I take it that the scare quotes are there to indicate pure marketing - you know, like 'Pepsi Max' as against 'Diet Pepsi' ? But you couldn't possibly comment
Digital that sounds like analog
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I take it that the scare quotes are there to indicate pure marketing - you know, like 'Pepsi Max' as against 'Diet Pepsi' ? But you couldn't possibly comment
I take it that the scare quotes are there to indicate pure marketing - you know, like 'Pepsi Max' as against 'Diet Pepsi' ? But you couldn't possibly comment
i have not always compared the Analogue Productions remasters to the original CD...but when i have, the FIM/Analogue Productions ended being my preferred version...sometimes by varying degrees. Even on the RVG Remasters and Verve Remasters (which in many cases are excellent)...i found them vastly superior to the hissy 1980's cd...Red Garland Trio and Thelonius Monk Genius albums are great examples imho. In any event, these days, i tend to wait til the Analogue Productions version comes out second hand and dont think about original vs remaster...and just go witih FIM or APO.
PM said that it sounds different on different transports and with different cables - which means they haven't isolated it well enough from common-mode noise effects and jitter. Which at 11k5 UKP you'd think they had the budget to lick totally, taking no prisoners...
I've just finished Alan Sircom's review and resonate with his subjective experiences about sound the NOS DACs. However he omits to point out that the experience can be had at a considerably lower price (we're talking $32) with one of these. This is where I started out on NOS nirvana : http://www.ebay.com/itm/High-end-DA..._Audio_Amplifiers_Preamps&hash=item2c656fac2b
PM said that it sounds different on different transports and with different cables - which means they haven't isolated it well enough from common-mode noise effects and jitter. Which at 11k5 UKP you'd think they had the budget to lick totally, taking no prisoners...
interesting...particularly since isolation was supposedly one of their key selling points!
Its a link on the page you originally drew our attention to, here : http://aletheia-audio.com/wp-content/uploads/2012/07/hifi85-dac-1-review-5.pdf
I learned from that that Alan's a bit of a philosophy buff, I'm also a fan of the phenomenologists so perhaps I should open a thread for myself and Alan to discuss Maurice Merleau-Ponty and Dreyfus' interpretations of him.
funny, i thought i was linking to the review i knew about...by Paul Messenger.
funny! great you sent it back to me! a good read!
Yes, the ironies keep piling up don't they? According to what I read, there's some EMI/RFI shielding material on the inside of the case. It won't do much good because the primary route for noise to enter is via the connecting cables. Elementary error to make for someone not really up to speed on EMC...
Yes, the ironies keep piling up don't they? According to what I read, there's some EMI/RFI shielding material on the inside of the case. It won't do much good because the primary route for noise to enter is via the connecting cables. Elementary error to make for someone not really up to speed on EMC...
does that meant the best way to shield for the entering connecting cable...is to shield the cable?
No, that's only part of the solution. A shielded cable can still carry noise from an 'aggressor' source component into a 'victim' component. Noise has to be filtered from the cable itself once inside the box. Feedthrough capacitors are used by those who know what they're doing, but the box then does have to be a total faraday screen, something I've never seen in any audio product but is routine in RF stuff.
Back to the elliptic filter - I have now put in the actual losses from the inductors I wound for the first prototype (in the picture) and as a result the FR shifted a bit. LTSpice doesn't simulate real inductor losses so the resistors in series do that, and the resistors here are what I measured as the inductor losses on my LCR meter at 20kHz. They're frequency dependent so I chose 20kHz as the worst case. I've now tweaked some values in an attempt to flatten out the response. Here's the revised schematic :
Here's the passband FR: -3dB just a whisker over 18kHz:
Here's the passband FR: -3dB just a whisker over 18kHz:
Looks like solid performance to me for a NOS DAC...they typically start to drop around 16khz-17khz dont they?
The typical NOS DAC starts drooping well before that frequency - 5kHz is where the roll-off begins if you eyeball the FR. But this isn't a typical NOS DAC as I have a trick for compensating that roll-off. I do it by adding in small delayed contributions from other DACs - with 1 and 2 sample delay relative to the main DAC. This forms a DAC-filter hybrid. The FR you commented on is just for the DAC's post-filter - its acting to soak up glitches and eliminate image frequencies.
interesting...because the NOS dac write ups i have read usually end up rolling off around 16-17khz. Clearly, you have found a way around that...gotta hear it someday!
Yes, the normal NOS has a roll-off which eventually reaches more than 3dB by 20kHz. Its not so much this amount at the top end that I think I hear, more the HF energy gradually being reduced the two octaves beneath 20kHz. I was very happy without correcting it for a long time as I was so enamoured of the NOS sound. Then one day I put this correction in and I realized what I'd been missing, so now I can't go back to uncorrected NOS. Nor could we persuade the more die-hard of the objectivists to try it with such FR colouration They might still object that it doesn't give them the full response up to 20kHz though, my correction is only reasonably accurate up to around 17kHz although I could always add more DACs and more delays to improve it further.
There are two other ways to correct for this NOS roll-off (or droop as I call it), neither of which I like. The first is to do digital processing, but then some dynamic range is lost as I have only 16bit DACs. The second is to implement an analog boost filter - however I don't think this can be done without further boosting the image frequencies which potentially cause tweeter IMD. This approach I have tried - it calls for a fairly high Q LC tank circuit.
They might still object that it doesn't give them the full response up to 20kHz though, my correction is only reasonably accurate up to around 17kHz although I could always add more DACs and more delays to improve it further.There are two other ways to correct for this NOS roll-off (or droop as I call it), neither of which I like. The first is to do digital processing, but then some dynamic range is lost as I have only 16bit DACs. The second is to implement an analog boost filter - however I don't think this can be done without further boosting the image frequencies which potentially cause tweeter IMD. This approach I have tried - it calls for a fairly high Q LC tank circuit.
Yes, the normal NOS has a roll-off which eventually reaches more than 3dB by 20kHz. Its not so much this amount at the top end that I think I hear, more the HF energy gradually being reduced the two octaves beneath 20kHz. I was very happy without correcting it for a long time as I was so enamoured of the NOS sound. Then one day I put this correction in and I realized what I'd been missing, so now I can't go back to uncorrected NOS. Nor could we persuade the more die-hard of the objectivists to try it with such FR colouration
There are two other ways to correct for this NOS roll-off (or droop as I call it), neither of which I like. The first is to do digital processing, but then some dynamic range is lost as I have only 16bit DACs. The second is to implement an analog boost filter - however I don't think this can be done without further boosting the image frequencies which potentially cause tweeter IMD. This approach I have tried - it calls for a fairly high Q LC tank circuit.
In for a penny, in for a pound...what happens if you add more DACs and more delays to keep pushing for flat response to 20khz? Any downside?
Good question - if the filter I'm describing is in place, then we'd need huge numbers of DACs to overcome its attenuation at 20kHz. Looking at the graph its -24dB there which is about a factor of 16. So I'd need 16X as many DACs for the HF boost than for the wanted signal. That many extra DACs would increase the glitching by the same factor which is what I set out to minimize
If the market really wanted response to 20kHz then it would be best to modify my filter to give that - it would either have to be twice as complex (say 14th order rather than 7th order) or we'd have to give up something in other areas. Now if I had the software to calculate the DAC-filter coefficients then I could give up some passband flatness in the passive filter and compensate for that in the DAC-filter. Which would be really cool, but I doubt it would gain us very much in terms of reducing the components in the passive filter, maybe lose us at most 2 inductors? It might turn out that my filter is unnecessarily good in its stop-band rejection (in simulation about -53dB) and we could give up something there without loss of SQ. I don't though have a filter design program at the moment to experiment with different filter parameters. I hope to find one in the future though!
If the market really wanted response to 20kHz then it would be best to modify my filter to give that - it would either have to be twice as complex (say 14th order rather than 7th order) or we'd have to give up something in other areas. Now if I had the software to calculate the DAC-filter coefficients then I could give up some passband flatness in the passive filter and compensate for that in the DAC-filter. Which would be really cool, but I doubt it would gain us very much in terms of reducing the components in the passive filter, maybe lose us at most 2 inductors? It might turn out that my filter is unnecessarily good in its stop-band rejection (in simulation about -53dB) and we could give up something there without loss of SQ. I don't though have a filter design program at the moment to experiment with different filter parameters. I hope to find one in the future though!
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