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Class D Switching Power Amplifiers and Power D/A conversion

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Old 26th December 2011, 09:38 PM   #1021
fredex is offline fredex  New Zealand
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@Bruno. Best wishes from a very happy customer (UcD180ADs). I progressed from tubes to class D via a little Sonic Impact...........ah the clarity.
Your latest efforts have me intrigued. I like the way you take the time to answer questions in a no-nonsense manner. UcD is good engineering.

Last edited by fredex; 26th December 2011 at 09:41 PM. Reason: typo
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Old 27th December 2011, 12:12 PM   #1022
tiki is offline tiki  Germany
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Hello,
Quote:
Originally Posted by Bruno Putzeys View Post
OK I'm off for the holidays.
Thank you, that you aren't.
You spent some recreative days hopefully.

80mW mean 79dB SPL in a 90 dB SPL/1W speaker, quite well to be heard, when switched on or off. As it is at my UcD180-amp without using the on/off control pin and at the PSC2.400, which uses the control as I believe. I can tolerate that short click although it could be less noticeable.

The 12" Woofers in the PSC driven monitors show at least 1mm (outward) offset after switching on. This is much worse because this shifts the operating point significantly, causing unnecessary Bl(x), Kms(x) and L(x) distortions just around the operating point in the "small signal" range.
50mV (not specified for UcD400 OEM) should show at the B&C 12NDL76, 4.5 Ohms, 18N/A, 3N/mm (Klippel data) negligible 0.01mm offset. It seems to be significantly more. I did not measure the offset voltage though.

Cheers, Timo
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Old 27th December 2011, 12:17 PM   #1023
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You misread my post. Its not 80 mW but 0,08 mW. That's 1/1000 or 30 dB less....
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Old 27th December 2011, 12:19 PM   #1024
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Quote:
Originally Posted by StigErik View Post
You misread my post. Its not 80 mW but 0,08 mW. That's 1/1000 or 30 dB less....
1/1000 is minus 60 dB.

Last edited by pieter t; 27th December 2011 at 12:22 PM.
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Old 27th December 2011, 12:21 PM   #1025
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No, it isnt. When talking about power the math is like this:

Decibel - Wikipedia, the free encyclopedia
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Old 27th December 2011, 12:24 PM   #1026
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You are right Stig Erik, I was thinking voltages...
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Old 27th December 2011, 01:33 PM   #1027
tiki is offline tiki  Germany
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Of course, I was wrong, thanks.
The clicks are well audible however, in particular because of the HF content.

The Klippel measurements for the interested
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Last edited by tiki; 27th December 2011 at 01:37 PM.
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Old 27th December 2011, 08:25 PM   #1028
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Quote:
Originally Posted by StigErik View Post
You misread my post. Its not 80 mW but 0,08 mW. That's 1/1000 or 30 dB less....
In any case, it's DC, so the result is not SPL but a tiny amount of woofer cone excursion.
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Old 27th December 2011, 11:42 PM   #1029
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Is there any drawbacks attaching the amp module direct to the woofer magnet? (Magnetic stray field intermodulation, fatiguing failures etc?)
If no, you may afford the very length of 5 cm Audioquest Everest
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Old 28th December 2011, 10:55 AM   #1030
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@tiki could you measure the DC offset on the PSC and let me know?
@wilbur-x I wouldn't do that. The inductor could get biased. According to an industrial customer of ours the've actually had failures caused by the amp module being to close to the magnet. The amp module at the time wasn't ours but I see no overriding reason why ours shouldn't suffer as well.
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