Burr Brown eval board DAC redux

strider

Many moons ago one of our resident DAC experts, Fred, was kind enough to karma an evaluation board for Burr Brown's PCM1792 DAC chip. His stipulation was that whomever won the karma would build the board out and use it. I won, building the DAC using a Placid bipolar supply from Twisted Pear to power the analog section, a power supply Fred included for the digital and DAC sections, and eventually adding a USB to S/Pdif convertor from miniDSP to get music off my computer.

Here is the link to Fred's build for those that are interested: http://www.polkaudio.com/forums/showthread.php?72911-DAC-Burr-Brown-PCM1792&highlight=burr+brown

Here's a link to the manual for the board: http://www.tij.co.jp/jp/lit/ug/sleu037/sleu037.pdf

With the fast pace of changes in the DAC world, especially in regards to high resolution files and computer audio, I feel like it's time to freshen up the DAC. It'll be slow, upgrading a section at a time as funds (and time) allow. The goals are: playing files up to 24/192 from a USB source, having a second BNC input for a connection from a cd players digital coaxial output, have as many inputs as possible (at least the USB) connected to the DAC board via I2S , with seperate power supplies for the analog, digital, DAC, and USB convertor, and have the power supplies et al in a different chassis then the stuff that handles signal, and have the USB convertor be asynchronous.

Right now the DAC functions as it sits. In terms of order of upgrade, I think the power section is most important. I have power supply boards from Salas, a poster on DIyaudio, for each of the sections of the DAC. Once I figure out the needs for the power supply boards, I'll turn to transformer selection and figure out how to mount them all.

As I get more involved in it I will report back, if there is any input that anyone has I'd welcome it.

Ben

strider

This is a link to the build guide for the shunt regulated power supplies I purchased: https://docs.google.com/document/d/1NDkXuYoX_sx1oiwRfGA9lE51UILIiGvNU6YYamCqlmk/edit?authkey=CM7d-IkL&pli=1

The chassis I plan to use is an old HP vacuum tube voltmeter. I have one for the power end of things, another for the DAC side. I should be able to get the 4 PS boards and the 4 transformers in the one case. Going with Neutrik's connectors on both cases for the power lines. Panel mount IEC for the power input, just going with one cord for all the transformers. What would be the preferred method to split the power to the individual transformers after it makes it into the chassis?

FTGV

I'm glad it has served you well Ben.I look forward to following your tweaking progress.That eval board lends itself well to mod's and should respond nicely to the clean DC source provided by the Salas reg's.I'm using a Salas for the analog section of my TP Buf III in the same chassis were your board used to reside.Does it still have the stock 5543's?

FTGV

FTGV wrote: »

5543's?

Make that 5534's.

headrott

Looking forward to seeing this and hearing your impressions of the upgrades you're planning Ben. Those Salas regulators are great! I am also using some Salas regs in my DAC for the analog output stage. Keep us posted!

SCompRacer

Kewl project Ben! I think you'll like the way I2S will sound with that DAC. You looked at any hi-res USB to I2S modules yet? TP is cose to releasing one, no idea of price but suspect in the hundred range. I am using an Amanero; it also does DSD over USB.

http://amanero.com/

You can do pretty good with a group buy at diyaudio. I've purchased two so far for ~ $62 shipped. Full price is $97 plus postage.

http://www.diyaudio.com/forums/vendors-bazaar/216474-usb-i2s-384khz-dsd-converter.html

Another popular USB to I2S module is the Luckit WaveIO. ~$129 US.

http://luckit.biz/new/product/waveio/

strider

FTGV wrote: »

Make that 5534's.

Still have the opamps it came with in there. When I get past the power end of things and start working on the DAC board I was planning on upgrading them based on what you'd posted in your build thread. I'd love to go with a discrete opamp, Audio GD has them for as low as $22.50 each.

http://www.audio-gd.com/Pro/diy/OPA/OPAEN.htm

strider

SCompRacer wrote: »

Kewl project Ben! I think you'll like the way I2S will sound with that DAC. You looked at any hi-res USB to I2S modules yet? TP is cose to releasing one, no idea of price but suspect in the hundred range. I am using an Amanero; it also does DSD over USB.

http://amanero.com/

You can do pretty good with a group buy at diyaudio. I've purchased two so far for ~ $62 shipped. Full price is $97 plus postage.

http://www.diyaudio.com/forums/vendors-bazaar/216474-usb-i2s-384khz-dsd-converter.html

Another popular USB to I2S module is the Luckit WaveIO. ~$129 US.

http://luckit.biz/new/product/waveio/

Right now I'm still looking at the USBStreamer from miniDSP. It does up to 24/192, which matches the limit of the DAC, really compact package, and outputs up to 8 channels via I2S. Also asynchronous, the feature that has me sold so far is that with a firmware change it will accept an external master clock.

http://www.minidsp.com/products/usb-audio-interface/usbstreamer

zingo

Once I sort out my preamp, I need to get my but in gear and build out my copy of this DAC board as well. It does look like a good design, and Fred has been a great help so far!

strider

SCompRacer wrote: »

Another popular USB to I2S module is the Luckit WaveIO. ~$129 US.

http://luckit.biz/new/product/waveio/

This one's interesting, too. I like that the I2S outputs are isolated from the DAC. Could have some fun with the leads for the sample rate lights.

Do you have an opinion on which feature would be more desireable, the isolated outputs on the Luckit or the ability to use an external clock on the miniDSP?

SCompRacer

Isolation with reclocking provides lowest jitter and lowest noise. I was surprised how quiet my Amanero is with no isolation, although I am powering it with a real good linear supply versus USB. The GND is still connected to PC though. Acko at diy made two isolation/reclock boards for my USB module which I have, just no time to assemble. One uses the ultra fast Potato chips. The boards are small with SMD; lighted magnifier work for me.

I read the datasheet on the miniDSP where it just says “Note that the USBStreamer can only operate as an I2S Master (clock being outputs from the device).” Is the firmware update mentioned in the forum? I haven’t seen much posted about the miniDSP at diy. If the Amanero wasn't available (384Khz 6.1Mhz capability for my DAC) I would have got the WaveIO.

Your DAC chip also offers I2C control. Add a controller, remote, LCD and write some code.

strider

Rich - In the unveiling thread in miniDSP's forum on diyAudio there was mention of a future firmware revision that would allow inputing a master clock signal.

http://www.diyaudio.com/forums/minidsp/214068-usbstreamer-multichannel-usb-audio-interface-2.html

Post #17

Haven't read anything about the firmware upgrade being available yet, though.

strider

What's the preferred method of wiring multiple toroids? I'll have one IEC inlet coming into the rear panel, then need to distribute power and ground to four toroids.

Speedskater

On wiring power toroids.
The incoming Safety Ground's only connection is to the chassis near the IEC connector. Then a fused pair to each toroid input. Each toroid's output hot's & center tap are connected to a DC supply input. The toroid itself is not ground.
Then exactly where are the DC supply output's grounded? Well it depends.

strider

Is there a preferred method for distributing the power from the hot leg on the IEC to each of the fused pairs? A distribution block of some type?

zingo

strider wrote: »

This is a link to the build guide for the shunt regulated power supplies I purchased: https://docs.google.com/document/d/1NDkXuYoX_sx1oiwRfGA9lE51UILIiGvNU6YYamCqlmk/edit?authkey=CM7d-IkL&pli=1

I'll be putting my DAC board on the bench shortly connected to the 3-way adjustable power supply to feed it. If it works and everything checks out, I may have to look into those Salas power supplies.

Keep us updated!

Speedskater

strider wrote: »

Is there a preferred method for distributing the power from the hot leg on the IEC to each of the fused pairs? A distribution block of some type?

Not really a preferred method, I could go up in my attic and find parts to do it a dozen different ways. Remember to keep each pair a twisted pair.

strider

Speedskater wrote: »

Not really a preferred method, I could go up in my attic and find parts to do it a dozen different ways. Remember to keep each pair a twisted pair.

Would you be willing to describe the way you'd prefer to do it?

SCompRacer

This is what I did Ben. Power enters through a Schurter fused w/switch/filter IEC power module Digi Key # 486-1291-ND. A short dongle of 14 gauge stranded off that, black/white. Three various lengths of 16 gauge stranded black/white attached to ends of 14 gauge, soldered/shrink tubing. These connect to insulated screw couplers where two trannys are connected to each 16 gauge leads. Got them couplers at Radio Shack, come in various length strips you can cut to length. Digi Key also has them. A basic rule is keep AC (actually all wiring) wiring 1/4" to 1/2" from chassis and twisted of course.

Through bulkheads you can find various anti-chafe products like rubber grommets or plastic bushings. I found the longer plastic bushings at an Ace Hardware. Various lengths allowed me to use them in the 1/4" aluminum tranny mount. The reason for so many trannies is for all the various power supplies (six total) and to maintain galvanic isolation with trannies that could have been shared (like for B+ supplies to DAC boards).

Yes, I broke some rules and did not twist my DC wiring. Went for that rifle straight/banded Naim look. I used standoffs and plastic clamps to keep wiring off the chassis. This thing is dead quiet at full volume with no music playing.

I've seen some folks use power strips to distribute AC, but I prefer limiting exposed AC approach.

strider

Thank you, Rich, that helps out tremendously!

SCompRacer

You are most welcome Ben. I sifted through many OP's (other peoples) and manufacturer builds for methods used. Aside from basic needed components, there is that material expense in DIY. I searched for same color/gauge wiring to extend my trannys. Less chance of making hookup mistakes if color code is followed.

A length of good quality CAT5 makes for great input/output hook up wire. Four colors, solid/striped pairs. Good CAT5 as in stranded 24 gauge copper, some use solid wire. Another source for small gauge wiring of various colors is old security/backing camera video cable, printer cables, computer serial cables. I've even saved the foil wrap to make my own shielded harness.

If you buy new hookup wire, get Teflon insulated. You don't get the insualtion shrinking back from joint when soldered. Tube Depot was a good source of wiring for me.

http://www.tubedepot.com/

Speedskater

I think that SCompRacer gave a much better example than I every could!
With the possible exception of low signal level balanced unshielded pairs, I would not hesitate to route cables in contact with the chassis.

IN some cases it may be ideal.
Tony Waldron touches on the subject in some of his papers:

http://www.fragrantsword.com/twaudio/
http://www.nutwooduk.co.uk/archive/Old_Archive/020722.htm

strider

Speedskater - Thanks for the links. Gotta admit I wouldn't check out a URL called fragrant sword unless someone else checked it out first.

Rich - I hear you on the material costs, my build list at Mouser is over $100 so far and I don't have anything but Neutriks on it. I've accumulated some older pieces of test equipment over the past few years, mostly so I could repurpose their chassis' for other projects. Tried to save everything I could use out of them, transformers, switches, knobs, wiring etc.

SCompRacer

Speedskater wrote: »

Tony Waldron touches on the subject in some of his papers:

Thanks for the linkage.

SCompRacer

I hear ya Ben. Good thinking and cost saving on the recycling/repurposing. I love them Neutrik D panel mounts. RCA, XLR, reversible USB, RJ45, BNC, etc. I like mounting them from the inside of chassis rather than have the mounting flange exposed on exterior.

strider

So it looks like the Neutrik powerCON connectors aren't going to be the best choice for DC out and in connections on the two chassis. The Salas power supplies have a remote sensing 4 wire "Kelvin" output. The outputs must be wired as 2 twisted pairs, one connected to the V+ and one to ground on the board being powered. It's important that the twisted pairs don't meet until the load, otherwise bad things may happen.

Long story short, I need a connector that is chassis mountable and has 4 poles. Highest voltage it will see is 15V, less then 300mA current. Could also use a 20 pole connector and just run one umbilical from the two chassis. Any suggestions?

SCompRacer

Try "aviation plug" searches. They are available in different pin outs. An example, though this one is from a seller in China.

http://www.ebay.com/itm/10pcs-4Pin-Aviation-Plug-Metal-Connector-Audio-CNC-Stepper-Motor-Connector-GX16-/130864114793?pt=LH_DefaultDomain_0&hash=item1e781bec69

Speedskater

'strider' think about 4 pin XLR connectors. I often use them for remote DC power supplies.

strider

Thanks for the links, guys. I ended up going with these:

http://www.ebay.com/itm/10pcs-4-Pin-29mm-Mounting-Military-Radio-RF-Male-Female-Cable-Connector-P4P-/380562816758?ssPageName=ADME:L:OC:US:3160#ht_1126wt_1018

Much cheaper then Neutrik 4 pin XLR connectors, I'm certain they're built cheaper also, but I like the look. On a side note, I found a transformer for the analog section from Antek. It was listed as a refurb on their Ebay store; as some of you may know they had a fire at their facility recently so they don't have a great deal of stock. Opened the box and got blasted by that unmistakeable smoke odor. Yummy.

SCompRacer

strider wrote: »

Opened the box and got blasted by that unmistakeable smoke odor. Yummy.

So they 'burned' the tranny in for you?:cheesygrin:

strider

Man, this build has been dragging on for two years. Finally have (hopefully) all the parts I need for the Salas boards. The toroids are mounted and wired, inputs and outputs are mounted and the circuit boards are layed out. May get this thing built after all.