krishu said:
The essence of nonos is that the resultant spectrum contains the baseband music spectrum and a series of ultrasonic images - i.e. the original music spectrum mirrored around multiples of the sampling frequency - that go on infinitely (actually roll-off according to the Sin(f)/f function if you want to be exact).
This means that when 20kHz is present in the music signal, the output will have 20kHz, 44.1kHz-20=24.1kHz, 64.1kHz, and so on.
hjelm said:
Actually there's nothing smart or 'estimating' going on, in fact what LL does bears no relation whatsoever to overtones related to the music signal. LL is simply a low-order digital low-pass, meaning that it passes on the lower images (see above nonos case) pretty much unattenuated. So again, with 20kHz present in the original signal, the output of LL will contain 20kHz and 24.1kHz.
It is, in effect, a half-way house between nonos and traditional brickwall Sinc(x)-based oversampling. Same thing as Wadia's Digimaster, BTW.
There you go ...
Thanks Werner,
Anyway i have figured that i might as well rip out the whole analog part. I have tewo suggestions for analog stages does anyone care to comment.
The buffers are either 2604 or BUF634, maybe not a fair match but still.
OPamps are 2604.
Any drawbacks with either of these configurations other than the fact that the first one has the psu in the signalpath directly.
Anyway i have figured that i might as well rip out the whole analog part. I have tewo suggestions for analog stages does anyone care to comment.
The buffers are either 2604 or BUF634, maybe not a fair match but still.
OPamps are 2604.
Any drawbacks with either of these configurations other than the fact that the first one has the psu in the signalpath directly.
Attachments
Hi!
Anyone know how much filtering theese dacs need?
The filter in my player seems to a third order filter at about 60kHz(A little guessing about the frequency)
I was thinking about something like the pre Carlos describes in the Chipamp section, with an suitable filter around it, as a outputstage for my player.
Do you think that would work?
Hjelm, would a dc compensation like you describe be stable enoug without a servo to be safe?
I would have used a multiturn bot for the resitor so you could adjust for zero dc.
Have a nice weekend!
Tor Martin
Anyone know how much filtering theese dacs need?
The filter in my player seems to a third order filter at about 60kHz(A little guessing about the frequency)
I was thinking about something like the pre Carlos describes in the Chipamp section, with an suitable filter around it, as a outputstage for my player.
Do you think that would work?
Hjelm, would a dc compensation like you describe be stable enoug without a servo to be safe?
I would have used a multiturn bot for the resitor so you could adjust for zero dc.
Have a nice weekend!
Tor Martin
Hi Tor.
I have considered a pot to adjust the offset.
I do not think i would use it n the first solution since it would be in the signalpath and i would like to avoid that.
The second solution is more interesting since it would be possible to replace the reference voltage and resistor with a current generator. It would be neat if i could make some form of feedback to adjust the current generator as a servo. The requirements would be that the cutoff frequency has to be small and i do not want to add too many components.
As for Carlos preamplifier design i start drooling when i see it. The man both has time to build it and the money to buy lots of 627 and BUF circuits to match them.
Did you find the complete schematics in his thread? I could only find the 627 and BUF circuit.
I am interested in his powersupply since there seems to be a lot of vodoo in those parts, and his seem to work. If i remeber correctly he stated somewhere that the 2604 op could sound very nice if you had caps very near the opamp.
I have considered a pot to adjust the offset.
I do not think i would use it n the first solution since it would be in the signalpath and i would like to avoid that.
The second solution is more interesting since it would be possible to replace the reference voltage and resistor with a current generator. It would be neat if i could make some form of feedback to adjust the current generator as a servo. The requirements would be that the cutoff frequency has to be small and i do not want to add too many components.
As for Carlos preamplifier design i start drooling when i see it. The man both has time to build it and the money to buy lots of 627 and BUF circuits to match them.
Did you find the complete schematics in his thread? I could only find the 627 and BUF circuit.
I am interested in his powersupply since there seems to be a lot of vodoo in those parts, and his seem to work. If i remeber correctly he stated somewhere that the 2604 op could sound very nice if you had caps very near the opamp.
Hi!
The reason I consider the carlos circuit is because I think I have all the parts for it laying around, and they seems that they like it alot.
Have you any idea of what kind of filter this dac needs?
Probably I don`t need to filter it at all, because my amp is a valve buffered gainclone with lowpassfilter. This together with the built in filter in the dachip should be enough. Anyway the original third order filter seems to be overkill with lots of parts in the signalpath. The datasheet doesn`t recommend any spesific filter design.
I`ll probably go for some high quality coupling caps for the coupling. I have some Black Gate Nx somewhere. But I would like to get rid of it though. Removing the output coupling cap made a huge vail dissapare.
Regards
Tor Martin
The reason I consider the carlos circuit is because I think I have all the parts for it laying around, and they seems that they like it alot.
Have you any idea of what kind of filter this dac needs?
Probably I don`t need to filter it at all, because my amp is a valve buffered gainclone with lowpassfilter. This together with the built in filter in the dachip should be enough. Anyway the original third order filter seems to be overkill with lots of parts in the signalpath. The datasheet doesn`t recommend any spesific filter design.
I`ll probably go for some high quality coupling caps for the coupling. I have some Black Gate Nx somewhere. But I would like to get rid of it though. Removing the output coupling cap made a huge vail dissapare.
Regards
Tor Martin
If you want a servo you could copy LC Audio's design in their the end millenium. There is a complete datasheet available for the schematics and i beleive it should be a nice solution.
As for the DC offset from the DAC i see no direct options other than the ones i suggested but then again i am fairly new to this.
As for the DC offset from the DAC i see no direct options other than the ones i suggested but then again i am fairly new to this.
If it is the 1716 then pioneer seems to have changed the
default value for the lpf filter.The pcm 1716 specifies 10uf while pioneer uses 4.7uf. This i assume means that they have moved the cutoff to a bit more than the 40k.
I also made some simulations of the attenuation in the analog stage, with a different OPA though (2604). This resulted in the following frequency response.
Maybe it is to compensate for the internal filter rolloff but i would prefer to straighten it out.
default value for the lpf filter.The pcm 1716 specifies 10uf while pioneer uses 4.7uf. This i assume means that they have moved the cutoff to a bit more than the 40k.
I also made some simulations of the attenuation in the analog stage, with a different OPA though (2604). This resulted in the following frequency response.
Maybe it is to compensate for the internal filter rolloff but i would prefer to straighten it out.
Attachments
Hi Hjelm!
Do you care to explain how this filter works, can`t seem to find it in the datasheet. I thought theese were just coupling caps between dac and ground and that theese pins at dac had 2.5 volt dc. Don`t know where I got that idea never measured for dc either.
Ok, here is something to try for you before you go through the bother of making a new output section:
Dissconect the whole analog section and take the output signal directly from dac through some good coupling caps.
Thorsten Loesch recommended this years ago as the only way to get theese lousy dacs to perform half decent (or something like that).
My cd player has been out for 14 days because I started to change the powersupply to the analog filter and never had time to get it working stright.
Today I had some time, and I just disconnected everything. Changed the coupling cap for a 4.7 BlackGate Nx, one leg soldered in the old spot, one leg free in air. Took the signal directly from the free leg to some new rca plugs.
And I have to tell you, this seems to sound a lot better than before! And my analog section was heavily modified.
And this is without any brake in for the Nx caps. It`s only 1Vrms out though.
At least try it out, its an easy fix if you don`t like the result.
Time to listen to some music!
Tor Martin
Do you care to explain how this filter works, can`t seem to find it in the datasheet. I thought theese were just coupling caps between dac and ground and that theese pins at dac had 2.5 volt dc. Don`t know where I got that idea never measured for dc either.
Ok, here is something to try for you before you go through the bother of making a new output section:
Dissconect the whole analog section and take the output signal directly from dac through some good coupling caps.
Thorsten Loesch recommended this years ago as the only way to get theese lousy dacs to perform half decent (or something like that).
My cd player has been out for 14 days because I started to change the powersupply to the analog filter and never had time to get it working stright.
Today I had some time, and I just disconnected everything. Changed the coupling cap for a 4.7 BlackGate Nx, one leg soldered in the old spot, one leg free in air. Took the signal directly from the free leg to some new rca plugs.
And I have to tell you, this seems to sound a lot better than before! And my analog section was heavily modified.
And this is without any brake in for the Nx caps. It`s only 1Vrms out though.
At least try it out, its an easy fix if you don`t like the result.
Time to listen to some music!
Tor Martin
Sounds interesting i will give it a try.
Looking at the schematic of the pioneer an interesting thing to note is that for the headphone amp there is another dc blocking cap in the signalpath before the buffers but there is nothing that should cause dc offset, except for the muting ciruit
Do you know if Thorsten Loeschs reccomendations are available on the net somewhere?
If i remeber the datasheet for the dac i think the load should be 5k or more so there should perhaps be no porblem.
Looking at the schematic of the pioneer an interesting thing to note is that for the headphone amp there is another dc blocking cap in the signalpath before the buffers but there is nothing that should cause dc offset, except for the muting ciruit
Do you know if Thorsten Loeschs reccomendations are available on the net somewhere?
If i remeber the datasheet for the dac i think the load should be 5k or more so there should perhaps be no porblem.
Hi!
You will find many of his thoughts about the subjekt here:
http://www.fortunecity.com/rivendell/xentar/1179/theory/vasfda/vasfda.html
By the way you mention Kuei in the other pcm1716 threat, Kuei=Thorsten.
All though you don`t loose coupling cap this way, you can make it a very good film cap. With 47K input impedance, probably 0,47 uF is enough. I`m thinking of Mundorf supreme silver in oil caps.
They are expencive, but not as expencive as the modyfied analog stage was.
I still think I`ll try the nonos TDA1543a solution in my player.
Regards
Tor Martin
You will find many of his thoughts about the subjekt here:
http://www.fortunecity.com/rivendell/xentar/1179/theory/vasfda/vasfda.html
By the way you mention Kuei in the other pcm1716 threat, Kuei=Thorsten.
All though you don`t loose coupling cap this way, you can make it a very good film cap. With 47K input impedance, probably 0,47 uF is enough. I`m thinking of Mundorf supreme silver in oil caps.
They are expencive, but not as expencive as the modyfied analog stage was.
I still think I`ll try the nonos TDA1543a solution in my player.
Regards
Tor Martin
Hi folks,
yesterday I soldered a bit ...
First, I must say: the silmics in thios player are NOT coupling caps but supply caps fpor the dac and two 4.7uF silmics connected to the EXTL and EXTR pins of the DAC (what the hell does that??)
What I did so far: change diodes to BYV27/150,
replace IC405 (NJM4558D-D) with AD8620 (amazing!!!!!) and tried two OPA627 here, too (clinical).
Maybe this is because the supply voltage for this opamp is +/-10volts in this player.
I removed coupling caps C432, C433 and put wires in.
I bypassed coupling caps C429, C430 with 8200pF KP caps.
I changed R1447 .. R1450 (all 470R) to 75R. This makes 150R output impedance. You might put 150R resistors instead of a 75 R pair and disconnect the muting transistors by doing that.
Also, I removed C474 and C475 to disconnect the headphone circuit.
This all did a lot!!! I already ordered mica capacitors to replace the poor filter caps in the analog output stage, I will replace all electrolytics with Panasonic FCs and replace C429 and C430 with Black Gate NX when I find the time to order them.
I am still speachless about the difference between AD8620 and two OPA627. But as said above, this may be caused by the low voltage.
Cheers
Christian.
yesterday I soldered a bit ...
First, I must say: the silmics in thios player are NOT coupling caps but supply caps fpor the dac and two 4.7uF silmics connected to the EXTL and EXTR pins of the DAC (what the hell does that??)
What I did so far: change diodes to BYV27/150,
replace IC405 (NJM4558D-D) with AD8620 (amazing!!!!!) and tried two OPA627 here, too (clinical).
Maybe this is because the supply voltage for this opamp is +/-10volts in this player.
I removed coupling caps C432, C433 and put wires in.
I bypassed coupling caps C429, C430 with 8200pF KP caps.
I changed R1447 .. R1450 (all 470R) to 75R. This makes 150R output impedance. You might put 150R resistors instead of a 75 R pair and disconnect the muting transistors by doing that.
Also, I removed C474 and C475 to disconnect the headphone circuit.
This all did a lot!!! I already ordered mica capacitors to replace the poor filter caps in the analog output stage, I will replace all electrolytics with Panasonic FCs and replace C429 and C430 with Black Gate NX when I find the time to order them.
I am still speachless about the difference between AD8620 and two OPA627. But as said above, this may be caused by the low voltage.
Cheers
Christian.
Thanks for sharing!
As for the EXTL EXTR that is a 2.5voltage reference point for the feedback loop of the internal OPamp. If i have understood it correctly. Apparently it is critical for the sound of the DAC that this is properly decoupled. Kuei stated that in another thread.
I am kind of interested to know if there is a point(or if it is possible at all) to actively stabilize that point. I.e. to set a 337 to 2.5 volt as the input to that pin. It would probably work if the vdd/2 is done by resistors but not if it is actively stabilized internally.
I wonder if the removal of c435 and c436 should make a less clinical sound. When i simulate the analog stage, previous post, there is a slight rise in the amplitude starting as early as 4k and peaking at 35k with a 1dB peak. It could be to compensate for early rolloff from the dac but i see no point.
I would change the 435 and 436 to something between 1100p and 1200p.
I know that is to fight the windmills when there are other things, read loudspeaker and room, that affect frequency response much more but my view is that if possible avoid building systematic errors in the system.
The analog PSU is unregulated is that also a possible cause for the 627 to feel uncomfortable in the environment.
As for the EXTL EXTR that is a 2.5voltage reference point for the feedback loop of the internal OPamp. If i have understood it correctly. Apparently it is critical for the sound of the DAC that this is properly decoupled. Kuei stated that in another thread.
I am kind of interested to know if there is a point(or if it is possible at all) to actively stabilize that point. I.e. to set a 337 to 2.5 volt as the input to that pin. It would probably work if the vdd/2 is done by resistors but not if it is actively stabilized internally.
I wonder if the removal of c435 and c436 should make a less clinical sound. When i simulate the analog stage, previous post, there is a slight rise in the amplitude starting as early as 4k and peaking at 35k with a 1dB peak. It could be to compensate for early rolloff from the dac but i see no point.
I would change the 435 and 436 to something between 1100p and 1200p.
I know that is to fight the windmills when there are other things, read loudspeaker and room, that affect frequency response much more but my view is that if possible avoid building systematic errors in the system.
The analog PSU is unregulated is that also a possible cause for the 627 to feel uncomfortable in the environment.
Hello Hjelm and others,
yes, i was told by a few people that OPA627 is more sensible to P/S than AD8620. But anyway, I will keep it as it is now. I will publish things by time on my website. (concerning this issue I did only in German until now).
Today, I replaced all the 1500pF and 1000pF caps (C435 .. C 442) with mica ones. I did not notice a big difference, if any.
Today, i plugged back the old opamp as well as the double OPA627 just to see if I "listended correctly" yesterday:
The differences apperared not that big to me now, but still OPA627 was not as warm as AD8620 and the old NJM thing was kind of nervous and maybe less detailed, but it sounded like music, though.
My Low ESR electrolytics are on their way ... I'll keep on reporting.
BTW, according to the data sheet of PCM1716, which is said to be underneath the cover of the pioneer DAC, 10uF is recommended on EXTL/R . I will try this as well, but can imagine it won't make such a big difference. I will replace all Silmics because some friends suggested to do so because these were overrated.
Cheers
Christian.
yes, i was told by a few people that OPA627 is more sensible to P/S than AD8620. But anyway, I will keep it as it is now. I will publish things by time on my website. (concerning this issue I did only in German until now).
Today, I replaced all the 1500pF and 1000pF caps (C435 .. C 442) with mica ones. I did not notice a big difference, if any.
Today, i plugged back the old opamp as well as the double OPA627 just to see if I "listended correctly" yesterday:
The differences apperared not that big to me now, but still OPA627 was not as warm as AD8620 and the old NJM thing was kind of nervous and maybe less detailed, but it sounded like music, though.
My Low ESR electrolytics are on their way ... I'll keep on reporting.
BTW, according to the data sheet of PCM1716, which is said to be underneath the cover of the pioneer DAC, 10uF is recommended on EXTL/R . I will try this as well, but can imagine it won't make such a big difference. I will replace all Silmics because some friends suggested to do so because these were overrated.
Cheers
Christian.
I got my low ESR electrolytics today and am still soldering ...
I found an AD8066 in my parts box and will try it, too.
I brought my AD8620 and doubleOPA627 away from home for taking photos, so I had to live with the old opamp yesterday and it was horrible ... so obviously opamp replacement was an improvement.
I have problems with the platter: it is everything but smooth running: It has kind of warps and therefore CDs are kind of lurching which can not be optimal for scanning. Any suggestions?
I haven't got the remote control. I saw in the service manual that there are two buttons for Volume Up and Volume Down on it. Are these working?!? (So I could save a pre amplifier?)
Thanks for help
Cheers
Christian.
I found an AD8066 in my parts box and will try it, too.
I brought my AD8620 and doubleOPA627 away from home for taking photos, so I had to live with the old opamp yesterday and it was horrible ... so obviously opamp replacement was an improvement.
I have problems with the platter: it is everything but smooth running: It has kind of warps and therefore CDs are kind of lurching which can not be optimal for scanning. Any suggestions?
I haven't got the remote control. I saw in the service manual that there are two buttons for Volume Up and Volume Down on it. Are these working?!? (So I could save a pre amplifier?)
Thanks for help
Cheers
Christian.
Hello again,
I changed nearly every electrolytic to larger panasonic fc* and bypassed them with EMZ KP 15500pF caps. I changed those caps on EXTL/R to 10uF/63V Panasonic FC and also changed the coupling caps to this type, bypassed with KP.
After one night of burning in it seems to mee that music is so much more relaxed now. When listening to piano music I (am suggested to) see more wood than I did before... just more natural and more dynamics.
I tried AD8066 but still am favoring AD8620.
I also replaced those three 0.01uF film caps (C316 and two others) with 47uF Pana FC plus 15.5nF KP. (Obvoisly they planned to put electrolytics there because plus and minus was printed on)
Next step would be to replace the transformer with a larger torodial one. But where to connect it??
Cheers
Christian.
*Like 220/15 -> 470/25 and so on
I changed nearly every electrolytic to larger panasonic fc* and bypassed them with EMZ KP 15500pF caps. I changed those caps on EXTL/R to 10uF/63V Panasonic FC and also changed the coupling caps to this type, bypassed with KP.
After one night of burning in it seems to mee that music is so much more relaxed now. When listening to piano music I (am suggested to) see more wood than I did before... just more natural and more dynamics.
I tried AD8066 but still am favoring AD8620.
I also replaced those three 0.01uF film caps (C316 and two others) with 47uF Pana FC plus 15.5nF KP. (Obvoisly they planned to put electrolytics there because plus and minus was printed on)
Next step would be to replace the transformer with a larger torodial one. But where to connect it??
Cheers
Christian.
*Like 220/15 -> 470/25 and so on
Hi,
Wish i had the time to start modifying.
As for the remote. I would not use it to remove a preamp. Nobody i have heard of prefers the digital attenuation. I haven't played with it too much but a quick test indicated degraded performance.
Afraid i have no way to get the AD8620 in sweden.
I am fiddeling, simulating mostly, with the idea to use a fixed dc offset compensation but it would require two opamps, both in inverting configuration though and one with a current offset at the output which is supposeed to be good (biasing to class A or almost).
I am not so experienced that i can estimate if a current source drifts or not. If not then i might get away with no DC blocking caps at all.
Wish i had the time to start modifying.
As for the remote. I would not use it to remove a preamp. Nobody i have heard of prefers the digital attenuation. I haven't played with it too much but a quick test indicated degraded performance.
Afraid i have no way to get the AD8620 in sweden.
I am fiddeling, simulating mostly, with the idea to use a fixed dc offset compensation but it would require two opamps, both in inverting configuration though and one with a current offset at the output which is supposeed to be good (biasing to class A or almost).
I am not so experienced that i can estimate if a current source drifts or not. If not then i might get away with no DC blocking caps at all.
Hello hjelm,
I am not too deep into it, but I think you must use a coupling cap between dac and opamp. When using a good opamp (opa2604 etc.) you do not need another dc-filter behind that. Make sure you have one in your power amp.
Regarding AD8620 I wrote you an email.
I am wondering where this volume control is in this player ... in a DSP?
Cheers
Christian.
I am not too deep into it, but I think you must use a coupling cap between dac and opamp. When using a good opamp (opa2604 etc.) you do not need another dc-filter behind that. Make sure you have one in your power amp.
Regarding AD8620 I wrote you an email.
I am wondering where this volume control is in this player ... in a DSP?
Cheers
Christian.
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