Long Term AC Power conditioning observations

[One and a half]

Many moons ago, a Topaz 2000VA transformer was used to power everything, particularly contributing to the now long thread 'Discussion of AC mains isolation transformers'.  The whole music system was moved vertically down the house some 3m, life got in the way, and the music system remained dormant and packed up for at least a year.

Over the latter half of 2023, the music system was restored to the new location, and the sound did bother me.

 

With discussions at WBF, on deciding the best course of action for dedicated lines and transformers, even 15kVA UPS, the consensus was that isolation transformers had to massively oversized to avoid the music being strangled, with the exception of Torus and Equitech transformers. In Aug 2023, I conducted an experiment between the Topaz and Equitech as tandem, Equitech on its own. The Topaz has its own circuit at the switchboard, the equitech was plugged into an outlet via  long extension lead direct at the main switchboard.

 

The results are on the enclosed paper For a balanced AC power to be effective, the voltages between the centre earth point and either high and low ends (X1, X2) terminals need to be the same. The Topaz with cabling could not match the Equitech as far as balance went, always 100mV out. The Equitech managed a very close voltage under any sort of load, I could not see any difference on the X!, X2, terminals. This experiment used an extension lead which is not the greatest and would not recommend it for a permanent cable, this would be 6mm / 10AWG or greater, but it illustrated the point. 

 

As long as the audio system sees a low impedance to the street is the main criteria, no isolation transformers like the Topaz will work effectively and won't provide the best sound. I used the Topaz since the Equitech on light loads would emit a hum. With music playing inaudible, at switch on always there. Using the scenario A removed that hum, since it provides an impedance for pulsed currents, and that was fine, at the expense of SQ.

 

For now, the Equitech is plugged into the wall, until I can find a good cabling system. There's plans to make network changes, removing the CAT5e and replacing with CAT6 for 10gbe cable system, so will install this at the same time as the AC power cable. The sound was still not quite right streaming from the Lumin to the DAC.

The chain Lumin -> Nordost Blue Heaven USB->  ifi Micro USB 3 (Acopian Linear PSU) -> Acoustic Revive USB split cable - > DAC was used same as before when the music system was upstairs. The main change was removing the Topaz and adding the Equitech....Hmm. Tried simple method first, less is more, Lumin -> Acoustic Revive USB split cable -> DAC. Wow, talk about night and day, SQ just opened up with the Nordost and the ifi removed from the chain. So the AC power made a significant impression on what was heard, the added components just messed with the SQ.

 

A few months back, the Accuphase P-4200 went dead, no lights, nothing. While this was repaired, I bought the Electrocompaniet AW250R power amp and this worked very well. I did miss the VU meters on the Accuphase when it returned, the pass through XLR from the AW250R was used, since there were no speakers connected to the Accuphase, it was plugged into an ancient Monster AV power conditioner HDP-900G+. Lived with that for a while, and tried bi-amping. The amp's characteristics are never the same, but the speakers can be tri-amped, so why not give it a shot. Nahh, the SQ wasn't that good, but managed to tweak the level down -3db so the highs matched the bass by ear.

 

Recalling the drama with the Topaz and many people just plugging amps into the wall, why not connect the Accuphase to the Equitech as before. For this purpose a box with two Furutech outlets was fashioned with 10 AWG SPC Teflon power cables, to run the AC Power Accuphase with the AW250R. Bellissimo! Coherent sound, no wandering, everything tightened up nicely and it runs loud, especially after tightening the drivers!

 

Sometimes tweaking and modifications are very quick and results are easily heard, but some take a long time to review and establish the cause, this is one of those!

 

Monster Power conditioner HDP-900G+ (only useful for IT gear)

 

 

Pass through XLR connection (Link) on AW250R

 

 

 

 

DOC_08272023_0001.pdf

[Speedskater]

Almost no audio components take advantage of a balanced AC supply.  Because power transformers are wound a asymmetrically with relationship to the component's chassis.   In fact many well designed components take care to correctly connect their power transformer.

[One and a half]

Yes, that’s your opinion, my ears tell it differently, have to agree to disagree.

[Speedskater]

More likely the audible differences are due to a combination of the following:

1] AC power wired as a "Separately Derived System"

2] very low impedance 'Safety Ground/Protective Earth' circuit.

3] Isolation from noise currents in other circuits.

4] and maybe reduced Bill Whitlock "Conduit Transformer" effect noise.