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

No problem! I'd be happy to modify any Hitchhikers equipment, or provide support.

I happen to have a spare, used, Power One HDBB-105W for anyone who has a G68 or 861.

Nick

Looking at the pictures of the G06 & G08 in Duncan's Meridian info, where the disc drive effectively occupies half the width of the player, I'm pretty confident the FG 905 supply would be suitable.

However the 800 has always been more of a challenge. The fan is mounted on the floor, the PSU on the inside front panel, and the filter board on the side panel, leaving very little space free for a larger supply. I expect the comapact Condor/Power One HTAA-16W solution won't be powerful enough, and the larger conventional supplies are too large.

Then I had a great idea, and did some test-fitting in an empty 861. With the fan removed (but the disc drive in position) it looks like the 160x100mm FG Elektronik supplies will fit either length-wise or width-wise on the base of the chassis. But who says it has to go on the base? With the SMPS removed, the FG 105 or 905 will mount neatly onto the the extrusions that retain the front chassis panel and the vertical motherboard. It could hang upside-down, with the heat-sink facing the fan.

Alternatively, the 905 could certainly be mounted on the inside of the front panel - where the SMPS is in the picture above, but mountd to the vertical panel rather than on the base. Depending on the position of the fan and the filter board, the FG 905 would probably fit there was well (again, with the heat sink close to the fan).

Feeling much happier now.

Nick

Here's a few pictures of roughly what the FG Elektronik NMC 905 would look like in a G61R. All the cards have been removed, and the LPS sits where the SMPS used to be, but I've put the latter back in for scale. As you can see, I've had to trim one of the backplane supporting brackets (only using a wire cutter - no sawing needed). The LPS could simply sit on some short, threaded stand-offs, like the 861 filter board uses. There's sufficient height clearance, even in the G61. It looks like it was meant to be there.





Alternatively, the FG 905 could be fitted upside-down, with the heat sink screwed to the chassis base. Not so pretty, but good for cooling, and the mains and DC wiring is short and neat. There's still room for four super-rgulators if wanted.





Nick

Is PSU shielding a consideration ?

You read my mind!

Edit: Quote from Wikipedia (http://en.wikipedia.org/wiki/Switched-mode_power_supply)
So the RF spectrum from a linear supply is presumably a lot less than a SMPS?

How funny, you chaps are busy looking at the pictures thinking PSU shielding, I'm looking at the pictures and finding "Park" and "Shine" in the wordsearch...

I think Nick used an optional metal enclosure for the 861 mod but obviously there's more space. Some brands appear to shield linear PSU's.

Am I right in thinking that the highest frequency in a linear PSU is simply the input mains frequency? I don't think there is much critical RF coming from such a supply.

As far as I'm aware it depends very much on the transformer design... You will also introduce mechanical vibration from the Tx so this should be damped.

Examples from gear I'm familiar with - the Weiss Medea has a double aluminium casing to prevent interference from external sources. However, internally only the DAC and analogue output stages are shielded

http://www.6moons.com/audioreviews/weiss/medea_open.jpg

One of the highest build quality music servers around, the Aurender has shielded everything

http://images.computeraudiophile.com/graphics/2011/1129/internal-clock.jpg

The shielding of an internal power supply IMHO would appear to be beneficial. An alternative is to have an external supply with an umbilical lead - this overcomes the shielding issues but introduces new problems with the power lead connection interface.

NAIM have successfully adopted the external PSU for many years. The NAIM Bundy cable, its connector and its internal strand layout evolved from many hours of measurements. Certainly from the listening perspective the arrangement is more positive than negative.

As with many things in hi-fi, sometimes it's a case of having to accept the lesser of two evils...

Thankfully as DIY tweakers, we are not obliged to compromise our objectives to meet EU paperwork or commercial product budgets, unlike the guys at HQ...

Some linear power supplies have optional steel cases, like this R3 Technology case on my 861V4:



I wouldn't have thought this matters too much, as the mains frequency is so low. I did worry that the analogue audio might have a bit of hum on it - not something that Meridian would have had to design out, but there was never any suggestion of this.

I'd have thought that shielding a linear PSU was less important that shielding the DSP boards from everything else.

Some of my LPS modifications have rubber grommet mountings for either the transformer or the chassis, though I'm not sure this is necessary either. Without a spacer to by-pass the bush, the mounting nut can't be very tight, and will need a lock-nut or thread-lock to stop it coming loose.

Nick

Following this thread with great interest. What about burson power regulators. Could these help with anything?

http://bursonaudio.com/burson_super_regulator.html

I prefer the Belleson guys who publish scope shots on their site but generically upgrading the quality of voltage regulator should always improve matters.

I was noting how many were present on the DSP boards for the 5.5k's... could be one hell of an upgrade but pricey too...