here.

 

[Bud Barnez]

Why ! You sacrifice the first Personal Computer PS ! Piece of collection 😉

May you can measure at SB input but after the Self at L20 (just behind the SB plug) because here this self coil makes a Pi filter after C4 and before the brown smd tantal caps...

I suppose that power pack is quite rare now, but it is a useful voltage for me and more useful in this application, for me at least.

I just tried measuring the power supply just after L20 for you. I can't observe any difference before or after L20. Probing after C133 shows to be much cleaner. This was using the original SB power supply but with 180uF on input.

The "improved" power supply is not accessible at the moment, but should be able to compare effect with that and measuring after the Pi filter another day.

 

[Eldam]

A fellow gave me the John Swenson 's name, maybe it can help you to tweak your SB Duet to another level.

DIY Request - John Swenson PSU for Squeezebox Touch

 

[GaryB]

On the subject of the additional caps for the power supply, do you know what the regulator on the wi-fi card is for? Is this used for anything important on the main board, or is it just related to the wi-fi? I will use Ethernet so wondering if it is worth any attention here.

I think that the Squeezebox shuts off the wireless card when you use Ethernet, so there's no need to worry about the wifi electronics. Others report and I have verified in my system that Ethernet sounds better than the internal wifi. My house isn't wired with ethernet so to try this I had to use an external wifi box which I then connect to the squeezebox via ethernet. I conclude that the internal wifi is generating some noise that somehow gets into the other parts of the squeezebox and subtly degrades the sound.
---Gary

 

[Eldam]

Gary, did you try the 2 caps lampizator tip near the regulator on the top of the SB wifi PCB ?

I believethe wifi as rj45 are bit accurate and buffered after in SB before traitment with the master local Clock. So it's maybe an internal local ground loop or change in local impedance somewhere in the SB because of PS dispatch when you use WIFI conf ?

I didn't myself...

@ Bud,

Strange that you notice nothing with the measurement after and before the smd self... maybe it acts like a band pass to stop some glitch of the poor PS... extremly rare than industrials uses components for nothing ?! But sometimes they do for audio reviews...if it looks good it sounds good.... But these Squueeze Boxs are hard to open and are consumers products more than hifi enthusiast products...

It would be interesting to see if the smd coil populate the SqueezeBox Touch yet ?

 

[Eldam]

spidf output

After the 74xxx chip I measure the C42 cap : around 75 nF ; r19 is 116 ohms, r38 is 216 ohms : all buzz with spidf output with my "voltmeter".

There is a self already before de spidf output after the resistor and cap : it's L5...

Gary, do you notice a huge difference with your additional self coil ?