Have you read D.Joffe's paper on mains interference?
Fig 5 applies to the pre > power link with the solution in the power amp.
Fig 6 applies to the source > pre link with the solution in the pre amp.
But read the whole paper to follow why a silent power amp can be affected by the way the source feeds the signals into the 2channel receivers
Fig 5 applies to the pre > power link with the solution in the power amp.
Fig 6 applies to the source > pre link with the solution in the pre amp.
But read the whole paper to follow why a silent power amp can be affected by the way the source feeds the signals into the 2channel receivers
The coaxial screen/shield is the return route for the current leaving the Source.
Any voltage drop on this return is interpreted as a signal voltage.
If some of that is interference, then that interference current times the return route impedance = interference voltage. That (interference current addition to signal current) cannot be removed once added.
The solution is to reduce the voltage by reducing the return impedance, or reducing the interference current, or doing both.
Figures 5 & 6 show where to insert the resistor/s to reduce the interference current without increasing the return route impedance.
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Hi all
Looking at this situation again, I have realised that maybe we're approaching this ground loop issue the wrong way:
Instead of tackling the ground loop at the signal cable, potentially affecting the quality of audio signal, why not make the isolation at the USB stage - eg - break the ground loop between PC and DAC box (Edirol UA-25). This way the audio signals coming from the UA-25 are free-floating, hence no ground loop with the amp...
I know this is an audio forum, but has anyone ever used a USB isolator?
Here's a page of them on ebay (UK)
usb isolator | eBay
Prices vary wildly.
Thanks
John
Looking at this situation again, I have realised that maybe we're approaching this ground loop issue the wrong way:
Instead of tackling the ground loop at the signal cable, potentially affecting the quality of audio signal, why not make the isolation at the USB stage - eg - break the ground loop between PC and DAC box (Edirol UA-25). This way the audio signals coming from the UA-25 are free-floating, hence no ground loop with the amp...
I know this is an audio forum, but has anyone ever used a USB isolator?
Here's a page of them on ebay (UK)
usb isolator | eBay
Prices vary wildly.
Thanks
John
does your dac have a sp-dif input? im avoiding that pc noise issue ( which bugged me on my last build) with my new build, by using the spdif input on a minidsp, rather than the usb input.
With a short optical cable running to my old hifimediy mini usb dac (which switches over to just usb/spdif converter when you plug an optical cable into the headphone socket)
i already had all the bits, so it was an obvious choice, but a hifimediy usb dac like mine costs about $30
ive heard mixed opinions re. usb isolators.
With a short optical cable running to my old hifimediy mini usb dac (which switches over to just usb/spdif converter when you plug an optical cable into the headphone socket)
i already had all the bits, so it was an obvious choice, but a hifimediy usb dac like mine costs about $30
ive heard mixed opinions re. usb isolators.
Thanks Robin
With the gear I've got - the DAC is an Edirol UA-25 (which does have spdif out), but the amp is an old Sansui (AU-2900) which of course doesn't have digital anything.
The UA-25 (allegedly) has decent DACs (and does 24bit-96khz) - so I'm not going to replace it. I've already found that if I run it from a laptop on battery - removing the PC's ground - there is no ground loop going into the amp.
So it makes sense to cut the ground loop off at the USB stage. It seems that some USB Isolators take their 5v supplies from an external PS (allowing the use of a 2-pin class-II supply), but presumably there's still ground from the PC in the signal lines of the USB - hence the need for a device which breaks this. Most USB Isolators don't use an external supply - they take the PC supply.
Looking further, I can see some USB are cheap - £10 if you don't mind them arriving from China in a month. But then there's more serious ones which cost around £200. They all seem to use the same Analog Devices chip (but the cheapy ones don't look like they've got any decent caps).
I wouldn't want to spend more than £20-30 on this - because I might as well just spend the money to upgrade to another amp.
John
With the gear I've got - the DAC is an Edirol UA-25 (which does have spdif out), but the amp is an old Sansui (AU-2900) which of course doesn't have digital anything.
The UA-25 (allegedly) has decent DACs (and does 24bit-96khz) - so I'm not going to replace it. I've already found that if I run it from a laptop on battery - removing the PC's ground - there is no ground loop going into the amp.
So it makes sense to cut the ground loop off at the USB stage. It seems that some USB Isolators take their 5v supplies from an external PS (allowing the use of a 2-pin class-II supply), but presumably there's still ground from the PC in the signal lines of the USB - hence the need for a device which breaks this. Most USB Isolators don't use an external supply - they take the PC supply.
Looking further, I can see some USB are cheap - £10 if you don't mind them arriving from China in a month. But then there's more serious ones which cost around £200. They all seem to use the same Analog Devices chip (but the cheapy ones don't look like they've got any decent caps).
I wouldn't want to spend more than £20-30 on this - because I might as well just spend the money to upgrade to another amp.
John
i wasnt suggesting to ditch your DAC..
you could purchase one of these (there is probably a cheaper option that does the same thing without being a dac too)
HiFimeDIY UAE23 USB DAC (ESS Sabre ES9023+Savitech SA9023)
and connect that to your pc.
then fibreoptic cable from there to your dac, which does its daccy thing, but completely isolated from the pc.
you could purchase one of these (there is probably a cheaper option that does the same thing without being a dac too)
HiFimeDIY UAE23 USB DAC (ESS Sabre ES9023+Savitech SA9023)
and connect that to your pc.
then fibreoptic cable from there to your dac, which does its daccy thing, but completely isolated from the pc.
Thanks Robin
Apologies beforehand if I'm misunderstanding what you're saying, but it would seem that the device you are talking about is simply a DAC - there is no digital spdif - it's USB in, analogue audio out only - in effect it does exactly the same job as my UA-25 (only not as well).
I've just noticed the motherboard on my PC has an spdif output jack - so that means I could theoretically run an spdif cable between PC and DAC. And I'd have to power the DAC with its own supply. That's if the DAC can operate self-standing, without being controlled by a PC (which I doubt).
Also - how do we know that going via a spdif connection (instead of USB) would break the ground loop between PC and amp?
Anyway - breaking the ground loop pre-DAC is surely the way to go.
John
Apologies beforehand if I'm misunderstanding what you're saying, but it would seem that the device you are talking about is simply a DAC - there is no digital spdif - it's USB in, analogue audio out only - in effect it does exactly the same job as my UA-25 (only not as well).
I've just noticed the motherboard on my PC has an spdif output jack - so that means I could theoretically run an spdif cable between PC and DAC. And I'd have to power the DAC with its own supply. That's if the DAC can operate self-standing, without being controlled by a PC (which I doubt).
Also - how do we know that going via a spdif connection (instead of USB) would break the ground loop between PC and amp?
Anyway - breaking the ground loop pre-DAC is surely the way to go.
John
I don't know of many desktop PCs that don't inject a mass of PSU hum and noise into the audio-out jack. That and the large ground loops many users wind up with in their systems, are an almost universal problem when interconnecting typical mains and chassis signal grounded devices like a desktop PC. Laptop PCs of course, can be battery powered and their charger PSUs are isolated. Thus, they don't normally have a mains ground connection or many hum problems at all - as you find.
Regardless of brand and which Asian factory the PC was built in, the problem of the PC's typical steel frame with a common Power + Signal Ground connection, has been around for safety reasons for a lifetime. My solution for the series of PCs I have used over many years now, is to use a USB/optical link (Toslink) with a quality external DAC - no more hum and no more mystery noises
Note that cheapo USB audio adaptors (simple DACs) are out there too are and good for checking problems like this but they are seldom up to an acceptable hifi audio standard. Buyer beware.
Regardless of brand and which Asian factory the PC was built in, the problem of the PC's typical steel frame with a common Power + Signal Ground connection, has been around for safety reasons for a lifetime. My solution for the series of PCs I have used over many years now, is to use a USB/optical link (Toslink) with a quality external DAC - no more hum and no more mystery noises
Note that cheapo USB audio adaptors (simple DACs) are out there too are and good for checking problems like this but they are seldom up to an acceptable hifi audio standard. Buyer beware.
Thanks Ian
I'm currently trying to drag myself into the 21st Century as we speak. Fibre-optic audio connections - beam me up Scotty.
So - a spdif/toslink fibreoptic link into a self-standing DAC box, going into the amp.
Just looking at DACs for this task, it looks like this one gets good reviews (Fiio D3) - £30 but apparently comparable to ones costing much more.
Digital to Analog Audio Converter - 192kHz/24bit Optical and Coaxial DAC SPDIF - | eBay
Has anyone had any luck with these self-standing DAC boxes?
Thanks
John
I'm currently trying to drag myself into the 21st Century as we speak. Fibre-optic audio connections - beam me up Scotty.
So - a spdif/toslink fibreoptic link into a self-standing DAC box, going into the amp.
Just looking at DACs for this task, it looks like this one gets good reviews (Fiio D3) - £30 but apparently comparable to ones costing much more.
Digital to Analog Audio Converter - 192kHz/24bit Optical and Coaxial DAC SPDIF - | eBay
Has anyone had any luck with these self-standing DAC boxes?
Thanks
John
More about this Fiio D3 - the £30 DAC.
Linked here is another long thread from this same forum - in a nutshell people were having trouble telling the difference between a Fiio D3 and another DAC which cost £1000s in a ABX test...
DAC blind test: NO audible difference whatsoever.
I think this is the answer to ground loop, and other noise and hum caused by using computers as the audio source.
John
Linked here is another long thread from this same forum - in a nutshell people were having trouble telling the difference between a Fiio D3 and another DAC which cost £1000s in a ABX test...
DAC blind test: NO audible difference whatsoever.
I think this is the answer to ground loop, and other noise and hum caused by using computers as the audio source.
John
Robin
Because I don't think my DAC works unless it's connected to, and controlled by, a PC. I tried to Google the question but couldn't find anything which said otherwise.
There's a whole genre of self-contained DAC devices similar to the Fiio D3 and these would be appropriate what I need. The UA-25 was originally intended as a recording device.
Thanks again,
John
The Roland Edirol gizmo seems to already have optical (Toslink) connector sockets, labelled as digital in/out. Is that correct? If so, you don't need another DAC - just a USB to SPDIF (optical) adaptor for your PC unless it already has optical out, as suggested. I would try something available locally before buying, if possible. Here's something that fits the bill but doubtless there are other and cheaper options. I think this one requires its own little wallwart power supply too:
SMAKN(R) Hi-Fi CM6631 USB to Coaxial / Optical SPDIF Convertor For DAC ASIO | eBay
SMAKN(R) Hi-Fi CM6631 USB to Coaxial / Optical SPDIF Convertor For DAC ASIO | eBay
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Hi Ian
Apologies in advance, perhaps you didn't see the last comment from me...
The Edirol UA-25 is not self-standing - it needs to be connected to the PC. So it can't do what you're suggesting. My PC has spdif output, as does the UA-25, so I could use either as the digital spdif 'out' from the PC, but at the other end of the spdif lead needs to be a DAC to output analogue audio into the amp.
Unless someone can think of a way of using the UA-25 - without being controlled by a PC - then I need something else.
Thanks
John
Hi,
I read through the description and it says
but I can't see a connector.
How does the optical exit the box?
The optical transciever is at the bottom of the 3.5 audio jack socket.. Clever huh? Need an adapter like this: toslink headphone adapter - Google Search
A few of the optical leads for sale include the adaper.
A few of the optical leads for sale include the adaper.
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