84 replies to this topic

[b4sound]

Not sure if it's worth the trouble but if you Vic boys would like to borrow my 6 and 10db before buying then just pm me.

[b4sound]

And yes I ordered from Clarke. Quite sure they didn't impose the 50 minimum on me unless it's a new policy.

[twwen2]

You may be able to run more than -16 as I have good signal lock with -21 Attenuators into both Lavry DA10 and
Audio GD DAC19

Is it beneficial to run a higher attenuation value?

[Arg]

Mario, impolite comments like that earn you an infraction. Arg, perhaps you should ponder why people respond to your provocative posts (a small number of your total posts) the way that they do? I must say that it's frustrating as a mod to read provocative posts and then have posters incensed at provocative replies!

Can do, prof. Maybe sarcasm on SNA should get a ... 'cos sometimes I lapse and it looks terrible on reflection! (OK, maybe a 'self-ban', then).

Back on topic, it is really intriguing that this topic is on a pre-dac device, which won't affect the level (loudness) of the dac output. So the usual requirement to match levels for a controlled listening test is automatically ensured. It makes a controlled listening test relatively easy to execute, as the M51 has multiple digital inputs, so quick switching is easy. Hmmm....

What exactly, one wonders, is the Audiophilleo 2 changing in the system performance? If I understand correctly, the OP was auditioning it on the input to a NAD M51, which is an asynchronous resampling dac? That should handle jitter very well.

It would be interesting if somone with access to the A2 tapped its input and output in actual operation on an M51, to see if even one byte is different. If no bytes are different, and the M51 handles jitter well anyway,.... what are we looking at?

[Shmonk]

Is it beneficial to run a higher attenuation value?

If I recall correctly, i first read about the possible benefits of digital attenuation when John Kenny was encouraging people to try it in the original AP2 thread. The higher the attenuation before losing lock with the DAC the better. I think it might have something to do with reducing reflections. I haven't tried it yet and still wonder what is the maximum attenuation for an AP2 and Lite DAC 83.

Edited by Shmonk, 07 May 2012 - 04:56 PM.

[kdoot]

What exactly, one wonders, is the Audiophilleo 2 changing in the system performance? If I understand correctly, the OP was auditioning it on the input to a NAD M51, which is an asynchronous resampling dac? That should handle jitter very well.

Post #18

It would be interesting if somone with access to the A2 tapped its input and output in actual operation on an M51, to see if even one byte is different. If no bytes are different, and the M51 handles jitter well anyway,.... what are we looking at?

I have absolute confidence that the Audiophilleo products are bit-perfect, unless you're using the AP1's internal digital volume control, which was certainly not the case in a test with the AP2. Their design intent is crystal clear: get the bits from the computer and deliver them with utter precision to the SPDIF receiver.

So if the sound is actually better as reported, with that particular computer system providing the data, then the AP2 + M51 SPDIF receiver must be better than the M51 USB receiver section in one of two ways: lower jitter, or lower electrical noise. Or maybe in another way that everybody has overlooked somehow. (No I don't think that's likely.)

[lebowski]

Is it beneficial to run a higher attenuation value?

I found so. You want maximum RF attenuation without losing signal.

[LuzArt]

And yes I ordered from Clarke. Quite sure they didn't impose the 50 minimum on me unless it's a new policy.

Unfortunately Clarke are imposing the $50 minimum order policy now.

Edited by LuzArt, 10 May 2012 - 07:40 PM.

[O.Sydney]

I was going to order two, a couple of months ago but stalled at this minimum.

I've got a quote from them, let join forces...

PM'd

[LuzArt]

post deleted.

Edited by LuzArt, 10 May 2012 - 07:40 PM.

[O.Sydney]

PM'd your PM to my PM

[Whatmore]

Pardon my ignorance but can someone explain what attenuation is in this instance?

[Nada]

.... can someone explain what attenuation is in this instance?

As I understand it the attenuators are designed not for audio use but for decreasing the radio frequency intensity of signals eg TV and luckily for audiophools there is one company that makes BNC to BNC true 75 ohm attenuators.

So the DIY mob tried these originally for the HiFace 1 which had a ridiculously hot SPDIF output many times over the standard.




The idea was to bring down the signal to the 0.5V standard for better matching of the SPDIF receiver specs.

Then it was hypothesised that signal reflections will have to travel twice through the attenuator thereby improving the signal noise ratio by a factor of two. John Kenny has done a lot of work in this area and championed the use of attenuators.

The mystery in this post is that someone has put the attenuators on the audiophilleo that has a within standard output. WHat!!!!!!

Was that inspired experiementing or was it a lucky misunderstanding thinking what works for the HiFace works for the AP and hey it did?

Maybe it is cutting down on reflections still?

Or maybe with the AP2 its creating a steeper impulse in the SPDIF receiver trigger zone, decreasing phase jitter?

Anyway whilst the HiFace1 could use 25dB attenuation it would be highly unlikely that would be suitable for the AP2.

I would speculate that about 5dB would be appropriate for most SPDIF receivers. Im surpised that a 10dB attenuator still locked on using the AP2.

Some rack setups wont tolerated an extra 5cm or so of attenuator out the back of the DAC.

Anyone seen a right angle true 75ohm male-male BNC adaptor to get over the extension length and torque concerns?

Edited by Nada, 15 May 2012 - 09:24 PM.

[Lil Caesar]

Last Night B4Sound and Holliswhy made it over to my pad, AP2 and JKSPDIF mk3 in tow.

The JK has built-in battery, whilst B4 had acquired Nada's excellent Aldi-sourced battery and splitter USB cable to achieve an off-the grid performance. We began with the M51 "naked" via its own USB before introducing the JK, then the USB-powered AP2, and finally the AP2 with battery power. An excellent exercise, leaving me utterly convinced that these devices do add tangible value to digital audio replay.

Of considerable fascination to the three of us was the difference between the JK and the battery powered AP2. The AP2 combo was regarded as slightly superior across all music genres - however the treatment of modern pop via the JK was preferred to that of the AP2+battery. In this case the JK provided the more pleasing result, the AP2+battery proving perhaps a little too revealing and accurate a treatment of highly produced recordings.

I was personally quite impressed that a discernible improvement was noticed when the AP2 was taken off the grid. A decent DAC with AP2+the new purepower solution would make for a formidable HiFi experience. Those using Nadas' Aldi solution have done very well indeed.

[b4sound]

It's quite hard to explain what these devices do but now that we've heard them in LC's setup, I am convinced it is a necessary component for computer sources. Imagine from a wall of sound in front of you to suddenly you are immersed in the audience with claps all around you and instruments swirling around.

[lebowski]

Now LC you should try the JK hiFace and AP2 with RF attenuators for another step up in computer audio

[Lil Caesar]

....we played with the attenuators at b4sounds' place and decided that we didn't like the effect, at least not with the ap2. I suspect it may be a very personal and system specific thing....ymmv, etc...

[jkeny]

Interesting discussion that I had not seen before.
Also interesting comparison of AP2 + Battery Vs MK3 (I presume?)
Can you say something about what way the RF attenuator effected the sound with the AP2?

[Lil Caesar]

JK, very hard to describe the effect, my initial impression was that of a magnifying glass, at first I liked the result but after removing it we decided that it seemed to be exaggerating the music. I guess it made the Nad M51 for example sound closer to something like a sabre based DAC with very high detail and enormous soundstage.

It may be that this was, just in fact, an even cleaner signal and the m51 working in optimal conditions but on that system in that room, we did not like the result.

[jkeny]

Thanks, & one last question - did the attenuator have the same overblown effect with the MK3 or did this same magnification bring the MK3 to the level of the AP2 + Battery?

[Lil Caesar]

Sorry JK, at the time we were playing with the attenuators, only the AP2 sans battery was present. Two different occasions have been blurred together in this thread. You raise a good point - perhaps an off-the-grid reclocker is the ideal time to use the attenuators...

[jkeny]

I know, so many variables, so much to learn, so little time,

[bhobba]

I came to the same conclusion about AP2 re value. i dont think it's worth going beyond the base model, or it's getting close enough to make the OR5 a better buy. I'd considered the OR5, but didn't seem to really make sense having a reclocker that cost more than the dac. I'd love to hear the two in an A/B test though!

I have done that many times with quite a few others. The OR is clearly better - more analog like - and everyone agreed. The issue was if you thought it was an order of magnitude better or just a bit better and hence if you thought it was worth the extra dosh or not. Of course I think it is an order magnitude better and easily worth the extra dosh - but opinions vary. As a minimum I think an AP2 or similar is mandatory.

I really don't understand why these large manufacturers can't build an equivalent circuit to the AP/OR into the DAC?! I mean the R&D budget of NAD must be huge compared to empirical/audiophilleo.

Yea - but listening tests are usually not part of it - that's more a small guy thing. The engineers that work on it for the large boys usually think people like us are crazy - they are more of the DBT types - but don't actually do DBT's themselves as part of their development.

Thanks
Bill

[bhobba]

What exactly, one wonders, is the Audiophilleo 2 changing in the system performance? If I understand correctly, the OP was auditioning it on the input to a NAD M51, which is an asynchronous resampling dac? That should handle jitter very well. It would be interesting if somone with access to the A2 tapped its input and output in actual operation on an M51, to see if even one byte is different. If no bytes are different, and the M51 handles jitter well anyway,.... what are we looking at?

Its been hashed out in other threads. For Async DAC's its thought common mode rejection is the culprit devices like the AP2 improve. However at the level of forums like this when people speak of jitter it usually means jitter and effects similar to jitter are lumped together.

Thanks
Bill

[jkeny]

Its been hashed out in other threads. For Async DAC's its thought common mode rejection is the culprit devices like the AP2 improve. However at the level of forums like this when people speak of jitter it usually means jitter and effects similar to jitter are lumped together.

Thanks
Bill

Bill, I don't think that's correct for the AP2 - it has no mechanism that would deal with common mode noise rejection, AFAIK.

[bhobba]

Bill, I don't think that's correct for the AP2 - it has no mechanism that would deal with common mode noise rejection, AFAIK.

The discussion was on the OR and Steve participated as well. Can you explain why the AP2 doesn't help with CMR and the OR does?

In fact I managed to dig up what Steve said:

'Bill - Async does enable the USB interface to isolate the jitter of the input signal from the jitter of the local oscillator. Neither will have zero jitter. I believe the reason that different cables and USB interfaces can sound different with async USB is mainly due to common-mode noise over USB. RFI may also be a factor, depending on the design and shielding. I proved this to myself by making a common-mode filter for USB and disconnecting the 5V wire in the cable. The improvement in SQ was immediate and noticable. The signals of USB are differential digital, similar to balanced in analog. The ground wire is only there to insure that the DC potential of the grounds of the two systems (computer and USB interface) are similar. Different USB receivers will have different levels of common-mode noise rejection. The reason that some USB interfaces dont sound as good as the Off-Ramp is that the local clocks have higher jitter, or jitter spectrums that are more undesirable for audio. The edge-rates of the S/PDIF output signals on USB converters also impact jitter, as well as any duty-cycle distortion caused by the master clock.'

The point though is more is going on than just Jitter. Its maddening that asyc interfaces are improved by better sources, but anyone that listens to stuff knows it is.

Thanks
Bill

Edited by bhobba, 03 June 2012 - 10:45 AM.

[jkeny]

Can you point me to the discussion on the OR first & I will read it? I wasn't aware that the OR directly addresses CM noise reduction/rejection. I know Steve identifies CM noise quite correctly as a distortion mechanism that results in audible effects very similar to & possibly confused with jitter. I know he has a device coming out in the future which addresses CM noise.

[kdoot]

Bill, I don't think that's correct for the AP2 - it has no mechanism that would deal with common mode noise rejection, AFAIK.

The output stage is fully differential. Wouldn't that do it?

[bhobba]

Can you point me to the discussion on the OR first & I will read it? I wasn't aware that the OR directly addresses CM noise reduction/rejection. I know Steve identifies CM noise quite correctly as a distortion mechanism that results in audible effects very similar to & possibly confused with jitter. I know he has a device coming out in the future which addresses CM noise.

Its in the following thread:
http://www.stereo.ne...p-in-dac-world/

It has been discussed in others as well but can't recall enough about them to dig them up.

I thought it was jitter somehow getting past the async - I was wrong.

Thanks
Bill

[bhobba]

The output stage is fully differential. Wouldn't that do it?

Yes - or rather I would have thought so. With guys like JK and Steve I tend to listen rather than put my meagre technical knowledge on display.

Thanks
Bill

[jkeny]

Ah, I see you added that after I posted.
Ok, but you are mis-interpreting what is said here!


He is identifying one reason why different cables sound different even when using async USB. This is a question often asked " how could different USB cables or software players sound different if we are using async USB which doesn't rely on the jittery clock in the Computer"

It doesn't mean that async USB rejects/reduces CM noise - it has no bearing on this. To address CM noise requires other mechanisms & I see none of these in place in the AP2. It's one of the reasons why the AP2 sounds better running off batteries. Running off batteries addresses CM noise as long as other elements are also adhered to.

I see some other posts have come in while I was writing this.

Fully Differential would address it but only if it's differential from transmitter to receiver - it is only internal to AP2 & has to be converted back to single ended SPDIF output.

Edited by jkeny, 03 June 2012 - 11:01 AM.

[jkeny]

Its in the following thread:
http://www.stereo.ne...p-in-dac-world/

It has been discussed in others as well but can't recall enough about them to dig them up.

I thought it was jitter somehow getting past the async - I was wrong.

Thanks
Bill

No, CM noise is a completely separate thing to jitter. It is noise that rides down the ground & signal wire together (common). It may well give rise to jitter depending on how the receiving end handles it. And this is why it is intertwined & often confused with jitter as this might be it's mechanism of action (it certainly sounds like jitter). But it is not jitter at the source, it is jitter at the receiver caused by it's disturbing the reference ground !

Edited by jkeny, 03 June 2012 - 11:09 AM.

[bhobba]

No, CM noise is a completely separate thing to jitter. It is noise that rides down the ground & signal wire together (common). It may well give rise to jitter depending on how the receiving end handles it. And this is why it is intertwined & often confused with jitter as this might be it's mechanism of action (it certainly sounds like jitter). But it is not jitter at the source, it is jitter at the receiver caused by it's disturbing the reference ground !

Yea - like I said - I was wrong. And indeed it is one of those things that has effects similar to jitter, and may even cause jitter further down steam, but it aren't jitter.

Thanks
Bill

[jkeny]

I already asked Steve about his ideas on CM noise when Kdoot asked Steve if his CM noise blocker would improve Kdoot's battery powered AP2. Steve answered that it would & I wanted to know what his basis for this answer was! But Steve never answered

Edited by jkeny, 03 June 2012 - 11:23 AM.

[jkeny]

Yea - like I said - I was wrong. And indeed it is one of those things that has effects similar to jitter, and may even cause jitter further down steam, but it aren't jitter.

Thanks
Bill

Yes, but it is also a completely different thing to async USB & therefore the AP has no direct mechanism for CM reduction. I don't know about the OR as Steve has not given much information on it but I know enough to have a good idea that there is no direct addressing of CM noise in the OR, either. If I'm wrong, I'm sure Steve will correct me & explain!

Edited by jkeny, 03 June 2012 - 11:21 AM.

[jkeny]

It is my experience in theory & in practise that battery powered (isolated power) USB-SPDIF or USB DACS avoid the CM noise issue altogether. So once certain criteria are adhered to such as ensuring that the source is also not grounded then CM noise is kept away from the sensitive signal handling functions of the SPDIF & D/A conversion. Hence my question to Steve about Kdoots battery powered AP2

Edited by jkeny, 03 June 2012 - 11:33 AM.

[bhobba]

Yes, but it is also a completely different thing to async USB & therefore the AP has no direct mechanism for CM reduction. I don't know about the OR as Steve has not given much information on it but I know enough to have a good idea that there is no direct addressing of CM noise in the OR, either. If I'm wrong, I'm sure Steve will correct me & explain!

Like I said on this sort of stuff with people like you and Steve I like to listen. But I would have thought with the AP2 with its direct injection of SPDIF its fully balanced driver would be of benefit. And I do know the OR is very sensitive to the quality of the SPDIF connecting it. On my NAD it took a big leap when I connected it by a better quality SPDIF cable instead of an AES/EBU I was using.

Thanks
Bill

[jkeny]

Like I said on this sort of stuff with people like you and Steve I like to listen. But I would have thought with the AP2 with its direct injection of SPDIF its fully balanced driver would be of benefit.

It's only of benefit for the length of the differential line which is inside the AP2 & very short. It has to be converted to single ended SPDIF BNC output & is no better than any other device at this point. This happens inside the AP2 also. Any ground noise or common noise can & will enter at this point. As far as I know, inside the AP, the ground is connected through from the USB to the SPDIF side so any noise on the PC ground is directly transmitted to the SPDIF ground

And I do know the OR is very sensitive to the quality of the SPDIF connecting it. On my NAD it took a big leap when I connected it by a better quality SPDIF cable instead of an AES/EBU I was using.

Thanks
Bill

So, that could well be down to the sensitivity of the OR to CM noise! Has anybody ever tried running an OR off batteries or some ungrounded PS?

Edited by jkeny, 03 June 2012 - 11:48 AM.

[bhobba]

It's only of benefit for the length of the differential line which is inside the AP2 & very short. It has to be converted to single ended SPDIF BNC output & is no better than any other device at this point. This happens inside the AP2 also. Any ground noise or common noise can & will enter at this point. As far as I know, inside the AP, the ground is connected through from the USB to the SPDIF side so any noise on the PC ground is directly transmitted to the SPDIF ground So, that could well be down to the sensitivity of the OR to CM noise! Has anybody ever tried running an OR off batteries or some ungrounded PS?

I haven't but Steve does offer such a PS so maybe someone reading this has.

Thanks
Bill

[jkeny]

I haven't but Steve does offer such a PS so maybe someone reading this has.

Thanks
Bill

It would also be good to ask him if his CM noise blocker box is needed on an OR powered by isolated power as he didn't/doesn't answer me