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

Hahaha! Good one Frank!

I think the 598 has the same switching supply as the G68.

My comments were speculation of course regarding the ferrites. However I did hear a bigger difference when I powered the 598 separate from the 568.

So my next experiment will be to run some EMI tests on the 598. I didn't get a chance to work on the 598 this past weekend.

The internal ferrites would help attenuate supply noise from the digital board from contaminating the analog section if there is noise there. High frequency RF noise only. M had run the two power lines parallel to each other. So I placed beads on both lines separately right near the analog and digital boards. Separated the power lines a little more too.

I suppose I could open up the 568 again and take some measurements to see if there is substantial noise conducted on those lines. I figured the extra ferrites on the AC lines would attenuate outside ambient noise like radio stations.

Keep in mined I had pulled off some ribbon cables between the analog board and digital board to install one of the ferrites and it could be I cleaned some pin connections by resetting the connectors. So the internal ferrites might not have done a thing. I'll admit to that. Powering the 598 separately was very noticable. Vocals are way more palpable. Something I never heard in my system before so it was a major change for me.

I can run some EMI tests this week at work on my 598. Maybe it will shed some light in that switching supply.

Ron

Ron,

On your 568, might want to try removing the ferrite beads and installing two Auricaps .47UF at least 600V (could also get 1500V). If it were me I would also add a 3rd Auricap .1UF 1500V. The caps are placed across line & neutral right at the IEC. This is the famous Auricap tweak. Red lead to line & black lead to neutral. I have used it manytimes on various components and always loved the result.

Could also install two large Bybee's (large size Bybee) (in addition to the Auricaps), one on the line leg and one on the neutral leg, just behind the IEC.

You can get the Auricaps quickly & easily from Sonic Craft. http://www.soniccraft.com/auricap.htm

The Bybees you can get from Parts Connexion: http://www.partsconnexion.com/catalog/accessories.html

Finally, If you have some ERS cloth (if not can get it from Parts Connexion on Bybee page - see ERS tab) I like to install some smaller size pieces around the power supply. Installs easily with hot glue.

All of the above is also in my G68. I have no affiliation with the above companies - just a happy customer.

Will be interesting to see what power Supply is in your 598.

I may take Anthony up on his offer to try out his power supply for my G68, and pay to keep it if I so choose. Will report my results.

Cool! Let us know when you do.

My major hesitation is whether I'd want to spend $600 on something I may well be getting rid of in a year or two if new formats take hold.

Yeah but it might be a lot better sounding. Still haven't had a chance to test my 598. Stay tuned!

Ron

Hope springs eternal for the obsessed. I'll probably do it.

A little birdie whispered in my ear that 3 more Aberdeen power supplies went out to Meridian owners.

Lets hear about the results!

Good to find a real debate on the forum - for me a welcome change from the 6k vs 7k... Shame on whoever removed the original debate.

I've been wondering about the switchmodes for a while - and a little knowledge is such a dangerous thing...

My listening experience leads me to think that a linear / Jung supperreg'd power supply is a must for analogue sections, with low impedance / ultrafast slew rates and unconditioned power from the wall all theoretically leading to buckets full of PRAT.

If you're a DSP user then you have no analogue sections to worry about in the G series gear but as I use M33's it may be worth me digging a little deeper.

For digital only units like my G98DH I can see little point in upgrading / changing the stock switchmode. In fairness, it's not any old supply, its ultralow noise made to medical specs etc Good idea to use LC filtering "power condition" here insode the unit ie after the cable but any resulting jitter from the PSU is FIFO'd in my G68J so I can sleep easy.. Only an A/B dem would convince me to part with the hard earned.

Meanwhile, back to the G68J.. Help! Has anyone dug deep enough insode to discover what DAC's & opamps the I/V analogue side of the DAC consists of? Ie are we using the +/-12v here or is that just for the display/control?

Say the analogue side uses only the +5V then could I exchange the switchmode for one with a higher voltage output, using the switchmode as a prereg and then feed into superregs to get my regulated 5v again?

This way I guess the order of powering up etc would remain the same and I don't have to wory about toroid eddy currents etc from a fully linear supply.

I only wish they hadn't left so much room inside the G series gear for such things to be possible!

Other points

First - A clean, dedicated earth makes a huge huge difference. See the Russ Andrews piece on mains power - it really does work and costs so little for some earth wire and a copper rod to stick in the lawn - I think Screwfix do a kit for a couple of quid.

Secondly - Trust your ears, as Nick has found with his mains cables. If you can't measure a difference that you can hear then you're simply measuring the wrong thing.

For the doubters out there, visit Signals in Ipswich. Ian will gladly do a blind A/B with your own mains cable and Nordost Valhalla (�2K!) on his �24K Naim / Neat system. Just leave your cheque book at home, you have been warned....

While I remember - Ron, you mentioned that you float the safety earth in the sources but ground the amps - I assume this to avoid loops?

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

Hi Dpaws,

I believe they're AD1852. (PSRR -60dB @ 1kHz, -50dB @ 20kHz FWIW).

http://www.analog.com/UploadedFiles/Data_Sheets/536821559AD1852_0.pdf

Don't know about the op-amps - sorry.

Cheers,

Mark.

PS: Ron - that's great data. I can see your point on emissions affecting other gear, but I'd be really interested in seeing your measurements for the internal supplies at the analogue components when you've done them. Clear skies!

I find taking a shower and using soap, which chemically attaches to oils, dirt and water really does help. The cleaner I am, the cleaner I find the sound to be. Some people say this is a psychotropic effect, but I don't care as soap is relatively inexpensive.

In all seriousness, Ive found that here where I live (Westchester, NY), that I put in a dedicated power supply to the room, isolation transformer, industrial surge protector that does not restrict current, dedicated lines for each speaker and separate circuits for audio and video equipment and a Radio Shack surge protector that has a video in and out to break any cable tv ground loops, and thats it. I tried power conditioners, etc, with no noticeable changes, but I would not doubt that these can help others who may not have had the ability to take care of the basics like I have. Still don't believe cables make a difference, no matter how clean they or I am.



best regards,
Jerry