Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Meridian - Systems New Linear G68 PSU from Nick - initial thoughts

Well done, that man! Inspirational. Are the two cable harnesses for your 5V and 12V lines respectively?

Cheers

George

Yes, excellent job!

I'm really pleased to see someone else doing a linear supply - well done KC. A few questions and comments:

You went for two connections after all - does that mean you kept the two return lines separate? And did you have a single connection for the +5V?

How do you earth the G68 - is that through the power supply?

When you say it sounded better - is that through the DSP6000's? When I did my switched vs linear comparisons, I was only using analogue outputs and passive speakers. I guess you're saying the LPS is better even when you use the digital outputs? Presumably there is less jitter? But it probably helps getting the PSU outside the box alogether.

If that's the case, I think there's a good justification for having linear supplies with players, and even with the HD621. They don't have much room inside, so an external supply would be a great advantage.

I fought shy of making an external supply, as I didn't know whether it would work at all. But this looks like an attractive solution now. If I was getting all ambitious, I might think about an external linear PSU with multiple outputs for the player, processor, etc?


Great stuff, Nick

Very nice work indeed.


When you are reporting sound quality improvements, is it for an all digital setup with DSP speakers, or analogue? I'm curious about sound quality improvement in an all digital setup.

Edit: I think my post crossed the previous one...

Very nice indeed!

The two cable harnesses consist of all seven wires for connecting the G68's circuit board. Each wire is separated. You can see on one of the photos that one connector is 3 pins while the other one 4 pins. It is a fool proof design eliminating incorrect connection. I selected Neutrik XLR connectors for their current handling capacity and reliability. The modified system will look better if all screws, sockets and plugs were black in colour.

The G68 and the external PSU are common ground to earth. One of the seven wires in the cable harness is earthed to G68's chassis.

My modified system definitely sounds better when I play 2CH with my DSP6k. I have not done an in depth audition for 5.1 movie with my analog center and rear. I think I shall redo my MRC later.

I may consider powering my HD621 with an external linear PSU. If the HD621 is powered by 12V and/or +/-5V DC, I guess I can simply power the HD621 using the existing CP498A for its redundant capacity. However, the rear panel of HD621 is not module by module. The trick used in G68 may not be applicable.

In this G68 modification, the most difficult part is to install G68's small replacement rear panel without drilling any hole. The available space for installing two Neutrik XLR sockets is very limited. Of course, there are many connectors that is multi-pins and compact enough to make the job easier. However, I still perfer to use Neutrik XLR.

The hottest point in CP498A are their power transistors: about 50 deg C. Insulating the PSU from G68 reduce the temperature of electronics inside the G68, aiming at lengthen its service life. The reliability of linear PSU is well known; and now I am more confident to allow the PSU and G68 to draw current in standby mode.

In Hong Kong, close to China, I have an advantage that it is not difficult to find a shop to machine one piece of precision rear panel using a laser machine. I am also lucky that I can buy a high quality aluminum chassis off the shelf in a hardware store.

Now, this is saying something:

It's Saturday night (usual rubbish on TV) and the family are quite happy listening to the M. G68J with the Linear PSU, fed by iTunes (MP3), into an Airport Express, Optical to G91, upsampled to G68.

Never before have we switched the TV of on a Saturday and enjoyed just music. It kind of feels nostalgic.

So much so, that the wife is sorting her stamps on the floor and the boy is sitting listening to the various instruments. He's 8 years old, he said "Oh Wow! You can hear the background!". Praise indeed and a potential M. customer (or at least after my gear when it's upgrade time).

I'm a happy bunny again.

Pete

Sorry, but the combination of an improved Linear Power Supply with MP3 and an Airport Express strikes me as a very strange combination

In addition, if you were to feed the Optical directly into your Updated G68, then you would also benefit from Apodizing........even though Apodizing and MP3 make strange bedfellows

Isn't apodizing only in the latest firmware (which I don't have)?

My point was that irrespective of the source, it sounds bloody fab. Even MP3, which surprises me too. Don't get me wrong, there are still rubbish masters out there, but I'm enjoying my music collection again.

The cable harness with 3 wires are for higher current (+5V, +5V, 0V) for the better current handling capacity of the 3 pins connector while the 4-wires cable for the others (+12V, 0V, -12V, GND).

FYI: The red wire (+5V) next to the yellow wire carries the highest current, 1.9A, in standby mode.

I am considering making external linear PSUs for G68 and HD621.

Wouldn't you isolate the two in order to prevent EMI conducting from HD621 to G68 amplification stage?

It had occured to me to use one, large, external LPSU to power more than one unit, but when you consider how cheap each PSU is, I think it makes sense to have separate supplies.

I now have an external power supply box with two LPSU's - just need to sort out the connections.

Nick