625R Zout, capacitor is 1200 pf ceramic NP0, -3db is then at 212 Khz. NP0/C0G types are supposed to be fine, especially when their effect are way out of the audio band....
I believe it will be an error to remove this NPO : NPOs are not said to be harsh.
What is the relation between 212 khz roll off and the upper digital frequencies applied by the upsampling !
Does someone read the review I linked in the digital filter thread about the interview of Rob Watt the tech behind the Hugo TT ( a commercial sucess so said to have a gound sound ?). He uses Spartan 6 ; does the layout here is close enough to pick ideas about its digital filter strategy ? Or is it just bull sheet answers for audiophile reviews ! I liked what he writed about isolator chips and upper upsampling frequencies : doesn't mix together ! Ah ? Are they not made for RF ?!
I would bet just for a little Lundhal output traffo to have a more naturel rol off on the non buffered SE : voltage and Z are enough for any modern Pre or amp ! I have a little shematic about the RC filter to apply to a standard Lundhal traffo (ann the one I tak about can be mod into SE to balanced !). Let me looking for it !
What is the relation between 212 khz roll off and the upper digital frequencies applied by the upsampling !
Does someone read the review I linked in the digital filter thread about the interview of Rob Watt the tech behind the Hugo TT ( a commercial sucess so said to have a gound sound ?). He uses Spartan 6 ; does the layout here is close enough to pick ideas about its digital filter strategy ? Or is it just bull sheet answers for audiophile reviews ! I liked what he writed about isolator chips and upper upsampling frequencies : doesn't mix together ! Ah ? Are they not made for RF ?!
I would bet just for a little Lundhal output traffo to have a more naturel rol off on the non buffered SE : voltage and Z are enough for any modern Pre or amp ! I have a little shematic about the RC filter to apply to a standard Lundhal traffo (ann the one I tak about can be mod into SE to balanced !). Let me looking for it !
NPO doesn't guarantee good sound any more than a film dielectric does. It just means it won't have the piezo-electric issues X7Rs etc. have.
The 212KHz (I've also read 270KHz and 150KHz mentioned) knee is nothing to do with upsampling, it's purely a function of the analog filter. A lower value may be better depending on what is going on at RF frequencies with his DAC, and what is circuit types are downstream..
Yes, I'll read anything Rob Watts has to say - he's an extremely clever guy. Thanks for sharing the article.
One thing I'm curious about is his claim that long filters are necessary for accurate reproduction of transients, whereas John Swenson prefers shorter filters. I'm not a DSP engineer, so who knows?
It's pretty much like one guy saying discrete class-a jfet buffers are necessary for best sound, another saying valves are best and a third claiming Audio Note silver wound transformers and Duelund Cast caps are the ONLY way to go.
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http://www.diyaudio.com/forums/blogs/abraxalito/1201-revisiting-mods-lite-dac-ah.html : shorter rol off in the analog domain ?
It sounds strange to me than this stable 1200 pF NPO is the cause of all the illness where the rol off is (150 K hz to 270 K hz
) !
Is someone interrested by a shematic I have somewhere with a Lundhal 70 euros traffo ? I use it in front of a buffer oap stage but maybe good enough to use without buffer in front of the non buffered amp ?
If such little filter with mu metal shielding and interwinding separation is ok for a filtering, can we get off the 1200 pF cap ?
Ah I read the rol off was 270 K hz, maybe my dog can hear it, dunno !
To solve the dynamic issues than some notice despite the different filter (Nige2000 testimonial with all the digital filter tried and mine with the stock one) maybe 100 uF to 470 uF Panasonic SEPC could be tried in // on the embeded Nichicon ? Whait is the actual ESR of the Panasonic CL Soren choosed ? Around 6 m oHms iirc ?
So no time for trying myself I come back to my AD1862 I have to finish before beginning this one, I have two PS shunt -/+ 15 V to do for a discrete diamond buffer stage on a verroboard !
Which will ne good to have several multibidac to benchmark the set up of this one more easily ! I want to sell mine by lacking of time (Ah I just finish my Aya 2 2014) but interrested members would want I give them for nothing Buy your self at Soekris at full price if your prefer, there is some decent limits, price is the one I putt on the swap met section ! pfffff! Sorry for this one : of topic...and so what !
It sounds strange to me than this stable 1200 pF NPO is the cause of all the illness where the rol off is (150 K hz to 270 K hz
) ! Is someone interrested by a shematic I have somewhere with a Lundhal 70 euros traffo ? I use it in front of a buffer oap stage but maybe good enough to use without buffer in front of the non buffered amp ?
If such little filter with mu metal shielding and interwinding separation is ok for a filtering, can we get off the 1200 pF cap ?
Ah I read the rol off was 270 K hz, maybe my dog can hear it, dunno !
To solve the dynamic issues than some notice despite the different filter (Nige2000 testimonial with all the digital filter tried and mine with the stock one) maybe 100 uF to 470 uF Panasonic SEPC could be tried in // on the embeded Nichicon ? Whait is the actual ESR of the Panasonic CL Soren choosed ? Around 6 m oHms iirc ?
So no time for trying myself I come back to my AD1862 I have to finish before beginning this one, I have two PS shunt -/+ 15 V to do for a discrete diamond buffer stage on a verroboard !
Which will ne good to have several multibidac to benchmark the set up of this one more easily ! I want to sell mine by lacking of time (Ah I just finish my Aya 2 2014) but interrested members would want I give them for nothing
Buy your self at Soekris at full price if your prefer, there is some decent limits, price is the one I putt on the swap met section ! pfffff! Sorry for this one : of topic...and so what !
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Thought this output RC filter is to filter out the switching noise of the ladder network as the output changes and 212k is a suitable roll-off though you may choose lower if preferred. Up sampling filters on the DSP are for the anti-aliasing functions.
For CD sample rate playback, long filters (meaning, they feature a long filter kernel producing a long impulse response) can result in the more accurate waveform reconstruction. This is particularly so with CDs, as their 44.1KHz sample rate affords a narrow band space between the signal bandwidth (20KHz) and the system Nyquist frequency (22.05KHz). That narrow band requires a brickwall reconstruction filter slope to well remove the highest frequency image products, which will be located at 24.1KHz and even closer.
Long filters provide a sharper brickwall cutoff slope, better rejecting the image products, which means a more accurate waveform reconstruction than with shorter filters, especially, the very common half-band type. Many people prefer the sound of very short filters that feature soft cutoff slopes that do not effectively reject the image products. The ultimate form of short filter is no reconstruction filter at all, ala NOS DACS.
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A DCB1 (B1 with dual supply and no output cap) has an output impedance of about 250 Ohm.
Have been running the dam1021 with unbuffered SE outputs into a dcb1 for a while now. Works like a charm
Did you compare it to running with the digital volume pot?
Hi Vgeorge,
thank you for the Info. If there's no output resistor, will the circuit oscillate very easily? Im thinking of using a cap paralleled to the load to avoid oscillation......
Don't be an diy audio girly-man
The pops when changing sample rate are annoying more than anything.
If you turn the DAM on before you power the amp on, and off after the amp is turned off you won't have any issues. And lets face it, the power down pop will not be fixed in firmware - it's going to require additional circuit to do so.
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