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Cheapest possible (<30$?) silent USB DAC+HPA for low impedance cans

Feelas

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#1
I'm looking for suggestions on working out the cheapest possible (sadly, the replacement PSU for the Dell E5470 spread so much noise that the minijack there is impossible to use) combo DAC+AMP that is possible to get new. Currently I'm targeting the Apple dongle, and E5470 is missing the USB-C, so I'd be getting an USB-A -> USB-C adapter, ending up around ~$20. Will be mostly driving the very sensitive K371's and, maybe, sometimes, KNS-8400 which are a lot less sensitive. The lower the noise floor, the better - I'll surely not complain about lack of power, since I'm used to low-level listening anyways.

Is there anything else worth recommending in the sub-30$ segment, or are the dongles the only solution?
 
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samwell7

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#2
Just chiming in, I've used the apple USB C to 3.5 adaptor out of a PC for the K371 as well as for less sensitive cans like the K702 or K240 studio and had no issues with volume.
 
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Feelas

Feelas

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Thread Starter #3
Just chiming in, I've used the apple USB C to 3.5 adaptor out of a PC for the K371 as well as for less sensitive cans like the K702 or K240 studio and had no issues with volume.
Great, and @samwell7 I can trust amir's measurements, that the output itself is dead silent when not playing anything? Just asking, since for the time being I'm mostly using an old TEAC CR-H100 with noise floor of -40-50dB, and mostly tired of the circuit noise.
 
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samwell7

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#4
Great, and I can trust amir's measurements, that the output itself is dead silent when not playing anything? Just asking, since for the time being I'm mostly using an old TEAC CR-H100 with noise floor of -40-50dB, and mostly tired of the circuit noise.
I hate hiss/unwanted noise and I haven't noticed any when there's nothing playing - with that being said I haven't really cranked it up, my volume slider is usually left at 8-16% depending which headphones I'm using.
I've also used it as a pre-out without hiss.
 
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Feelas

Feelas

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Thread Starter #5
So it seems I'd be stupid to overthink the issue with a 30 bucks setup :D Thanks!
 

samwell7

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#6
So it seems I'd be stupid to overthink the issue with a 30 bucks setup :D Thanks!
I got 2x USB A to C adaptors for the computer for around $6AU from Amazon so it's closer to $20.
I need the USB C to 3.5mm adaptor for my phone anyway so it was a no-brainer for me.
But yeah don't overthink it!
 
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Feelas

Feelas

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Thread Starter #7
Well, in the end I got myself one - but sadly in EU it's A2155, which is the 0.5V version, well. Still, I won't be driving anything big from it and it's great - worse thing is that it seems that something's still spraying noise, in fact so much HF that the headphone cable picks it up... Lol!
 

samwell7

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#8
Well, in the end I got myself one - but sadly in EU it's A2155, which is the 0.5V version, well. Still, I won't be driving anything big from it and it's great - worse thing is that it seems that something's still spraying noise, in fact so much HF that the headphone cable picks it up... Lol!
If the voltage output is linear with the output from the computer 0.5V is plenty - that's assuming that 11% volume on the 1V version is equal to 22% volume on the 0.5V version.

That's really strange with the HF frequencies, maybe try plugging everything into a powerboard with EMI/RFI filtering? They're available fairly cheaply at hardware stores here in Aus.

If the cable on your headphone is replaceable maybe look at one with higher noise rejection (not sure if twisted pair cables are a thing in the headphone world)
 
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Feelas

Feelas

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Thread Starter #9
If the voltage output is linear with the output from the computer 0.5V is plenty - that's assuming that 11% volume on the 1V version is equal to 22% volume on the 0.5V version.

That's really strange with the HF frequencies, maybe try plugging everything into a powerboard with EMI/RFI filtering? They're available fairly cheaply at hardware stores here in Aus.

If the cable on your headphone is replaceable maybe look at one with higher noise rejection (not sure if twisted pair cables are a thing in the headphone world)
Yea, 0.5V is aplenty. The HF is annoying and I will still be looking for the source; maybe it's just that the terrible laptop PSU replacement sprays so much, I can hear it switching even w/o headphones, so it may well be inducing into the cable.

So far I'd not had this problem with KRK, only w/ more sensitive K371.

What TP does in Ethernet, you'll get from balanced cables (differential signaling); won't get one for K371 since they're on 3-pin mini. Gonna look at some new cables, maybe solder something myself, even...
 

samwell7

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#11
Yea, 0.5V is aplenty. The HF is annoying and I will still be looking for the source; maybe it's just that the terrible laptop PSU replacement sprays so much, I can hear it switching even w/o headphones, so it may well be inducing into the cable.

So far I'd not had this problem with KRK, only w/ more sensitive K371.

What TP does in Ethernet, you'll get from balanced cables (differential signaling); won't get one for K371 since they're on 3-pin mini. Gonna look at some new cables, maybe solder something myself, even...
Yeah no harm in making something up, mini XLR is fairly cheap - even though it's only 3 pin couldn't you still have 2x TPs and then solder the grounds together on each end, or would that still introduce some noise? I was going to suggest a ferrite choke bit that might mess with something else.

If it's getting sprayed you'd probably notice it change as you move the cable toward and away from the source, also the coiled cable might help?

Either way I'm glad it's working, your old receiver might not have been the issue?
 
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Feelas

Feelas

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Thread Starter #12
This is probably a shot in the dark, but worth a try. Amir has reviewed a product from a company (referred as Douk Audio, One Little Bear, and Nobsound). He did not review a DAC/amp, though. On eBay, I saw DAC/amps from this company at very interesting prices. It's worth a check.

I would also consider something like this.
Thanks, I actually bit the bullet and got the Apple dongle!

I it's getting sprayed you'd probably notice it change as you move the cable toward and away from the source, also the coiled cable might help?

Either way I'm glad it's working, your old receiver might not have been the issue?
And that's exactly what happens, when the cable runs nearby the power plugs, noise seems to ramp up and when running the cable in some distance, it starts to drop. I'll surely check the coiled cable (happily K371s have it packaged), since I've got the same idea - and anyways it seems somehow thicker, might be shielded better, perhaps.
 

samwell7

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#13
Thanks, I actually bit the bullet and got the Apple dongle!


And that's exactly what happens, when the cable runs nearby the power plugs, noise seems to ramp up and when running the cable in some distance, it starts to drop. I'll surely check the coiled cable (happily K371s have it packaged), since I've got the same idea - and anyways it seems somehow thicker, might be shielded better, perhaps.
Thanks, I actually bit the bullet and got the Apple dongle!


And that's exactly what happens, when the cable runs nearby the power plugs, noise seems to ramp up and when running the cable in some distance, it starts to drop. I'll surely check the coiled cable (happily K371s have it packaged), since I've got the same idea - and anyways it seems somehow thicker, might be shielded better, perhaps.
Let me know how it goes with the coiled cable!
All of my past experience was with getting rid of ground loops, either using a galvanic isolator for the USB or a Behringer Hum Destroyer but neither would work here I'm afraid, potentially some sort of external shielding like copper tape tied to the ground pin of your mini XLR might work but it's getting messy!
 
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Feelas

Feelas

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Thread Starter #14
Let me know how it goes with the coiled cable!
I'll keep looking for this, but it seems to happen and disappear randomly.

Anyways, thanks for feedback, since the lower THD+N is delightful. And no more of that pesky noise!
 
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