Hi, hoping I can get some help here on a pesky hum problem. I've been advised to ask for Hugh on this forum.
Setup: Focusrite Clarett interface 2x balanced outs → TRS cable (as per RA-100 manual) → unbalanced ins on Alesis RA-100 power amp → NS-10Ms (connected by two-core desklamp type mains cable). The computer (Win 11), power amp and interface are all plugged into the same board.
This, as expected, gives a slight (tolerable) hum.
The problem happens when I connect the Focusrite USB to the PC, when I get an additional hum (not tolerable). The Focusrite (unearthed mains) isn’t even switched on. I suspect an earth loop. I’ve tried plugging the USB into all the various ports on the PC; I’ve even tried powering the Focusrite from a different wall socket; but all to no avail and I’m now out of ideas.
Any electrical geniuses out there?
I found this but I’m not sure how relevant it is to my situation, as it’s the amp that’s the balanced end. https://forum.cockos.com/showthread.php?t=113721
Earth loop problem
Earth loop problem
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
It does appear to be a ground-loop between the PC and the power amp, via the ground of the USB cable and that of the audio cables between interface and amp.
Consequently, there are two locations where you can safely break the ground-loop:
1. The USB cable between computer and interface.
2. The audio cables between interface and power amp.
For option 1, there are plug-in USB isolators now that operate at full USB2.0 speeds. This should work well, in theory, but results seem to vary unpredictably!
For option 2, the simplest solution is to use a line isolation box containing transformers (one for each channel). The transformers convert between the balanced interface output and the unbalanced input to the power amp, while keeping the grounds of both systems completely separate, thus breaking the ground loop.
My go-to product for this purpose is the ART DTI box. It is reasonably priced, uses transformers of good quality (for the money), and has a good range of interfacing options to make connections easy and straightforward.
https://www.soundonsound.com/reviews/art-dti
In your application, I'd place the box near the power amp, running long balanced cables from the interface to the box, and then short unbalanced cables from the box to the amp.
Be aware that the transformers in the box are sensitive to stray magnetic fields such as that from the mains transformer in the power amp. If its too close it will pickup radiated mains hum!
You won't be happy if you cure the ground-loop hum, but induce mains hum instead... so keep the box away from the power amp's transformer! You may find that rotating the DTI box removes or reduces and magnetic hum induction.
I hope that helps.
Other transformer line isolation boxes are available from other manufacturers at a range of prices. Higher prices generally reflect better quality transformers, but its a case of diminishing returns and the DTI won't be the limiting factor in your monitoring set up.
Ideally, I'd swap our the RA100 for an amp with a proper balanced input which would solve the problem in a more elegant way... but the DTI should get the job done well enough.
Consequently, there are two locations where you can safely break the ground-loop:
1. The USB cable between computer and interface.
2. The audio cables between interface and power amp.
For option 1, there are plug-in USB isolators now that operate at full USB2.0 speeds. This should work well, in theory, but results seem to vary unpredictably!
For option 2, the simplest solution is to use a line isolation box containing transformers (one for each channel). The transformers convert between the balanced interface output and the unbalanced input to the power amp, while keeping the grounds of both systems completely separate, thus breaking the ground loop.
My go-to product for this purpose is the ART DTI box. It is reasonably priced, uses transformers of good quality (for the money), and has a good range of interfacing options to make connections easy and straightforward.
https://www.soundonsound.com/reviews/art-dti
In your application, I'd place the box near the power amp, running long balanced cables from the interface to the box, and then short unbalanced cables from the box to the amp.
Be aware that the transformers in the box are sensitive to stray magnetic fields such as that from the mains transformer in the power amp. If its too close it will pickup radiated mains hum!
You won't be happy if you cure the ground-loop hum, but induce mains hum instead... so keep the box away from the power amp's transformer! You may find that rotating the DTI box removes or reduces and magnetic hum induction.
I hope that helps.
Other transformer line isolation boxes are available from other manufacturers at a range of prices. Higher prices generally reflect better quality transformers, but its a case of diminishing returns and the DTI won't be the limiting factor in your monitoring set up.
Ideally, I'd swap our the RA100 for an amp with a proper balanced input which would solve the problem in a more elegant way... but the DTI should get the job done well enough.
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- Hugh Robjohns
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Re: Earth loop problem
Worth mentioning a couple of things to add to Hugh's comments
1. The el-cheapo audio isolation transformers sold on Amazon, such as this one
(link below) are not going to be as good as Hugh's recommended solution but they are a good way of proving that spending that money is worth while since they do indeed do what they say they will, for £8 - and in fact they aren't that terrible, to be honest - I'd certainly look at these as a cheap way of proving where the problem lies. [I've actually got one on my Seqtrak, which is a terrible source of noise otherwise, and it sounds fine]
https://www.amazon.co.uk/Smof-Ground-Is ... hdGY&psc=1
2. USB isolators are a wonderful thing. However as Hugh says the USB 2.0 full-speed ones can be a bit touchy - the technology is pretty new. The USB 1.1 isolators will handle up to around 4 audio channels perfectly well though BUT the gotcha is that the isolated downstream 5V supply they provide is only capable of around 400mA so for bus-powered audio interfaces, you have to splice in a specially made cable to add power e.g from a phone charger. This works because the charger is double insulated, and so you CAN use these things to absolutely eliminate weird computer noises, they are a miracle cure, as long as you understand how they work.
1. The el-cheapo audio isolation transformers sold on Amazon, such as this one
(link below) are not going to be as good as Hugh's recommended solution but they are a good way of proving that spending that money is worth while since they do indeed do what they say they will, for £8 - and in fact they aren't that terrible, to be honest - I'd certainly look at these as a cheap way of proving where the problem lies. [I've actually got one on my Seqtrak, which is a terrible source of noise otherwise, and it sounds fine]
https://www.amazon.co.uk/Smof-Ground-Is ... hdGY&psc=1
2. USB isolators are a wonderful thing. However as Hugh says the USB 2.0 full-speed ones can be a bit touchy - the technology is pretty new. The USB 1.1 isolators will handle up to around 4 audio channels perfectly well though BUT the gotcha is that the isolated downstream 5V supply they provide is only capable of around 400mA so for bus-powered audio interfaces, you have to splice in a specially made cable to add power e.g from a phone charger. This works because the charger is double insulated, and so you CAN use these things to absolutely eliminate weird computer noises, they are a miracle cure, as long as you understand how they work.
Re: Earth loop problem
I did come across that ART DTI box so it's good to get a confirmatory thumbs-up. I might well try that route first as it sounds like a handy piece of kit to have around anyway.
It had also occurred to me to change the amp, although it's not mine so I'd have to talk the owner into selling it (long story).
I didn't really understand the tech stuff about the USB isolators so I'll probably give them a miss for now.
Well, I guess that's solved so thanks very much guys!
[PS]
Just a thought: this DTI box gets rid of the general hum AND the extra from the USB connection, right?
It had also occurred to me to change the amp, although it's not mine so I'd have to talk the owner into selling it (long story).
I didn't really understand the tech stuff about the USB isolators so I'll probably give them a miss for now.
Well, I guess that's solved so thanks very much guys!
[PS]
Just a thought: this DTI box gets rid of the general hum AND the extra from the USB connection, right?
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
It should do, yes.
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- Hugh Robjohns
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Re: Earth loop problem
USB isolators sound like some kind of snake oil but what they actually do is that they convert the electrical signal to an optical one, and then they pick that up on the other side and re-transmit it as an electrical signal again. They have a little 5V isolated power supply that takes the 5V on the input side and creates an isolated downstream 5V supply.
This breaks the ground connection between the two USB-connected devices. It's not a new idea; MIDI has always done this, using an opto-isolator to prevent ground loops, which is why MIDI over DIN doesn't cause ground loops. The downside is that the downstream 5V power supply is tiny - it's a little cube about 1cm in size - and it can't supply much power. That's a problem if your downstream device is bus powered. In that scenario you have to splice in a separate PSU like a phone charger to get enough power.
But why would breaking the ground connection fix so many scenarios where there are hums and buzzes?. Well, it comes down to the fact that 'ground' as a concept is never perfectly realised. Within modern computers the CPU runs at very low voltage - perhaps only 1V - but at very high currents - perhaps as high as 50 amps. These switched currents flow through the internal circuitry and back through the 0V rail, which is usually connected to the chassis or is at least nominally a ground reference.
But 50 amps is a lot of current and even a big stout chunk of metal looks like a resistor if enough current flows through it. By Ohm's Law, E (voltage) = I X R. If your piece of metal has a resistance of 0.001 ohms and you put 50 amps across it, Mr Ohm would tell you that you'll see 50 X 0.001 = .05V = 50mV.
But 50mV is, as an audio signal, quite substantial. So if your supposed "ground" reference is actually wiggling around by 50mV and you connect that up to some other piece of equipment - which is probably also grounded - then you can inject that spurious signal into sensitive audio inputs. Because, remember, a preamp is amplifying the DIFFERENCE between the signal wire and ground. It doesn't matter whether the signal wire jiggles around with a signal, or the ground wire jiggles up and down. Either way you have a difference. This is why balanced inputs help enormously, because then in this situation, the difference signal is between the two signal wires. These shouldn't be affected by ground loops, whereas unbalanced inputs will.
And that 50mV voltage source has what we call a very low impedance. A speaker is typically 4 or 8 ohms. A microphone is typically at least several hundred ohms. But this noise source is 0.001 ohms. This means it can deliver that 50mV across what you'd think of as a short circuit - the kind of thin wire that USB connectors are made of, for example. At which point you have hum, buzzes, whining noises and so forth. Some computers are worse than others, simply because of how their internal circuitry is designed. If their analogue ground points are outside the current paths associated with the CPU and other digital circuitry, they tend not to cause ground noise issues. If, on the other hand, their analogue ground points are associated with current paths, then they become noise sources and drive their owners crazy.
This breaks the ground connection between the two USB-connected devices. It's not a new idea; MIDI has always done this, using an opto-isolator to prevent ground loops, which is why MIDI over DIN doesn't cause ground loops. The downside is that the downstream 5V power supply is tiny - it's a little cube about 1cm in size - and it can't supply much power. That's a problem if your downstream device is bus powered. In that scenario you have to splice in a separate PSU like a phone charger to get enough power.
But why would breaking the ground connection fix so many scenarios where there are hums and buzzes?. Well, it comes down to the fact that 'ground' as a concept is never perfectly realised. Within modern computers the CPU runs at very low voltage - perhaps only 1V - but at very high currents - perhaps as high as 50 amps. These switched currents flow through the internal circuitry and back through the 0V rail, which is usually connected to the chassis or is at least nominally a ground reference.
But 50 amps is a lot of current and even a big stout chunk of metal looks like a resistor if enough current flows through it. By Ohm's Law, E (voltage) = I X R. If your piece of metal has a resistance of 0.001 ohms and you put 50 amps across it, Mr Ohm would tell you that you'll see 50 X 0.001 = .05V = 50mV.
But 50mV is, as an audio signal, quite substantial. So if your supposed "ground" reference is actually wiggling around by 50mV and you connect that up to some other piece of equipment - which is probably also grounded - then you can inject that spurious signal into sensitive audio inputs. Because, remember, a preamp is amplifying the DIFFERENCE between the signal wire and ground. It doesn't matter whether the signal wire jiggles around with a signal, or the ground wire jiggles up and down. Either way you have a difference. This is why balanced inputs help enormously, because then in this situation, the difference signal is between the two signal wires. These shouldn't be affected by ground loops, whereas unbalanced inputs will.
And that 50mV voltage source has what we call a very low impedance. A speaker is typically 4 or 8 ohms. A microphone is typically at least several hundred ohms. But this noise source is 0.001 ohms. This means it can deliver that 50mV across what you'd think of as a short circuit - the kind of thin wire that USB connectors are made of, for example. At which point you have hum, buzzes, whining noises and so forth. Some computers are worse than others, simply because of how their internal circuitry is designed. If their analogue ground points are outside the current paths associated with the CPU and other digital circuitry, they tend not to cause ground noise issues. If, on the other hand, their analogue ground points are associated with current paths, then they become noise sources and drive their owners crazy.
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- alexis
Longtime Poster - Posts: 5282 Joined: Fri Jan 10, 2003 12:00 am Location: Hampton Roads, Virginia, USA
Home of the The SLUM Tapes (Shoulda Left Un-Mixed), mangled using Cubase Pro 14; W10 64 bit on Intel i5-4570 3.2GHz,16GB RAM;Steinberg UR28M interface; Juno DS88; UAD2 Solo/Native; Revoice Pro
Re: Earth loop problem
Likewise, ajay_m, even I understood that, more or less 
The delivery of the ART DTI box is imminent so I'll report back with the results.
The delivery of the ART DTI box is imminent so I'll report back with the results.
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
ART appears to have discontinued the DTI; I had one and have got another on order. Not sure what the best alternative might be, though from experience I’d usually want none, sometimes 1 or 2 and seldom, if ever, more. Nevertheless, me being me, I could use a couple more as the belt to my braces.
Re: Earth loop problem
I'd be really surprised if they have. It's got to be a good seller! It's still listed on their website:
https://artproaudio.com/noisereduction/ ... 246724/dti
...along with it's close cousin, the Cleanbox2 (which has the same internals but only Jack sockets in and out):
https://artproaudio.com/noisereduction/ ... cleanboxii
And a quick search suggests the DTI is currently available from Thomann, Farnell, Bax, Gear4Music, Absolute, Leisuretec, and even Amazon....
There are lots of similar alternatives from other manufacturers too, although few have the plethora of connection formats which I find so useful.
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- Hugh Robjohns
Moderator -
Posts: 43689 Joined: Fri Jul 25, 2003 12:00 am
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In my world, things get less strange when I read the manual...
Re: Earth loop problem
Oops! Red face time again! Just a misleading series of searches on my part. Careless not to find it on the ART website, though that seems to decide to show me stuff almost randomly, probably due to my limited computer skills dwindling further!
I am a recent DTI convert, largely because I decided to integrate, or try to integrate my listening system (traditional hifi) and editing system (the computer and all that) which I previously kept apart to avoid the troubles the DTI is so good with. So far it’s been great; I need another to link my desktop monitors and amp which are essentially hifi rather than studio gear. Tomorrow I should get all that sorted.
You may recall I asked aloud what to do with my Mackie 824s a couple of months back.
After running three sets of speakers and laboriously changing them over, I worked out more or less how to cope with the variations in presentation (time will tell!) so I have two sets of speakers in my listening/work room and can take the Mackies out when I need monitors on location. Or so I hope. Regardless, the DTI is a nifty bit of kit, simple enough for me not to have made a mess of connecting it up.
I am a recent DTI convert, largely because I decided to integrate, or try to integrate my listening system (traditional hifi) and editing system (the computer and all that) which I previously kept apart to avoid the troubles the DTI is so good with. So far it’s been great; I need another to link my desktop monitors and amp which are essentially hifi rather than studio gear. Tomorrow I should get all that sorted.
You may recall I asked aloud what to do with my Mackie 824s a couple of months back.
After running three sets of speakers and laboriously changing them over, I worked out more or less how to cope with the variations in presentation (time will tell!) so I have two sets of speakers in my listening/work room and can take the Mackies out when I need monitors on location. Or so I hope. Regardless, the DTI is a nifty bit of kit, simple enough for me not to have made a mess of connecting it up.
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- alexis
Longtime Poster - Posts: 5282 Joined: Fri Jan 10, 2003 12:00 am Location: Hampton Roads, Virginia, USA
Home of the The SLUM Tapes (Shoulda Left Un-Mixed), mangled using Cubase Pro 14; W10 64 bit on Intel i5-4570 3.2GHz,16GB RAM;Steinberg UR28M interface; Juno DS88; UAD2 Solo/Native; Revoice Pro
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- Hugh Robjohns
Moderator -
Posts: 43689 Joined: Fri Jul 25, 2003 12:00 am
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In my world, things get less strange when I read the manual...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
Re: Earth loop problem
Hugh Robjohns wrote: ↑Wed Oct 30, 2024 8:31 pm
To be fair, they do hide it under the 'noise reduction' section which, while kinda relevant is counter-intuitive.
Well, yes, they’re taking advantage of me not having much grip left to lose …
Re: Earth loop problem
The DTI box has arrived and it has killed the nasty extra hum from the Focusrite->PC USB connection. All that's left is the residual hum from the un-balanced cabling from the DTI to the power amp, which is to be expected until I upgrade the cables.
Really appreciate the contributions here, thank you very much, all of you!
Really appreciate the contributions here, thank you very much, all of you!
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
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- Hugh Robjohns
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Posts: 43689 Joined: Fri Jul 25, 2003 12:00 am
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In my world, things get less strange when I read the manual...
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In my world, things get less strange when I read the manual...
Re: Earth loop problem
I'm slightly surprised and disappointed that there is any hum left at all.
With the DTI feeding the power amp there can be no ground-loop via the audio cables and, with nothing but the speakers connected to the power amp, there's no other possibility of a ground-loop there.
So the only sources of hum that remain possibilities are that the amp itself is hummy — possibly due to failing power supply capacitors — or that there is some degree of magnetic induction either into the audio cabling or the DTIbox transformers (an issue I warned of earlier)..
Although possible, it's rare to have hum induced in the unbalanced audio cabling — unless it's very long and running close to mains cables.
Magnetically coupled hum into the DTI box is more likely, but easy to resolve by moving or re-orientating the box away from strong hum sources — usually big mains transformers in other equipment.
Some questions:
Is the low level hum present when the amp inputs are disconnected?
If yes, the problem is a failing amp.
If no, then the hum is from something upstream — the cables and/or DTI box.
So, does the level of hum change if you relocate the cables and box well away from other equipment and cables?
With the DTI feeding the power amp there can be no ground-loop via the audio cables and, with nothing but the speakers connected to the power amp, there's no other possibility of a ground-loop there.
So the only sources of hum that remain possibilities are that the amp itself is hummy — possibly due to failing power supply capacitors — or that there is some degree of magnetic induction either into the audio cabling or the DTIbox transformers (an issue I warned of earlier)..
Although possible, it's rare to have hum induced in the unbalanced audio cabling — unless it's very long and running close to mains cables.
Magnetically coupled hum into the DTI box is more likely, but easy to resolve by moving or re-orientating the box away from strong hum sources — usually big mains transformers in other equipment.
Some questions:
Is the low level hum present when the amp inputs are disconnected?
If yes, the problem is a failing amp.
If no, then the hum is from something upstream — the cables and/or DTI box.
So, does the level of hum change if you relocate the cables and box well away from other equipment and cables?
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- Hugh Robjohns
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Posts: 43689 Joined: Fri Jul 25, 2003 12:00 am
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In my world, things get less strange when I read the manual...
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In my world, things get less strange when I read the manual...
Re: Earth loop problem
Hi, sorry about the delay in replying, I was getting Bad Gateway errors.
Ah, the value of stripping things right back like you should have done at the start! It turns out that a lot (most!) of the residual hum was from a dodgy amp to speaker cable (thick mains fyi) so now I've got nice short cables from the good wire. I think the amp is a bit hummy but it's very slight. In fact, it's the quietest it's ever been.
As for positioning the DTI box, I've found that for this amp 3 inches or so is the drop-off point for interference, so thanks for that tip.
Ah, the value of stripping things right back like you should have done at the start! It turns out that a lot (most!) of the residual hum was from a dodgy amp to speaker cable (thick mains fyi) so now I've got nice short cables from the good wire. I think the amp is a bit hummy but it's very slight. In fact, it's the quietest it's ever been.
As for positioning the DTI box, I've found that for this amp 3 inches or so is the drop-off point for interference, so thanks for that tip.
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
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- Hugh Robjohns
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Posts: 43689 Joined: Fri Jul 25, 2003 12:00 am
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Technical Editor, Sound On Sound...
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In my world, things get less strange when I read the manual...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
Re: Earth loop problem
It's back!
(Actually, it's been back a while but Christmas got in the way...)
It came back when I plugged a mic into one of the analog inputs on my Clarett and never went away. Now, what on earth (pun not intended btw!) made that happen?
It's not a steady hum, there's a irregular crackle too. With my old mono leads going interface to amp (balanced to mono) it's barely audible but with my new, gold-plated, 1m TRS leads it's intolerable. I hope that's down to the quality of the leads (Tisino, not cheap) showing the problem up, rather than adding to it.
Any thoughts?
Duncan
(Actually, it's been back a while but Christmas got in the way...)
It came back when I plugged a mic into one of the analog inputs on my Clarett and never went away. Now, what on earth (pun not intended btw!) made that happen?
It's not a steady hum, there's a irregular crackle too. With my old mono leads going interface to amp (balanced to mono) it's barely audible but with my new, gold-plated, 1m TRS leads it's intolerable. I hope that's down to the quality of the leads (Tisino, not cheap) showing the problem up, rather than adding to it.
Any thoughts?
Duncan
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
It's very unlikely to be caused by the microphone* and more likely that something moved or got disturbed by the act of plugging the microphone in. I'd look for loose or damaged connectors or cables, or something newly added (especially power supplies) near cables.
But if it was previously quiet you should be able to recreate that state and then figure out what changed.
*I have come across a situation where a mic created an unwanted ground-loop. The mic support was earthed metal (a clamp on a radiator!), with that ground contacting the metal mic body via its metal mounting ring, and hence creating a ground-loop via the preamp.
But if it was previously quiet you should be able to recreate that state and then figure out what changed.
*I have come across a situation where a mic created an unwanted ground-loop. The mic support was earthed metal (a clamp on a radiator!), with that ground contacting the metal mic body via its metal mounting ring, and hence creating a ground-loop via the preamp.
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- Hugh Robjohns
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Posts: 43689 Joined: Fri Jul 25, 2003 12:00 am
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In my world, things get less strange when I read the manual...
Re: Earth loop problem
Hi Hugh, thanks for getting back.
On further investigation, I now have the interface switched off and the USB unplugged at the PC end, and I have a very loud buzz. If I connect the USB (in fact, as soon as the plug makes contact with the socket) it changes to an ethereal random sort of noise. But if I disconnect the mains from the (switched off) interface it disappears completely.
Setup reminder: interface > TRS > ART DTI > TRS > mono inputs on power amp. The interface has a 2-pin plug. The DTI has an earth point which I may be able to use.
Hope that sheds some light.
On further investigation, I now have the interface switched off and the USB unplugged at the PC end, and I have a very loud buzz. If I connect the USB (in fact, as soon as the plug makes contact with the socket) it changes to an ethereal random sort of noise. But if I disconnect the mains from the (switched off) interface it disappears completely.
Setup reminder: interface > TRS > ART DTI > TRS > mono inputs on power amp. The interface has a 2-pin plug. The DTI has an earth point which I may be able to use.
Hope that sheds some light.
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
DoctorDunc wrote: ↑Wed Jan 08, 2025 3:07 pm ...interface switched off and the USB unplugged at the PC end, and I have a very loud buzz. If I connect the USB (in fact, as soon as the plug makes contact with the socket) it changes to an ethereal random sort of noise.
This suggests the interface is getting its ground reference via the USB connection, and that makes sense when:
...The interface has a 2-pin plug.
The 'ethereal noise' is being generated in the computer and getting into the audio circuitry via the ground to the interface.
But if I disconnect the mains from the (switched off) interface it disappears completely.
This makes little sense from a grounding point of view as, with a two-pin plug, there is no ground connection. However, it does suggest that the power unit is radiating RF nastiness into the cabling (or EM nastiness into the DTI box) nearby.
So I'd experiment with relocating or reorienting the interface power supply.
Setup reminder: interface > TRS > ART DTI > TRS > mono inputs on power amp.
If I remember rightly, the amp is an Alesis RA100 which has unbalanced inputs on TS sockets. In which case you really need to use TS cables from the output of the DTI box (which should be reasonably close to the amp), not TRS.
The potential problem with TRS cables is that the transformer secondary in the DTI box is wired between the tip and ring contacts, but there may not be a ring contact in the Alesis amp. (If it's working there probably is, but it's an unnecessary risk.
By using a TS cable, the cold side of the transformer secondary will be shorted to the shield terminal via the long sleeve at the DTI box, providing the required unbalanced output.
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- Hugh Robjohns
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(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual...
Re: Earth loop problem
Thanks again, Hugh. I'll have a fiddle. The reason I was using TRS to the amp is that's what the manual recommended.
And I always assumed the socket earth sleeve would be long enough too earth the ring on the plug but it seems not.
And I always assumed the socket earth sleeve would be long enough too earth the ring on the plug but it seems not.
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- DoctorDunc
New here - Posts: 8 Joined: Tue Oct 29, 2024 12:38 pm
Re: Earth loop problem
DoctorDunc wrote: ↑Wed Jan 08, 2025 5:53 pm And I always assumed the socket earth sleeve would be long enough too earth the ring on the plug but it seems not.
TS sockets are often just TRS sockets with the ring connection removed (so using a TRS plug would leave the ring disconnected) although I have encountered a TS socket where the tip connection falls on the insulation between the tip and ring on a TRS plug.
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- James Perrett
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Posts: 16986 Joined: Mon Sep 10, 2001 12:00 am
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