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Old 8th April 2012, 11:14 AM   #3511
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Quote:
Originally Posted by robbbby View Post
Thanks for your input it is much appreciated. Like already mentioned the designer of the dac said it is totally normal and that lots of reference quality source equipment has that kind of small amount of DC. The tech there checked the dac on the bench and it actually had 29mV, which is slightly higher than mine.

I've been talking to another knowledgeable person just to get opinions on what I should do and he also suggested caps. He told me I should try capacitors only to see if the input impedance would work as the resistive part of the filter before adding resistors. He suggested 1uf caps with the 104k ohm input impedance since that would give me a 1.6Hz cutoff frequency. He also said it is trickier with the balanced inputs and that I definitely don't want to unbalance them so the 2x caps per channel I use need to match exactly and be with 0.1% or better of each other.

Since I know the 500mV of DC probably wouldn't really hurt anything when turning on the speakers and that i'll probably never hear the extra distortion, i'm taking my time and trying to figure out the 100% best way to do this so I don't have to do it twice. Anyone have any input on the numbers I just mentioned above?
Come on do you really think it matters if the cutoff is 1.6 hz in one phase and 1,584 hz in the other ? What a crappy tech ! Resistors would be something else.

Anyway my friend who had the NC during some days will not buy this amps. They are fantastic in many ways but the music is not free of the speakers he said.
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Old 8th April 2012, 11:16 AM   #3512
robbbby is offline robbbby  Canada
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Originally Posted by Erlend Sæterdal View Post
Anyway my friend who had the NC during some days will not buy this amps. They are fantastic in many ways but the music is not free of the speakers he said.
Maybe if he had the intended and properly working power supply for the amps he would think differently

Last edited by robbbby; 8th April 2012 at 11:37 AM.
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Old 8th April 2012, 11:17 AM   #3513
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Originally Posted by Julf View Post
Ah, that's what I call a proper DIY project
Thats history !
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Old 8th April 2012, 11:38 AM   #3514
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Originally Posted by robbbby View Post
Maybe if he had the intended and properly working power supply for the amps he would think differently
Well I have heard many Class D with " Proper " supplys ! In that case the situation with sound from a little " box " was even worse . But to be honest I can not tell if Brunos supply is much better.

In fact I have a little hum. But I did not have time to further exsperience since it was " finnished " half an hour before it went out of my place.

I am working on it now.

Do you know Niels Larsen from Denmark. He made the first Primare 928 and also Some Gryphon amps. I modded a NLE 1000 he made . It is a 500 W amp.
Really good work he said. SO it can not be that bad !
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Old 8th April 2012, 11:48 AM   #3515
Julf is offline Julf  Europe
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Quote:
Originally Posted by robbbby View Post
No sense in trying to argue anything with them or trying to get them to fix it
Fair enough

Quote:
He told me I should try capacitors only to see if the input impedance would work as the resistive part of the filter before adding resistors. He suggested 1uf caps with the 104k ohm input impedance since that would give me a 1.6Hz cutoff frequency.
That would work just fine for getting rid of the DC on the speaker output - the resistors would be to try to lower the energy of the transient if you turn the DAC on or off with the amp on. 1uF is fine, but you would be OK with even 0.1uF - giving a cutoff of 16 Hz.

I suggest a pair of polycarbonate or polypropylene caps (25V is more than enough) per amp (or go teflon/PTFE if you want to be fancy).

Quote:
He also said it is trickier with the balanced inputs and that I definitely don't want to unbalance them so the 2x caps per channel I use need to match exactly and be with 0.1% or better of each other.
Not sure I agree with that. There is a lot of superstition about balanced just because it is less common. Somehow people think in terms of signals with reference to the ground, when they should understand that the input of the amp only cares about the voltage between the + and - inputs, and doesn't care about ground at all.
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Old 8th April 2012, 11:50 AM   #3516
Julf is offline Julf  Europe
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Quote:
Originally Posted by Erlend Sæterdal View Post
In fact I have a little hum.
You never answered my question about your grounding strategy - somehow I got the impression that you might have gone for a star topology?
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Old 8th April 2012, 11:52 AM   #3517
robbbby is offline robbbby  Canada
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Quote:
Originally Posted by Erlend Sæterdal View Post
Well I have heard many Class D with " Proper " supplys ! In that case the situation with sound from a little " box " was even worse . But to be honest I can not tell if Brunos supply is much better.

In fact I have a little hum. But I did not have time to further exsperience since it was " finnished " half an hour before it went out of my place.

I am working on it now.

Do you know Niels Larsen from Denmark. He made the first Primare 928 and also Some Gryphon amps. I modded a NLE 1000 he made . It is a 500 W amp.
Really good work he said. SO it can not be that bad !
I was just messing around with you, I had to go back and edit my post to put a smiley face just so you knew I was joking around and having some fun.
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Old 8th April 2012, 11:54 AM   #3518
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Originally Posted by Julf View Post
You never answered my question about your grounding strategy - somehow I got the impression that you might have gone for a star topology?
No its more a bus than star I would say. But the gnd from the power supply to the input section must be connected somewhere. Earlier I asked if it could be a idea to use one of the four gnd leads from the board to connect the " little supply ". ???
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Old 8th April 2012, 11:56 AM   #3519
robbbby is offline robbbby  Canada
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Thanks again Julf, i'll start with just the caps. Would be nice to find some caps with actual insulated flexible leads, going to be hard to incorporate those regular cap with single bare wire leads into my case, especially 2 of them.
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Old 8th April 2012, 12:00 PM   #3520
Julf is offline Julf  Europe
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Quote:
Originally Posted by Erlend Sæterdal View Post
No its more a bus than star I would say.
OK, so where does signal ground connect to chassis/power ground?

Quote:
But the gnd from the power supply to the input section must be connected somewhere. Earlier I asked if it could be a idea to use one of the four gnd leads from the board to connect the " little supply ". ???
We are talking about Vsig, the symmetric supply to the op amps? It's ground connects to the same ground as the main power supply, pins 3,4,9 and 10 on J7. I assume you are not connecting the optional driver supply voltage (Vdr, pin 11) at all?
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