Metrum Quad DAC power supply upgrades

Paul Hynes · « **on:** 29 May 2012, 05:33 pm »

I was pleased with the sound that the Metrum Quad Dac produced in stock form, as it had the fundamentals of music replay well organised. It exhibited good timing, timbre, sound staging, and sounded richer than the stock Altmann DAC. Although perhaps a little rough around the edges I could happily listen to the system with the Metrum installed, without fatigue, and enjoy the music it produced. I recognised similar traits with the Altmann Dac when I first listened to the system with this installed and it responded very well to upgrading the power supply.

I fitted one of my custom designed 250VA mains transformers a while back and this was a nice improvement over the mains transformers that Metrum use. The sound stage was bigger and more stable dynamically. The dynamic range expanded and the bass was more powerful and more natural. The high frequencies were better portrayed and I heard more heart and soul in the music. I did not post anything on the forum, as I wanted to finish the regulator upgrades first.

I installed a set of regulators in the DAC over a week ago and I have to say the result was more than I expected. The Stock DAC is very good and certainly punches above its weight in the performance stakes, but it really is a giant killer with a set of high performance shunt regulators and mains transformer installed even without much burn-in time.

The sound stage has expanded again and is now rock stable under all dynamic conditions and the image depth is much better with sound source locations well defined. The dynamic range is exceptional. Timbre and tempo are very good indeed. I have played musical instruments in the past and I am particularly sensitive to Timbre and Tempo. Most items of equipment damage these two parameters to a degree. The modified Metrum just excels here and it makes it so easy to understand the way the musicians are playing their instruments and the singers are presenting their songs. All the subtlety of the interplay shines through.

There are a couple of points to consider with this modified DAC.

Firstly with 6 shunt regulators fitted the operating temperature is elevated and the case gets quite warm to the touch. There are two options regarding this. One is to use the Dac with the top plate removed and the other is to transplant the metrum board to a larger case with good air ventilation.

Secondly, good recordings are very well presented but bad recordings are plainly obvious, as you can easily hear what is wrong with them. That said, my poorly recorded CDs were still listenable, even though compromised, as it was still possible to hear the musical message to a reasonable degree. There is no obvious digital glare with well-recorded music, but some edginess is apparent on some poorly recorded music. This is not the DACs fault.

CEES has done a very good job with his digital circuitry selection, and application, at his chosen market price level. Of course, at this price level he would not be able to apply such regulation and mains transformer upgrades. It is a credit to CEES that he achieved such good performance with LM317 type three terminal regulators in the stock form.

I have attached a photo to show the internal modifications.

http://i700.photobucket.com/albums/ww7/paulhynes/210512download024.jpg

http://i700.photobucket.com/albums/ww7/paulhynes/210512download025.jpg

These modifications can be fitted to the Metrum Octave DAC too.

Regulator kit price
Quad DAC 6 regulators £198
Octave DAC 8 regulators £258
Insured carriage and packing to the UK will be £8, To Europe will be £12 and to the rest of the world will be £15.

Regulator fitting charge £100 plus return carriage for the DAC at cost.

Regards
Paul

adhesiv · « **Reply #1 on:** 30 May 2012, 05:33 am »

you've got my attention...Why did you decide to start with the Quad and have you heard the mods on an Octave? I have an Octave and would love to take it to the next level if possible. It's pretty amazing as is but if you're hearing that much of a difference with the regulator upgrades I can't deny the idea of doing it myself.

Are you planning on doing any other mods to the unit?

What's the all in price, installed and shipped back to US? (Octave)...is it £373?

Can you recommend any local "installers" in the US?

--Jayson

Paul Hynes · « **Reply #2 on:** 30 May 2012, 06:02 pm »

Hello Jayson,

My budget was limited at the time I ordered and my daughter required a Laptop for Christmas to allow her to work at home on some school projects, so I settled for the Quad DAC and ordered a laptop for her.

I have not had a chance to compare the Quad with the Octave in my system at all, stock or modified, however, as the Octave DAC has the same digital processing circuitry and power supply distribution arrangements with LM317LM337 type regulators as the Quad DAC, it is entirely reasonable to expect the same results when upgrading the regulators and mains transformer in the Octave DAC.

I will be fitting a 75 ohm BNC for the spdif input and the input isolation pulse transformer is a prime candidate for attention. I plan on doing this two mods over the next two weekends. These mods can be applied with the regulator upgrades once I have verified their worth.

Return insured carriage for the modified DAC will be £10 in the UK, £20 to Europe and £30 to the rest of the world. This will make the all in price for the Octave installation shipped back to the US £388. This does not include a mains transformer.

For those not into DIY I can provide a fully built AC power supply for the upgraded Metrum if required. The minimum size I would use is 50VA and I can also offer a 250VA unit. These power supplies will use my custom-built high performance mains transformers.

The 50 VA power supply unit costs £180 and a 1 metre high performance lead for connection to the Metrum DAC is £35. Insured carriage and packing in the UK is £10, to Europe is £22 and to the rest of the world is £33.

The 250 VA power supply unit costs £325 and a 1 metre high performance lead for connection to the Metrum DAC is £35. This one is a heavy beast and it will have to be shipped via a parcel carrier as it is over the 2Kgm small packet rate. The insured carriage and packing cost for this will be £25 in the UK, £65 to Europe and £98 to the rest of the world.

I do not have any installation agents in the USA at present.

Regards
Paul

adhesiv · « **Reply #3 on:** 30 May 2012, 08:10 pm »

Thanks for the reply...I also wanted to replace the Coax with a 75-ohm BNC connector, my source (stock logitech transporter) has BNC out.

Keep me updated on the rest of your mods, If i do decide to go for it I'd like to see where you end up first and go for the "platinum" package if you know what I mean...especially with shipping prices like that.

adhesiv · « **Reply #4 on:** 30 May 2012, 08:12 pm »

Also forgot to mention, if you start shipping in bulk let me know. I'm in the international freight business and can assist with this...we do everything from the full ocean containers to partial container (LCL based on Weights or Measure) and even Parcel. As it is I'm going follow up with my UK counterparts about a more affordable shipping solution should one exist. £98 + £30 shipping for the mains + modded dac is tough to swallow.

Paul Hynes · « **Reply #5 on:** 30 May 2012, 10:03 pm »

I agree with you Jayson, shipping charges from here are heavy. There are no lower cost international shipping options from here at present unless you are prepared to wait for surface transit. You may be able to organise a pickup via your own contacts at reduced rates. I am happy to prepare a parcel for pickup if you can do this as long as you cover the packaging costs.

At present I am a one-man band, although my office lass may poke me in the eye for saying that. Essentially I build everything myself to order and there is a limit to the amount I can build in any one year. Under these circumstances I will not be mass marketing product so quantity shipments to the USA are not going to happen under the current regime.

Bearing in mind the relatively small number of sales in the USA, if you can organise a lower cost conduit, I would thank you on behalf of all customers in the USA.

Regards
Paul

serengetiplains · « **Reply #6 on:** 31 May 2012, 12:01 am »

Jayson and Paul, I wonder if the extra heat could be dissipated by drilling several holes in the top and bottom of the original case. That would be easy enough.

Do either of you know how the output of this DAC is configured? Is there any DCV at the output of the DAC chips?

serengetiplains · « **Reply #7 on:** 31 May 2012, 03:20 am »

It looks like it's a direct output. Here's a snippet from the 6Moons review:

"These chips were designed to drive 75Ω loads so there's no need for any output buffer. In the Octave you have 4 chips per channel working in parallel. 8 chips total are connected by eight 330Ω resistors to create an output impedance of 82.5Ω. The other four chips at the end of the board meanwhile handle the digital input and glue logic to match the octet of dacs whose outputs—coupled directly to the output RCAs via those resistors—are routed between the six layers of the PCB to the edge of the board."

Paul Hynes · « **Reply #8 on:** 31 May 2012, 05:12 pm »

It is not quite as easy as drilling holes in the lid and base as the PCB will stop airflow. It works fine with the lid off.

Regards
Paul

adhesiv · « **Reply #9 on:** 4 Jun 2012, 06:44 am »

Paul, regarding your comment about the pulse transformer...someone on another forum made the following change and said it was a no brainer...

Quote

...taking out the Murata pulse transformer and replacing it with the Lundahl LL1572...

They also replaced the Coax with BNC to similar effect. I had a conversation with Chris Sommovigo (of Stereolab/Tron/Black Cat Cable fame) and he mentioned that putting a true 75ohm connector on the Metrum would probably make a significant different.

Paul Hynes · « **Reply #10 on:** 5 Jun 2012, 12:55 pm »

At the same time as the regulator upgrades I can also fit a Lundahl LL1572 isolation transformer and BNC 75 ohm connector on then SPDIF input for £45 including fitting charge.

serengetiplains · « **Reply #11 on:** 5 Jun 2012, 05:59 pm »

Probably an upgrade to the Lundahl is an Audio Note digital transformer, though these carry Audio Note pricing. Serge Schmidlin also winds a digital transformer, but again for more money. Both these are toroids.

Feastrex probably could wind one also, using their Finemet metal. Personally, I would not skimp for something as important as a coupling device for that tiny signal. That signal---its fidelity---is everything, yes?

sugarman88 · « **Reply #12 on:** 9 Jun 2012, 03:35 am »

Paul, I sent you a mail regarding the upgrade for the metrum octave DAC, kindly reply. Many thanks

Paul Hynes · « **Reply #13 on:** 10 Jun 2012, 12:51 pm »

The Audio Note digital transformer is rather large for a comfortable installation in the Metrum, although it (and other large transformer types) could be set up in an external enclosure with the standard internal transformer removed and the PCB pads bridged. I can do this if required.

sugarman88 · « **Reply #14 on:** 14 Jun 2012, 01:48 am »

Quote from: sugarman88 on 9 Jun 2012, 03:35 am

Paul, I sent you a mail regarding the upgrade for the metrum octave DAC, kindly reply. Many thanks

Paul, please check email and reply. Many thanks

Paul Hynes · « **Reply #15 on:** 14 Jun 2012, 02:06 pm »

There are hundreds of e-mail enquiries in my in box at present. I am working my way through them in chronological order during breaks in my work schedule. All will be answered in due course.

adhesiv · « **Reply #16 on:** 16 Jul 2012, 04:06 am »

Hey Paul,

Now that this mod has been in place for a little while and had a time to break in some more any further thoughts on the improvement and/or comparisons to other DACs?

Have you further considered replacing the pulse transformer?

Paul Hynes · « **Reply #17 on:** 8 Aug 2012, 12:08 pm »

Hi Jayson,

All the usual refinements with burn-in have been happening. I have been rather busy lately with work and holidays, so little listening time. I can say that the musical presentation is very good and I can happily use either the Metrum Quad or the Altmann when listening to music. There are differences between the two with regard to tonality, with the Altmann having a slightly warmer sound and the Metrum more towards a neutral sound. Parameters like tempo, dynamic scale and image stability are stable and sound natural with both the Altmann and the Metrum, which is not surprising as they both now have the same high performance supply voltage shunt regulator circuit topologies. This reduces inter-stage interaction to very low levels allowing the signals to be processed more accurately. This happens with all the equipment I have upgraded so far, although some items of equipment gain more than others depending on the signal circuit integrity.

I have had no alternative DACs in for modification recently so cannot comment on how the Metrum compares to other DACs.

I have Lundahl LL1572 pulse transformers on back order as they have been out of stock at my supplier. These are due for shipment to me on 14th August according to the supplier.

Did you manage to find a low cost fast shipping option?

Rosewind · « **Reply #18 on:** 13 Aug 2012, 07:54 pm »

Hi Paul.

Having (for) now abandoned my wannabe-DIY Buffalo dreams, I will be receiving a Metrum Octave DAC on August 16. So the fact that you also make improvements to this little gem of a DAC comes as a pleasant surprise. I will pop you an email later in the year for a quote with shipping to Denmark.

Keep up the good work!

Best wishes,
Peter

Gopher · « **Reply #19 on:** 19 Oct 2012, 02:27 pm »

Has there been any user feedback on these upgrades pertaining to the Metrum Octave? I've got one which is quite the little DAC and I'm intrigued by the possibility of improving it at a reasonable cost.