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Old 22nd July 2012, 08:51 AM   #121
chaparK is offline chaparK  Luxembourg
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Quote:
Originally Posted by dahlberg View Post
Do you have a list of software functions ?
You'll find the usual XO and EQ tools such as delay, IIR, FIR and gain. Dynamics processing will be included, but might come only with the second release depending on time. Custom filters for serious tweekers are also included (i.e. the loading of a transfer function from a file).

I had written in a previous post that processing blocks are organized into "themes", which are collections of processing strategies. Within these 'themes' there are processing blocks that are specific to loudspeaker management, which is something that I haven't seen anywhere else and that's why I'm not going to develop on this topic until the boards are here

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Originally Posted by Indemini View Post
Hello chaparK

Here in germany we are also interested in your project.
I will make some advertisement in the DIY-Community.
Hi Indemini,

Thanks for that, that's much appreciated!
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Old 22nd July 2012, 11:10 AM   #122
ds23man is offline ds23man  Netherlands
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Two big tips for the CS3318:

1. The hardware mute line may not be left floating! It will pick up logic noise and will degrade the ouput quality. I discovered this on my protoboard. Everytime there was activity on the control bus, the output distorted.

You tie it up logic level or ground ( the last option requiers a different register setting)

2 Bypass caps for the analog voltage rails. In the datasheet they use one 100nf and a 10uf over the + and - rail...... Not so effective, should be two of them to analog ground!
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Old 22nd July 2012, 11:46 AM   #123
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Originally Posted by ds23man View Post

2 Bypass caps for the analog voltage rails. In the datasheet they use one 100nf and a 10uf over the + and - rail...... Not so effective, should be two of them to analog ground!
I always wonder why people do that. Is that for cost or is it an improvement ? I would have thought that it was much less effective for a single ended or half bridge output stage.
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Old 22nd July 2012, 11:52 AM   #124
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When I've done this its because my power supply lines are noisy and I don't want to dump that noise onto my signal ground. Perhaps they listened, had noisy supplies and found that a single cap sounded better?
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Old 22nd July 2012, 12:22 PM   #125
ds23man is offline ds23man  Netherlands
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Originally Posted by Trevor White View Post
I always wonder why people do that. Is that for cost or is it an improvement ? I would have thought that it was much less effective for a single ended or half bridge output stage.
A decoupling cap between the the rails is doing nothing, I think it is a bad habbit from logic designers who do "some" audio.
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Old 22nd July 2012, 12:25 PM   #126
ds23man is offline ds23man  Netherlands
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Quote:
Originally Posted by abraxalito View Post
When I've done this its because my power supply lines are noisy and I don't want to dump that noise onto my signal ground. Perhaps they listened, had noisy supplies and found that a single cap sounded better?
A little refreshment course:

Decoupling capacitor - Wikipedia, the free encyclopedia
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Old 22nd July 2012, 01:27 PM   #127
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Originally Posted by abraxalito View Post
When I've done this its because my power supply lines are noisy and I don't want to dump that noise onto my signal ground. Perhaps they listened, had noisy supplies and found that a single cap sounded better?
but then you are just coupling the noise onto the opposing rail and relying on the power supply to shunt it to ground. The large loop impedance and output impedance of the supply makes this a dubious practice.

maybe for single rail opamps it will work for obvious reasons but for split rail I just cannot see it doing anything better than having two good caps grounded right at the opamp.

Perhaps it's assuming there is a poor ground connection on the board or is it trying to force a star grounded connection right at the power supply ? I saw them so this on the Silicon Chip DAC project which only uses a double sided board so there is no proper ground plane so this practice appears to be widespread.

Last edited by Trevor White; 22nd July 2012 at 01:36 PM.
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Old 22nd July 2012, 01:40 PM   #128
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Quote:
Originally Posted by Trevor White View Post
but then you are just coupling the noise onto the opposing rail and relying on the power supply to shunt it to ground.
Yes but 'shunt to ground' depends on the ground impedance. There's no perfect ground, so some of the noise current now appears as a voltage on the ground. In this situation, the cap rail-to-rail is not to reduce the noise on the supplies - we rely on the PSRR for that - rather its to provide low impedance power for the IC its feedling.

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The large loop impedance and output impedance of the supply makes this a dubious practice.
I'm not following you here.

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maybe for single rail opamps it will work for obvious reasons but for split rail I just cannot see it doing anything better than having two good caps right at the opamp.
I don't use a rail-to-rail cap on its own as I've found opamps can still oscillate when I do only that. What I do is include smallish caps to ground, but only through small series resistors (say 1R - 10R, depending on opamp) so as to attenuate any induced RF voltage in the ground. The alternative is to ensure extremely well regulated supplies (discrete super regs or something similar, with good RF rejection). Seeing as I'm a cheapskate I try to get decent sound for lowest cost

<edit> At RF, all grounds are poor grounds because wire inductance dominates over resistance even at the top end of the audio band.
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Last edited by abraxalito; 22nd July 2012 at 01:43 PM.
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Old 22nd July 2012, 02:41 PM   #129
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Originally Posted by abraxalito View Post
Yes but 'shunt to ground' depends on the ground impedance. There's no perfect ground, so some of the noise current now appears as a voltage on the ground. In this situation, the cap rail-to-rail is not to reduce the noise on the supplies - we rely on the PSRR for that - rather its to provide low impedance power for the IC its feedling.



I'm not following you here.



I don't use a rail-to-rail cap on its own as I've found opamps can still oscillate when I do only that. What I do is include smallish caps to ground, but only through small series resistors (say 1R - 10R, depending on opamp) so as to attenuate any induced RF voltage in the ground. The alternative is to ensure extremely well regulated supplies (discrete super regs or something similar, with good RF rejection). Seeing as I'm a cheapskate I try to get decent sound for lowest cost

<edit> At RF, all grounds are poor grounds because wire inductance dominates over resistance even at the top end of the audio band.
but you are not dealing with RF. You are dealing with audio.

follow the current flow. If you use an opamp with class B or class AB output and the positive side is conducting then the current flows through the load back to the power supply common point. The cap across the split supply is doing a lot less to provide a low impedance point to ground as it is now in series with negative supply impedance. Even if it is used to shunt noise between the +/- rails it is still of no concern to the signal driving the load. Similarly for a negative going output signal. You are relying on the supply line and power supply impedance to be low which may not be the case in a simple single or double layered board with no dedicated ground plane.

If you had a fully differential configuration which did not reference ground then the cap across the +/- supply rail would make perfect sense but for a half bridge configuration with ground reference it doesn't make sense at all.

Maybe I am missing something but it sounds like a kludge that is trying to solve some other deficiency such as a poor board layout.

Last edited by Trevor White; 22nd July 2012 at 02:43 PM.
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Old 22nd July 2012, 02:50 PM   #130
ds23man is offline ds23man  Netherlands
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Quote:
Originally Posted by abraxalito View Post
Yes but 'shunt to ground' depends on the ground impedance. There's no perfect ground, so some of the noise current now appears as a voltage on the ground. In this situation, the cap rail-to-rail is not to reduce the noise on the supplies - we rely on the PSRR for that - rather its to provide low impedance power for the IC its feedling.



I'm not following you here.



I don't use a rail-to-rail cap on its own as I've found opamps can still oscillate when I do only that. What I do is include smallish caps to ground, but only through small series resistors (say 1R - 10R, depending on opamp) so as to attenuate any induced RF voltage in the ground. The alternative is to ensure extremely well regulated supplies (discrete super regs or something similar, with good RF rejection). Seeing as I'm a cheapskate I try to get decent sound for lowest cost

<edit> At RF, all grounds are poor grounds because wire inductance dominates over resistance even at the top end of the audio band.
Better to (re)read the Wikipedia artikel:

"A decoupling capacitor is a capacitor used to decouple one part of an electrical network (circuit) from another. Noise caused by other circuit elements is shunted through the capacitor, reducing the effect they have on the rest of the circuit."
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