Jitter reduction, best device?

Read up on Benchmark DAC1 also. They pretty much stake their product on its low jitter output even in the face of any extremely jittery input. No reviews with proper measurements have found fault with it, so far, although listeners may like or dislike it, according to taste - same for any product.

Your dac received a so-so review on it's debut in S'phile from Robert Harley. The Digital Lens would help, but a new version will debut this year, so I wouldn't purchase one unless you really want it(I've had four and sold the last two few months ago).

Reducing jitter may clean up some of the edges, but I doubt it's going to turn a somewhat clinical sound into a meaningfully richer or more musical experience. I think you'd be better off looking for a DAC that sounds more musical to you rather than trying to make your DAC sound a certain way when it may just not want to go there (I'm in a similar situation with my own DAC). As an example you've probably seen the review of the MSB Gold DAC on enjoythemusic.com comparing it to the Audio Note before and I don't mean this to disparage your DAC as it's obviously well respected, but DACs have come a long way in just the past few years so it may really be worth it to at least check out what some of the newer ones can do (including reduce jitter on their own) before throwing money at this one. Either way you'll be in a better position to make the right decision and you may even have some fun in the process.

Best of luck.

I agree you are probably better off trying a different DAC rather than trying to adjust what you have.

How about a tube dac? I can vouch for the mhdt DACs based on my very positive experience with the Paradisea. These can cost under $500 used.

Or the Benchmark is another way to go worth considering for around a grand.

i would stay away from the benchmark if you are thinking of using the usb port, it is inferior to the coax port.

i would agree that a jitter device will not perform miracles of converting a inferior signal to a fantastic signal. won't happen.

i have multiple setups using jitter devices and external dacs and they "all" have made a big difference in the sound. all connections induce jitter and some devices handle it better than others. why not use a jitter device to clean up the signal before it gets to the dac. garbage in, garbage out. another low cost dac is from audio alchemy if you want to go an inexpensive route. ps audio was at rmaf and they went over some new equipment that they will be coming out with that deals with the jitter issue.

the new audio research dac sounds promising. i heard it at rmaf and it sounded good and the AR rep indicated that they got the usb port down where it is equal to the other ports. something that the current dacs can't claim.

also, if you are using a music server, i isolate mine from the jitter device by using a toslink cable instead of a copper cable. there is no chance of any noise of the computer or the AE to get on this type of cable. if you isolate the jitter device, then you can use a coax or aes cable from the jitter device to go into your external dac.

Boleary3
I believe the Digital lens outperforms all the others, you mention.I got two in my system.One is hooked between the ML-31 transport(extremely well designed) and Sonic Frontiers sfd2-mk2 dac.The sound is awesome.I just can't imagine how it could further improved.The jitter reading I am getting is 14 and when the transport warms up it goes down to 13.I can confirm that the digital lens DOES improves the sound.If you decide to get another dac ,consider the Sonic Frontiers tube dac.
George

For my lawnsale system, I found the Meridian 518 to be the missing link in my PC audio experiments. Jitter without a doubt was my issue and the 518 delivers. I have further utilized this unit as a digital switcher for my sources including the (I know) XM signal out of my HD satellite box.

With solid state amps (Haflers) I'm running my Cal Alpha DAC. With My Rogue 120's I'm running my Museatex Melior DAC (unmodded).

For Redbook, I'm content with my Toshiba SD 9200 into the 518 with either DAC as mentioned above.

Oh by the way, the 518 is also my preamp, running through my DAC directly to my amps. Besides the features I HAVEN'T mentioned, I believe that the Meridian 518 delivers all around in my camp for the price of a cable.

Wow. Appreciate the responses, email included. Though I won't be getting another dac anytime soon, I'll keep the above recommendations for future reference. So has anyone ever published comparisons of the various devices that reduce jitter? From the reading I've done and the posts in this thread, it certainly seems that the digital lens and the meridian 518 are among the best.

Hi you might want to try empirical audio pace car 2 its one of the best jitter reduction devices out their. The cost is around $1500 and it works with computers via usb.

There's a very old (1996) article from Hi-Fi News on the Monarchy website where four "jitter-busters" were tested and measured. The Monarchy was apparently the only one that successfully reduced jitter. I'm sure that in 2009, the jitter reduction devices would be measuring far better.

Personally, I've just ordered the Monarchy DIP Classic to put between the Wadia 170i and an Audio Note 1.1x Signature DAC (which does no internal de-jittering).

I plan on posting a review of the system in the next month or so.

This may have been addressed in other threads, but how does one know for sure that jitter is the issue when not satisfied with the digital sound?

I use a Meridian 518 and besides jitter, I rely on its gain function which overcomes the low recording level of many discs issued in the 80s. I would also recommend the EAD 7000 Mk I-III. Still serviceable, and handles jitter and sound is warm. I use an EAD Theatermaster 8000 that incorporates the jitter technology of the above dac. Reasonably priced used. Another possibility is the Apogee Big Ben which is a reclocking device that is not often seen on Audiogon because of its professional use, but many on Ebay and supposedly does a bang up job as to lowering jitter

Mig007, I also have a EAD DSP-7000 Mk II with the balanced output option that I picked up on the 'Gon. Sounds great with my Haflers and my GFP-750 in passive mode. Have you ever experimented with the 4x/8x oversampling switch? I've never opened mine.

By the way, to the original poster Boleary3 - I just want to be clear that I am not claiming the 518 to be the best device to reduce jitter. I am quite certain that Audioengr may be able to supply you with a more qualified answer. I found the 518 to be a budget alternative in taming the jitter as a result of the path I took with my PC audio endeavor. I was ultimately pleased with its performance and versatility. I just couldn't see investing big bucks for marginally better performance for an audio "transport option" that is still being developed.

I have fiddled with that switch on an EAD Theatermaster Classic and noticed little difference if any. Really did not experiment. I've since switched the processor out with an EAD Theatermaster 8000. The 518 may not be the best anti-jitter device, but it certainly is the best bargain for taming digitalis.

Again, thanks for the responses, this has really been a pleasure and an education. I recently acquired the MSB Gold dac and yesterday I flipped the upsampling switch. It made a big difference in reducing the the edginess of the sound.Prior to the msb I just used an M-Audio Audiophile usb dac connected to my computor. It sounded significantly inferior to my cd player so I hardly used it. Now the computor, with the msb, upsampled, in the chain sounds far better than the cd player. At this point Im wondering how big a jump in sound quality an anti-jitter device will make. If the new more expensive devices will make a substantial improvement I'll patiently save my nickels and dimes (as well as my marriage!)and get one in the hopefully not to distant future. If nearly the same improvement can be gotten with a used older device for less than half the price of the latest available I'll be impatient and get one now. If, on the other hand, adding another device in the chain won't make that big a difference why add an anti-jitter device? Obviously I'm a newbie at this and have done just enough reading to be dangerous.....but hey, you gotta start somewhere......Thanks in advance for any more replies that happen here.

Further to Mapman's question, which was not answered. How does one know if jitter is a problem? "Digitalis"? Does that mean the shrill (un-tubelike) sound of many CDs?
Mike19

Mmarvin19,

I've read a good bit on line about this and it is still clear as mud to me how to diagnose a jitter problem as opposed to other forms of unpleasant things in sound reproduction.

I think I understand what jitter is and how some kinds can be offensive and others not, similar to various distortions found in vinyl playback. In both cases, the only thing I find I can trust is my ears to tell me whether things are going right or not.

I would consider buying a jitter reduction device if I knew how to conclusively diagnose a jitter issue, but I don't.

I have found different DACs can make a world of difference in regards to good digital sound but I have no clue about how much jitter is introduced by any particular device, though I do believe all devices, even those with the best clocking mechanisms introduce some.

After all, nothing is perfect. In the end, all I know for sure is to trust what I hear.

Well, I describe it as hard edged, as oppose to warm like, but shrill works.

mapman
i disagree on your theory that your ears can tell if you have jitter or not. all i can tell you is if you hook up the jitter device between the source component and the dac, you will hear a big improvement, something you won't hear until you hear hear the difference. just like going from a mid-fi system to a hi-fi system. you might think how can music sound any better than this mid-fi system. you won't know until you hear a system that produces music that you haven't heard before. also, i'm not talking about a shrill sound becoming warm or rough edges. a jitter device is not going to make a bad system great. my den system consists of a dk design integrated amp, dvp9000es, adcom gda-700 dac, totem speakers and subwoofer, and a connection from my music server. a decent system for a den. when i placed a cheap audio alchemy jitter device (get my feet wet with jitter devices), my sub was way out of adjustment (more powerful and way too loud), and the whole soundstage opened up. when you get a better jitter device, it opens up the sound even more. bottom line, i got as much improvement from the jitter device as i did placing the dac in the system.

In truth, Digitalis would be from the Foxglove plant and the origin of Digoxin, a heart medication. Digititis would be the proper audiophile term for an unpleasant sharp and edgy sound derived from digital sources, such as compact discs. Just to be precise!

So back to the original question, which device is best, and why, please?

I'm not sure how audiophiles can diagnose a jitter problem except by trying jitter reduction devices and listening. In general, upsampling DAC's will be more immune to jitter because they re-clock the signal to a higher rate. The re-clocking will filter out a lot of the jitter in the original signal. I haven't seen any way to measure jitter except for using expensive lab equipment.

Pmi_guy,

I think you are right.

I suppose whichever devices do the re-clocking task best would work the best also.

not necessarily. why does esoteric build a $10k external clock? why does dcs build the 3 box setup for $60k. thats like saying you can buy the cheapest cd player but the dac will fix all symptoms. those pieces sound wonderful but at a price. IMO, you want to use the best quality pieces that you can spend to get the best sound. you are not going to buy a cable that will perform miracles with a mediocre dac or cd player. the only way to tell if something will work or not is to demo it. or just leave things like they are and be happy withwhat you got. but you can't say you trust your ears and you would know what you are missing.

Rbstehno, I do not doubt for a second that some serious clocks can be had for that kind of change.

I would just like to point out that chances are quite good that audiophiles have a number of CD's in their collection that was digitally mastered utilizing a Meridian 518 or 618 (pro version). I just can't comprehend what spending 60k is going to achieve beyond what the mastering engineer had produced in the first place. My opinion is "good enough for the engineer, good enough in my system."

Jitter is noise in time domain. Jitter produces sidebands at very low levels but audible since not harmonically related to root frequencies. Jitter free sound has more clarity (free of noise).

Many CD were made from poorly digitized tapes and contain A/D converter jitter that cannot be removed.

As for device - Benchmark DAC1 does excellent job with jitter. Its jitter bandwidth of only few Hz translates to about 100dB of jitter suppression at few kHz.

Jitter comes from recording, transport, cable (reflections on impedance boundaries and noise) and DACs clock jitter.

Yes, I'm becoming increasingly aware that jitter is indeed a real threat to digital sound quality.

If you have good ears and a decent DAC and your digital sources sound good compared to other sources, then you're rig probably has a handle on the jitter. If not, then jitter is a likely culprit. You'll probably only know its a problem once its gone.

The best way I know to reduce jitter to the lowest possible levels is to do it internally inside the player/unit where the unit is extracting digital information from a CD/DVD/SACD disc or a hard drive. This is done via a internal clock replacment with a ultra low jitter fine tuned clock. Either by replacing a master clock or clocking that feeds a chip that extracts the information.

If you add in some other "reclocking device" after the fact (ie: outside the box...) you are just bandaiding the problem. Fix the problem at the source, which is the poor jitter/phase noise feeding the DSP chip responsible for all the decoding (a very cheap crystal oscillator). This is accomplished by inducing an ultra low jitter clock signal (stable frequency) to the mix. The results are astonishing!!!! You can now realize the true performance the artists intended! I hope this helps you guys out!

Asi_tek,

That may not be effective in all cases, as I understand it.

For example, in my system, a Roku Soundbridge feeds my DAC via TOSLink. Data is sent to the Roku via wireless connection from my Vista laptop functioning as a music server, where files are ripped to disk from the onboard multformat Pioneer optical drive.

The Roku caches/buffers data in dynamic memory before forwarding to the DAC.

In this case, it is the Roku I believe that provides the clock for the DAC, so I think that (the Roku) is where the accuracy of the clock would matter.

I also concurrently feed the DAC from a Denon CD player/recorder via coax. In this case, the clock on the Denon provides the timing for the DAC I believe.

Prior to introducing the outboard mhdt Paradisea tubed DAC, I just ran the Denon analog output direct into the pre-amp. In this case, the internal DAC was used.

So what about jitter with the various configurations I've used?

Honestly, I have no clue really.

All I know for certain is that since introducing the external tubed DAC, I am hard pressed to hear any sonic artifacts that would indicate that the source is digital and that any articfacts of jitter is audible.

Prior to the outboard DAC, I could clearly hear some things that might typically be attributable to digital and perhaps jitter, specifically, I could hear a subtle wavering in pitch on lengthy notes played by massed strings in many larger scale orchestral recordings that I did not hear on other reference systems I listened to in comparison.

Was the subtle wavering in pitch due to jitter?

I would say maybe but I do not see how.

What I can say for certain is that going to the outboard DAC seemed to resolve the problem.

The thing is that I do not believe the Paradisea does any re-clocking or other special processing to address jitter, as say the BEnchmark DAC supposedly does. So I am hard pressed to conclude that the problem was due to jitter.

Also, many who try the BEnchmark, which supposedly does address jitter, still often complain about a harsh digital sound.

The best thing I can assume here is that assuming the BEnchmark does address jitter, at least the addressable jitter introduced during playback, then maybe it is the crisp transient response possible with digital that irritates some.

Some believe that it is just the inherent limits of resolution of the Redbook format that is the problem but that has neer been an issue for me.

I am very interested in understanding these factors relating to digital rigs better, so please if anyone ca offer me any additional insights, please do!

Mapman,

It sounds like you may be hearing beat frequencies. This is a subtle effect that could come from a number of things - including your room setup and/or listening position. It is, as you say, nearly impossible to be conclusive that any specific audible effect is from jitter. Jitter is a detail that does not necessarily stick out like a sore thumb. The industry continues to argue about the thresholds of its audibilty....

Shadorne,

The description of beat frequencies fits what I heard.

It was very consistent though with many CDs I played even listening in different rooms on different speaks to the same source.

I never heard it in several high end reference systems I listened to at the time.

Changing to the Paradisea from the Denon's built in DAC seemed to end it, so I suspect it was some artifact resulting from the Denon's DAC.

Jitter is a mysterious bugger indeed!

so I suspect it was some artifact resulting from the Denon's DAC.

It can often be subtle but everyone agrees that DAC's do sound different. Whether this is the effect of jitter reduction or simply the result of a different output stage (tubed) or both is nearly impossible to say.

Asi_tek - Upscaling, also called asynchronous resampling is not bandaiding. It is instead (and not on the top) of traditional extraction of data.

In typical CD-player, as far as I know, stream of data coming from the laser has jitter and varying frequency. Phase Lock Loop is used to sync DAC converter clock to average frequency of the data stream. I believe that now they use double PLL to improve response and FIFO buffers to provide more stable DAC clock.

Upscaling reclocks data with asynchronous clock of much higher frequency. Benchmark DAC1 does manipulation of data equivalent to 1 million times oversampling making DAC clock accurate to 5ps. DAC1 also has PLL but very crude and fast - just to get input data.

Typical CD player has some analog circuitry that mutes the output in between tracks or during invalid data. This circuitry is audible according to some users who tried to disable it. Benchmark detects valid signal and does muting in digital transmitter chip.

bottom line: the only way to tell if a jitter device will do something in your system is to try it. everybody could guess all day long about things. but in the end, you won't know if it works or not for you until you test it. also, all the room tuning devices, ac filters, 20 or 30 amp dedicated wiring, room lens, different speaker positioning, claws, beaks, better cables, better power cables, etc... i don't think you can say that none of these will not have an impact in your system until you try them.

Rbstehno is right.

Like most gadgets, all that really matters is if you hear a difference for the better thats worth it to you.

If it works, who cares how it did it?

Mapman

"If it works, who cares how it did it?"

That's true - but understanding helps to narrow search. Sounds of upsampling, oversampling and non-oversampling DACs are different. Many people don't like sound of upsampling converters (Muralman - are you there?) while I praise clarity and transparency of Benchmark DAC1 and would look for similar one in future. Understanding what jitter is and how to prevent it helps as well.

There is nothing wrong in understanding!

There is a renewed interest in jitter because of the new PC-based servers. The data from a hard drive is read in blocks without an inherent clock. An SPDIF clock is generated at the same time that the SPDIF data is created. It's this clock that has the troublesome jitter. Most PC manufacturers and even sound card manufacturers don't care that much about jitter. It's only a few audiophile nuts like us who are concerned about it.

I'd like to see SPDIF jitter measurements standardized and published for PC's and PC soundcards that output SPDIF signals. Then we could really tell how bad the jitter was and whether we need outboard jitter reduction. (The SPDIF signal is what goes between the PC and the DAC, either in optical or coax cable)

I'd be skeptical of any device, like PCs, not specifically designed for good sound.

DACs like the benchmark and others that re-clock during upsampling would seem to be the way to go when the source is a generic computer.

From the sound of it in my system, the Roku Soundbridge seems to do a very good job caching/buffing the bits received over the wireless connection from the laptop PC server and then providing the clock and delivering bits at the right time to the mhdt tube DAC.

The Roku has been a fantastic $129 investment for my system.

Well I've now tried the Monarchy DIP Classic (non-upsampling) reclocking device with the Wadia 170i and the improvement in resolution was quite staggering - like the noise floor dropped significantly.

I don't know if this is the result of a reduction in jitter or the amplification of the signal voltage by the DIP but I was shocked by the impact. More details can be found in a review I posted here for the Wadia 170i but the bottom line is that with a DAC which doesn't reclock or reduce jitter (AN 1.1X Sig.) this jitter reduction device made a significant difference.

Hens,

the bottom line is that with a DAC which doesn't reclock or reduce jitter (AN 1.1X Sig.) this jitter reduction device made a significant difference.

Interesting. Your observations suggest that for those connecting gear through digital interfaces it is worth investigating this issue when selecting a DAC. For those with a DAC already (particularly an older generation DAC that rarely had anything other than a simple PLL), this points the way towards a postential improvement.

Shadorne, that certainly fits with my findings. I intend to see if I can borrow a benchmark DAC or DACMagic in the next few weeks to see if the DIP makes a difference with a DAC with its own jitter reduction system. I would expect much less impact in such a scenario but if there is still a significant difference it could also suggest that the strngth of the signal is also an important factor as the DIP amplifies this signal from around 0.5 volts to 5 volts. Should be interesting.

hens - i also use the monarchy in my audio system. i also heard a huge improvement when i inserted this device before the dac. i also use other brand jitter devices in my den and rec room and they also made a large improvement in the quality.

mapman - if your skeptical, then you will probably never be happy with a setup like this because in the back of your mind, you think other alternatives will be better. why don't you think a pc can read a cd as well as a cd player? check out who makes the transport mechanisms in "all" the world. probably 2 or 3 companies: philips, sony, are probably the most popular. so what has the most smarts: computer or cd player? what has the most memory/buffer to hold data read off the cd before sending it down its channel?

i am a computer nerd and when i hear people say that pcs/macs aren't capable to produce good sound, i get frustrated because it isn't true.

do you think that reading music off a cd player is any different than reading bits off a cd when loading a program onto your pc? how many times have you had issues loading a program off the cd with corrupted data or issues that the bits couldn't be read properly off the cd?

now as for sound quality, the pc/mac isn't very good, but thats were jitter devices and external dacs come in. the roku will not improve the sound any, you need much more equipment to do that.

also, reclocking is not done at the level you are talking about. normally a clock device has to talk on a peer-to-peer basis with the source (say a cd player) so the 2 devices can get in sync with each other. the benchmark will not do that. the esoteric clock and transport devices do that, along with the dcs pieces.

my advice to you is to go listen to a good quality system or go read some of the articles that state that ripped cd's can sound better than the original disk if done properly. you might be surprised.

Rbstehno,

I know a PC can provide a good digital source because I am doing exactly that in my system alongside feeding from a CD player/transport.

In my case though the true source from the DACs perspective is the Roku Soundbridge, which is a device designed for good sound at its price point. The laptop computer source is not even known to the DAC.

I do think it is more hit or miss from computer to computer in general though, depending on details and specific configuration and topology, because different components and interface implementations exist in different computers and many, particularly older ones, are not necessarily designed for performance levels that audio buffs expect.

For $200, the Roku or other devices like it like the Squeezebox take source computer mostly out of the equation regarding sound quality, so it is a good approach in my mind.

Not to say some computers may offer up great sound directly as well. I'm sure some do but I'm not sure that all do.

I started out at first with an analog feed from my computer to my system. That was a halfway decent but ultimately flawed approach. Where I am at now is pretty much where I think most audiophiles would like to be.

"do you think that reading music off a cd player is any different than reading bits off a cd when loading a program onto your pc? "

No. Reading music versus other kinds of files from a CD optical, magnetic hard drive or even physical menmory is no different at all.

But re-constructing an analog signal in the DAC, based on the clock, is an additional scenario that comes into play after wards in digital sound reproduction. I believe different sources do this differently with varying degrees of accuracy. For example, USB uses a software driver. Some may be better than others I would suspect.

The result if the bits are not processed at the DAC at exactly the right time is jitter, as I understand it, and jitter frequencies and levels do affect the resulting sound.

I was HIGHLY skeptical about the Monarchy DIP but recently tried a DIP Classic (no upsampling) in my system and was very impressed with the results. I use a Monarchy DAC 24 with Matsushita tubes, Ayre AX7e and Green Mountain Europas, either an inexpensive Integra player or Cambridge audio DVD player for transports.

The results were as dramatic as changing tubes. The separation and clarity was increased, vocals in harmony became much clearer, cymbals more sonorous, and room reverberation or reverb sounded much more integrated. I did not experience this as a softening of transients, more like a layer of grit being scraped away. Another audiophile describes this as a window that had been cleaned.

As I said, I was very skeptical and spent a lot of time doing real time switching comparisons with a variety of music.

It does seem as though this function should be built into a well designed DAC. My understanding is that the newer DAC chips that parellel inputs do not have significant jitter issues.

Yes, Virginia, jitter reduction devices are still alive and kicking ass! I currently use both the classic but alas no longer available Genesis Digital Lens (from PS Audio) and the Audio Alchemy DTi-Pro 32 jitter reduction devices with great effect, using them not with CDs but with high inherent jitter digital sources such as XM/Sirius satellite radio. Both work very well, but the Digital Lens has a narrow edge in sound quality and more inputs (5 vs 3). These devices went out of favor starting about ten years ago when stand alone DACs and CD players began to have more effective jitter reduction circuitry built into them. However, even most current DACs that have jitter reduction circuitry are designed only to handle the levels found in CD drives which are much lower that those found in satellite radio or many computer interface devices. Therefore, I (and others I know) have resurrected my Digital Lens and AA DTi-Pro and send the digital signal from my Polk XM tuner to them (in two different systems) , via its digital outputs (either optical or coaxial--coaxial, Wireworld, is better, but the Wireworld glass optical Toslink cable is amazingly a close second!) and thence to my DACs (one system has an AA DAC and the other a Theta DAC). The reduction in jitter and hence improvement in sound quality on the best of the XM stations is nothing short of astonishing. I have gone from barely being able to tolerate more than half an hour listening to XMs jazz and classical music stations, to listening to them for hours on end. Except for the still somewhat reduced or narrow stereo channel separation (similar in effect to the "blend" setting on FM tuners--somewhere between mono and stereo), the sound is VERY close to the best CDs in almost all respects. Jitter, apparently, more than just signal compression protocols, is the far bigger culprit to poor sound quality from satellite radio. Because satellite radio uses 3 different compression schemes, depending on the station (talk and news/weather being the worst, with jazz, classical and "classic"standards stations being the least compressed) reducing jitter alone will not improve substantially most of the stations. However, on the best or least compressed stations, whole new worlds of sound open up.

Interestingly, PS Audio is about to reintroduce a stand alone Digital Lens jitter reduction device because of the many new digital audio sources that are being used, especially in regard to computers, but which have higher jitter rates than most stand alone DACs can substantially reduce or eliminate. I have read several blogs on the advantages of using jitter reduction devices along with the Wadia iTransport/iPod and various music server devices, but I have not seen anything elsewhere regarding the benefits to sound quality from satellite radio or satellite/cable set top boxes (STBs), many of which have digital outputs. I have heard considerable improvement in sound quality from a Comcast STB when used with an AA Dti-Pro, but Verizon's Fios optical cable STB will NOT output LPCM thru its digital outputs--only DDS which neither the AA Dti-pro nor Digital Lens can handle (nor can most stand alone stereo DACs).



Unfortunately in regard to satellite radio, Polk has stopped manufacturing its XM tuner and it is only available now through the used market. I do not know of any other satellite radio tuners that have digital outputs, except for the mega buck Magnum-Dynalab units. The Polk tuner used by itself improved the sound of XM radio somewhat, but not anything like the improvement using its digital outputs and a jitter reduction device. I obtained some improvement in sound quality by going directly to the DACs from the Polk, but not nearly as much as using the jitter reductions devices in the path.

Astro,

I used to have a Theta TLC into two Pro 32's then changed to the '32's with a Digital Lens. It's better to use two Lens' in tandem since the chip thethe PRo 32 is no longer supported by Dusty Vawter. If it burns out, that's it.