[sedah]

Ok, I've been reading through the aforementioned thread on modding the SB. Its been a long time since I was in the guts of digital circuit design (I'm a mathematician, not an EE) and a fair bit of it flew over my head...

That said, for those of you who aren't keen on reading a 9 page thread, here are some of the 'gems':

...

I have no doubts that these fancy outboard supplies are better than the supplied wall wart. However, that will not affect the jitter that is generated by the poor supply that feeds the clock and SPDIF output chip. And that is what will really make a difference.

If the guys that make these outboard supplies were as clever as they like to imagine that they are, they would find a way to make one that provides for a clean supply dedicated to that part of the SB2/3. But, that would involve modifying the guts of one. Not as easy as making some over-priced accessory that anyone can plug into the power connector.

...

I have no doubts that these fancy outboard supplies are better than the supplied wall wart. However, that will not affect the jitter that is generated by the poor supply that feeds the clock and SPDIF output chip. And that is what will really make a difference.

Yep Pat.  It seems rather silly to spend more on a power supply when simply disconnecting the clock and clocking it externally, as the pacecar does, yields a much better result at a cheaper price.  Although I may eventually get a pacecar, because I don't know of other similar products, I think Steve's solution could be done cheaper.
http://home.socal.rr.com/audio_gestalt/default.htm

If you, or someone, could create such a device at a reasonable price (say below Aus $500) then you would have at least one customer (me).

Some people claim they can hear jitter of 2ps.  I would like that claim put to a blind listening test some day.  Burson audio has a clock with jitter about 5-10 ps - maybe a bit higher.  They claim never to have found anyone that can detect that level of jitter.

Of course that is using an external DAC.  The claim is with these power supplies, and mods, the internal DAC sounds 'fantastic', beating things like a Wadia (not that I am a fan of Wadia mind - but that is another story).  I have a lot of respect for some of the people making that claim, but believe a well designed external DAC being fed a low jitter signal will outperform it.

Thanks
Bill

and also this one:

Paul:

I am not trying to knock the "competition" (they really aren't competition, since we are not in the business of doing those sorts of product mods. ) I am merely pointing out that it make little sense to stick on an expensive outboard supply, and ignore a key problem. Seems to me that at least one of those guys would have thought of that already.

Don't know much about SN's stuff. I get the idea he has an external clock that you pump into the unit. Yes, that is one way to solve the problem. Still, the chip that does the clock also does the SPDIF output. (I believe more than one of us has pointed out that the 48 kHz clock can be disabled.)

If you only have one internal supply, (and a SMPS at that) to power the big FPGA and all of that stuff, it is going to be hard to completely isolate the noise it places on the rail from the critical chips.

The problem arises since the PSRR of  CMOS gate is only 6 dB at the midpoint. Which is around the point when the logic levels are changing states. Not the right time to have things wandering around, due to noise on the rails.

As for how much jitter you can hear??????

Well, I dunno. I would not say that one can actually "hear" the jitter. More like one can better detect lack of jitter. Jitter has to be quantified as to both magnitude and frequency spectrum. To say "It is 20 pSec", without having the spectral content known, is not really helpful.

But, back to your question:

A lot of folks that I work with claim that when you get jitter measurements down into the single digits (pSec-wise), you can not detect much of a change.

It also depends if the jitter is Gaussian or data-dependent. The latter being more discernable, in a negative sense.

Jitter is much less of a problem in CD players. The main way data-dependent jitter is introduced is when they use the filter chip to generate the clock. SPDIF is a different animal. Tons of data-dependent jitter.

So with the SBs, it sounds like the PSUs mostly affect the analog output, and barely touch the digital. That if you want the most bang for your buck you go after 'fixing' the spdif / clock. That said, its worth pointing out that a very good DAC could theoretically make up for a 'decent' digital source. I suppose that fixing up the output here is going after what my prof referred to as the 'Japanese approach'. 

[oneinthepipe]

Wait a minute - how come I got jumped on but Jim didn't?   

Anyone is fair game can present interesting comments for discussion, but by the time Jim returns from building speakers, we have usually come to our senses resolved any technical issues.

This was a very informative thread, despite perhaps overly illuminating the passion which we have for music and music reproduction and the zest with which we apply various methods of audio decision-making.

floresjc, what do you have in store for us next?   

You guys are the best.

[funkmonkey]

okay floresjc, from what i can remember after following this thread on and off today...

I'm using a Logitech device (Transporter (Modwright)) with a Mac to stream FLAC from an external hard drive.  Works (and sounds) great.  I do not use iTunes for this device though you can use your iTunes library with SqueezeCenter (the user interface software that SqueezeBox uses).  I maintain two music libraries, one in FLAC for use with my stereo and a second set of compressed MP4 files (iTunes library) for use on my iPod.  All files are ripped from CD using MAX (http://sbooth.org/Max/) into the FLAC library, and then converted <also using MAX> into MP4 for iTunes.  It took me a bit to get used to the process but it works great.

The Transporter is hooked to my iMac via eathernet network.  This works better than wireless IMO and practically sets itself up, no encryption to worry about, no IP address issues (I had some of those before I went wired), and zero drop outs.

SqueezeCenter does allow you to control everything from your computer, and from the remote, and from the controls on the actual device.  You can set it so that the server software starts up with your computer.  It is then accessible through the System Preference panel on the computer.  It also allows you to customize its functionality a by utilizing third party plug-ins.  I use a couple to enable playlists much like the iTunes "smart playlists."  I think if your iTunes library is shared with SqueezeCenter that it will also be able to use your iTunes playlists, but it will not fully sync with iTunes...  (tracks played are not updated in iTunes or anything like that) this is my experience and one of the very few frustrations I have with SqueezeCenter, if anyone knows how to get them to play more completely together, please let me know

The direction that this thread took was a little surprising to me, but then again anytime a strong opinion is expressed, there is some form of opposition... and in the audio world the same underlying issues seem to come up over, and over again.  I like to read what other people think about gear that they have heard, wether I agree or disagree.  Thats why I am here.

Mike-  thanks for this very interesting and informative post, and for spawning the few others that are directly related to it.  We could all learn a bit from your objectivity and willingness to experiment.

A few semi random thoughts...

If you are going to a DAC, there should be absolutely no difference.  The bitstream either puts out should be EXACTLY the same as the original CD.  In this case, the DAC determines the sound quality.

The bit stream should be the same, but that is not always the case. The redbook CD standard includes an error correction mechanism to try to fill in any missing bits whe a disk it not properly read. How often this kicks in will depend on the quality of the disk and the quality of the player. One of the advantages of a hard disk based system is that since the disk does not have to be read in real time, it can be re-read to verify the bit were read correctly. There are a few, very expensive, transports that do this but they are not the norm. The new, hideously expensive, Boulder that is in this months Stereophile is one such device. I believe the PS Audio Perfect Wave Transport does this as well.

Even if the data is exactly the same, there are unfortunately other things that can cause trouble. The obvious one is jitter, which are timing errors. Modern DAC's are much less sensitive to this but it can still be a problem. Bits are still the same but not necessary decoded at precisely the correct time.

Another thing that can muck it up is the integrity of the waveform. It should be a perfect square wave, fully on or fully off. But things can cause trouble and lead to potential errors. Noise in the supply rails can raise the zero level, the leading edge can become slightly rounded, ringing can occur. These can make it more difficult for the DAC to decode the signal and can impact the timing in the case of a rounded leading edge. There is a excellent thread on digital signals by Pat from Analog Research Technology with a heading something like "improving the Squeezebox digital output". He is an RF engineer and has posted TDR traces showing what a digital output should and should not look like. IMO it's well worth the time to find and read, regardless whether one owns a squeezebox or not.

As to the efficacy of a power supply on the squeezbox. Some years ago when I first started playing with them I built a solid linear supply and a battery powered supply. Both used the same regulators and similar filter caps. I fitted a toggle switch in the box and there is sufficient capacitance in the SB to allow real time switching with no noise or dropout. Since they were both regulated at 5V there was no change in level, so it was a fair comparison. At a get together I asked for feedback from the folks present. While not double blind, it was single blind in that I was the only one who knew what supply was in use. All participants could tell them apart and much to our surprise the AC powered supply was preferred. I'm sure this isn't definitive enough for many folks but it was quite clarifying for me.

Just my nickels worth, YMMV.

mike

Cheers

[zybar]

But I still can't understand why when using the SB's digital outputs it could make any difference.
- Jim

That's what I've been wondering this entire time, thus my disbelief in them. 

Wait a minute - how come I got jumped on but Jim didn't?   

Nuance,

Because Jim didn't attack and slander other vendors here at AC like you did.

You can't make the statements like you did about two of our more well respected vendors (without even hearing, testing, and measuring their products) and expect to not be challenged. 

George

[zybar]

Jim, I have asked a friend who is much more technical than myself to respond to your questions.  If he doesn't I will give it a crack.  BTW, not last year, but the year before, there were quite a few people in the David Ellis room who got to hear SB power supplies from Wayne at Bolder Cable and Hugh at AKSA Audio and all agreed that they heard improvements over the stock PS. 

George

The power supply I used at RMAF was supplied by one of the two you mention.  I can definitely see the benefits if you were listening to the analog outputs (and I imagine most of those hearing the difference were).  But I still can't understand why when using the SB's digital outputs it could make any difference.

- Jim

Jim,

I hope Mike's post and the link I provided to Pat's thread shed some light on why there are differences in transports and how they can produce a different sound through the same DAC.

As always, in the end, it is perfectly ok that with disagree and have differing opinions.

George

[Big Red Machine]

Anyone here use a squeezebox with a Mac or PC? If I'm not mistaken, you install a program on your computer and it simply streams from your computer, it doesn't actually hold the files itself. If I'm not mistaken, someone said Jim demos hooked up to a squeezebox, but I have to wonder if he brings a computer along or has some nifty setup.

I'm trying to figure out the best way to get my songs across the room into an Insight preamp. Can you run a squeezebox off of iTunes or do you have to use their separate music server?

Have you received a sufficient answer to your initial inquiry? 

[jsalk]

Jim,

I hope Mike's post and the link I provided to Pat's thread shed some light on why there are differences in transports and how they can produce a different sound through the same DAC.

As always, in the end, it is perfectly ok that with disagree and have differing opinions.

George

A few random thoughts...

I will have to find some time to read Pat's thread.  Hopefully I can learn something.  Also, note that I am not disagreeing, I am merely questioning in the hopes of resolving the issue in my own mind.

There are areas we definitely agree on.  I think that using a cleaner power supply will improve an analog output.  And the quality of a DAC can differ greatly.

I visited Frank Van Alstine last week and looked at scope measurements of various DAC's reproducing a square wave at various frequencies.  All I can say is there was quite a difference.  So there are obvious quality differences between DAC's.

As for jitter, in my recording studio, ALL digital components are clocked off an external EXTREMELY accurate and stable clock.  Thus, they are all in sync with almost no jitter.  Unfortunately, it is not easy or practical to do this with consumer audio equipment (pro equipment is often set up to work with either internal or external clocks). 

A few months ago, I ran a test comparing a Jennifer Warnes (Blue Raincoat) CD with the same cuts from my SB through a DAC.  I set them up so that I could switch inputs and A/B compare the two instantly.  The CD was clearly superior.  This didn't make sense to me.  In trying to sort it out, I noticed I was playing a remastered CD.  I then ripped this remastered CD to my computer and sync'd up the two sources so I could switch back and forth instantly.  Since I was alone, I switched back and forth until I lost track of which was which and continued to compare.  At this point, I did not know which source was playing at any give time and could not hear any differences at all as I switched back and forth.

As to jitter, the jury is still out on how audible this is.  It would seem to me that a well-designed DAC with a stable, accurate clock should be able to handle reasonable amounts of jitter with no problem.  (I'm no expert here as I have never taken the time to investigate this.)

To sum up, I would still like to understand what differences in various digital sources fed to the same DAC would result in clearly audible differences and whether or not a blind listening test would confirm these differences.  Unfortunately, I do not have various transports to test.  If anyone in the area has a transport other than an SB and would like to run some tests, I would be more than happy to host a listening/testing session.

- Jim

[zybar]

Jim,

Later in the summer, I would be happy to lend you some of my digital gear so you could run a test.  Depending on how things play out, I can give you a SB with a Bolder Cable modified Elpac PS and maybe even my Modwright Transporter.

I know your day job keeps you busy, but if you want to borrow some gear for testing purposes, I would be happy to assist.

Maybe I am a little dense this morning (or every morning), but in the test you mentioned in your post, it is unclear to me what you exactly tested?  Did you have a transport or cd player with the physical media in it connected to the same DAC as your SB?  If so, what was the transport or physical cd player?

Are you saying that using the same DAC that there was no difference in sound between the transport or cd player using physical media and the SB using ripped media (same exact cd) off the computer?

I can run that type of test for anybody who wants to come over and let them decide for themselves if there is a difference.  The Modwright TP accepts a digital input so we could use any of the cd players or dvd players I own (or that somebody wants to bring over) to play the physical media and directly compare it to the ripped media that is stored on my computer and played via SqueezeCenter.

Anybody in the Boston area want to come over and try this?  If so, shoot me a PM.

George

[TF1216]

Please count me in George. 

[Nuance]

Nuance,

Because Jim didn't attack and slander other vendors here at AC like you did.

You can't make the statements like you did about two of our more well respected vendors (without even hearing, testing, and measuring their products) and expect to not be challenged. 

George

Two vendors?  The only company I talked about was Bolder (I stated that I realized Dan = Modwright, of which I HAVE heard their products and like them), and I said I doubt their power supply would effect the sound (I doubt any vendor's would when using the digital output).  That just my opinion based on previous listening tests.  I haven't taken measurements, but measurements don't always prove humans can actually hear the difference.  How is that attacking and slandering?  I guess our definitions differ, or perhaps you are just looking to pick on someone this week.    Whatever it is, I can take it.

In short, I am taking the same stance as Jim; I'm just more vocal about it.  When someone doesn't believe a piece of equipment will make an audible difference, that pretty much includes all the vendors that make that device.  If that upsets you, or you think I am directly bashing what you own, that's not the case.  As I said earlier, if you say you hear a difference, that's all that matters.  If you want to pay $950 for Bolder's Ultimate Power Supply, go for it.  Personally, I think the analog mod would make a much larger difference, as would an outboard DAC (as I've stated previously).    But seriously folks, let's keep it civil hear.  I stated my opinion, and that's that.  No need to get heated over it.  This is a place to come, learn and share experiences and opinions.  If I am going to get crap for doing that, I'll stop - just say the word.

[jsalk]

Jim,

Maybe I am a little dense this morning (or every morning), but in the test you mentioned in your post, it is unclear to me what you exactly tested?  Did you have a transport or cd player with the physical media in it connected to the same DAC as your SB?  If so, what was the transport or physical cd player?

Are you saying that using the same DAC that there was no difference in sound between the transport or cd player using physical media and the SB using ripped media (same exact cd) off the computer?

George

George -

In order to be able to switch back and forth, I used a Panasonic XR57 as the DAC.  I used the digital output of a Sony CD/DVD player into one digital input and the digital output of my SB into another digital input.  This allowed me to switch back and forth instantly.

Granted, if I would have used a better DAC/Pre/Amp, the sound quality would have been better.  But for purposes of this test, I just wanted the DAC/Pre/Amp to be consistent so I could hear the difference between the CD and the SB using the digital bitstream from both.

Once I ripped the remastered CD and streamed this from the SB, I could hear no differences between that and the original CD playing on the Sony.

I hope that made sense.

- Jim

[Big Red Machine]

So Jim, was one an optical and one an SPDIF?  If so, that may be apples and oranges for the more technically savvy.

[jsalk]

So Jim, was one an optical and one an SPDIF?  If so, that may be apples and oranges for the more technically savvy.

Both optical as I recall.

- Jim

[mr_bill]

I would be very interested if anyone has any findings on whether there is a difference using a CD Transport or Duet or Transporter to feed signals to a high quality external dac.

[zybar]

I would be very interested if anyone has any findings on whether there is a difference using a CD Transport or Duet or Transporter to feed signals to a high quality external dac.

What do you mean by findings?

Myself and others have already posted our opinions on this topic over the last few years here on AC.

Clearly I am in the camp that feels a computer can offer superior transport abilities when feeding an external DAC (which can include a Duet, Transporter, USB DAC's, etc...).

George

[Nuance]

Clearly I am in the camp that feels a computer can offer superior transport abilities when feeding an external DAC (which can include a Duet, Transporter, USB DAC's, etc...).

George

+1.  I feel the same.

My apologies to the OP on behalf of all of us for getting off topic.  Hopefully your questions were answered to your satisfaction.  Also, my apologies to Wayne at Bolder cable.  I meant no disrespect, as I think his analog and digital mods will work wonders to the stock squeezebox.  He seems to have a great company.

[Big Red Machine]

I would be very interested if anyone has any findings on whether there is a difference using a CD Transport or Duet or Transporter to feed signals to a high quality external dac.

Pretty much the same answer.  I found that the SB feed was more "clean", or as they say, had a blacker background to it.  Subtle but enough over time I actually sold my CDP and went sans any mechanical drive.

[Kris]

Maybe Jim's system is not resolving enough to hear any differences? 

[kobbi]

I would be very interested if anyone has any findings on whether there is a difference using a CD Transport or Duet or Transporter to feed signals to a high quality external dac.

Pretty much the same answer.  I found that the SB feed was more "clean", or as they say, had a blacker background to it.  Subtle but enough over time I actually sold my CDP and went sans any mechanical drive.

Interesting..... I have the opposite experience.  When I bought my Duet, I was dissapointed in its sound quality. I ran it through the same DAC that my transport was connected to, and the Duet was NOT as good as the transport. I kept using the Duet because I liked so much about it, but eventually quit because I couldn't stand the sound.
If you guys are able to get a "clean" digital feed out of one, then maybe I am doing something wrong. Any suggestions?

Thanks

[Big Red Machine]

I would be very interested if anyone has any findings on whether there is a difference using a CD Transport or Duet or Transporter to feed signals to a high quality external dac.

Pretty much the same answer.  I found that the SB feed was more "clean", or as they say, had a blacker background to it.  Subtle but enough over time I actually sold my CDP and went sans any mechanical drive.

Interesting..... I have the opposite experience.  When I bought my Duet, I was dissapointed in its sound quality. I ran it through the same DAC that my transport was connected to, and the Duet was NOT as good as the transport. I kept using the Duet because I liked so much about it, but eventually quit because I couldn't stand the sound.
If you guys are able to get a "clean" digital feed out of one, then maybe I am doing something wrong. Any suggestions?

Thanks

I screwed up!  My SB (at that time, not the one I have now) had the Digital mod by Bolder on it.  I forgot that important piece.