Supra DC-trap, good results removing annoying dirt from power wall socket.

I own a Supra LAN that' about it, it' great but I also read on this forum and others these noise type suppressors do like wise to the sound, that' why I avoided them. Be interesting to hear some actual experiences.

I have a DC Offset filter,  I made it myself based on an established design/theory.   I expect the Supra DC blocker is the same type.

My filter has a positive improvement on SQ & does not cause a degradation of SQ.   I believe this is true of all DC filter of this design type.   

Naim does not recommend the mains noise suppressors or 'conditioners',  however these are not DC filters.   They invariably have C&D mode choke(s) & as such will include X&Y capacitors in shunt across L,N&E,  these X&Y caps are believed to have a negative effect on SQ.   

Hey guys.

It's a good thing there's NO filtering from these DC blockers, therefore they will not degrade audio quality. DC blockers play the audio transparent without coloring.

Regarding hum noize from power amp like my NAP150, is that a design flaw on all Naim power amps making these amps to hum on random hours day and night? Why did Naim make such a design and annoying flaw? Me hates hum! Amp should be quiet!

Where I live, there's no earthed wall outlets in my apartment building because it's almost a 60 year old house, only my kitchen have a ground outlet.       My Naim is connected to a non ground outlet, maybe this could cause the amp to hum when I don't use a DC blocker?          I will be very happy when I get my DC blocker.

Toroidal transformers hum.
Naim have used toroidal transformers in their equipment as they are one of the best transformers to use for the best possible audio sound quality.
It is not a design flaw. It's a by-product of using the toroidal transformer.
Turn up the music and you won't hear the hum.

blythe posted:

Toroidal transformers hum.
Naim have used toroidal transformers in their equipment as they are one of the best transformers to use for the best possible audio sound quality.
It is not a design flaw. It's a by-product of using the toroidal transformer.
Turn up the music and you won't hear the hum.

 

Not just Naim amps, many others, and the hum problem is common - but though sometimes can be loud enough to hear during quiet music passeges, it is when the music is not playing that it is annoying (if the amp is left on). The same physical amp can suffer differently in different locations, because the hum discussed by the OP is caused by DC offset in the electricity supply, which could be caused by other equipment in the user's house, or could be on the incoming mains, and can vary, from minute to minute or day by day, depending on the cause of the DC. The solution discussed by the OP, blocking DC, is one of two ways of eradicating it - the other is to track down and remove the cause(s) of the DC. 

I am unfamiliar with the particular solution, but if it stops teh hum and doesn't cause a deterioration in sound quality it must be good!

If my amp buzzed or hummed I'd ask for a refund.

Iconoclast posted:

If my amp buzzed or hummed I'd ask for a refund.

If it is the hum/buzz discussed in this thread, it is not the fault of the amp, but a symptom of bad electricity supply, though different individual transormers (e.g in  different individual examples of the same amp) may exhibit varying degeees of noise.

If I owned several amps, none of which buzzed/hummed, and then bought one that did I'd return it.

I had ground loop issues at one point that I found really irritating. I eventually got them sorted but it made me realize just how much I value pitch black silence from my gear.

thanks guys for clarifying the hum issues.

There is nothing wrong with my NAP150, the only issue I have is hum noise which is heard randomly. I still love my Naim stereo although it's approx 17 years old.

I used to have amps from H/K, Arcam and Rotel in the past, these amps never hummed, I let them be switched ON round the clock, never heard any hum. Must be different construction design between hifi brands.

There is another UK brand for DC-blocker named MCRU, is it a good high end product?

kowalski posted:

 

There is another UK brand for DC-blocker named MCRU, is it a good high end product?

I know MCRU & have bought parts from them, they sell a lot of diverse mostly cable related stuff,  incl DIY.  I have not seen their own DC filter,  it must be new,  also not seen any independent reviews so I can't say much.   My first reaction is it has no current rated, & judging by the size of the case I would be concerned.  My own design is rated at 1000VA  (4.17amps)  & I'm not sure I could fit my parts inside that case.   

Technical info on Supra website for their DC-blocker is 3.68 kw maximum power load. That's 3680 watts of power. There's plenty of juice to handle and still have lots of leftover for extra components.

Supra LoRad MD01-16-EU - DC Blocker for Mains AC

Now, Supra Cables has taken yet another step to minimize the impact from malicious elements like DC (Direct Current) superimposed on the mains AC (Alternating Current) in most modern households and industries!

DC voltage derives from a number of electrical appliances and will cause an offset on to you alternating mains power. This offset is the result of electrical consumers that do not equally load the AC positive and negative phase. In the ideal mains power supply there should be no DC-offset at all. Refer to figure below.

This DC offset limits the power supply efficiency in most multimedia and hifi equipment and causes transformers to saturate (the iron core). It increases iron core heat build-up and may even cause transformers to sound with a humming noise. Finally it may prolong life of the equipment by means of lowering the heat dissapation inside the device. The sonic impact is in most cases quite dramatic and again it will scale off audible sounds that do not come from the recording. You will listen to music, movies but not to your mains power irragularities.

Again Supra Cables is leading the way by offering a very efficient DC-blocker stopping DC up to 3.6 Volt making it future proof also for next generations of electrical consumers giving DC-offset. It is very easy to add-on to your existing power feed. It does not require protective ground to operate, but we strongly recommend it for a number of other reasons. Your equipment will sound much better and all other Supra mains power devices in the LoRad product range will work ideally.

Again Supra Cables have launched a product that in comparison costs a fraction. We do not spend on bling, just bang for the buck. Our No-Nonsense strategy means that almost all hifi enthusiasts will afford a Supra Cable Product, making exactly the same benign impact.

It is rated 16 Ampere and consequently allows for 3,680 Watt of power. The connection cord is optional and we recommend our Supra Lorad Mains Cord rated for 16 Ampere for optimal operation. Note that the DC-blocker input connector is rated 16 Ampere.

N.B. The filter will not dampen any dynamics. When the sound is much cleaner and tighter after the filter is connected, sometimes listeners perceive the dynamics to be reduced. When there is a difference in music and sound reproduction that will remove parts not really belonging to the source, this is a quite common reaction. On the contrary, bringing down the noice from the equipment will undoubtedly increase dynamics and often substantially reduce the duration of e.g. a bass pulse. Now it will most likely be possible to hear every tone in the bass range, also from each tuned drum skin.

Important! When connecting and disconnecting the Supra DC-filter, follow this procedure. Pull the mains cord connector from the wall socket. Wait until all power LEDs have went out from the stand-by position. Now you can connect the existing mains power cord to the filter, connect the optional mains power cord to the filter and finally connect it to the wall socket. When disconnecting, always start with wall socket and wait until all connected devices LEDs go out. By doing this you make sure that no electrical charge remains in any of the devices or in the DC-blocker.

Features and benefits

• Removes DC from AC mains - Silence noise floor substantially
• Tighter bass reproduction - Outstanding beat from drums, bass and percussion
• Reduces transformer hum - No irritating noise from the devices
• Reduces power supply heat dissapation - May prolong life span
• Filters up to 3.6 V_DC - Added capacity for future demands
• No dampened dynamics - Audible true dynamics
• Correct reference voltage - Substantially reduced harshness from DAC chips

Technical data

3680 Watts (AC power should be rated in VA not watts, but hey ho lets assume its the same).        3680/230 = 16 amps  .....  amazing it's the same rating as the IEC C19 plug/socket, & it seems the IEC plug is considered the maximum rating. 

Power rating DC blockers is not straightforward,  it has two major components,  capacitor bank & diode bridge.    The capacitors can carry current up to a saturation point where no more current can pass,  at that point power is shared with the diode bridge.   I rate my DC filter at 1000VA (4.17 amps @ UK 240v)  which is the maximum current the capacitor bank can handle,  if/when the capacitors are saturated they share the current with the 35 amp diode bridge.  However the filter assembly is connected with UK 13 amp plug/socket at both ends,  so using the Supra logic I should 'rate' the filter at 13 amps  x  240v (UK volts) =  3120VA (Watts)         

In the real world,  my filter will only 'overload' to share power with the diode if all my audio equipment units power up at the same time when the transformer in-rush is more than 4.17 amps.  However even with the system running at disco volume levels I have a in excess of 65% amperage reserve.

Most important thing is that a DC blocker can handle hifi units not cutting the power. My Naim gear is not that high on watts and power, I believe Supra DC blocker would handle my gear without problems?

Like Mike-B I have built a capacitor based 'DC blocker', and like Mike the components in mine would be too tight a fit in a case that size, even though I only rate mine at 3.5A.  Again like Mike I base my rating calculation on the maximum AC current it can deliver whilst still blocking the DC current.  The safe continuous overload current in my case is limited to 15A, but this extra capacity is only there to allow for switch on surge (it can actually handle a 50A switch on surge for about 50ms).

As Mike also points out the current rating for domestic items in the UK can't exceed 13A (equivalent to 3120VA nominal) due to the UK mains plug.  In the case of DC blockers however, this is the maximum continuous permitted safe overload current, not the maximum operating current at which it blocks any DC component (this value will be much lower).

did you buy your DC blocker as a do it yourself kit?

In Sweden we have 220V, maybe Supra rated their blocker a little lower in VA than an equivalent DC blocker sold in the UK?

No, not a kit, I did the design work from first principles.