[GBB]

It's been a couple of years since I first modified my Squeezebox 3 as reported in this forum:
http://www.audiocircle.com/index.php?topic=24353.msg215677#msg215677

Since that original thread, I changed my opinion and found that the SB3 sounded better using the SPDIF output driving an external DAC.  Probably because of the limited output capability of the DAC chip, the sound taken directly from the analog outputs of the DAC chip didn't have the drive of a good external DAC.  Over the last few years there have been some very good op amps that have come on the market, so I thought it was time to go back and see what could be done to improve the analog outputs of the SB3.  National Semiconductors has come out with a great dual op amp. the LM4562, and I decided to see what could be done with that chip.

The simplest version of this modification just replaces U1, a JRC2041, with the LM4562.  Doing that alone gives you an analog output that is better than the single ended outputs of the Transporter.  The SB3 uses electrolytic coupling caps, so this version lacks a bit in ultimate resolution but the sins are sins of omission and the sound is actually quite listenable.  Many people will be satisfied with this sound.

To take it up a notch further, you've got to replace more parts.  First off the input and output coupling caps need to be upgraded.  The input caps are labeled C16 and C20 and have been removed in the picture below, which I borrowed from another thread on modifying the Squeezebox (thanks DoS).  The output coupling caps are the 10uf caps underneath the headphone jack.  They can be seen on the right side of the picture below.  I replaced the input caps with 10uf 50v type N Blackgate caps and the output caps with 4.7uf 50v type N Blackgates.  You also need to upgrade C15, which is a 1uf electrolytic.  I used a 1uf film cap that I got at a local surplus place but something like Vishay/BC 1uf 63v polypro cap (digikey # BC2076-ND) would work fine.  Finally, you can update the high frequency filtering caps (C14 and C18), which are 330pf surface mount parts.  Changing these isn't absolutely needed.  I changed these to some silver micas but the benefit isn't that large.

Besides the changes documented here, I also upgraded the DAC chip from the stock PCM1748 to the higher grade version PCM1748KE and I also used a good quality 5v linear supply as discussed earlier. 

With these changes, the Squeezebox is a revelation.  The quality of the sound out of the analog outputs is so good that I've retired my external DAC.  Needless to say, it's tremendously better than the stock Transporter.

Happy soldering.

---Gary







 

[Folsom]

Did you just think the output was not high enough at 1.1v? I find straight into my Gain clone to be plenty of power, but I have no idea what amplifier you are using. My rca cables are also microphone cables so they are pretty sensitive.

You know if you wanted to you could solder on an adapter for dual single opamps, and use 627's. This might require some case modifications, but maybe not.

I think there is a possibility you like the sonic signature changes added by the opamp and more Blackgates, a matter of personal taste. I highly recommend doing modifications based on personal taste by the way, why not do it?

I do have to mention my Squeezebox directly feeds my Gain clone, and that is going to change with a passive pre-amplifier, so perhaps later I will pick up interest in this modification.

[Occam]

Gary,

Thanks much for sharing your results!

As a slight expansion, one needs the MA verision of the National chip, in SO-8 smd configuration. Either the LM4562MA
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=LM4562MA-ND
or the LME47920MA
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=LME49720MA-ND
which is the same but with numbering which jibes later released audio opamps

[GBB]

As a slight expansion, one needs the MA verision of the National chip,

Paul,
Thanks for the assist.  I should have listed the Digikey part numbers.  I also wasn't aware of the renumbering so that's an added bit of help I didn't even realize I needed.

Did you just think the output was not high enough at 1.1v?

DoS,
The new mods weren't driven by the output level - it was all about sound quality.  And it's not really about adding more colorations since one can hear a real improvement even before adding the Blackgates.  I think having an output stage with a lot of drive current capability (not voltage) is an important contributor to good sound.  Perhaps that's why I've never been a big fan of passive preamps.  This mod is highly recommended especially for those of you trying to eliminate the preamp stage and drive an amplifier directly.  I was actually thinking about you, DoS, when I wrote this up.  I know you've been through a tough time modifying your Squeezebox and I felt bad about offering up a new and better mod just when you'd finished the old one.  Sorry for not getting this one documented earlier. 

You know if you wanted to you could solder on an adapter for dual single opamps, and use 627's. This might require some case modifications, but maybe not.

I know about adapters to use single op amps in dual op amp footprints.   For example:
http://cimarrontechnology.com/index.asp?PageAction=VIEWPROD&ProdID=19
I'd have to check to see if this is really practical, but since it requires 0.610", I suspect it's not.  Even if it did fit, I would not use the OPA627.  I've tried them in other applications and found them to be not to my liking.  I find them dark sounding and lacking in high frequency details.  Given the quality of the LM4562, I can't imagine anyone finding the 627 an improvement but there's no accounting for taste.

---Gary

[Folsom]

I will be honest, this does make me want to do some more modifications. My troubles were quiet silly with the router. The rest was well I should of just got the good RCA's to begin with, but I am not a big spender so even little things I try to save money on.

I am going to do the DAC first. The rest might be a long way down the road. Then again get Blackgates while you can. I thought someone was start to manufacture them again after they got dropped originally, but most website still say they are going to run out... What will we do then .

Why did you not make C15 a Blackgate?

I am going to do these mods now I am pretty sure, you are an evil man, but I like evil it appears.

I made a list of parts everyone will need. The Blackgates are from Parts Connexion http://www.partsconnexion.com (my favorite source, they are the best in my opinion for almost everything), http://welbornelabs.com/mica.htm , and http://www.digikey.com

Needed

2x BLKGATE-     60098     N     4.7    50v     5 x 11     $3.25 ($6.50) C16 & C20

2x BLKGATE-     60099     N     10     50v     8 x 11     $4.25 ($8.50) C21 & C23

1x BLKGATE-     60097     N      1      50v     5 x 11     $2.65 C15
or
1x Vishay/BC 1uf 63v polypro cap Digikey # BC2076-ND $1.48 C15

1x National Semiconductors LME49720MA Digikey # LME49720MA-ND $5.70

Optional:

2x Mica Silver 330pF http://welbornelabs.com/mica.htm $.70 ($1.40)  C14 & C18*

*Note if you want to properly remove the stock surface mount ones you need two soldering irons. I however have found one usually works fine but if you nudge the capacitor they snap off on the side without the soldering iron applied too. This means you can never put it back in though!

RCA Connectors with the nut on the side that makes it all easy! Well you have to trim the PCB board the original ones where mounted too a little bit, and scrape the original hole  in the case for the RCA's with a pocket knife for about 10 seconds. However there is one issue if you have already done this... I am about to cover that. (Not cheap but these are really nice, the plastic in them does not melt either, and make sure to connect the ground with it not in circuit because it requires a lot more heat, I set my soldering iron to 900 for doing it)

CARDAS-     62010     GRFA S THIN Female jack, gold/rhodium - mounting hole 0.44" $16.95/pr

If you, like me, have already performed the output capacitor modifications, then may of already removed the original PCB board spot to attach the positive too. However after looking over the schematic it shows that this is not really an issue, the only thing you have to really work around is the fact that you might have to move the original wires you ran out of the way to do this. You should be able to just run from the pads on C16 and C20, on the side without the cut corners, new wires that connect to the RCA's side of the Blackgate 4.7uf Type N capacitors you put in.

Texas Instruments PCM1748KE DAC Digikey #PCM1748KE-ND $2.93

Signal Wire, whatever you want, 23awg is a good size, I used some Jupiter with cotton shielding.

I would also like to point out that it might be easier to have the output caps by the RCA's for room constraints.

[tonyptony]

Gary, I'm wondering if you had tried to bypass the inductor just before the RCA digital out, as Pat had suggested in another thread a while back. I've done and had done a number of mods as well, but when a suggestion is backed up by measurements, as Pat had done in the case of the whole digital out discussion, I have to suspect there may be a good reason to give it a try. As you have been doing a lot to the SB3 I was hoping you had given this one a try.

[GBB]

Why did you not make C15 a Blackgate?


2x Mica Silver 33pF http://welbornelabs.com/mica.htm $.40 ($.80)  C14 & C18*

DoS,
I didn't make C15 a Blackgate because I didn't have any handy.  I'm sure a Blackgate would work fine there.  But 1uf is small enough that you can also use a good quality film cap and fit it in, so why not use that?

Regarding the silver mica caps - they should be 330pf, not 33pf.  And you can get those from Digikey too.

---Gary

[GBB]

Gary, I'm wondering if you had tried to bypass the inductor just before the RCA digital out, as Pat had suggested in another thread a while back. I've done and had done a number of mods as well, but when a suggestion is backed up by measurements, as Pat had done in the case of the whole digital out discussion, I have to suspect there may be a good reason to give it a try. As you have been doing a lot to the SB3 I was hoping you had given this one a try.

Tony,
Thanks for the suggestion.  I agree that the measurements from Pat are really valuable and provide some good tips on improving the SPDIF beyond what I did in my original thread.

Regarding the removal of the inductors, if you look back on my thread from 2 years back you'll see that I suggested removing those inductors back then and I've included that in all my mod since then.  It does make a large improvement in sound quality.

Thanks,
---Gary

[Folsom]

Why did you not make C15 a Blackgate?


2x Mica Silver 33pF http://welbornelabs.com/mica.htm $.40 ($.80)  C14 & C18*

DoS,
I didn't make C15 a Blackgate because I didn't have any handy.  I'm sure a Blackgate would work fine there.  But 1uf is small enough that you can also use a good quality film cap and fit it in, so why not use that?

Regarding the silver mica caps - they should be 330pf, not 33pf.  And you can get those from Digikey too.

---Gary

Corrected it!

[tonyptony]

Regarding the removal of the inductors, if you look back on my thread from 2 years back you'll see that I suggested removing those inductors back then and I've included that in all my mod since then.  It does make a large improvement in sound quality.

Thanks,
---Gary

Ah, right. Forgot about that thread! You removed both L8 and L9 if I recall. Which one is the one Pat was referring to in his thread with the TDR?

[GBB]

Ah, right. Forgot about that thread! You removed both L8 and L9 if I recall. Which one is the one Pat was referring to in his thread with the TDR?

I'm sure that Pat removed both of them.  He wouldn't have gotten the good measurement results if he hadn't.

---Gary

[Folsom]

Gary do you think un-soldering the headphone jack will cause the feed to the RCA's to be cut off? I am wondering because it is sort of in the way and will never be used by me most likely. The schematic says no, but it does not show me what is inside of the J3/4 headphone jack either. My guess would be if it did I have to short out the ground to the positive on the headphone jack's PCB tracing.

[GBB]

Gary do you think un-soldering the headphone jack will cause the feed to the RCA's to be cut off?

The headphone output and the RCAs are unconnected so feel free to get rid of the headphone output jack.  While you're at it, get rid of the  headphone driver IC.  It's a TS486i chip from ST labeled U4 on the board.

---Gary

[jbeard]

I am looking for the best analog sound out of the SB3. 

Is this still one of the better mods?

What would be recommended instead of Blackgates as they seem to have all but disappeared?

Thanks!

[Audi0]

A question for GBB, Destroyer of Smiles or anyone?
I have read this thread with great interest as I am currently modding an SB3, my question is regarding capacitors and choices other than Blackgate N series? These are near impossible to find now, would anyone like to suggest alternatives?
Any help would be greatly appreciated!

[GBB]

I have read this thread with great interest as I am currently modding an SB3, my question is regarding capacitors and choices other than Blackgate N series? These are near impossible to find now, would anyone like to suggest alternatives?

The Elna Silmic II caps are very good. You can get them at Digikey.
http://parts.digikey.com/1/parts/46697-cap-4-7uf-25v-elect-audio-rad-rfs-25v4r7me3-5.html
http://parts.digikey.com/1/parts/46698-cap-10uf-25v-elect-audio-rad-rfs-25v100me3-5.html

---Gary

[Audi0]

Cheers mate, I'll post some pic's once completed

[Audi0]

Just thought that I would give you guy's an update, especially seeing as though this thread was one of catylysts to me modding my Squeezebox.
I am also noting the mod's I am attemting in a blog on the diyAudio site.
Surface mount components are new to me, I did try to change a receiver chip on an adapter board once, but stuffed it completely lifting a few tracks  so I was very wary about applying to much heat in fear of the same happening.
I have seen that low melt solder stuff used for desoldering on YouTube and the net, but I don't believe that anybody is selling the stuff in Australia yet? Could be wrong?
So the modification as described above is done, I used a Brown Dog adapter and it worked very well.
The result is very good, to me the sound is more dynamic and I am very happy with the results so far. I am still running the wall wart at the moment, the linear supply is still being built, I cant wait to hear the results with that. 

[GBB]

Just thought that I would give you guy's an update . . .
 
The result is very good, to me the sound is more dynamic and I am very happy with the results so far. I am still running the wall wart at the moment, the linear supply is still being built, I cant wait to hear the results with that.

Steve,
Congratulations on the successful mods.  I know that working on SMT parts for the first time is stressful and it's easy to mess things up.

Regarding the power supply mods, did you happen to read this thread:
http://www.audiocircle.com/index.php?topic=50284.msg452073

It details another path to good sound using a power conditioner with the switching power supply.  The linear supply you're building will sound good but it's not the only path to improved sound.

Happy building.
---Gary

[col_s]

I have seen that low melt solder stuff used for desoldering on YouTube and the net, but I don't believe that anybody is selling the stuff in Australia yet? Could be wrong?

Jaycar now sell Chipquik
http://www.jaycar.com.au/productView.asp?ID=NS3050