[tomb]

This is up to the OP, but I think this thread got quickly off-track.
 
When faced with audio components, having the transformer outside of the audio device internals is always best.
 
That's because removing the noise from the AC-portion of the circuit is one of the primary goals in audio component design.  Put a transformer in the same box as the rest of the audio and you may forever find yourself trying to eliminate hum.  So why do people ever put the transformer into an audio cabinet?  Because, not every voltage and power rating is available as a ready-made wall adapter or separate power supply.  Also, for very involved audio devices, building a separate power supply can be a PITA for the end user.  I'm not saying that people don't do it - there are some very, very nice audio components available that use an entirely separate power supply cabinet.  However, it's still a hassle to the end user.  The umbilical is often specially-made, the secondary cabinet can be quite heavy and it simply becomes very inconvenient to place and house the equipment in a home environment.
 
In the case of smaller, lower-power devices, the DC voltage required may be readily available with a wall adapter.  Thus, it becomes a no-brainer to design the device to utilize such a device.  It would even be much more expensive and impractical to locate a transformer inside such a box as the Schiit Magni.
 
If different voltages are needed for the same device, or as stated earlier - the voltage and power ratings are not readily available in a cheap wall adapter, then the other option is locating the transformers inside the same cabinet.  In this case, placement and type of transformer can be very important, so as to minimize the potential for hum.  This can be successfully done with a good design however, and the result is a single, unified casework device with only an AC cord used to plug the device in.  The convenience is much better for the customer.  When you are considering DACs, very often multiple voltages are needed for many separate sections.  Separate wall adapters would be almost impossible and a separate custom power supply with umbilical also becomes impractical.
 
BTW, I'm not sure that the transformer type is really that important - assuming the hum is removed through proper placement - as long as the voltage and power rating is sufficient.  However, there's a lot more that goes into making an audio-quality power supply than just the transformer and its rectification.  You can still produce ripple or any number or distortion components if the power supply is not rigorous enough.

 

[ginetto61]

Hi and thanks a lot indeed for the very helpful advice.
I had this feeling that
 
Quote:

When faced with audio components, having the transformer outside of the audio device internals is always best.

 
and now i have an important confirmation. Thanks again because this for me it is a very important point. A design basis.
 
But still i wonder why in Schiit Audio they have decided to keep out only the voltage transformer and to feed the unit with AC.  I mean .... there must be a technical reason why they have not decided instead to go for a much more common DC external power supply (sadly i'd say because i have already at hand an excellent DC power supply that i could use i guess with nice outcome - 0.1mV of residual ripple).
 
Al the other headphone amps with separate power supply that i have are all DC powered ... all.
 
As i have bought now a Magni 2 (not the Uber version depicted at the beginning of the thread)  i would be even willing to mod the unit in order to make it to accept a DC power supply (i do not know if a single or dual is needed ... i have to look inside).
A good section mic cable would be excellent as umbilical.
Someone advised me once to keep diode bridge close to the transformer for instance, but i did not understand clearly why.
 
However .... if You had to choose what what would you do ? DC or AC external power supply ?
 
Anyway one thing is very clear to me ... the transformer out solution is very fine ... very.
I did some rudimental experiments with a DIY line pre ... fantastic. It is only important to put some uF close to the circuit but when the current draw is limited not a big issue at all.
But i had no scope to show graph or figures to sustain this opinion ... only my ear.
 
Thanks a lot again,  gino

 

[tomb]

There is no transformer to make DC voltage.  Transformers are AC to AC, period.  The question becomes what exactly is included in a DC wall adapter?  Often, not much - perhaps only rectifiers.  The result can be an un-regulated, noisy mess when it comes to audio.  Modern DC switching supplies are not much better.  They have a lot of high-frequency hash that can distort harmonically into the audio band.  Some people are starting to have good luck with them, but the gold standard is still a linear-regulated power supply conversion to DC.  There are very, very few wall adapters that have that capability.  Search Jameco.com for "linear-regulated power supplies" and you will find some, but they are very limited and Jameco are about the only ones.
 
Why is this?  Because the nature of linear-regulation is inherently very inefficient.  You essentially burn voltage through a regulator on a heat sink to gain perfectly quiet voltage regulation.  So, if you build a wall-adapter with linear-regulation, it's bigger, heavier, and has to have cooling vents.  That's not a very competitive product in the competition for the masses.
 
Thus, if you have an audio device that's relatively small - as in the Schiit Magni, you want to try to make it linear-regulated.   It makes little sense to include a giant transformer inside the case.  As a matter of fact, you would have to artificially increase the size of the case just to get some distance between the transformer and the rest of the circuit.  This is what it takes to prevent transformer 60Hz hum from infecting the DC portions of the circuit.
 
All of that means an AC walwart.  DC would be massively inefficient - you would be rectifying twice and anything inside of the DC walwart besides the transformer would be a waste of money.  You would always end up with less voltage than what you started with, too.  So, the logical choice is to put the DC power supply on the PCB and then feed the whole thing with an AC walwart.  There is no additional transformer inside the Magni.
 
What you're really asking about are design considerations.  What kind of device does one contemplate, what are the power requirements, and what is available on the open market?  You try to answer all of these questions in the process of design.  As I said, for little components, you would have to make them un-necessarily big to get some distance between the transformer and the DC part of the circuit.  At the same time, smaller components often have lower power needs.  Both facts combine to an easy decision for using a wall adapter.  A larger amp, a very sophisticated DAC, or a tube amp with needs for both high-voltage and low-voltage supplies may need a special transformer.  Sometimes those go in the box, sometimes they don't - all design considerations in making a product. 

 

[mcandmar]

Old school lump of iron DC supplies are now outlawed in Europe thanks to some bureaucratic BS about energy efficiency, hence all you can buy these days is switching supplies.
 
I suspect Schiit went with an AC adapter so they can design/control the power supply without having to source expensive DC adapters that they cant sell all over the world.  I also suspect they are taking the AC input and half rectifying it into + and - supply rails feeding into + and - voltage regulators to give a nice quiet dual voltage supply to drive the opamps.  Try doing that with an external wall wart

 
Honestly, i dont think there is anything to be gained by just switching the transformer, the internal power supply of the amp is far more important.

 

[ginetto61]

 
Quote:

  There is no transformer to make DC voltage.  Transformers are AC to AC, period. 

 
Hi ! thanks a lot for the very valuable reply and please let me explain better my situation.
First i would like to add that in the meantime i have purchased a nice Magni 2 headphone amp and waiting to receive it.
I have this doubt ... i see many units with an external power supply.
The vast majority of them comes with an external  DC power adapter.
Instead the Magni for instance comes with an AC transformer.
So i was wondering why. 
I was a little sad because i have already a very good external lab grade DC power supply that i could use.
This is the situation.

The question becomes what exactly is included in a DC wall adapter? Often, not much - perhaps only rectifiers. The result can be an un-regulated, noisy mess when it comes to audio.
Modern DC switching supplies are not much better. They have a lot of high-frequency hash that can distort harmonically into the audio band. Some people are starting to have good luck with them, but the gold standard is still a linear-regulated power supply conversion to DC. There are very, very few wall adapters that have that capability. Search Jameco.com for "linear-regulated power supplies" and you will find some, but they are very limited and Jameco are about the only ones.
Why is this? Because the nature of linear-regulation is inherently very inefficient. You essentially burn voltage through a regulator on a heat sink to gain perfectly quiet voltage regulation. So, if you build a wall-adapter with linear-regulation, it's bigger, heavier, and has to have cooling vents. That's not a very competitive product in the competition for the masses.

 
Thanks a lot for the very valuable advice.
I understand that the quality of common DC adapter is usually very low.  Good to know.
Actually i guessed that and in case i would use a better quality DC linear power supply
 

Thus, if you have an audio device that's relatively small - as in the Schiit Magni, you want to try to make it linear-regulated. It makes little sense to include a giant transformer inside the case. As a matter of fact, you would have to artificially increase the size of the case just to get some distance between the transformer and the rest of the circuit. This is what it takes to prevent transformer 60Hz hum from infecting the DC portions of the circuit.
All of that means an AC walwart. DC would be massively inefficient - you would be rectifying twice and anything inside of the DC walwart besides the transformer would be a waste of money. You would always end up with less voltage than what you started with, too. So, the logical choice is to put the DC power supply on the PCB and then feed the whole thing with an AC walwart. There is no additional transformer inside the Magni.  

Yes !  i will do that  Replacing the small original transformer with a much better one.  I am sure that it could be benficial
Then i will also look at the internal ps caps ... they seem quite normal ... i will replace them with something really good.  Caps are another of my obsessions
 

What you're really asking about are design considerations. What kind of device does one contemplate, what are the power requirements, and what is available on the open market? 

Exactly

 i would like to understand, as i have asked at the beginning, if the external DC approach is better than the Schiit AC approach.   Both of high quality of course.
Someone advised me that diode bridges, for instance should stay as close as possible to the transformer.   The Schiit design shows that is not the case ... that the rectifying diodes can be placed far away from the transformer without any particular issue. This is extremely important for me to understand.  If the two approaches can be equally very good.
 

You try to answer all of these questions in the process of design. As I said, for little components, you would have to make them un-necessarily big to get some distance between the transformer and the DC part of the circuit. At the same time, smaller components often have lower power needs. Both facts combine to an easy decision for using a wall adapter. A larger amp, a very sophisticated DAC, or a tube amp with needs for both high-voltage and low-voltage supplies may need a special transformer.
Sometimes those go in the box, sometimes they don't - all design considerations in making a product.

Thanks a lot again.  Given that i read some experiences of transformer buzzing with the Magni  (the stock transformer must be necessarily cheap given the total price of the unit) i will only use a better transformer.
As i see 16 VAC are needed, i wonder if a series of two secondaries of 8VAC could work. Is it ok to use the secondaries in series to power this unit ?
 
http://schiit.com/public/upload/general/magni%202%20rr%201000.jpg
 
Thanks a lot again,   gino

 

[tomb]

Hi ! thanks a lot for the very valuable reply and please let me explain better my situation.
First i would like to add that in the meantime i have purchased a nice Magni 2 headphone amp and waiting to receive it.
I have this doubt ... i see many units with an external power supply.
The vast majority of them comes with an external  DC power adapter.
Instead the Magni for instance comes with an AC transformer.
So i was wondering why. 
I was a little sad because i have already a very good external lab grade DC power supply that i could use.
This is the situation.

Lab-grade DC power supplies do not mean that they're audiophile grade.  Regardless, as you surmised from the other posts, the real "guts" of the Magni's power supply is on the Magni PCB, not in the wall adapter.
 

Thanks a lot for the very valuable advice.
I understand that the quality of common DC adapter is usually very low.  Good to know.
Actually i guessed that and in case i would use a better quality DC linear power supply

 
There's no guarantee that your lab-grade power supply is linear ... in fact, probably not.
 

Yes !  i will do that (get some distance between the transformer and the rest of the circuit). Replacing the small original transformer with a much better one.  I am sure that it could be benficial
Then i will also look at the internal ps caps ... they seem quite normal ... i will replace them with something really good.  Caps are another of my obsessions

 
Replacing the transformer is not going to do anything, especially about getting more distance between the transformer and the rest of the circuit.
 
Let me make myself clearer: the transformer steel has nothing to do with causing noise in the amplification circuit.  It's the AC current.  Once the AC current is rectified to DC, the quality of the transformer means nothing.  The only concerns with power transformer steel and winding are whether it can develop the rated power without over-heating or whether the steel/windings are poor enough so that it buzzes in a close enough proximity to irritate your listening experience.  It's true that the AC and magnetic flux is much more powerful at the transformer.  In addition, the transformer itself can pick up a lot of noise/interference if there are other devices in its proximity.  Nevertheless, it's the AC current that causes the hum in an amplifier circuit by "infecting" the DC portions of the circuit.  Carrying the analogy further, you can keep from being "infected" by two methods: staying away from the pathogen itself (distance) or creating some sort of barrier (robust, clean regulation).  In a carefully designed power supply, you often do both to be completely certain the AC current has been eradicated.
 
Replacing power-type capacitors have very little impact on the sound quality.  In most cases, it's the quality of the power circuit and regulation itself.  I seriously doubt it will make any difference that will be audible in the case of the Magni.
 

Exactly 

 i would like to understand, as i have asked at the beginning, if the external DC approach is better than the Schiit AC approach.   Both of high quality of course.
Someone advised me that diode bridges, for instance should stay as close as possible to the transformer.   The Schiit design shows that is not the case ... that the rectifying diodes can be placed far away from the transformer without any particular issue. This is extremely important for me to understand.  If the two approaches can be equally very good.

 
As I've tried to explain, it's not an either/or function.  It depends on the product design and its goals.  In the case of the Magni, the qoals were quality sound and low expense.  If you arrive at a design that can use readily available AC adapters (24VAC and below), then it makes the best sense:

• You don't need to purchase a specially-designed transformer (expensive).
• You don't need to worry about where and how to locate the transformer to reduce the AC current infection due to proximity. (expensive design/prototyping process)
• You don't need to worry about the quality of an off-the-shelf DC wall adapter because you've included those items on your PCB's design. (better quality)

 
I suspect that all of these goals were met with the Magni.  There may have been other goals of which we're not aware.  Note that two out of the three goals I suggested above are cost.  If your goals tended toward absolute audiophile quality, then the AC wall adapter scenario may no longer apply.  (Most likely it will not in all cases.)  For instance, if you wanted to build a tube amp, swing more voltage, or include a much more elaborate circuit, then these considerations will not apply because you need more voltage than the 24VAC adapter will provide.
 
One thing that makes the AC adapter market so cheap in the US is that there are many sub-industries that are legally allowed to run wiring, electrical components, etc., without electrical licensing requirements.  The residential and commercial security and building controls industries work this way.  They are allowed to run up to a maximum of 24VAC without electrical licensing requirements.  This means there's a ready-made market for AC wall adapters/transformers in the US that makes them cheap, powerful, and easy to obtain.  It's another factor to consider if your design goals are low cost.
 
The only reason someone is saying the diode bridges need to be close to the transformer is to limit the length of the AC current traces, to reduce the hum infection into the DC circuit.  That's only in the case of a transformer located in the same enclosure or on the same PCB as the amplifier circuit.  As mentioned, it's the AC current that causes the "infection."  Anything before the rectifiers (diode bridges) is AC.  So, you want to minimize those lengths or paths carrying the AC current if it's in the proximity of the amplifier circuit.  In the case of the Magni or any other design using a separate AC power adapter, the rectifiers are located at the entrance of the AC connection to the case or PCB.  The wiring carrying the AC current from the wall adapter to the amp is of no consequence unless you put the wall adapter so close to the amplifier that it ends up picking up noise from the transformer directly.
 

Thanks a lot again.  Given that i read some experiences of transformer buzzing with the Magni  (the stock transformer must be necessarily cheap given the total price of the unit) i will only use a better transformer.
As i see 16 VAC are needed, i wonder if a series of two secondaries of 8VAC could work. Is it ok to use the secondaries in series to power this unit ?
 
http://schiit.com/public/upload/general/magni%202%20rr%201000.jpg

 
Buzzing with the Magni transformer is not going to have any effect unless you are close enough to it that it bothers your listening experience.  I need to impress upon you the futility of replacing the transformer.  You're trying to gold-plate a CMoy with little or no effect.
 
Yes, you can use two secondaries and combine them to a greater voltage.  I don't know why you would want to do that, though, because the usual reasons are 1) you need the lower voltage at the same time you need the higher voltage (you don't in this case), or 2) you are trying to use an 8VAC transformer to save cost. (unlikely cost savings in this instance).
 
Anyway, all of this discussion is sort of moot with what you're trying to do.  I'm just trying to be nice by explaining some of the principles.  Buy a better amp if you are this concerned.

 

[ginetto61]

Lab-grade DC power supplies do not mean that they're audiophile grade.  Regardless, as you surmised from the other posts, the real "guts" of the Magni's power supply is on the Magni PCB, not in the wall adapter.
There's no guarantee that your lab-grade power supply is linear ... in fact, probably not.  

 
Hi and thanks again for the kind patience and very valuable advice.
The fact that the Magni has a AC socket has made the idea to use the lab-grade DC PS a no option. By the way it is this one here:
 
http://www.komteh.hr/download/radio/mascot/acdc/719.pdf
 

 
 
they say linear and regulated.  But it is useless with the Magni. Of course. 
 
 

Replacing the transformer is not going to do anything, especially about getting more distance between the transformer and the rest of the circuit.
Let me make myself clearer: the transformer steel has nothing to do with causing noise in the amplification circuit.  It's the AC current.  Once the AC current is rectified to DC, the quality of the transformer means nothing.  
The only concerns with power transformer steel and winding are whether it can develop the rated power without over-heating or whether the steel/windings are poor enough so that it buzzes in a close enough proximity to irritate your listening experience.  It's true that the AC and magnetic flux is much more powerful at the transformer.  
In addition, the transformer itself can pick up a lot of noise/interference if there are other devices in its proximity.  
Nevertheless, it's the AC current that causes the hum in an amplifier circuit by "infecting" the DC portions of the circuit.  Carrying the analogy further, you can keep from being "infected" by two methods: staying away from the pathogen itself (distance) or creating some sort of barrier (robust, clean regulation).  In a carefully designed power supply, you often do both to be completely certain the AC current has been eradicated.

 
Thanks for the very important advice. But then if AC is what can cause noise and so on, it makes sense to me using a high quality external power supply rather than arrive with AC voltage at the amplifying unit.
I understand that most of stock DC power supply are cheap SMPS and so noisy.  I mean, the concept of a DC power supply is the best, but well executed only on expensive units ?
This again for me it is very important to understand, because if the circuit is supplied with dual voltage i could even provide the amp box with dual DC voltage high regulated bypassing the diode bridge inside the unit.
This would give even a more clean supply and make the work for the internal regulators easier. 
I do not know by the way the PSRR of the Magni circuit ... if it is very high maybe the improvements will not be very big. 
 

Replacing power-type capacitors have very little impact on the sound quality.  In most cases, it's the quality of the power circuit and regulation itself.  I seriously doubt it will make any difference that will be audible in the case of the Magni.
As I've tried to explain, it's not an either/or function.  It depends on the product design and its goals.  In the case of the Magni, the qoals were quality sound and low expense.  
If you arrive at a design that can use readily available AC adapters (24VAC and below),  then it makes the best sense:

• You don't need to purchase a specially-designed transformer (expensive).
• You don't need to worry about where and how to locate the transformer to reduce the AC current infection due to proximity. (expensive design/prototyping process)
• You don't need to worry about the quality of an off-the-shelf DC wall adapter because you've included those items on your PCB's design. (better quality)

 
Sorry, do you mean that the Magni could be operated with an AC voltage up to 24 V ???  this is very interesting because i have already a very good quality transformer 12-0-12 that i could use. 
I see 16VAC on the power socket ... is not 24V too much ?  

I suspect that all of these goals were met with the Magni.  There may have been other goals of which we're not aware.  Note that two out of the three goals I suggested above are cost.  
If your goals tended toward absolute audiophile quality, then the AC wall adapter scenario may no longer apply.  (Most likely it will not in all cases.)  

 
well i cannot pretend to have a high end sound from this little and very cheap box ... it is a miracle but up to a point if not it would revolutionize the market completely.
I just would like to get the most possible out of it and stop.  Put it in the best working conditions. 
 

For instance, if you wanted to build a tube amp, swing more voltage, or include a much more elaborate circuit, then these considerations will not apply because you need more voltage than the 24VAC adapter will provide.

 
I have only two commandments in my religion:
1) never use tubes
2) never use analog, LP or tapes ... never.
 

One thing that makes the AC adapter market so cheap in the US is that there are many sub-industries that are legally allowed to run wiring, electrical components, etc., without electrical licensing requirements.  The residential and commercial security and building controls industries work this way.  They are allowed to run up to a maximum of 24VAC without electrical licensing requirements.  This means there's a ready-made market for AC wall adapters/transformers in the US that makes them cheap, powerful, and easy to obtain.  It's another factor to consider if your design goals are low cost.

 
Thanks for the info. But again .... do you think that a 24 VAC adapter would do fine with the Magni ? that would increase the options. 24V are much more common voltage. 
 

The only reason someone is saying the diode bridges need to be close to the transformer is to limit the length of the AC current traces, to reduce the hum infection into the DC circuit.  That's only in the case of a transformer located in the same enclosure or on the same PCB as the amplifier circuit.  As mentioned, it's the AC current that causes the "infection."  Anything before the rectifiers (diode bridges) is AC.  
So, you want to minimize those lengths or paths carrying the AC current if it's in the proximity of the amplifier circuit.  In the case of the Magni or any other design using a separate AC power adapter, the rectifiers are located at the entrance of the AC connection to the case or PCB.  The wiring carrying the AC current from the wall adapter to the amp is of no consequence unless you put the wall adapter so close to the amplifier that it ends up picking up noise from the transformer directly.

 
Perfect ! i think i have understood a very important thing.  To minimize the AC length inside the amp box.   This is a very important design requirements that i print in my mind. 
 

Buzzing with the Magni transformer is not going to have any effect unless you are close enough to it that it bothers your listening experience.  
I need to impress upon you the futility of replacing the transformer.  You're trying to gold-plate a CMoy with little or no effect.
Yes, you can use two secondaries and combine them to a greater voltage.  I don't know why you would want to do that, though, because the usual reasons are
1) you need the lower voltage at the same time you need the higher voltage (you don't in this case), or
2) you are trying to use an 8VAC transformer to save cost. (unlikely cost savings in this instance).

the main reason is that it seems that 16VAC is a not very common value.   The most common are 12 and 24.
Then i see 8+8, 10+10, 12+12 .... 
So the idea is to use 8+8 = 16 VAC.
But if you are positive with the info that the Magni can be powered with up to 24VAC  

  that increase the options immensely.  There is a huge number of possible transformers able to provide that voltage.
That would be nice.  

Anyway, all of this discussion is sort of moot with what you're trying to do.  I'm just trying to be nice by explaining some of the principles.  Buy a better amp if you are this concerned.

 

I really wonder what would be a clear step above the Magni and how much would it cost.
300 USD ? to get a clearly better and maybe for me definitive sound ?  
I am not into tube ... hybrid at maximum.
Thanks a lot again.
Regards,  gino  

 

[tomb]

Hi and thanks again for the kind patience and very valuable advice.
The fact that the Magni has a AC socket has made the idea to use the lab-grade DC PS a no option. By the way it is this one here:
 
http://www.komteh.hr/download/radio/mascot/acdc/719.pdf 

 
0.3mV ripple is not a great audiophile standard.  It's OK, but far from what you can achieve by building even cheap audio-specific power supplies.
 
This is going to be my last post, because honestly - you need to study a lot more before you start hacking up power supplies and amps.  There are things you state and conclusions you draw that are just incorrect and I can't explain everything to you.
 
For example, there is no "AC socket" on the back of the Magni.  There is only a standard wall adapter power jack.  The implication of an "AC socket" would mean there's an IEC inlet on the back and that you could connect a standard power cord from it to the wall.  Nothing of the sort is going on with the Magni.
 

Thanks for the very important advice. But then if AC is what can cause noise and so on, it makes sense to me using a high quality external power supply rather than arrive with AC voltage at the amplifying unit.
I understand that most of stock DC power supply are cheap SMPS and so noisy.  I mean, the concept of a DC power supply is the best, but well executed only on expensive units ?
This again for me it is very important to understand, because if the circuit is supplied with dual voltage i could even provide the amp box with dual DC voltage high regulated bypassing the diode bridge inside the unit.
This would give even a more clean supply and make the work for the internal regulators easier. 
I do not know by the way the PSRR of the Magni circuit ... if it is very high maybe the improvements will not be very big. 

 
You're drawing the wrong conclusions.  A power supply can be inside the amp or outside, it can be fed with AC directly or from a wall adapter.  The transformer can be inside the case, outside, or in a wall adapter.  For that matter, you can build an external power supply as a wall adapter.  I've done it on a number of occasions.  The key is whether the power supply is designed correctly.  As for the other factors, it has to do with the factors I mentioned before: cost, performance relative to cost, convenience, etc.
 
You asked early on what were the reasons for why the Magni is powered the way it is.  I gave them to you.  For another amp, those reasons may not work out.  It's that simple.  Don't draw conclusions that aren't valid.  You have no idea how the Magni is powered on the PCB.  I could probably tell by following the PCB traces and the components, but a schematic would be best.  The point is, just what are you going to do to improve an already optimized $100 amp?
 
This is pointless and most of your conclusions and strategy will outright destroy the amp.
 

Sorry, do you mean that the Magni could be operated with an AC voltage up to 24 V ???  this is very interesting because i have already a very good quality transformer 12-0-12 that i could use. 
I see 16VAC on the power socket ... is not 24V too much ? 

 
No, no, no.  I said "24VAC and BELOW."  I was speaking in the general sense, only - not specific to the Magni.  Schiit has applied the recommended voltage rating with the adapter they include.  Further, they label it on the input jack.  That means don't go over it, period.*  Again, I can't explain all of the physical laws governing power, AC, and DC voltage to you - I don't have that much time or capability to type.  Suffice to say that rectification of 24VAC can yield up to 35VDC.  Rectification of the Magni power supply at 16VAC can yield over 22VDC.
 
* Why is this important?  Because there are real limits to the capacitors' voltage ratings, opamps and transistors.  For instance, very few opamps used in audio are going to have voltage capability beyond 24VDC.  Some go up to 30, but as you can see from the above, a 24VAC recitified supply will put out more than that.  Now, one often regulates that voltage down to some lower amount, but every bit you lower is rejected in heat through the regulator and its heat sink.  This in turn will require increased cooling of the amp and the power adapter will have to be rated for higher power.  It's a shame, because all that extra would be wasted through the heat sink.  The amp isn't going to use it.  So, there are motivations for specifying a voltage limit on the supply - both once the amp is built and even back when it's being designed.
 

well i cannot pretend to have a high end sound from this little and very cheap box ... it is a miracle but up to a point if not it would revolutionize the market completely.
I just would like to get the most possible out of it and stop.  Put it in the best working conditions.

 
It's not a miracle.  Schiit as a company might be referred to as a miracle, but the Magni is simply an inexpensive, reasonably performing solid-state amp that's value-priced.  Would you really like to get the most possible out of it?  Then follow their recommendations and stop.
 

I have only two commandments in my religion:
1) never use tubes
2) never use analog, LP or tapes ... never.

 
No offense, but your religion is based on ignorance. 
 

Thanks for the info. But again .... do you think that a 24 VAC adapter would do fine with the Magni ? that would increase the options. 24V are much more common voltage.  

 
I said no - use what they recommend or be prepared to blow it up.
 

 Perfect ! i think i have understood a very important thing.  To minimize the AC length inside the amp box.   This is a very important design requirements that i print in my mind. 

 
Yes, but I already explained to you: the connection is made immediately to the PCB inside the Magni.  The rectifiers are immediately after that connection.  There is no "AC length" to reduce, because they have designed it correctly.  If they hadn't then hundreds/thousands of customers would be complaining about hum in the Magni.  I was talking about the general method of designing something from scratch - just as they have done when they made the Magni.
 

the main reason is that it seems that 16VAC is a not very common value.   The most common are 12 and 24.
Then i see 8+8, 10+10, 12+12 .... 
So the idea is to use 8+8 = 16 VAC.
But if you are positive with the info that the Magni can be powered with up to 24VAC  

  that increase the options immensely.  There is a huge number of possible transformers able to provide that voltage.
That would be nice.

 
Just my guess, but if you look back up at my statements on voltages achieved through regulation, I would bet they picked 16VAC as the closest they could get to 24VDC once rectified on their PCB, with a margin of safety factor.  Just an FYI, but I imagine Schiit is big enough that they could simply contract an order for a few thousand wall adapters from China at that 16VAC.
 
No, the idea is not to use 8+8.
 
I never, ever said you could power the Magni with 24VAC.  (I'm thinking maybe I should have at this point. 

)
 

I really wonder what would be a clear step above the Magni and how much would it cost.
300 USD ? to get a clearly better and maybe for me definitive sound ?  
I am not into tube ... hybrid at maximum.
Thanks a lot again.
Regards,  gino 

 
Sorry, but it sounds like your "religion" would not allow you to hear a better amp even if you found one.
 
That's it for me.  Good luck.

 

[JohnDriks]

Yes you are right using the transformers inside do not create any kind of much interference noise to the audio amplifiers. Using them outside make them to bulky and also it become too complicated to handle them. Also the noise affects through the wires. In the case of AC you must have to take care of the noise.
 
pcb price

 

[ginetto61]

Hi !  thanks for the valuable advice.
More or less on topic i notice a problem.
I am using now a Magni 2 with external AC adapter ...  

When i switch it on i see a strong disturb in the image on the tv (the amp is connected to the TV out rcas on the back and the AC adapter is on the same power strip of the TV power cable).
Is this a sign of a bad AC adapter ?
The disturb is very strong at the point that i leave it on always and use the breaker on the power strip.
 
Instead i like a lot the sound of the Magni 2 ... it is a very good amp
I am using a Beyerdynamic dt880 (600 ohm)
Anyone knows where i can find a list of the mods performed in the Uber version ? to understand the weak spots in the basic version
Thanks and regards, gino