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OPA1688 Super CMOY, 2x 9V with real ground and headphone relay - PCBs
OPA1688 Super CMOY, 2x 9V with real ground and headphone relay - PCBs
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Old Yesterday, 05:11 PM   #341
WoodyLuvr is offline WoodyLuvr  Thailand
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This RECOM RW-0509D DC-DC CONVERTER POWER SUPPLY MODULE has been on now for more than 36 hours straight and running very cool while coupled to the 40 x 40 x 9 mm aluminum heat sink. Easily handled with bare fingertips. I am pleased to say the least!
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Old Yesterday, 08:34 PM   #342
Barsk is offline Barsk  Sweden
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Quote:
Originally Posted by WoodyLuvr View Post
Here is the thread in which agdr introduces the RECOM DC-DC Converter. All comes down to "noise" thus the reason why agdr was so interested in testing the adafruit split dc power supply that I had stumbled upon and mentioned in a post way back when.

I didn't find any specific mentioning about noice in the postings I read. But I guess the reason is there is a DC connection from supply to load with non-isolated converters, where the isolated one does have a completely separeted ground. Exacly how that works I am not sure about though.
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Old Today, 03:14 AM   #343
WoodyLuvr is offline WoodyLuvr  Thailand
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Quote:
Originally Posted by Barsk View Post
I didn't find any specific mentioning about noice in the postings I read. But I guess the reason is there is a DC connection from supply to load with non-isolated converters, where the isolated one does have a completely separeted ground. Exacly how that works I am not sure about though.

Apologies good man for not being more direct ... these threads do tend to get very long in the tooth and very easy to miss certain key details... here is the particular line by @agdr that I was referring and had linked:

"...Mouser has cheaper ($8) DC-DC converters that are 4.5V to 5.5V in and 111mA out, but they run at 45KHz. They are also SIPs that are about the same height as the 3.5mm jacks on the board. This one runs at 100KHz to 150KHz, out of the audio band, and is low profile DIP..."



Also, from @agdr in regards to "noise" and "switching frequency" in reference to DC Conversion:

"...the switching frequency is a clue as to if you will get audio noise from it. If the frequency is up in the 100's of Khz or a Mhz, probably no trouble. But if it is close to the audio range, like 40KHz, could be big trouble (switching noise in the audio)..."



@agdr's testing of the Adafruit Switching Split Power Supply (12V 500mA) AC-DC Wall Wart:

"...I did some tests on the Split power supply today! I received 3 of them a couple of weeks ago. I'll post scope shots tonight, but the summary is that it seems OK.

The switching frequency appears to be around 67KHz, with a 100mV peak spike. Above the audio frequency range. Well, sort of. Feed in square waves to an audio amp and the Fourier series can go out to 100KHz to get nice sharp corners on the wave. For that reason some folks build audio amps with a 100Khz bandwidth even though hearing is around 20KHz. But for our purposes here all should be good..."


"...Well... pretty d*mn good, I would say! No major frequency spikes through the 20KHz audio band. The few lines that are there are tiny, 10dBFS or so. Note the scale on the left, all of this is wayy below the hearing threshold. Some of the noise floor rising from 5KHz to 0Hz (leftmost) is most likely due to environmental noise pickup in the room here (fluorescent lights with electronic ballasts)..."
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Last edited by WoodyLuvr; Today at 03:18 AM.
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Old Today, 06:42 AM   #344
Barsk is offline Barsk  Sweden
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Ah, ok. So switching noise it is then.
But that indicates that "isolated" is not the key aspect of this device. So if one finds a suitable device (or two separate) that can create +/- 9V at a non-audible switching frequency then we would have a go?
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