Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems Power supply upgrade

Bin the heater!

I fully agree there's no need for that load resistor with a linear power supply, simply wasting power.

All the best,

Steve.

+1
You do not need this load on a linear PS (they have their own ways to waste energy).
While you have your v4 opened it should be easy to measure currents in the +5, +12 and -12 lines. We'll be very grateful

It depends HOW the PS is designed.

Every voltage regulator need a certain load in practice. This load is just some mA and when PS have a smart design then its included in the PS otherwise it's a not professional PS.

What could happen is that when the power is switched off, the output voltage of the PS is higher as the input voltage and then the voltage regulator can be destroyed.

But again, in a professional PS that issue also have to be solved-just with a diode across the voltage regulator (in reverse direction of coarse).

So if you want to be shure, look for the schematic of the PS if you can get one, or better on the PCB if for every regulator have a diode are present and a minimal output load that's a resistor parallel to the output terminals.

Robert

If you must have a load on the 12v line wire up the heater on one of these;
You'll have the first valve operated Meridian

+1

Replace your Meridian's new-fangled SMPS with a nice old-fashioned linear supply, and that's rather like what it'll sound like.

It will also run a little warmer, but not quite that hot.

What do the engineers on this board think about this:

Linear-Netzteil 230 V 60 Watt NMC 100 also available with 115V

I don't know.

Peter....want's the best, not the cheapest PSU

Hi Peter,

Looks like a good find.

Although there are various other LPS makers, like Emerson, Quarteck, Omega, SPC Technology, ELPAC & AC/DC Electronics, I was beginning to wonder if the real choice was boiling down to a generic Condor or Power One HBAA40 or HCBB75, with their '60s design and considerable height and length. The FG Elektronic supplies are more compact, and may be compatible with the slimmer M controllers, and even some of the players.

The specs seem to be comparable with other supplies, though I'm particularly interested in the NMC 105, which has just 2mV ripple - the best of all the triple output models (though some Acopian single output models get down to 0.75mV). I think it would be ideal for the 808 and G68, and it's not even that expensive. The models of interest would be the NMC 305S (15W), NMC 905 (30W) and NMC 105 (60W), and I found some English datasheets here:

http://www.fg-elektronik.de/powersystems/standardgeraete/ac-dc/linearnetzteile.html
http://www.produktinfo.conrad.com/d...127-da-01-en-LINEARE_STROMV_NMC_305A.pdf
http://www.produktinfo.conrad.com/d...0180-da-01-en-LINEARE_STROMV_NMC_905.pdf
http://www2.produktinfo.conrad.com/...0233-da-01-en-LINEARE_STROMV_NMC_104.pdf

OK, I've binned the heater, updated my spreadsheet, and reluctantly measured the DC loads on the V4. This has taken enough time already, but it turned out to be quite worthwhile, as I was under a few misapprehensions.

Firstly, seemingly identical power supplies have different efficiency. The V4's lower power consumption was down to the greater efficiency of the Lambda LPS over the hot & noisy R3 Technology LPS.

Secondly, the V4's internal DC power consumption isn't as low as I thought, nor the V2's as high. I found it difficult to get consistent and repeatable load results, which was a matter of comparing like with like. Because the 861 has so many different configurations, the real requirements have to be established on an individual basis. I no longer distinguish between the two versions, but just take worst case measurements.

Thirdly, I disconnected the 33R load on the filter board on both controllers, and both carried on working normally (phew). The load on the supply now totals just 18W, which gives more flexibility with suitable linear supplies. Once the 33R is removed, almost anything will power the 861, and almost anything will fit.

2.20A @ +5V = 11W
360mA @ +12V = 4W
210mA @ -12V = 3W

Finally, I've added specs for various FG Elektronik supplies, which are looking very promising. Most have similar base dimensions to the 800/861 filter board, to give some perspective. It looks like the NMC 105 would be ideal for the 861, 800, 808 and the G68, and the NMC 905 might be the answer for the G61 and G series players. The NMC 305S might even drop right into the HD621, for obsessives like me.

I also noticed that there's an interesting Ultra-linear control module with a single channel rectifier and regulator that has less than 1mV p-p riple and noise. It needs a separate transformer, a nice custom toroid is no problem, and that could be an answer for ambitious folks. Nice

I added this information into the spreadsheet:

Did you consider and reject an outboard battery based solution?

Yes; I've read a lot about what battery supplies can do for DACs and pre-amps, and I expect a battery supply would sound better than a mains supply.

However, I'm looking for a reasonably large improvement from a relatively easy modification, which is what I think I've found.

As I've already mentioned (I try not to waste any words) its taken too long already, and I can't put any more resources into it than that.

Nick

Since the R3 Technology LPS that I fitted to the 861v2 was a bit noisy, I decide to replace it with something different, and get some more experience with other options.

I bought a big, old Condor HDBB-105 supply off E-bay for a few bucks, and it arrived this week. It looks like a supply for a 20th century power amp rather than a 21st century processor, with a huge transformer and smoothing caps and thick wires, but it works beautifully. It�s virtually silent, the voltages are spot-on, and unlike smaller supplies, every output is remote-sensed, protected and adjustable.

That might be rather useful. People keep reporting SMPS problems, which may simply be due to the processor needing 5.2V rather than 5.0V � the most common output voltage. When I was measuring internal DC loads, the simple act of placing an ammeter in series with the 5V could be enough to stop the 861 starting-up, which was confusing at first. Sometimes it would, sometimes it wouldn�t, so there�s clearly not much margin. Being able to adjust the 5.0V output up to 5.2V is probably desirable. It�s a common option, but some of the small supplies like the FG NMC 305 aren�t adjustable.

The HDBB case is huge, and nearly fills even the 861 � the filter board has to go back on the side panel, as there�s no room on the base. It may seem overkill, but that didn�t do Naim any harm, and these mods can be done for a few pounds � not thousands (which is what I think they�re worth).

Nick