[Paul Hynes]

Hi Nic,

The only ground reference the regulators should see is at the load. The local regulator 0v terminal will be connected to the load 0v, which will be at close to ground potential, as it will be connected to the local ground plane. The pre regulator will be left completely floating with respect to ground and it’s 0v terminal will be connected to the local regulator 0v terminal as this is it’s ideal reference point to provide tight regulation for the local regulator. See Post 6 for a link to a drawing showing how the regulators are connected to each other. If you wire each power supply to each individual stage in this way there will be no ground loops via the power supplies.

A clean ground plane cannot be achieved with one common pre-regulated power supply supplying all the local regulators on the buffalo board. If you connect the 0v terminal of one pre-regulated supply to the Buffalo board 0v next to the VD terminal all the return currents from all the board regulators have to pass through the ground plane causing noise pollution at high frequencies as outlined in my previous post. Connecting a wire from the 0v terminal of one pre regulated power supply individually to each 0v terminal on the five board regulators, provides 5 parallel paths for the PSU ground returns creating multiple ground loops that still pass return currents through the Buffalo board ground plane as this is common to all the board regulator 0v terminals.

Regards
Paul

[NicMac]

Hi Paul,
Thank you for the concise answer. So in my understanding the perfect situation requires equal numbers of pre- and local regulators (and transformers I guess...). I think this might bust my budget and chassis space with PR3G2 as pre-regs...
I have never seen anybody using more than one pre-regulator for the Buffalo II DAC, maybe because there is so convenient onboard access to VD. Room for significant improvement - only one way to find out!
Cheers,
Nic

[Paul Hynes]

Hi Nic,

Actually this applies to all multistage signal processing systems. Unfortunately it is too expensive to implement in the consumer equipment market and rarely taken to it’s full extent in the high end audio market. I have been using this method of power supply structure on my own system since 1984 and on my custom high-end projects since the 1991. In fact the first time I used it commercially was when one of my consultancy clients, Russ Andrews, asked me to apply it to a custom built system for a customer of his. The resulting system using the loudspeakers Russ had designed was demonstrated at the Penta Hotel HiFi show at Heathrow airport in 1991. It caused quite a lot of show talk at the time and was the main topic of conversation in the bar. Paul Messenger made some very nice comments about the system on page 176 of HiFi Choice December 1991. Unfortunately I cannot reproduce the page, as this is his copyright.

At the time I didn’t use pre-regulators, but all signal processing stages in the entire system had their own regulated galvanically isolated power supply. There were 6 off 1KVA transformers for the power amplifier output stages (six power amps in tri-amp mode) and another 16 off 500VA transformers for the signal processing stages. Even the Sota turntable was powered with my regulated power supply design. No headroom issues with this system.

Regards
Paul

[steve2701]

''only one way to find out!
Cheers,
Nic''
Yup, thats exactly what I thought, picked up the phone and the result is this thread. As Paul N states - it is going to take some experimentation with dual mono and single, and also some playing around with boxes, but the whole thing will end up being fun in the end.
It may seem insane to some that a tiny chip could require the amount of psu's and faffing around to get an end result, but when the law on diminishing returns sets in (in pretty much anything audio) things start to get real fun as far as I'm concerned. Has anyone been down this road yet? I honestly don't know, but the journey sure looks fun.
Paul (N) if I screw up a dac chip then I know who to sing out to!! I would need a scanning electron microscope to see the thing, along with a load of beta blockers to keep my hands that steady.

[gstew]

<SNIP>
At the time I didn’t use pre-regulators, but all signal processing stages in the entire system had their own regulated galvanically isolated power supply.
<SNIP>

Regards
Paul

Paul, this is a very interesting direction of inquiry. It falls in the realm of 'of course I knew that', but adds evidence of HOW important optimizing this part of a system really is.

What level of 'galvanic isolation' is required for this to work well. Separate transformers per section or would multiple secondaries suffice in many situations? Also, I assume this also strongly implies a need for full dual-mono construction!

Greg in Mississippi

P.S. Steve, sorry to hijack your thread a bit, but I suspect the answers will be relevent to those following your build, if not to your build directly.

[Paul Hynes]

Hi Greg,

It’s vital to organise the power supply properly if you want truly outstanding performance instead of just acceptable performance from high performance signal processing circuits.

A separate transformer for each supply is the best optimisation as there is less cross coupling of circulating currents between the transformer windings.

Dual mono construction will reduce channel cross-talk via all points of common connection, however if there is any significant difference in the ground reference impedance in any of the stages between the left and right channels this can upset the soundstage image stability. Identical construction throughout the channel signal path will minimise this problem.

Regards
Paul

[kpavey]

Greetings all, another to the fold...

I have a Buff2, and recently placed an order with Paul after reading several positive reviews of his stuff. Had a nice telephone conversation with him last night also - a nice friendly chap to boot 

FWIW, in my system it's a single Buff2, digital volume control with the Volumite with a modded Lite Audio MV02 for remote control, running P.Hynes regs (soon!), with single ended output (using 1 phase of Buff2 output, other 1Mohm to ground) into a John Broskie Aikido Cathode Follower and that into an LC Audio Millenium XP power amplifier (120W/8R). Nice simple and elegant solution with the convenience of remote control.

I would be happy to support a guide on how to install Hynes regs in the Buff2 in collaboration with others, including this ground plane tweaking. I know Paul will provide me with a basic sketch which will help.

Now these independant supplies could be quite small, right? Most of the currents we are talking about here are in the order of 100mA or less aren't they? So I'm hoping we can identify suitable nice readily available small encapsulated transformers and then make up some soft recovery/shottke diode bridges (or use the Hexfred bridges from Parts Connexion) to suit. Keeping it small helps with packaging and cost to some degree. Recommendations welcome. Cheers

[kpavey]

OK well I now have my 5 regs plus 1 pre reg from Paul. All are nicely built and labelled so am proceeding to upgrade one by one, with the Vd and AVCC ones first which are the easiest to arrange with board mods. I will most likely go down the individual pre reg route with multiple PSUs later, as long as it will fit in my 2U box.

Prior to receiving the regs, I was using a soft recovery bridge followed by a 15kuf Jensen 4 pole into a CRC network to get my Vd. So it was unregulated. Replacing this with the Hynes pre reg (keeping the rectifiers and 15kuf Jensen) was a nice improvement. Mainly improvements in inner detail, layering of the presentation, stage depth, more analogue sounding and better rhythm and pace.

Replacing the AVCC regs (noting pinout, the TPA board has four pins, of which only 3 are used - the pin nearest the digital header is left unconnected) was more of the same and another step in the right direction. More inner detail, lovely listening to EST's From Gargarin's Point of View and the ride cymbal rivets trailing off gradually. Voice is extremely engaging (on other tracks) and piano on the aforementioned track natural, which is no mean feat.

I was expecting the pre reg to have the rectification on board, and I believe Paul makes them this way but what I had is a reg only??? Package wise the all in one would be preferable. I also talked to Paul about requirements of the transformers - he originally recommended 30VA per reg!!! I will probably settle for around 10VA given this is about 100x more than required it should work OK.

Next step is to remove those under board inductors on the TPA Buff 2 and wire in these other 3 regs. Will do them one at a time. I'm also keen to try the synchronous clock from the Hiface mod which allegedly can sound better.

I have some more detailed listening notes at home - if anyone is interested PM me. Cheers, Kendrick

[kpavey]

SNIP

The PR3PPRAP (PR3 pre and post regulator application) shows the ideal connection system for one sub circuit section load. Using two regulators in series (Pre and Post regulation) provides a double layer of mains power supply line interference rejection making the equipment less prone to performance variation when the mains power is dirty during high grid usage.

One PR3PPRAP is used for each sub section of the equipment circuitry. Circuit sections requiring a negative voltage rail would use NR3PPRAP constructed using negative voltage regulators. The 0V connection from the post regulator to the load should be connected to the ground terminal of any local load decoupling used in the subsection to be powered. The post regulator +VE connection should go to the positive terminal of the local decoupling. This keeps the ground return currents of each section out of the main earth reference system on the board allowing a very clean earth reference for the whole system. This makes a big difference to the resolution of dynamic scale and micro detail presentation. Timbre and tempo are improved and there is a reduction in confusion in the soundstage particularly when the music gets busy. Music just sounds more like real people playing music.

Setting up the power supply properly where the equipment to be powered has many subsections can be rather expensive and time consuming. Few will venture along this path. Steve is one of the few.

Regards
Paul

Hi Paul

If doing it this preferred way in the context of the Buff 2, the 0V ground plane is still connected on the board to all these separate supplies - won't this still have ground plane issues? I have your pre and post regs ready to install.

Also is there any issue if I mounted the post reg on the output terminals of the pre reg and ran slightly longer wires -say 10-15cm long to the Buff?

Cheers Kendrick

[Paul Hynes]

Hi Kendrick,

The power supply return currents no longer cross the ground plane.

You really need the post regs on the Buffalo board for best regulation.

Regards
Paul

[GordonJ]

Hope it's OK to jump in on this thread. I'm planning to work towards the best implementation I can manage for a BII, with seperate pre- and post-regs for each supply being the end goal. As an intermediate stage I'm going for the standard set of 5 PH post regs, and two pre-regs - one Z1P5V5 and one PR3P5V5. Plan is to use the Z1P to supply VDD, VDD_XO and DVCC and the PR3 for the 2 AVCC supplies. I don't have any particularly sound theoretical basis for this choice, but my thinking is that perhaps the higher bandwidth of the Z1P is best deployed at the digital end, and that it wouldn't hurt to have a shunt pre-reg supplying the one series post reg in the set (VDD_XO). Any thoughts or experiences from those already on this path would be welcome. And note to Paul - I guess you'll be on top of the best current setting for the Z1P in this application. Will I need to change things if/when I add further pre-regs?

All the best

Gordon

[steve2701]

Hello to anyone still out there and reading this.
It has been a very long while since I started this thread, and indeed the DAC project.
Let me be polite and say 'life' decided that the project was going to take a major hiatus along with a good many other things.
Anyways, enough of all that.
I'm back here, the project is again up and running and I'm anxious to pick up from where I left off.

While I've been away Paul has made a few changes to his design for the parts I need for this, so I will list what I am now about to order.

For the two Buffalo dacs:-

2 off S1701v2ADJ @ £36                       
6 off Z7803v3ADJ @ £36                       
2 off Z7803v3ADJ HP@ £36                   
10 off PR3iDC-05v4ADJ @ £80             
10 off PR3iAC-12ADJ @ £100             

For the two Legato boards
2 off PR3iAC-15ADJ @ £100                 
2 off NR3iAC-15 @ADJ £100                 

Paul has made a revision to my requirements for transformers, so now I am looking at 'Centre Tapped' variety,

10 @ 12-0-12 & 4 @ 15-0-15.
To allow for an ocean of headroom I have decided to run with 100Va for each one at present. These are awaiting a quote from Canterbury Windings in their Audio Grade design setup, ie, very low noise with low stray fields etc.

I have some ideas as to how this is going to go together now in my head, but getting from there to actually working is something slightly different.

One things for certain - it's one hell of a big PSU for a dac & output stage.

[steve2701]

So everything is now on order - the wait begins for parts to arrive 

I know Paul is exceptionally busy at present so his stuff will start arriving with me late January.
transformers due just after the Christmas break.

I've been re-reading hundreds, if not thousands of posts on various threads on forums across the web about Buffalo and Legatto, but unfortunately in the past few months everything seems to have moved to markIII versions.
Fine and well, but all my existing stuff is MkII!

In the meantime I am making ways on connecting all the transformers correctly and making certain a clean as possible Earth is available to the entire system.

Anyone else still building these or are they all done now?

[rklein]

I have all of the Buffalo III/Legato parts needed which I ordered back in July/August.  I also have Paul's regs and am waiting on the SR3-12 which should be here anytime.  I probably will begin my build after the holidays.

Regards,

Randy

[GordonJ]

Hi Steve
Good to hear you're back to the project! Mine is currently up and running as described in post 30 above. Less ambitious than yours in that I only got one BII in the last stampede so I'm going for best possible stereo implementation for now. Sounds fantastic! Surprise was the difference it made putting everything in a well shielded box. Knocks spots off any other DAC I've tried in my system (Linkwitz Orion). Currently fiddling about with peripheral stuff - remote control of volume, on/off switch, delayed trigger for power amps etc. via a Dantimax remote board. When funds allow I'll add more of Paul's pre-regs so that each part of the BII is supplied seperately. Still waiting for the TP USB board, and using a HiFace in the meantime which works fine. Left room in the box to go dual mono eventually if I can source another BII or decide to move to BIII's, and for SPDIF switching and even possibly an ADC board.

[steve2701]

Still biting my fingernails in anticipation here, but keeping myself busy reading up on what I would still love to put into the chain and just how to go about it.
Wondering which (if any) resistors to swap out for Z foils, caps etc, then there is the case work (indeed, just how many cases!) 
I'm making inroads into the basic power supply housing and siting (outside of the main room) and that is going to be very well shielded along with each transformer being mounted on it's own anti vibration mounting (no surprises there then )
I'm also being ultra careful ref keeping the raw mains shielded all the way to and from the transformers (I'll put up more on that one later).
I have ordered a set of Supertex FETS to swap out the existing ones (these are what are now used in the Buff III) just need to remember to solder them in bacwards as pins are reversed.
I'm also ordering a box load of cannon XLR's tomorrow, ready for the connections.
In between all that I've been making a few more bass traps for the room - I had one of the 'Floyd immersion box sets' & decided that I couldn't be bothered in keeping the collectors stuff collectable for someone else to enjoy when I snuff it so the scarf is now a 5' long first reflection point trap (well, thereabouts) and the rest of the pics will be on the front wall as traps as well.

It keeps me busy and away from decorating the stairs at home!

I'm also hoping the TP USB board becomes available sometime soon, and that they are producing a lot as waiting for other stuff has been - ahem - amusing..
They have had Buff III boards available for quiet a few days currently though.

[steve2701]

It's still going ahead - honest!
Transformers arrive on Monday, so I've been making a large 'one in fourteen out' box to allow for the feeds to the individual transformers fed from a 5Kv isolation transformer upstream.
Switching on the 14 x 100Va toroids all at once may be a slight challenge for the MCB - even a c curve, so I have been looking at vaious soft start modules, thermistors etc. All very interesting - and highly variable in price. I did find a  very nice way of doing it from Germany, but the 14 modules would end up costing 50% more than the transformers - elegant, & they eliminate inrush totally, but a non starter at that price.
I'm still pondering that one for now.
I have a bunch of Stainless set screws / nyloc nuts and washers on order to clamp everything together, an order in with Farnell for some smaller bits, and a transformer cupboard that is in need of slight localised strengthening.
Plenty to go at for now.
I'll put some pictures up next week when I'm happy with how it looks.

[steve2701]

A few pictures of the progress this week.
Made a 1 in - 14 out (2x7 a side) connector box for the transformers and fitted it into the transformer box on the outside wall of my office. It already houses a 2Kv balanced for the Cd player and a 3Kv balanced for the Pre.  As I said before the incoming will be fed from a 5Kv isolating transformer.
I have left a plate in the box ready to mount two soft start modules. This will allow for the seven a side configuration and also allow for all the transformers to be powered at once.
Mounted some of the transformers onto their boards and set the wiring up to them.
Nearly ready to go into their permanent new homes.

[serengetiplains]

Fantastic, Steve.  Are the blue/brown wires shielding screens in the transformers?  And how did you drill the marble (pseudo-marble?)?

[NicMac]

Absolutely top notch!
I think the green/yellow wire is the screen connection and the blue and brown 240VAC.
They look like audiophile Canterbury windings TX's.
Can't wait to see more pictures of this build.....
Cheers,
Nic