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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A little OT, but still interesting in-line with the discussion of negative voltage sources aka a possible alternative to the RECOM device.
This little buddy creates an equal, regulated low-noise, negative voltage from a positive voltage up to 5.5 volts. Ok, not entirely 9V here, but +/-5V from USB power is not bad and will work fine for a lot of users I think. The LM2776. Costs about $1.
One drawback though, it has an output resistance of 2.5 ohm. That might be a problem. Or not?
This little buddy creates an equal, regulated low-noise, negative voltage from a positive voltage up to 5.5 volts. Ok, not entirely 9V here, but +/-5V from USB power is not bad and will work fine for a lot of users I think. The LM2776. Costs about $1.
One drawback though, it has an output resistance of 2.5 ohm. That might be a problem. Or not?
One comment regarding the discussion of isolated vs non-isolated DC-DC converters. The isolated converters have advantage of eliminating ground loops, especially when signal and power come from the same source, e.g. when using computer line out for signal and USB port for power. There may be many other situations where ground loop may also occur, for example if power source feeding DC-DC converter and signal source share protective ground connection through the wall socket. For me isolated DC-DC converters are the way to go since they allow higher degree of isolation between various circuits.
Volume knobs finally arrived from China and I decided on this bronze metal one.
An externally hosted image should be here but it was not working when we last tested it.
Many thanks!Looks great Woodyluvr!
And I dig the enclosure.
What headphones and DAC will you be pairing with it?
HEADPHONES: Blur 美魔女 300Ω | Nhoord Audio Red v2 32Ω
LINE OUT CABLE: 3.5mm ♂ to ♂ Rean MogamiW2893
SFF SILENT PC: “UV SIAMESE 2” (HDPlex H1.S V2 Fanless Chassis; 160W DC-ATX Direct-Plug; 80W Internal AC-DC Adapter)
DAC: Realtek ALC1150 (Gigabyte H170N)
OS: WIN10 v1803
MUSIC PLAYER: foobar2K v1.4
PLUG-INS: Meier Crossfeed; TDR VOS SlickEQ v1.2.2
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Now in it's place sitting beside "UV Siamese 2" Silent Fanless SFF PC.
An externally hosted image should be here but it was not working when we last tested it.
I've been looking for a S/S replacement for Muting transistors. What, if any, AC distortion would you expect to encounter across the series MOSFETS with a Line-level signal?? I am replacing the output board in a AM/FM tuner that uses obsolete unobtainable ICs for Muting.
Also, I am extremely impress with your Super-CMOY and want to buy the PC boards. I need a headamp this size for testing Tuners w/out a power amp. I currently use a Mini3, but keep blowing opamps because of the virtual ground whereas the Super CMOY has "real" ground.
Do you accept PayPal??
--Bill
Also, I am extremely impress with your Super-CMOY and want to buy the PC boards. I need a headamp this size for testing Tuners w/out a power amp. I currently use a Mini3, but keep blowing opamps because of the virtual ground whereas the Super CMOY has "real" ground.
Do you accept PayPal??
--Bill
You might try to contact @agdr via his website... it appears he has stepped away from the hobby as of late.
Power!
Holy cow! I have had to set foobar2k down to -16dB so it won't blow up my Nhoord Reds or Blur 美魔女 300Ω ear buds! It pushes my drivers way too hard especially on a few low bass tracks that I have (e.g. @ 03:03 on Gustav Holst: The Planets, Op.32/H.125: vii. Neptune, the Mystic; Andante Original Ending - Mark Elder; Hallé Orchestra & Choir).
System volume (Win10) is still set at 100%.
Holy cow! I have had to set foobar2k down to -16dB so it won't blow up my Nhoord Reds or Blur 美魔女 300Ω ear buds! It pushes my drivers way too hard especially on a few low bass tracks that I have (e.g. @ 03:03 on Gustav Holst: The Planets, Op.32/H.125: vii. Neptune, the Mystic; Andante Original Ending - Mark Elder; Hallé Orchestra & Choir).
System volume (Win10) is still set at 100%.
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Full Specs for agdr Audio OPA1688 Parallel Super CMOY
Output Current (peak): 150 mA per channel
Output Current (rms): 106.05 mA per channel
Output Impedance: ~0 ohms
Voltage Gain: 1x ("unity-gain amplifier")
Voltage Cut-Off Level: 8.4 V nominal
Voltage Swing (peak): 7.4 Vdc
Voltage Swing (rms): 5.23 Vrms
So this 'little dual-chip head amp that could' should be able to handle not only the power hungry HE6 but the AKG K1000 as well... albeit only up to 97 dB SPL which is still doable for all but the most dynamic pieces.
HiFiMAN HE6
AKG K-1000
Output Current (peak): 150 mA per channel
Output Current (rms): 106.05 mA per channel
Output Impedance: ~0 ohms
Voltage Gain: 1x ("unity-gain amplifier")
Voltage Cut-Off Level: 8.4 V nominal
Voltage Swing (peak): 7.4 Vdc
Voltage Swing (rms): 5.23 Vrms
So this 'little dual-chip head amp that could' should be able to handle not only the power hungry HE6 but the AKG K1000 as well... albeit only up to 97 dB SPL which is still doable for all but the most dynamic pieces.
HiFiMAN HE6
An externally hosted image should be here but it was not working when we last tested it.
AKG K-1000
An externally hosted image should be here but it was not working when we last tested it.
Apologies, I inadvertently moved the above linked images...
HiFiMAN HE6
AKG K-1000
HiFiMAN HE6
An externally hosted image should be here but it was not working when we last tested it.
AKG K-1000
An externally hosted image should be here but it was not working when we last tested it.
Would there be any reason why I could/should not power the following USB-Powered SPDIF Optical ES9018K2M DAC (<80mA power usage) right off the same USB 2.0 power cable going into my amp, feeding power to my RECOM RW-0509D DC-DC Converter?
Just wire it in at the power +/- input points on RECOM Power Supply Module Board like so:
Just wire it in at the power +/- input points on RECOM Power Supply Module Board like so:
An externally hosted image should be here but it was not working when we last tested it.
From my own experiments, what you want to do will definitely work.
So long as you’re not using a USB 1.0 port or a buss powered USB hub that will only deliver 100mA. Most typical computer’s 2.0 ports or powered hubs deliver the full 500mA which is more than enough for the Super Cmoy and that particular DAC. Plus, since the Recom converter is transformer isolated the two devices shouldn't (?) adversely affect each other.
I tried out some other low power usb devices in parallel with the Super Cmoy and they all still worked on my computer without issue.
As a safety precaution though, I would first power it off a phone wall charger so if something is wired incorrectly you don’t risk damaging your computer
Something that I haven't experimented with (but have been reading about) is what to do with the unused D+ and D- USB data lines. I left them floating in my experiments and it worked fine on my Apple wall chargers and my Macbook Pro. But I've read sometimes they should be shorted together, other times they should have resistors added in a certain configuration...
One more thing I noticed that I'm trying to figure out and if it's related to the data pins configuration is on all my Apple phone chargers and Macbook Pro, it only drew the appropriate current it needed, but on cheap generic brand chargers it pulled WAY more current (amps vs mA) than required and the Recom converter obviously got a lot warmer. I don't have the exact current/temperature measurements on hand but I'd love to get some thoughts on this from others
So long as you’re not using a USB 1.0 port or a buss powered USB hub that will only deliver 100mA. Most typical computer’s 2.0 ports or powered hubs deliver the full 500mA which is more than enough for the Super Cmoy and that particular DAC. Plus, since the Recom converter is transformer isolated the two devices shouldn't (?) adversely affect each other.
I tried out some other low power usb devices in parallel with the Super Cmoy and they all still worked on my computer without issue.
As a safety precaution though, I would first power it off a phone wall charger so if something is wired incorrectly you don’t risk damaging your computer
Something that I haven't experimented with (but have been reading about) is what to do with the unused D+ and D- USB data lines. I left them floating in my experiments and it worked fine on my Apple wall chargers and my Macbook Pro. But I've read sometimes they should be shorted together, other times they should have resistors added in a certain configuration...
One more thing I noticed that I'm trying to figure out and if it's related to the data pins configuration is on all my Apple phone chargers and Macbook Pro, it only drew the appropriate current it needed, but on cheap generic brand chargers it pulled WAY more current (amps vs mA) than required and the Recom converter obviously got a lot warmer. I don't have the exact current/temperature measurements on hand but I'd love to get some thoughts on this from others
Sincerely appreciate the advice and feedback.From my own experiments, what you want to do will definitely work.
So long as you’re not using a USB 1.0 port or a buss powered USB hub that will only deliver 100mA. Most typical computer’s 2.0 ports or powered hubs deliver the full 500mA which is more than enough for the Super Cmoy and that particular DAC. Plus, since the Recom converter is transformer isolated the two devices shouldn't (?) adversely affect each other.
I tried out some other low power usb devices in parallel with the Super Cmoy and they all still worked on my computer without issue.
As a safety precaution though, I would first power it off a phone wall charger so if something is wired incorrectly you don’t risk damaging your computer
Something that I haven't experimented with (but have been reading about) is what to do with the unused D+ and D- USB data lines. I left them floating in my experiments and it worked fine on my Apple wall chargers and my Macbook Pro. But I've read sometimes they should be shorted together, other times they should have resistors added in a certain configuration...
One more thing I noticed that I'm trying to figure out and if it's related to the data pins configuration is on all my Apple phone chargers and Macbook Pro, it only drew the appropriate current it needed, but on cheap generic brand chargers it pulled WAY more current (amps vs mA) than required and the Recom converter obviously got a lot warmer. I don't have the exact current/temperature measurements on hand but I'd love to get some thoughts on this from others
Yep, luckily, I was being intelligent and tested with a phone charger first and will do so again.
My DIY USB 2.0 cable is a "power only" model so just two wires (black and white)... but I am happy to have that info in regards to the data lines. I will have to remember that in the future.
I figured that the RECOM DC-DC converter at max is using under 1W (<300mA @ <5V and the proposed DAC unit above is well under 0.5W (<80mA @ <5V). So as you have confirmed to me the maximum allowable for USB 2.0 is 2.5W (500 mA @ <5V) so all well within those parameters.
I plan to wire in the DAC's USB power cable right at the 5V power +/- input points (2|3 and 22|23) on the RECOM Power Supply Module Board.