Shall we DIY mod the Squeezebox 2?

goskers · « **Reply #40 on:** 24 Aug 2005, 05:36 pm »

Josh,

Considering I am in the same boat as yourself I am very interested in modding the SB2 for the best digital out possible. A digital trannie whether it be smd or not sounds like a great option.

Vinnie R. · « **Reply #41 on:** 24 Aug 2005, 08:00 pm »

Quote from: Davey

Paul,

Here's a question for you. Why do you have to drop the voltage from the battery to 5 volts? Why not just hookup the battery and forget about it? The SB2 internal regulators shouldn't care if their input voltage is a bit higher eh?

Cheers,

Davey.

Hi Guys,

I recall someone asking Sean Adams a similar question on the Slim Forum, and Adams stated that the operating range is about 5V +/- 400mV (ie, 4.6V to 5.4V), and that some components stop operating outside this range. There is also a protection circuit on the input (resettable fuse), to shut supposedly shut everything off safely in the case of overvoltage...

Powering the SB2 directly with a 6V SLA will probably not work out....use a regulator(s)...

Regards,

JoshK · « **Reply #42 on:** 24 Aug 2005, 08:28 pm »

Thanks for the input Vinnie.

Based on initial poll response in this thread, it looks as though everyone is interested in the digital section and most are also interested in the analog. First things first, the most bang for the buck and obvious point of improvement will come with the PS as stated earlier.

Given the talk in the SD forum about jitter performance (which is fantastic btw) I personally have written off any hope of improving things based on clock upgrade. In fact, the likelihood that you will mess things up with an uber clock is pretty high. The more I read, the more I learn that clocks are not a plug and play upgrade and serious measurement equipment is needed to ensure a good outcome.

We have some former Ham radio guru's in our presence and someone has volunteered (more or less) to do some calculations on the optional length of the SP/DIF cable to avoid reflections of even harmonics of the transmission frequency. In english, you want to make sure your cable length itself isn't causing jitter. Ideally you want as few connections as possible.

It is highly recommended that no matter what else is done in terms of mods that you take aforementioned measure length of whatever's clever coax cable and hardwire it directly onto the board, eliminating the RCA connector. This way you will only have one resistance on the load side to worry about. We DIYers are not fickle Nancies, so I don't want to hear anyone crying that they can't swap digital cables that way.

I do think that digital transformers will be an interesting thing to explore, but it seems that in terms of low hanging fruit and most return for work done this is nearer to the end of the line. First we need to hammer down the PSU revisions, then we can ponder next steps. (I always am getting ahead of myself

)

For the analog output side, once PS revisions are done, Occam has outlined some very good ideas on how to approach improvement to the analog output. One needs to think a bit about whether a little over 1Vrms is enough drive for your application. If it is then a cap bypassing the opamp is fine and dandy but then cables should be really short (i.e. ~6inches) and again should be hardwired or else you will be throwing away Khz off the top end.

If you want more than 1Vrms then Occam has provided a very good choice for a suitable replacement opamp.

Ideally it would be great if we can get the yet-to-be-named fellow to design and sell us a daughter card that has the appropriate regulators and analog output section that we can jumper in.

Occam · « **Reply #43 on:** 24 Aug 2005, 09:47 pm »

Quote

If you want more than 1Vrms then Occam has provided a very good choice for a suitable replacement opamp.

Not exactly..... I mentioned the AD8066 as it subjectively is a very nice opamp, and would provide the following -
More current drive, allowing the technical ability to drive longer capacitive interconnects.
Dircect coupling of the DAC to the opamp eliminating that need for an interstage capacitor.

But inherent with direct coupling is running the 8066 with that same 5v single rail driving the DAC (yes we could use a separate regulator), and while the AD8066 runs quite nicely at that voltage and single rail, that 5v rail would allow minimal possible amplification, and it would be easier just to configure it as a voltage follower, providing more output current.

As my current thoughts are towards a 6v SLA regulated down to 5volts, we really don't have any voltage that would allow us to get substantially above appox 1+Vrms that is already provided by the DAC itself.

Alternative topologies such as direct coupling the DACs Ocm and Vout to an instrumentation amp could provide output >= to 2Vrms, and also eliminate the need for an output capacitor, would require a split supply of at least +5 and -5Vdc. Power from a 6v SLA would make this somewhat difficult, unless we use switching supplies.

As immitation is the sincerest form of flattery, for the time being, I'm content to immitiate Vinnie and Wayne, and take analog output, via a cap, directly from the DAC. I may well have overstated the downsides of this approach.

If we do perform that surgery needed to bypass the opamp, I do think it useful to at least investigate changing the 78xx regulators powering the DAC and opamp, running off a switcher, changing then to LT1761s @ 5v and 3.3v to provide linear regulation for the DAC, off the 6v SLA. As we'd void the warranty when bypassing the opamp, in for a penny, in for a pound.

bryman79 · « **Reply #44 on:** 6 Sep 2005, 03:21 pm »

Hello All,

Does anyone have pictures or schematics of the innards of the SB2? In particular of the SPDIF output stage?

Although I have not played around with one of these units myself, I have seen one playing. I immediately thought to myself that one of these would be a dynamite box if the RCA jack for SPDIF out was nixed and replaced with an appropriate BNC bulkhead. Josh, although the best solution is to have no jacks at all to maintain a constant impedance, I've been told by those with TDRs that the Trompeter jacks do an excellent job. I can verify this as soon as I get my hands on a TDR of my own...

As for the SPDIF output buffer, take a look at my M-Audio Transit mod here: http://www6.head-fi.org/forums/showthread.php?t=131150. Not sure if it would be applicable here as I have no idea what lies within...

The advantage of bringing digital out properly is that you can for the most part ignore the power supply. The audio transformer solves that problem. And Josh, you may want to look at the Newava S22083. Here is some relevant discussion on the SC and Newava transformers (long thread, but a good read): http://www.diyhifi.org/forums/viewtopic.php?t=284

And Josh... I'm glad to see you are concerned with the length of the SPDIF cable. I currently have 4 SPDIF coax cables terminated in Trompeter wrench crimps, per Jocko's suggestion: 2m, 3m, 4m, and 5m. Just the other night I was trying them all in my system, and boy what a difference they make. FWIW, the 3m hit the spot in my system (hard to explain how, but all I can say is that Diana Krall - Peel Me A Grape just sounded right and tended to give that spine-tingling, goose-bumpy feeling...), but it will vary from system to system. On that note, I would suggest listening and not solely relying on calcs.

Sorry for the rambling discussion... I don't mean to derail the thread or step on anyone's toes...

Regards,
Bryan

JoshK · « **Reply #45 on:** 7 Sep 2005, 03:13 pm »

Bryan,

Thanks for your comments, and no toes are stepped on.

This is a friendly community and we are always open to new suggestions and ways of thinking about things. That is what it is about after all.

I am really a newbie myself, but I am willing to try and learn what I need to. When I start a thread like this, it is just to start the ball rolling, it isn't that I have the answers myself.

I have never heard of "trompeter" jacks, do you have further info about them? Thanks for the other links, I will try to read them later when I get a chance.

This project on my end is progressing at a snails pace as I am currently neck deep in a bathroom remodel, heating/air system installment, "While we're at it, why not redo the electrical and plumbing??"-sort of jobs. It may be a little while before I get enough time at my bench to try some of this out, so I am mostly just researching it myself.

bryman79 · « **Reply #46 on:** 8 Sep 2005, 05:54 am »

Josh,

Trompeter (trompeter.com) is the brand of BNCs that were recommended by Jocko Homo (i.e. DIYAudio and DIYHiFi) and other experienced DAC builders. Jocko apparently owns a TDR, and he used them professionally, so I figured what the heck. The ME in me liked them, as they are built to last... I was impressed. And the wrench crimp cable terminations are very easy to work with and do not require expensive crimping tools (which you can still manage to screw up if you crimp them wrong).

I'm hesitant to give out part numbers because they make one for most every variety of cable, but what the heck. Here are part numbers, pics, and datasheets for the connectors used for Belden 1505a cable.

UPL20-2 Cable Termination
Datasheet: http://www.trompeter.com/assets/product/pdf/1-0369.pdf
Pic: http://img.photobucket.com/albums/v458/bryman79/TrompterUPL20-2.jpg

UBJ27 Bulkhead
Datasheet: http://www.trompeter.com/assets/product/pdf/1-0132.pdf
Pic: http://img.photobucket.com/albums/v458/bryman79/TrompeterUBJ27.jpg

The Married Couple
Pic: http://img.photobucket.com/albums/v458/bryman79/TrompeterConnected.jpg

BTW, I would call Trompeter and confirm that you have the correct part numbers for your desired cable before purchasing. And FWIW, I got mine at Newark.

Regards,
Bryan

JoshK · « **Reply #47 on:** 16 Sep 2005, 05:05 pm »

FWIW,

Occam mentioned that markertek.com might have Trompeter BNCs and indeed they do.
http://www.markertek.com/Product.asp?baseItem=UPL2000%2DD2&cat=CABLESCONN&subcat=VCONNECT&prodClass=BNCCON&mfg=Trompeter&search=0&off=

A whole lot cheaper than Newark.

bryman79 · « **Reply #48 on:** 17 Sep 2005, 04:17 am »

Josh,

These are the crimp models, which require an expensive crimping tool. And you run the risk of screwing up the crimp. I'll stick with the wrench-crimps...

Bryan

JoshK · « **Reply #49 on:** 17 Sep 2005, 02:22 pm »

awww....yeah I wondered why such the difference in price.

multibit16 · « **Reply #50 on:** 20 Jan 2007, 02:27 pm »

Just found this thread when searching around for modding the Squeezeboxes:)
So anybody got any further yet?
I have a lightly modded SB3

Mods so far is

Diy external supply ALW super reg set to 5v using a LM1084 pre-reg
Op-amp changed to AD8066, the 1uf biasing cap for the op-amp changed to 1uf Red Wima
Lowered the cap going across the fb resistor to 33pf
Removed the 12mhz crystal

My SB3 already uses the PCM1748KE grade dac so that saved me a job.
Next thing is the 4 x coupling caps, any idea's? I'd also like to mod the SPDIF out circuit

JoshK · « **Reply #51 on:** 20 Jan 2007, 06:35 pm »

Coupling caps are like wine, choose your preference. I kinda like SonicCaps for a reasonably priced cap, but I haven't tested a gammut of them yet. Some really like Auricap and some of the pro-modders have used those (and VCaps & Soniccap Platinums).

I planned to experiment with the Soniccaps bypassed by Russian teflon caps (sourced off ebay reasonably). The Russian teflons are huge so only values small enough for bypass have a chance to fit.

I sort of dropped the ball on this thread because I had too many irons in the fire. I still plan to resurrect it with my own personal experience once I get back to tinkering. Right now I just built a linear PSU with some good stuff. That is a big item to not overlook.

multibit16 · « **Reply #52 on:** 20 Jan 2007, 06:53 pm »

Thanks Josh,

I've modded quite a lot of cdps and dacs but the SB is fairly new to me, the usual thing is the space or lack of it

Caps I've tried in the past are Auricaps , Multicap RTX, Audyn KP-SN, PIO ,Ansar super sound and a few others.
I didn't like the Auricaps or PIO's at all tbh, one of my current favourites is Evox SMR which is PPS.
Problem with all the film types is the size of them.
I've not tried the Sonicaps yet but have read varying reviews about them, I may give them a go next, bypassing with the Teflons sound a good idea.

Apart from the coupling caps I was hoping to get some more idea's what to do with the SB3, although its sounding better since doing the mentioned mods its still quite behind my modified cdp.
If I can't get the analogue outs much better I'll try a 1:1 pulse transformer in the SPDIF circuit and use it with my diy dac

JDUBS · « **Reply #53 on:** 20 Jan 2007, 07:04 pm »

Quote from: JoshK on 20 Jan 2007, 06:35 pm

Coupling caps are like wine, choose your preference. I kinda like SonicCaps for a reasonably priced cap, but I haven't tested a gammut of them yet. Some really like Auricap and some of the pro-modders have used those (and VCaps & Soniccap Platinums).

I planned to experiment with the Soniccaps bypassed by Russian teflon caps (sourced off ebay reasonably). The Russian teflons are huge so only values small enough for bypass have a chance to fit.

I sort of dropped the ball on this thread because I had too many irons in the fire. I still plan to resurrect it with my own personal experience once I get back to tinkering. Right now I just built a linear PSU with some good stuff. That is a big item to not overlook.

Josh, what stuff did you use in your PS?

-JIm

JoshK · « **Reply #54 on:** 20 Jan 2007, 07:15 pm »

I used an IXYS bridge > Jensen 4 pole > LT1085 > Jensen 4 pole. The circuitry around the LT1085 I used what I had on hand, which was a couple resistors and a Nichicon gold electrolytic. The circuit came from the application notes for the LT1085. Do a search here for "LT1085" and you should find the previous thread where we were discussing this with mgalusha.

multibit16 · « **Reply #55 on:** 20 Jan 2007, 07:56 pm »

Hi Josh,

What value Jensens are you using before and after the reg? I use the 4-pole T-network caps in my UCD's psu and really like these caps.

Cheers

JDUBS · « **Reply #56 on:** 20 Jan 2007, 08:27 pm »

Quote from: JoshK on 20 Jan 2007, 07:15 pm

I used an IXYS bridge > Jensen 4 pole > LT1085 > Jensen 4 pole. The circuitry around the LT1085 I used what I had on hand, which was a couple resistors and a Nichicon gold electrolytic. The circuit came from the application notes for the LT1085. Do a search here for "LT1085" and you should find the previous thread where we were discussing this with mgalusha.

Yep, got the circuit down. Really just curious about the caps you chose...the Jensens are a popular choice for this supply. Good stuff!!

Thanks,
Jim

JoshK · « **Reply #57 on:** 21 Jan 2007, 12:39 am »

They are 47,000uf each. Not cheap.

multibit16 · « **Reply #58 on:** 21 Jan 2007, 12:49 am »

47,000uf on the output of a regulator

I'm amazed that reg isn't ringing like mad

Are the Jensens ultra low ESR? I was thinking about fitting a T-network to feed my ALW super reg.

JoshK · « **Reply #59 on:** 21 Jan 2007, 12:52 am »

No there is a Nichicon smaller value 'lytic cap on the output of the regulator. I am just going from memory here... I know there is two of those big jensens in there.

Poll

What sort of mod are you interested in for your SB2?

Shall we DIY mod the Squeezebox 2?