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Buy USB isolator for E70 Velvet? E50? E30II?

mike7877

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So I want my DACs to perform optimally. They're in different systems - most important is the E70 Velvet - it's the digital source for my high end 2.0 system. The amplifier in that is an LA90 Discrete, and when the time is right, I will either be getting two more to use in bridge mode to bi-amp the woofers, or a Benchmak HB4 (or whatever their flagship stereo amp is called).

Do all of these DACs have built-in USB isolation? If not, which don't?

All of the measurements done on these DACs (here and elsewhere) - are they done with USB isolators?
 

staticV3

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solderdude

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When one is plagued by weird noises or hums that disappear when the USB cable is removed then it makes sense to add USB isolators.
When your system is totally quiet when no music is playing (or digital 'zero') then there is no need nor any benefit of adding USB isolators, EMC filters, reclockers or whatnot.

An USB isolator can be used for solving certain groundloop problems but is of no use when there is no groundloop (through USB or SPDIF connection).
 
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DVDdoug

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If you have some kind of problem and you need an isolator it's usually ground loop noise or power supply noise (with a DAC that's USB powered).

So if you are trying to solve a noise problem, make sure the isolator isolates the power & ground. It won't do any good to isolate the data. Digital data is usually immune to noise... As long as a 1 remains a 1 and a zero remains a zero there is no data corruption and everything is cool... One of the main benefits to digital... These forum posts go all over the world through all kinds of connections and if there's an error you can be pretty sure it's a human typo and not data corruption. ;)
 
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mike7877

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Something I've noticed with the E30 II and E50 (both of which have separate power and USB data inputs) is when the USB data and USB power are coming from the same device, no matter which device, the noise from the SMPS comes through, probably at -40dBfs. It's LOUD. Even using a cheap 5V 500mA charger from 15 years ago instead of my best PC (which is powered by an MSI A850GF which from 0-100% load on the 5V rail puts out no more than 15mV ripple/noise) pushes this to like -80 or 90. Ten years ago when I tried to use that charger for my (then) new phone, when I tried to use it when it was plugged in, I couldn't - the noise screwed so badly with the capacitive touchscreen that clicks wouldn't register, randomly register, or register in the wrong place, so the fact that it's nearly silent while the PC with minimal noise is thousands of times louder speaks to design, though I'm not exactly sure how...

It's not a huge problem using a couple spare Samsung phone chargers I had laying around to power them (the 15/18 watt things they shipped with everything from the S4 to maybe 20?), but it is a little annoying. Spending over $100 for each the E 30II / E50 would probably be more annoying though lol.

About the E70 Velvet... I haven't noticed any noise from it - the reason I'm asking for it specifically is the documentation for Topping's second generation USB isolator shows it basically lowering the noise floor from -105dB to -150dB - no 60Hz hum in the example. I just want to make sure I'm getting everything from the DAC. It is in a highly revealing system, harmonic distortion from the speakers doesn't peak higher than -70dB from 150Hz to 20kHz and is mostly second order from 150-2100 (not as sure of the type on the tweeter) - preamp is an A70 Pro, amp LA90 Discrete, so it's not necessarily for nothing. Of course it all depends on the severity of the problem, and if there's even a problem in the first place.

The A70 Pro has a switch to "float", the PSU for my LA90 Discrete died 3 days ago so I'm using my [isolated] linear lab supply for the moment. Unfortunately the E70 V doesn't have a "float" option... If I could float everything I'd know for sure that alllll is good. Maybe if I power the E70 V from my 300W sinusoidal inverter running from a 12V SLA battery... (I'm joking of course lol, the USB isolator would be MUCH less of a hassle)
 
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mike7877

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Is there a way to know that my DAC is blue, not grey?

When one is plagued by weird noises or hums that disappear when the USB cable is removed then it makes sense to add USB isolators.
When your system is totally quiet when no music is playing (or digital 'zero') then there is no need nor any benefit of adding USB isolators, EMC filters, reclockers or whatnot.

An USB isolator can be used for solving certain groundloop problems but is of no use when there is no groundloop (through USB or SPDIF connection).

Is there a way to know that my DAC is blue, not grey? (other than buying the isolator lol)

1712021438390.png
 

staticV3

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Is there a way to know that my DAC is blue, not grey? (other than buying the isolator lol)
Use Toslink to connect to your PC.
It'll prevent ground loops just like an isolator would.

If your PC doesn't have Toslink, then you can add it via a Hifime UT23.
 

JustJones

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There's a link to measurements of the E70 Velvet in the first post.

 
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mike7877

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There's a link to measurements of the E70 Velvet in the first post.


I've seen it... I don't have the same PC or house wiring or, or, or, or
 
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mike7877

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Use Toslink to connect to your PC.
It'll prevent ground loops just like an isolator would.

If your PC doesn't have Toslink, then you can add it via a Hifime UT23.

Ah, it does have toslink! Will jitter be an issue, or do you think that doesn't matter with the newest chips?

The PC that has optical out, its motherboard is an Asus P8PZ68-V... It's a little old, but works absolutely fine. It's got a 2500K in there running at 4.8GHz @ 1.39V, 32GB DDR3 2133 C10, CR1 @ 1.72V, and obviously one of the fastest SATA SSDs available lol. Hope it doesn't die! (not sure if you know much about [old] PCs, the 2500K @ 4.8GHz is like a stock 7600K, or a 9100)
 

solderdude

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Is there a way to know that my DAC is blue, not grey? (other than buying the isolator lol)

View attachment 360757

Yes, you have to buy an AP555 and measure in situ.

Not audible noise = not audible noise. When you do not hear any noise at the listening position with your amp turned all the way up to the level where you won't be listening to normally then you do not need to worry.
The noise floor of any recording is already much, much higher than the grey measurement (whatever it is) and will mask the noise you see here in that particular measurement in those particular conditions.
This noise floor has nothing to do with sound quality anyway.
 

Oldson

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why dont all the dac manufacturers build in galvanic isolation in to their usb inputs?
 

Gradius

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why dont all the dac manufacturers build in galvanic isolation in to their usb inputs?
Short answer: Just use a good power supply like Mean Well, and problem solved. Something like $20 or less.

Long one:
A DAC where it completely separates the input receiver section from the audio section, be it USB or S/PDIF, since they need to be connected in some way. So there will always be some residual contamination of the "clean" audio section from the "dirty" input section. Minimizing that residual can get complicated and expensive.

Besides, it can loss some audio resolution too.
 
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