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

So � how to decide what linear power supply to chose? There are several questions to answer, including:

What are the PSU requirements?
How much space is available?
Is forced cooling required?
Type and form factor of PSU?
Is duty cycle or peak load important?
Who manufactures these supplies?
Who distributes and stocks these supplies?
Are there any options regarding design, quality, safety, supply chain, etc?
Do I need output protection, output adjustment, remote sensing, etc?

Remember all those links a few posts back? There seems to be lots of options and variables, but what works in our favour is that the market for linear PSUs is mature and well-established. Requirements and designs haven�t changed much for many years, and a set of industry standards, specs and designs have become established that pushes such supplies into commodity status. There are several manufacturers and products, but they�re so similar you�d think they were clones. The answers to the questions above are pretty much identical, irrespective of manufacturer, and selection can probably be on the basis of price and availability.

The PSU form factor can be external, rail-mount or closed-frame, but these are usually for single-digit or three-digit outputs.
Linear supplies produce more heat than switchers, but not that much more � they�re about 50% efficient vs 70%. They're not like class AB amplifiers.
LPSs are usually convection cooled, with no fans, and the operating temp range is generally 0 � 50 deg C.
For pre-amps and processors, power demand is pretty steady, and peak loads aren�t so important.
Supplies are CE marked, and certified to MIL-STD-810D and BS / EN / ISO / UL 60950 (all the same thing).
They have isolation testing to 3750 volts, ground leakage below 50 uA, and over 200,000 hours MTBF.
Unlike the kit supplies, they all have over-load, over-voltage and short-circuit protection, so they�re pretty solid!

Here�s a list of manufacturers that I�m aware of who make these supplies:

Condor
Power-One
Calex
Sola HD
TDK-Lambda
R3 Technology

The links are in post 148731. There are other manufacturers, but I think Power-One and Condor in particular have cornered the market, and are widely available from Digikey, Farnell, RS, and yes, eBay. Each manufacturer has a very similar range of single, double and triple-output supplies that are built to the same specs and form factors, and are pretty much interchangeable. They often use the same case size nomenclature, and some even use the same part numbering scheme. So � how to chose the right model � what do we really need?

Nick

Meridian SMPS are usually seen rattling around in a huge space � and it turns out they�re also loafing along when it comes to generating power.

When I was lugging my 861 around recently, I noticed that it didn�t actually seem very heavy once the top and side panels had been removed; the SMPS contributes ounces, not pounds. A linear supply is going to change all that. I don�t think anyone here will be too worried about losing 100 notes to buy an LPS, but it�s going to add a lot of weight, and take up a lot of space. This won�t be a problem for the 861 (there�s room for a power amp in there) but any of the slim G-series units, or anything with an optical drive, is going to be more challenging. So we need to make sure the supply requirements aren�t over-stated.

Thanks to everyone that provided info on the current SMPS, which is rated at +5V/6A, +12V/2A, -12V/0.5A. This adds up to 55W max if all outputs are fully loaded. But what really happens? If you look at the rear panel of an 800 or 861, it will say the power consumption is 100W max. G-series players and processors say 40W max. If anyone can tell me if they use the same SMPS, or a smaller one, that would be useful information.

I have a suspicion that those ratings are conservative, and I looked at current specs and data sheets, which stated that the power consumption was 25W. It didn�t matter whether it was a G-series or an 800 series unit, or whether it was a player or a processor. I figured a player might have higher consumption than a processor due to the disc drive, but that didn�t seem to be the case. Going back in time a bit, I wanted more information, and the first thing I did in this exercise was to measure the actual consumption of my 861.

On a 239V mains supply, I measured around 140mA / 33W consumption with the unit on and running. With my Sony 9100, I found that consumption varied significantly depending on which input was selected. With the 861 it hardly made any difference, but I did want to make sure I got the worst case. Interestingly, when I went into standby, the consumption only dropped to 135mA / 32W, and it only dropped to zero when I switched off at the rear. That�s not very green, but it all shows that the real requirement for an LPS is probably lower than 55W.

What I now wanted to know is where the power is going, and measure the internal loads, which proved to be interesting �..



Nick

Very interesting work here Nick, thank you!

Cheers

George

Hi Nick,

Have you seen this page WiKi - Equipment Power Ratings? It may be of help, it does tally with you 861v4 power measurements, with the 861v6 being reported as being lower.

Very interesting thread thank you.

Regards
Carl

Nick,

You are doing a lot of work here, thanks for all the info :-))

Keep in mind that you need an oscilloscope to measure the real power rates.
There are current peaks that your DVM cannot pick up.

The Meridian PS have 40 watts see link in my last post.

Just calculate the power outputs together you get 60 watts, but it's specified to 40 watts. So when all loads at maximum together the PS will limit the outputs, but I suspect the real current requirements are much lower.

We will see when you measure the RMS current with your DVM.

Is there a special reason why you want to know the current consumption of the different supply voltages?

Robert

Now I get to make an actual contribution, rather than repeating what has been said before.
This is a summary of Connection / Voltage / Current / Power for the SMPS outputs, and for my measurements:

There�s not many numbers, but lots of interesting analysis.
I�m only listing worst case measurements � eg. the +12v current dropped to 870mA in standby.
The power drawn on the +5v and -12v lines is very low, and the most significant parameter is the current drawn on the +12v line.
Although the 861 itself is only drawing about 33W, the internal load is a lot less than the spec, especially on the 5v line.
SMPS usually achieve around 75% efficiency, but that�s only at full load, and in this application it appears to be less than 50%.
The power capacity between the different outputs on this SMPS is typical of many supplies, where that 5v line accounts for around 40%.
Surveying the data sheets, there�s a wide choice of both linear and switching supplies with +/-12v & 5v outputs.
However, the current capacity of the 5v line is ALWAYS the same or greater than the 12v line.
It�s probably impossible to buy an embedded linear open frame supply that won�t meet the +5v & -12v requirements.
Dual and triple output supplies generally have symmetrical +/-12v outputs, though generic type CP498-A is an exception.
There appear to be two other generic types of LPS that meet the need � see the next post.

Nick

In case anyone should want to be foolish enough to follow in my footsteps, perhaps after they see how I get on, I compiled a table of possible linear power supplies. The likely candidates are colour coded - the 40W, 70W and 90W supplies - and show that much the same model is made by several different manufacturers. They don't all come out the same Chinese factory though - they are all different, even when they have the same part number (very convenient, that).

I think there are three key parameters to look out for.

1) Supplies are conveniently named by their overall power output, so I highlighted that column. Although the SMPS has a 55W capacity, I think 40W units would be sufficient, though a safety margin is probably desirable. I used a bit of peotic license to give comparable models the same designation.

2) From what I measured, The +12V output current needs to be at least 1.0A, but other equipment may be different - the HD621 certainly is. Although many of them are described as having +/-12V outputs, these are often adjustable to +/-15V

3) These power supplies really need to sit on their base. The rear face has the transformer and several regulators sticking out, so it won't bolt into the base of the unit without cutting holes or using stand-offs. That means at least 102mm is needed for the 20W & 40W supplies, or at least 124mm for the 50W to 150W LPS.

The space inside of the 861 measures 433 x 184 x 140 mm, so filter board permitting, pretty much anything will fit. The G68 is somewhat smaller, and I think the critical dimension is the internal height. It measures 132mm on the outside, and though the feet aren't as deep as the 861, I doubt the 124 mm supplies will fit (which is most of them). The weights and dimensions are mostly the same for equivalent models, though the dimensions for all but the R3 Technology units are those of the frame, not the overall dimensions

Other equipment such as the 808, G61, G98 or HD621 will be more difficult, as there's less length or height available. If anyone else can help out with the dimensions of the internal spaces, that would be great. I assume, for example, that the players loose half the width to the transport?

Actually finding an LPS isn't that easy, as distributors and sellers classify and describe them in different ways. I found that searching by part no was the most effective - just search for HBAA40W or CP498A for example, and you get loads of returns wherever you look, and very few spurious returns. There are a huge number of Condor and Power-One supplies out there, though its worth looking for the others, too.

Nick

I was also looking for a linear power supply (but not for my Meridian). I came across Acopian Technical Company - Power Supplies. Their specs are excellent. One leading audio designer called them overkill for audio.

I would be inclined to use it as an external ps. Seems like it would greatly simplify things and add isolation.

It looks like you could call them and discuss your project.

Good luck.
George

Nick,

You have done an admirably rigurous work here, compiling data, thanks.

However for anyone reading this, it must be clear that unless VERY handy with a/screwdriver b/soldering iron and c/multimeter, better let this things to the DIYer or technical people. Even one-box solutions will need some thinkering and adjustement.

Then, when you are into DIY and brave enough to do this (PS replacement - upgrade), you know there are alternative ways to just replace one box (original SMPS) for another (alternative one-box LPS).

For example, and this will be my path (some day), I will use some of the boards I linked with separate transformer(s) and thus may distribute parts inside the M box. In the 861 there is much space, but in other units this may be the only way.

Or, as GGA pointed above, get rid of the PS (or just the transformer) inside the M unit and do an external PS.

As for the specs, space permitting, the higher rating the better (ask Naim users how the sound of their gear changes with 'overkill' PSs). Will not go with anything under 60W (4x required) but you need to look at the individual current capacity: most commercial PS have powerful +5 lines and weak -12 ones because they are computer oriented, and we have a different requirement here.

If you investigate a bit further the circuits you will understand why the +12V line needs to be good, and has such a (relative) heavy load: because many local regulators use this line to provide +5V to their local chips.

I have nothing opened here but from memory most modern M gear is provided +5 directly only for some logical circuits, and all the audio-related ones working at +5 (such as DAC chips) have the supply from the +12V line with a local regulator. This explains why the 'analog audio' lines (+-12V for opamps and so on) use just around 3W each, and there are another 8W used on the +12V for this. And why the +5V line use just 1W.

The 'one box' commercial solutions you list are quite different (as I said, probably because computer-oriented) and have a high rated +5V line and comparatively weaker +12 and -12 lines. This is why I underline the recomendation to use a different, maybe less 'easy', but better, PS. Oh and the original M SMPS are like those too, ie, not optimal in my view for the way their gear is designed (in fact I DO like the general design very much!).

Sorry for the long post (and I hope not too technical... I try to write easy to understand with my poor english!).

Cheers,

Josep

+1

Thanks for all the input guys.

I like the look of the Acopian supplies. Although they're expensive, having a closed frame might be an advantage, and they can be mounted on either their base, side or rear, which helps installation flexibility. They also don't have transformers and transistors sticking out the sides. What caught my eye straight away was the ripple spec - just 1mV. However, that's an RMS value, while the others quote pk-pk. IIRC, the conversion is 2 x SQRT 2, or about 2.83, so its actually comparable with many of the open frame supplies.

The Acopian specs are now added to the table below. The HT11 and HT16 cases are too big for anything - the 861 does actually have 17"x7"x5" to play with, but 7.37" is just too wide. I think the GT9 and GT13 would fit horizontally in both the 861 and G68, and will even go their sides in the 861. The T6 & T9 variants may give some more options for the "problem" installations, but I still don't think they'll go in the slim G-series units (90mm high - like the G61). BTW - again, if you just punch those part numbers into eBay, you get lots of good returns.

The voltage, current, power and dimension requirements for the 861 are also added to the table. If people can help populate some of the requirements for other units, I will update them.

Having an overkill second-box supply is very attractive. I'm mindful of how much effort other manufacturers put into their power supplies, and maybe it would help installations with limited space, like the 808, G08, G61 & HD621. However, what I'm doing here is a proof-of-concept trial with a relatively inexpensive 861V2, where I'm not taking THAT much risk. At this point, I'm not actually after the best possible sound quality. I just want to see if I can get to work at all, and if it does - is there ANY improvement to sound quality? Its very convenient to plug 240V directly into the box, and if I went for a second-box supply, realistically I'd run the risk of never finishing it.

If it works out well, I'll take a look at doing the same thing to an MHR-capable processor, then maybe a player. I spent a lot of time recently modifying the power supply on my Jap-spec Sony DA9100 amp. I made a lot of mistakes and learned a lot on the way, so I dont' want to go direct to the final, ultimate, target, assuming that everything will work out as I expect.

I'll give you an example - I've made a mistake already, and nobody spotted it. I was concerned that I might need separate 5V supplies, as the existing SMPS may have them isolated to keep digital noise from the analogue supply. Therefore I removed the SMPS and filter boards and had a look on the reverse sides. (I can post pics if you like.) I found that 5V connections on both the SMPS and the filter boards are common, and aren't isolated. It just happens that there are two sets of connections and cables - maybe to achieve adequate current capacity (as on my Sony 9100).

The first result of this is that a single 5V supply line should be adequate, given good connections. However, it also means that my load measurements weren't valid, as my DVM was shunted by the other connection. Although the meter resistance will be low when measuring amps, the other wire will surely be lower, and will be carrying a higher, unknown current.

I'm not too worried about this, as the 5V supply in ANY multi-output supply has a lot of capacity in hand, but I wanted to know the real load. I repeated the 5V load measurement, and got 2.0A, which didn't vary with any user settings. That means the 5V, 12V & -12V power requirements are 10W, 11W & 3W respectively, which totals 24W. These loads are approx half the capacity of the stock supplies, and about 70% of the input power. This all sounds much more sensible than what I initially thought, and I'm a lot more confident that I've got a proper handle on what the requirements are.

Of course, this does make me wonder what else I might have overlooked....

Nick

Food for thought..