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Old 9th July 2010, 05:50 PM   #1
fwki is offline fwki  United States
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Default High frequency SMPS for audio

I recently completed an amp based on the Class D Audio SDS-224 with an embedded PC. Initially I used an external linear supply for the amplifier do to space limitations, but to integrate the whole system into one case, I added a 500W SMPS.

I thought my big problem would be EMI, but that has not been an issue. However, I do notice a not insignificant change to the music when comparing the SMPS to the linear supply. Please just take me at my word on that to avert a rabbit trail discussion.....

In order to improve the transient reponse of the SMPS, my EE friends suggested looking for a higher switching frequency unit. When I mentioned a 250 Khz unit, they balked, suggesting more like 1 Mhz.

So my question is what is the highest frequency SMPS available to provide 35VDC at least 500W. My EE friends are not audio specialists, but do use mHz scale switchers for various ADC projects, albeit at lower power.
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Old 9th July 2010, 06:47 PM   #2
star882 is offline star882  United States
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Have you actually used an oscilloscope to check? You might not have enough filtering.
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Old 9th July 2010, 07:17 PM   #3
Nisbeth is offline Nisbeth  Denmark
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If you increase the switching frequency you get lower losses in the magnetics, but higher losses in the electronics (FETs and diodes) so it is not a free lunch. Most switchers with power ratings around "audio-level" have switching frequencies in the 70-150 kHz region, so lack of filtering or capacitance is a more likely cause of your problems.

/U.
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Old 9th July 2010, 08:43 PM   #4
fwki is offline fwki  United States
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I have access to scopes, so I will test the input voltage to the amp across various musical loads using both the SMPS and the switcher. I may need some help on interpretation. My office mate here tells me the scope takes "snapshots", so will endeavor to post the results. Thanks.
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Old 9th July 2010, 10:26 PM   #5
AP2 is offline AP2  Italy
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Hi,
High switch frequency not have sense with transient response,. 100-200KHz allready good for PSU. problem is amplifier error (integrates on pwm). this are very slow on the chip.
Other problem is nature (concept) of pwm driving trafo ( this change inductance continuos on trafo) and create very RFI-EMI while power change continuos (when amplifier running). all producers of chip, not think really use of psu for audio (amplifier is a current fast modulator).

Regards
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Old 13th July 2010, 08:21 PM   #6
AP2 is offline AP2  Italy
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Hi,
I was perhaps a little too pessimistic, but what I said is reality (it is obvious that refers to an esoteric system) on the audio business is not very important. important is the reliability and good power.
will seem absurd, but the psu cleaner and the PWM with fixed (unfortunately has the problem that the voltage varies with the VAC, at 50-60 volts is not a problem, but at 80-90V is a lot of variation (ratio transformer is on driving from +1.41).
even simple psu with fixed pwm requires special interventions to reduce EMI / RFI.

Regards
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Old 13th July 2010, 08:27 PM   #7
sendler is offline sendler  United States
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Default My SMPS sounds better than linear

Quote:
Originally Posted by fwki View Post
I recently completed an amp based on the Class D Audio SDS-224 with an embedded PC. Initially I used an external linear supply for the amplifier do to space limitations, but to integrate the whole system into one case, I added a 500W SMPS.

I thought my big problem would be EMI, but that has not been an issue. However, I do notice a not insignificant change to the music when comparing the SMPS to the linear supply. Please just take me at my word on that to avert a rabbit trail discussion.....

In order to improve the transient reponse of the SMPS, my EE friends suggested looking for a higher switching frequency unit. When I mentioned a 250 Khz unit, they balked, suggesting more like 1 Mhz.

So my question is what is the highest frequency SMPS available to provide 35VDC at least 500W. My EE friends are not audio specialists, but do use mHz scale switchers for various ADC projects, albeit at lower power.
That's odd because my listening tests show the MeanWell S-350-36 SMPS to sound much better than my big linear supply when driving a TK2050 amp and the MeanWell is only switching at 25KHz.
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Old 13th July 2010, 08:34 PM   #8
AP2 is offline AP2  Italy
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Quote:
Originally Posted by sendler View Post
That's odd because my listening tests show the MeanWell S-350-36 SMPS to sound much better than my big linear supply when driving a TK2050 amp and the MeanWell is only switching at 25KHz.
Hi Sendler,
Hi agree with You,(ultra-high frequency is not necessary).
to you it went well because the powers involved are small and low voltages.
only problem might be your psu beat with an amplifier (frequency too low), the rest is ok.

Regards
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Old 13th July 2010, 08:48 PM   #9
fwki is offline fwki  United States
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Quote:
Originally Posted by sendler View Post
That's odd because my listening tests show the MeanWell S-350-36 SMPS to sound much better than my big linear supply when driving a TK2050 amp and the MeanWell is only switching at 25KHz.
I looked at some Meanwell units but they were too long for my application. The embedded PC takes up a good bit of space. The higher switching frequencies do allow for smalller form factors.
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Old 14th July 2010, 08:23 AM   #10
AP2 is offline AP2  Italy
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Quote:
Originally Posted by fwki View Post
I looked at some Meanwell units but they were too long for my application. The embedded PC takes up a good bit of space. The higher switching frequencies do allow for smalller form factors.
Hi,
Yes, one good reason is space save if psu have high frequency of switch.
if I can help you (also for dimensions), can see DPS-500, it is regulated power supply and solve low psrr on class D amplifier. Absolute noise free and ripple at power.(innovative power supply for audio).

Regards
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