Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems The new Clean Debate about Clean power supplies

dpaws,

Yes I float to avoid loops and it does sound better. I tried a few different grounding options before I settled on what I have now. After this topic came up on the switching supply, I opened up my 568.2 and found it had a transformer and no switching supply but I knew my 598 had a switcher. So I decided to isolate the AC connection of my 598 from my 568 to see if in fact the 598 was contributing to any noise with my 568 audio playback and found it did. My 568 is more laid back and has more depth. It sounds pretty darn good. Some music was a tad bright with sometimes hard to hear vocals. Like compressed rock music can sometimes sound. It was always good but I knew it could be better from higher end systems I had heard. I can hear the vocals much better now and the individual instruments in space on stage easier now that the 598 AC feed is isolated.

I also measured conducted emissions noise from the 598 and ran a harmonic current test on the power suppy. It's a typical switching supply. The line filter does a good job of attenuating the conducted emissions in the required range (150kHz - 30MHz) from getting out of the the 598 although I can still see it has a 100khz switching frequency. The line filter only worked well above 200kHz. Internally it probably has a lot of ripple. The supply does have a metal shield around it and there is a small board with small electrolytic caps to help smooth out ripple. M was not happy with the supply as sourced or else they wouldn't have added a small distribution board with extra caps. I didn't make any internal measurements yet. The harmonic currents are typical for switching supplies although it does pass the CE requirements. I have seen much better switching power supplies than what is in the 598. I live in the US so I ran the test at 60hz to evaluate what noise was injected into my own system. I can only believe that the harmonic current emissions and filter dumping the switching frequency to ground is poluting my 568. I still need to take measurements internally. The harmonic test runs out to the 40th harmonic of 60hz in this case or 2.4kHz. In Europe it would be the 40th of 50Hz or 2kHz. I measured current as high as 220mA on the 3rd harmonic. The 5th, 7th and 9th harmonic were above 100mA. The supply peak current while playing a disc was 1.9 amps. Again this was all at 120VAC. Perhaps lower harmonic currents would yield tighter bass?? My bass is tighter since I isolated the supply. I would suggest anyone with a 568 get a power regeneration system just for the 568 to keep out any AC noise from switching supplies. Give the transformer in the 568 nice clean power. It really sounds a lot better for me. Will the 598 sound better without the switching supply? Don't know yet. I bet it will. That line filter must be dumping RF current on to the chassis and the SPDIF connection uses that ground. The safety ground in the AC line cord has way too much inductance to damp RF current. I'm pretty sure there is some ripple on the chassis ground. More measurements needed eventually. I still need to add my SDI option so I will have it open again in a couple weeks.

Cheers,

Ron