Need help with AC interference on DC power supply output

[cyclonite]

  If the phono amp and the preamp both have ground connected power cords that may be the cause. try plogging both power cords in to the same power outlet, if they aren't all ready.

Hello,
 
The Phono amp IS the Pre-Amp. Here's the setup:
 
Turntable -> Pre-Amp -> Amp + Speaker
 
The turntable's tone arm is unpowered (because there no built in Pre-Amp)
 
The Pre-Amp is powered by AC -> DC Adaptor that isn't earthed. I've manually earthed the unit.
 
Amp + Speaker is irrelevant because the buzzing stops when I disconnect the phono stage from the Pre-Amp. The issue is the interference prior to being pre amplified; and the interference is being amplified and made louder by the pre-amp itself.

 

[tomb]

 

  If the phono amp and the preamp both have ground connected power cords that may be the cause. try plogging both power cords in to the same power outlet, if they aren't all ready.

Hello,
 
The Phono amp IS the Pre-Amp. Here's the setup:
 
Turntable -> Pre-Amp -> Amp + Speaker
 
The turntable's tone arm is unpowered (because there no built in Pre-Amp)
 
The Pre-Amp is powered by AC -> DC Adaptor that isn't earthed. I've manually earthed the unit.
 
Amp + Speaker is irrelevant because the buzzing stops when I disconnect the phono stage from the Pre-Amp. The issue is the interference prior to being pre amplified; and the interference is being amplified and made louder by the pre-amp itself.

 
You need to be more specific about your equipment.  I think there may be some issues with component definitions going on.
 
Traditionally, there's never been a phono amp that didn't need further pre-amping before going to a speaker amp.  All a separate phono amp provides was a line-level signal (and RIAA equalization) suitable for pre-amping.  Once the phono amp is provided, it's still the same as a CD player, tape deck or tuner - you need to process it through a pre-amp, the pre-amp section of an integrated amp, or the pre-amp section of a receiver - before it can be adequately amplified by a speaker amp.  The levels are way too low with a magnetic phono cartridge - even worse with a moving coil one.
 
Unlike all other components that provide signals to a pre-amp, integrated amp or receiver, a phono cartridge required a pre-pre-amp with RIAA equalization - to boot - before it was even ready to plug into a pre-amp.

 

[cyclonite]

   
You need to be more specific about your equipment.  I think there may be some issues with component definitions going on.
 
Traditionally, there's never been a phono amp that didn't need further pre-amping before going to a speaker amp.  All a separate phono amp provides was a line-level signal (and RIAA equalization) suitable for pre-amping.  Once the phono amp is provided, it's still the same as a CD player, tape deck or tuner - you need to process it through a pre-amp, the pre-amp section of an integrated amp, or the pre-amp section of a receiver - before it can be adequately amplified by a speaker amp.  The levels are way too low with a magnetic phono cartridge - even worse with a moving coil one.
 
Unlike all other components that provide signals to a pre-amp, integrated amp or receiver, a phono cartridge required a pre-pre-amp with RIAA equalization - to boot - before it was even ready to plug into a pre-amp.

 
Ahh OK I wasn't aware that there is was another pre-pre-amp. In my case, the turntable is connected directly to a Phono Pre-Amp that supports both moving magnet and moving coil. The output of this is a RCA line-out that can be connected to any amplifier's Aux-in or line-in. The Phono Pre-Amp also does RIAA equalization. Maybe they have incorporated things in such a way that only 1 Pre-Amp stage is required.

 

[tomb]

 

   
You need to be more specific about your equipment.  I think there may be some issues with component definitions going on.
 
Traditionally, there's never been a phono amp that didn't need further pre-amping before going to a speaker amp.  All a separate phono amp provides was a line-level signal (and RIAA equalization) suitable for pre-amping.  Once the phono amp is provided, it's still the same as a CD player, tape deck or tuner - you need to process it through a pre-amp, the pre-amp section of an integrated amp, or the pre-amp section of a receiver - before it can be adequately amplified by a speaker amp.  The levels are way too low with a magnetic phono cartridge - even worse with a moving coil one.
 
Unlike all other components that provide signals to a pre-amp, integrated amp or receiver, a phono cartridge required a pre-pre-amp with RIAA equalization - to boot - before it was even ready to plug into a pre-amp.

 
Ahh OK I wasn't aware that there is was another pre-pre-amp. In my case, the turntable is connected directly to a Phono Pre-Amp that supports both moving magnet and moving coil. The output of this is a RCA line-out that can be connected to any amplifier's Aux-in or line-in. The Phono Pre-Amp also does RIAA equalization. Maybe they have incorporated things in such a way that only 1 Pre-Amp stage is required.

 
Aux-in or line-in still goes to a pre-amp before it goes to a speaker amplifier.  If you have a receiver or integrated amplifier instead of a true component pre-amp, then the pre-amp operation is still going on inside the box.  If you truly have a component speaker amplifier, this is not going to work.  A component speaker amplifier is only going to take the output from a component pre-amp (not a phono amp).
 
Why not tell us what you really have (specific brand, model, etc.)?  Then we can look it up and help you better once we understand.

 

[cyclonite]

   
Aux-in or line-in still goes to a pre-amp before it goes to a speaker amplifier.  If you have a receiver or integrated amplifier instead of a true component pre-amp, then the pre-amp operation is still going on inside the box.  If you truly have a component speaker amplifier, this is not going to work.  A component speaker amplifier is only going to take the output from a component pre-amp (not a phono amp).
 
Why not tell us what you really have (specific brand, model, etc.)?  Then we can look it up and help you better once we understand

Ahh OK thanks for clarifying that.
 
Sure, my setup isn't too fancy. Here goes.
 
1) Turntable = Pro-Ject Essential II (there is no electrical connection between the motor power unit and the tone arm in this model because it doesn't have a built in Pre-Amp).
2) Phono Pre-Amp = Pro-Ject Phono Box (supports both Moving Magnet and Moving Coil)
3) Speaker = Bower & Wilkins Zeppelin Air (this is an iPhone dock speaker that has 5 drivers driven internally by individual audiophile grade amplifiers - mono block)
 
As I've mentioned earlier, the Turntable is connected to the Phono Box using 3 cables (left, right and ground). I've earthed the Phono Box to an adjacent power socket's earth terminal.
 
Please feel free to ask any other questions

 

[tomb]

 

   
Aux-in or line-in still goes to a pre-amp before it goes to a speaker amplifier.  If you have a receiver or integrated amplifier instead of a true component pre-amp, then the pre-amp operation is still going on inside the box.  If you truly have a component speaker amplifier, this is not going to work.  A component speaker amplifier is only going to take the output from a component pre-amp (not a phono amp).
 
Why not tell us what you really have (specific brand, model, etc.)?  Then we can look it up and help you better once we understand

Ahh OK thanks for clarifying that.
 
Sure, my setup isn't too fancy. Here goes.
 
1) Turntable = Pro-Ject Essential II (there is no electrical connection between the motor power unit and the tone arm in this model because it doesn't have a built in Pre-Amp).
2) Phono Pre-Amp = Pro-Ject Phono Box (supports both Moving Magnet and Moving Coil)
3) Speaker = Bower & Wilkins Zeppelin Air (this is an iPhone dock speaker that has 5 drivers driven internally by individual audiophile grade amplifiers - mono block)
 
As I've mentioned earlier, the Turntable is connected to the Phono Box using 3 cables (left, right and ground). I've earthed the Phono Box to an adjacent power socket's earth terminal.
 
Please feel free to ask any other questions

 
This gets more confusing all the time, unfortunately.  I feel like we've been turning circles in the desert.
 
So what does the Pro-Ject Phono Box connect into?  I assume you mean the powered speaker box, which pretty much negates all the conversation we've previously had.  pre-amp, amp, and speakers are all rolled up into that single device.
 
Just an FYI, but typical walwarts that convert AC to DC do not continue with the line ground to the component.  I am actually surprised that you reduced the buzz more by connecting a separate ground wire from the Phono Box to the line ground at the wall.  Typically, the grounds are separated in an AC to DC power supply because grounding the DC to the AC ground can often result in "infecting" the DC with your 50 Hz hum.  There are literally hundreds of thousands (millions?) of audio devices powered by a two-wire (positive and negative) separate DC power supply that do not result in line power grounding issues.
 
Honestly, after looking at the products you purchased and re-reading all of this thread (a couple of times), I think the key is in what you stated in your first post:

 Now that the buzz is at 40%, I went on searching for other remedies. I've noticed the the Pre-Amp's metal box is vibrating at 50Hz when I run my fingers over the metal surfaces.

 
If the wall adapter is converting from AC to DC, this is impossible.  There should be nothing in the Pro-Ject Phono Box that would cause vibration at 50 Hz - it's all running on DC.  Even the worst AC/DC walwarts are not going to have more than a few tens of mV of AC hum or ripple - not enough to cause vibration in a DC-powered device that has no AC connection or AC transformer inside.  Either your wall adapter is bad or the Pro-Ject Phono Box is bad.

 

[cyclonite]

   
This gets more confusing all the time, unfortunately.  I feel like we've been turning circles in the desert.
 
So what does the Pro-Ject Phono Box connect into?  I assume you mean the powered speaker box, which pretty much negates all the conversation we've previously had.  pre-amp, amp, and speakers are all rolled up into that single device.
 
Just an FYI, but typical walwarts that convert AC to DC do not continue with the line ground to the component.  I am actually surprised that you reduced the buzz more by connecting a separate ground wire from the Phono Box to the line ground at the wall.  Typically, the grounds are separated in an AC to DC power supply because grounding the DC to the AC ground can often result in "infecting" the DC with your 50 Hz hum.  There are literally hundreds of thousands (millions?) of audio devices powered by a two-wire (positive and negative) separate DC power supply that do not result in line power grounding issues.
 
Honestly, after looking at the products you purchased and re-reading all of this thread (a couple of times), I think the key is in what you stated in your first post:
 
If the wall adapter is converting from AC to DC, this is impossible.  There should be nothing in the Pro-Ject Phono Box that would cause vibration at 50 Hz - it's all running on DC.  Even the worst AC/DC walwarts are not going to have more than a few tens of mV of AC hum or ripple - not enough to cause vibration in a DC-powered device that has no AC connection or AC transformer inside.  Either your wall adapter is bad or the Pro-Ject Phono Box is bad.

 
Tomb,
 
Thank you for your patience and attention. I really appreciate it.
 
Here's the Phono Box:
 
http://www.project-audio.com/main.php?prod=phonobox&cat=boxes&lang=en
 
It has a Phono connection as input and Line-Out as output. That's it. It sits between the turntable and the speaker system (Zeppelin Air)
 
>If the wall adapter is converting from AC to DC, this is impossible.
 
I'm sorry I have to disagree with this statement. I have many household devices that are 'DC Powered' that exhibits the same issue. Even my Dell laptop's palm rest has the same issue. It don't think it's a 'leak' from the AC source. It's probably the way the circuit in the wall adaptor is turning on and off 50 times per second or a capacitor being cycled at that frequency. I have the same issue even on my bench battery chargers and just about any DC equipment that has a metal body.

 

[tomb]

 

   
This gets more confusing all the time, unfortunately.  I feel like we've been turning circles in the desert.
 
So what does the Pro-Ject Phono Box connect into?  I assume you mean the powered speaker box, which pretty much negates all the conversation we've previously had.  pre-amp, amp, and speakers are all rolled up into that single device.
 
Just an FYI, but typical walwarts that convert AC to DC do not continue with the line ground to the component.  I am actually surprised that you reduced the buzz more by connecting a separate ground wire from the Phono Box to the line ground at the wall.  Typically, the grounds are separated in an AC to DC power supply because grounding the DC to the AC ground can often result in "infecting" the DC with your 50 Hz hum.  There are literally hundreds of thousands (millions?) of audio devices powered by a two-wire (positive and negative) separate DC power supply that do not result in line power grounding issues.
 
Honestly, after looking at the products you purchased and re-reading all of this thread (a couple of times), I think the key is in what you stated in your first post:
 
If the wall adapter is converting from AC to DC, this is impossible.  There should be nothing in the Pro-Ject Phono Box that would cause vibration at 50 Hz - it's all running on DC.  Even the worst AC/DC walwarts are not going to have more than a few tens of mV of AC hum or ripple - not enough to cause vibration in a DC-powered device that has no AC connection or AC transformer inside.  Either your wall adapter is bad or the Pro-Ject Phono Box is bad.

 
Tomb,
 
Thank you for your patience and attention. I really appreciate it.
 
Here's the Phono Box:
 
http://www.project-audio.com/main.php?prod=phonobox&cat=boxes&lang=en
 
It has a Phono connection as input and Line-Out as output. That's it. It sits between the turntable and the speaker system (Zeppelin Air)
 
>If the wall adapter is converting from AC to DC, this is impossible.
 
I'm sorry I have to disagree with this statement. I have many household devices that are 'DC Powered' that exhibits the same issue. Even my Dell laptop's palm rest has the same issue. It don't think it's a 'leak' from the AC source. It's probably the way the circuit in the wall adaptor is turning on and off 50 times per second or a capacitor being cycled at that frequency. I have the same issue even on my bench battery chargers and just about any DC equipment that has a metal body.

 
Then you line power is cr*p.  Sorry.  The days when everything you connected into the wall vibrated at 60 Hz are long gone in the US.  I have to conclude that your voltage is varying so much that any power adapter simply can't keep up and is injecting significant amounts of AC into the DC conversion.

 

[tomb]

I would still contact Pro-Ject and let them know of your problem.  Maybe you have the wrong adapter, maybe it's bad, etc.
 
I was going to suggest a linear-regulated wall adapter.  Jameco has some nice ones that are very cheap.  However, you would have to power them through a voltage convertor.  Plus, none of the Jameco ones are based on 18VDC output.  That's sort of an inconvenient, in-between voltage.  There are plenty of 24VDC adapters and plenty of 12VDC adapters, the ones at 18VDC are little more scarce.  Edpac is another name that makes linear-regulated adapters.  These would actually perform better and cost less than a bench power supply.

 

[cyclonite]

  I would still contact Pro-Ject and let them know of your problem.  Maybe you have the wrong adapter, maybe it's bad, etc.
 
I was going to suggest a linear-regulated wall adapter.  Jameco has some nice ones that are very cheap.  However, you would have to power them through a voltage convertor.  Plus, none of the Jameco ones are based on 18VDC output.  That's sort of an inconvenient, in-between voltage.  There are plenty of 24VDC adapters and plenty of 12VDC adapters, the ones at 18VDC are little more scarce.  Edpac is another name that makes linear-regulated adapters.  These would actually perform better and cost less than a bench power supply.

Hi,

Yes I have spent almost an entire day searching for 18v ones to no avail. To further complicate matters, I am not sure whether the Phono Box has a built in voltage regulator so I had to make sure the wall adaptor is regulated.
 
You've raised a good point about the AC line quality. I'll have to check that out one day.
 
I have now purchased a 24v unregulared DC adaptor. I will use this to power a Buck (step down) DC to DC converter that is designed for high end audio applications. I'll set the converter to output 18v DC. I hope that this will 'cut off' the Ac interference buzz. If it does, I'll package the whole thing nearly in a project box enclosure.
 
I'll probably give Pro-Ject a call in the new year as everything is still shut here in Britain.