Here's a photo with markings to show the 4 changes; 2 cuts (red) and 2 links (black). Self-explanatory ?
I forgot to add a marking for the trace running under the WM8805 with the through hole - it is the spdif from the USB receiver. Since I'm going to remove the USB and I don't need the 4th input at this point, I'll ground that too. I can change it later as the input is via C8 (just to the left of the table for output settings).
An externally hosted image should be here but it was not working when we last tested it.
I forgot to add a marking for the trace running under the WM8805 with the through hole - it is the spdif from the USB receiver. Since I'm going to remove the USB and I don't need the 4th input at this point, I'll ground that too. I can change it later as the input is via C8 (just to the left of the table for output settings).
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And some more photos showing the ams1117 replaced with adp151, with a Sanyo sh 47uF 6.3V input cap.
The adp datasheet says it is stable with 2uF x7r on input and output, so here there is the 47uF oscon on the input and 22uF 20V oscon + 100nF cap ? C2, C8, etc, the silver block caps; I don't know what brand or type they are but I will check at some point.
Anyone know ?
The underside shows the adp for the xo, the solid-core copper wire to re-route the 5V power trace, and the space where the cm102 usb receiver was.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The adp datasheet says it is stable with 2uF x7r on input and output, so here there is the 47uF oscon on the input and 22uF 20V oscon + 100nF cap ? C2, C8, etc, the silver block caps; I don't know what brand or type they are but I will check at some point.
Anyone know ?
An externally hosted image should be here but it was not working when we last tested it.
The underside shows the adp for the xo, the solid-core copper wire to re-route the 5V power trace, and the space where the cm102 usb receiver was.
An externally hosted image should be here but it was not working when we last tested it.
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Hi datasheet says that ADP151 is stable with 1 uF on in- and output. The absolute minimum is 0.7 uF. I use them with SMD 1 uF PPS film caps and it is OK. Both caps should be of the same value !
The silver caps are "naked" (open construction) MKT or polyester caps. I guess they are NOS as I don't see those often anymore. The value can be changed by sanding the upper side.I would recommend not doing so but this was a popular method in that time. The green silver ones were MKC or polycarbonate. Both types are mechanically more fragile than the enclosed/molded types and they are also more sensitive to moisture and dust. When soldered for too long the lead wires simply fall off.
In other words: you don't see so many molded caps without a reason
The silver caps are "naked" (open construction) MKT or polyester caps. I guess they are NOS as I don't see those often anymore. The value can be changed by sanding the upper side.I would recommend not doing so but this was a popular method in that time. The green silver ones were MKC or polycarbonate. Both types are mechanically more fragile than the enclosed/molded types and they are also more sensitive to moisture and dust. When soldered for too long the lead wires simply fall off.
In other words: you don't see so many molded caps without a reason
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Hi,
Thanks for the help !
I got the idea they should be the same too but then when I went back and re-read it, I couldn't find where it said that.
The board doesn't have an input cap so I had to add one. The two caps I'm using either side are both oscon and the same physical size so similar esr if not exactly the same (22uf 20V and 47uf 6.3V) so I think this should be fine ?
Well, it's all I have in my parts tray anyway... ;-)
Thanks for the help !
I got the idea they should be the same too but then when I went back and re-read it, I couldn't find where it said that.
The board doesn't have an input cap so I had to add one. The two caps I'm using either side are both oscon and the same physical size so similar esr if not exactly the same (22uf 20V and 47uf 6.3V) so I think this should be fine ?
Well, it's all I have in my parts tray anyway... ;-)
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Hi,
Yes, I found it - page 12. "If greater than 1uF of output capacitance is required, the input capacitor should be increased to match it."
I'll change the 22uF on the board to identical 47uF just to be certain, however, my output cap is smaller (22uF) than my input cap (47uF) so I don''t think it'll be a problem. But nevermind, it'll take a couple of mins only. And at some point I'll replace the open MKT with some enclosed ones. I think I have some 1837 somewhere...
Do you know if there is a better quad differential receiver than the one used ? It is a DS26C32ATM. Any ideas ?
The datasheet says the am is obsolete. 19ns delay doesn't seem very good.
Interface - RS-422 - DS26C32AT - TI.com
Thanks again ! Its time to clean up the board then have a listen....
Yes, I found it - page 12. "If greater than 1uF of output capacitance is required, the input capacitor should be increased to match it."
I'll change the 22uF on the board to identical 47uF just to be certain, however, my output cap is smaller (22uF) than my input cap (47uF) so I don''t think it'll be a problem. But nevermind, it'll take a couple of mins only. And at some point I'll replace the open MKT with some enclosed ones. I think I have some 1837 somewhere...
Do you know if there is a better quad differential receiver than the one used ? It is a DS26C32ATM. Any ideas ?
The datasheet says the am is obsolete. 19ns delay doesn't seem very good.
Interface - RS-422 - DS26C32AT - TI.com
Thanks again ! Its time to clean up the board then have a listen....
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Hi,
Best way to be sure - I checked on the scope - no oscillation. So I won't bother to change the caps. It seems to be working as it should. Any reason for your concern about the cap size / esr ?
I also checked the Sanyo datasheet and the C6 size has an ESR of around 0.05 ohms.
I'm curious to know if the adp has a limit.... the datasheet doesn't give any info about max uF values or min ESR and only says larger output caps improve transient response. Anyone tried ?
BTW, the board has a very low ESR cap on the input too - a Chemicon PS 470uF 10V - with 0.012 ohms ESR.
I've been listening for the last couple of hours - albeit there's been no time for things to burn in, but the improvement is obvious. There is much more definition and clearer positioning, with more bass slam and clarity too.
However, I found an idiosyncrasy that the mods have not affected - there appears to be a very faint "ticking" on unlocked channels when my upsampling CD player is connected and running. To be precise - if I stop the player and select another input that has a signal, then keep on selecting through the unconnected channels, the ticking has completely gone = stopping the CD drive stops the tick.
It is only present when the CD drive is running and I'm listening to an unconnected channel. It is not present on any locked channels and creates no interference of any kind. It's almost as if the receiver is tutting at me for listening to nothing, when I could be listening to music. ;-) This even happens through the toslink optical from the CD with nothing else connected. It doesn't happen with any other connected sources, only the CD, and again, it's only heard on an unconnected input channel. It is also very faint. The player itself makes no significant physical noise. So it's really just a little weird.
I still need to try adding some 22r resistors on the i2s output, but I have to say, weird behaviour aside, I'm very pleased with this receiver, and no question I'd recommend it if you're willing to work on it a little - and don't mind it tutting for playing a CD and listening to nothing...! Actually, I suspect my CD player is the culprit... it wants attention like a naughty child...
Cheers,
Tom
Best way to be sure - I checked on the scope - no oscillation. So I won't bother to change the caps. It seems to be working as it should. Any reason for your concern about the cap size / esr ?
I also checked the Sanyo datasheet and the C6 size has an ESR of around 0.05 ohms.
I'm curious to know if the adp has a limit.... the datasheet doesn't give any info about max uF values or min ESR and only says larger output caps improve transient response. Anyone tried ?
BTW, the board has a very low ESR cap on the input too - a Chemicon PS 470uF 10V - with 0.012 ohms ESR.
I've been listening for the last couple of hours - albeit there's been no time for things to burn in, but the improvement is obvious. There is much more definition and clearer positioning, with more bass slam and clarity too.
However, I found an idiosyncrasy that the mods have not affected - there appears to be a very faint "ticking" on unlocked channels when my upsampling CD player is connected and running. To be precise - if I stop the player and select another input that has a signal, then keep on selecting through the unconnected channels, the ticking has completely gone = stopping the CD drive stops the tick.
It is only present when the CD drive is running and I'm listening to an unconnected channel. It is not present on any locked channels and creates no interference of any kind. It's almost as if the receiver is tutting at me for listening to nothing, when I could be listening to music. ;-) This even happens through the toslink optical from the CD with nothing else connected. It doesn't happen with any other connected sources, only the CD, and again, it's only heard on an unconnected input channel. It is also very faint. The player itself makes no significant physical noise. So it's really just a little weird.
I still need to try adding some 22r resistors on the i2s output, but I have to say, weird behaviour aside, I'm very pleased with this receiver, and no question I'd recommend it if you're willing to work on it a little - and don't mind it tutting for playing a CD and listening to nothing...! Actually, I suspect my CD player is the culprit... it wants attention like a naughty child...
Cheers,
Tom
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Hi I indeed thought of possible oscillation as a maximum value is not mentioned. If it is quiet on the oscilloscope then it is OK.
I have the same board for quite some time now and I stopped working (could not find a through hole 12 MHz 3.3 V oscillator) on it. I recall having the 110 Ohm EAS/EBU connector removed. Your enthusiasm is infective. Will find it and try again.
Hi, why did you change these tracks ? I think i am missing something !?
I have the same board for quite some time now and I stopped working (could not find a through hole 12 MHz 3.3 V oscillator) on it. I recall having the 110 Ohm EAS/EBU connector removed. Your enthusiasm is infective. Will find it and try again.
Hi, why did you change these tracks ? I think i am missing something !?
Hi,
I'm not that happy with any pcb trace that cuts across the I2S output. Ideally, I would like the I2S output to have 22r resistors at the output to stop reflections, and also run over the ground plane until they exit the board, to limit interference.
This board has two traces that could potentially interfere with the wm8805. In fairness to the designer, they run perpendicular which is good practice if you must have them cross, but better to avoid this right ? One is a 5V pcb trace - it can be easily re-routed and the disconnected copper can then be used as part of the ground plane. The other is the usb spdif line. This can be grounded too near C8. So that achieves a ground plane of sorts, although it would be better yet if it was fully contiguous.
I was surprised by how much noise my scope was showing. I think I should investigate more. But the adp had no more noise than anywhere else and, what I was looking for, no sign of oscillation; no waveforms at any frequency; just the noise hash. I was not too concerned by the noise because the sound is very good, however, this would seem like the next step if I want to squeeze more out of it. It could be a polluted ground.
I guess the next step is to isolate the receiver ( no source, no DAC ) and then get measure some test points. TBH though, there's not much else I know to do to improve it so I'd probably be chasing my tail.
cheers
Tom
I'm not that happy with any pcb trace that cuts across the I2S output. Ideally, I would like the I2S output to have 22r resistors at the output to stop reflections, and also run over the ground plane until they exit the board, to limit interference.
This board has two traces that could potentially interfere with the wm8805. In fairness to the designer, they run perpendicular which is good practice if you must have them cross, but better to avoid this right ? One is a 5V pcb trace - it can be easily re-routed and the disconnected copper can then be used as part of the ground plane. The other is the usb spdif line. This can be grounded too near C8. So that achieves a ground plane of sorts, although it would be better yet if it was fully contiguous.
I was surprised by how much noise my scope was showing. I think I should investigate more. But the adp had no more noise than anywhere else and, what I was looking for, no sign of oscillation; no waveforms at any frequency; just the noise hash. I was not too concerned by the noise because the sound is very good, however, this would seem like the next step if I want to squeeze more out of it. It could be a polluted ground.
I guess the next step is to isolate the receiver ( no source, no DAC ) and then get measure some test points. TBH though, there's not much else I know to do to improve it so I'd probably be chasing my tail.
cheers
Tom
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The naked bypass caps were included because they were "audiophile" but they are a terrible design choice for digital bypass. They are too physically large and too far away to do any serious high freq noise shunting.
As far as I know, they aren't good for coupling the digital signals either so eventually you should remove them all from critical locations.
I have this board too and its gonna be hard to fix it.
For power to pin 1, you should move the OScons (can anyone verify that they're real?) to where the naked bypasses are (drill a new hole for the gnd led and scrape off the paint to solder to gnd plane) and then put small sm caps as close as possible to the 8805 (scrape off paint on pwr trace so sm cap is touching power pin and scrape gnd side to solder to gnd plane)
Good luck and keep taking pics!
Cheers,
Jeff
As far as I know, they aren't good for coupling the digital signals either so eventually you should remove them all from critical locations.
I have this board too and its gonna be hard to fix it.
For power to pin 1, you should move the OScons (can anyone verify that they're real?) to where the naked bypasses are (drill a new hole for the gnd led and scrape off the paint to solder to gnd plane) and then put small sm caps as close as possible to the 8805 (scrape off paint on pwr trace so sm cap is touching power pin and scrape gnd side to solder to gnd plane)
Good luck and keep taking pics!
Cheers,
Jeff
Hi,
Thanks - that's something I overlooked. Pin 1 is dvdd so that needs local decoupling with 0.1uf x7r, easy enough, and I think pin 11 is the supply for the pll - pvdd - so that needs the same, but isn't so convenient.
I have no idea if the os-cons are genuine, so I just tested one that I removed before. My DMM and it says it is 29uF. The sheath says 22uF but my DMM is very unreliable with large cap values so it could be correct. However, I have some 10uF 35V Rubycon ZA in my tray so I'll try them instead (0.33 ohm ESR @ 100Khz, and 350mA ripple).
I haven't been able to find an upgrade for the quad line receiver - most have very similar specs it seems.
Thanks,
Tom
Thanks - that's something I overlooked. Pin 1 is dvdd so that needs local decoupling with 0.1uf x7r, easy enough, and I think pin 11 is the supply for the pll - pvdd - so that needs the same, but isn't so convenient.
I have no idea if the os-cons are genuine, so I just tested one that I removed before. My DMM and it says it is 29uF. The sheath says 22uF but my DMM is very unreliable with large cap values so it could be correct. However, I have some 10uF 35V Rubycon ZA in my tray so I'll try them instead (0.33 ohm ESR @ 100Khz, and 350mA ripple).
I haven't been able to find an upgrade for the quad line receiver - most have very similar specs it seems.
Thanks,
Tom
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Hi,
I'd like to keep it, but find a better part.... but no chance it seems. Hey ho.
Here's a photo of the top side. I scraped off some of the screen on the edges of the gnd so I could solder them together and create a more contiguous gnd plane. Hopefully, it will help with noise levels a little. It looks a mess and needs another clean but the connections are all good and it should work better than before. You might say it is an ugly master chef ?!
It's also been suggested I try to float/suspend the xo to avoid vibration. I could suspend the whole board when this gets boxed up...but it needs chassis mounting... hmmm... need to think about how to do that.... maybe just some foam under the xo and replace the solid wire with flexible stuff.
Before :
After :
Effectively :
I'd like to keep it, but find a better part.... but no chance it seems. Hey ho.
Here's a photo of the top side. I scraped off some of the screen on the edges of the gnd so I could solder them together and create a more contiguous gnd plane. Hopefully, it will help with noise levels a little. It looks a mess and needs another clean but the connections are all good and it should work better than before. You might say it is an ugly master chef ?!
It's also been suggested I try to float/suspend the xo to avoid vibration. I could suspend the whole board when this gets boxed up...but it needs chassis mounting... hmmm... need to think about how to do that.... maybe just some foam under the xo and replace the solid wire with flexible stuff.
Before :
An externally hosted image should be here but it was not working when we last tested it.
After :
An externally hosted image should be here but it was not working when we last tested it.
Effectively :
An externally hosted image should be here but it was not working when we last tested it.
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I confess I'm confused about how the WM8805 divides the master clock, and in particular whether any ONE clock speed can be optimal for different samplerate-families.
Please consider the scenario of a WM8805, under software control, sharing a common external clock with an ES9023 DAC -
can someone please tell me:
i) what would be the optimal XO for 44.1/88.2 material?
ii) what would be the optimal XO for 48/96 material?
As I understand it, the WM8805 in software mode will accept external clock freq up to 27MHz,
and the ES9023 will accept external clock freq up to 50MHz.
Thanks.
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