Building a Buffalo IIIse/Sonore USB/Tube Output DAC

[Mags]

Hello all,

 

I'm new here, and I wanted to share my DAC build adventure, if that's OK.

 

A few weeks ago I had an audio meeting at my home and one of the participants brought a DIY Buffalo IIse DAC, which sounded rather nice in comparison to the Zero One Mercury CD/HD player I was using. The Zero One is no slouch, having a built-in dual mono PCM1704 DAC with a single-ended solid state output stage, but the Buff III had what seemed like more solid bass and clearer highs (limited listening time impression). This got me to thinking that I'd like to explore building one of these on my own and do some further comparisons. My experience is more on the tube side of DIY, having built tube preamps and amps in the past.

 

My tube preamp features the #26 directly heated triode tube, with silver-wound Bent Audio Slagleformer output autoformers/volume controls, CCS-fed VR tube shunt regulators, remote control and a separate power supply with all choke input filters. The idea hit me that it has just enough room in the preamp box to fit a Buffalo IIIse DAC and Sonore USB board with Salas Reflector-D regulators...so this project was born! The key is that I'll be using the excellent tube preamp as the output section of the Buffalo IIIse DAC, thus saving an additional stage and thus giving better transparency.

 

A couple pictures of the tube preamp and power supply as it exists pre-DAC are attached below. The regulators and DAC/USB boards will fit down the side of the preamp box where there is about 3" of open space front-to-back.

 

The plan is to feed the differential voltage outputs of the DAC into a Lundahl LL1676 amorphous core transformer configured for 2:1 stepdown, then to the 26 tube grid. Since the tube is already connected to the input section of the preamp I have added a high-quality relay that will fire when the DAC power is switched on and will switch the input to the tube from the preamp to the LL1676/DAC.

 

I upgraded the 9V power supply in the PS box to a 4A capable choke input LC with a LDO regulator to feed 9VDC into the preamp box, where it will power the DAC and USB board regulators, control the relays, and also operate the remote control and switching functions of the preamp. In the preamp box there will be an additional LC section for each DAC channel to ensure decoupling from each other and the other functions using the power.

 

So far the power supply is done and the relays have been implemented...now it's time to add the DAC and USB boards and regulators and see what happens.

 

Stay tuned.

[Mags]

Here's a picture of the power supply after the addition of the DAC section. Looking at the picture, the two identical circuits on the right are choke input supplies for each of the 26 tube filaments, the circuit in the left center with the C-core chokes is the high voltage (400VDC) choke input supply for the 26 tube (HV transformer and tube rectifier located on top plate thus not shown), and the circuit on the far left is the upgraded 9V PS for the DAC/USB boards. The original 9V supply was a simple transformer/cap/LM317 regulator affair to supply a decent 9V for controlling the volume, input selection, etc; it is now a 4A capable improved supply using a schottky diode bridge, a 5A input choke, a 22mF cap and a LDO regulator - in the preamp box will be another pair of chokes and caps (one for DAC and one for USB) feeding the Salas Reflector-D regulators for the DAC and USB boards.

 

I spent some time last night making a perfectly square hole in the back of the preamp box to fit the USB connector; a lot of filing and test fitting but it's now a perfect fit. Tonight I'll make some further progress on that side.

[Mags]

Last night I added the second LC sections to the Preamp/DAC box for the DAC and USB circuits (picture 1) and ran the wires up to the Salas Reflektor-D regulators (picture 2). If you're familiar with these regulators, you'll notice that I cut off the AC section of the boards (Dremel and cutting wheel works well) in order to shorten them so I can fit them both in the box. Looking at picture 2 above the regulators you can see the open space where the USB board, DAC board and the output transformers will fit, and the square hole for the USB connector. Tight but manageable - not bad considering I had no intention of doing this when I built the preamp three years ago; it pays to leave some space sometimes...

 

In the upper left corner of picture 2 you can see the small board I built with telecom relays which will switch the DAC output into the 26 tube and switch out the preamp inputs upon powering up the DAC.

 

You may also notice the mounting scheme for the 26 tube sockets (top of picture 2) is a bit complex, consisting of a double layer of 4mm aluminum sandwiching a layer of Soundcoat sheet, all suspended on Deflex bushings and coupled to the aluminum chassis with wooden supports. The intention of all this is to reduce the pickup of vibration by the 26 tubes, which are known to be microphonic, using the added mass, vibration damping, and dissimilar materials - it works a charm!

[shadowlight]

Nice. Have you started exploring on your computer setup yet?

[Elberoth]

Looks like a very nice project. I bet it sounds great !

[Mags]

Thanks. Have not addressed the computer part of this at all yet. Initially, I'll be using my Zero One Mercury CD/HD player as a transport into this DAC using the S/PDIF port, playing files from the hard drive. Once I get a computer system up and running I'll have a chance to evaluate the USB connection - the Sonore board is PCM and DSD capable and has it's own oversampling filter running at 384kHz that I can compare to the standard Buffalo IIIse filter.

 

This approach seems like a nice simple way to get going with a computer system:

 

How to build a music server | PS Audio

[Mags]

OK, the DAC is complete (more or less). See pictures.

 

About the sound, all I can say is WOW!

 

This is the missing link for me. I completely gutted and rebuilt my speakers a few years ago (Infinity RSIIb), then I built the 26 tube preamp, then I built 200wpc SET tube monoblocks, and at each step the sound improved. I still felt, however that there was something more I could get out of the sound, so I addressed the last piece of the puzzle, the source, with this project.

 

This new DAC has removed those last veils (audio-speak for it sounds awesome!) from the sound...I'm using my Zero One Mercury now as simply a transport, passing the 44.1kHz digital signal unfiltered to the DAC using S/PDIF with 75ohm coaxial cable and letting it do the oversampling and filtering. What a difference!

 

The sound is cleaner, clearer and with ZERO "digital edge". I listened for several hours yesterday and I'm hearing deeper into the recordings than ever. I think the LCLC choke input power supply with the Salas Reflektor-D and the V3.0 Trident regulators on the DAC have a lot to do with the smoothness, there is just no grain I can detect. None.

 

The DAC feeds the balanced output signal into Lundahl LL1676 amorphous cobalt core transformers, where the balanced output is converted to single-ended, the DAC DC offset is removed, absolute phase is flipped (to compensate for the 26 triode doing the same), the voltage is stepped down 2:1 because of the 8X gain of the 26, and the -9V battery bias is added to the secondary of the transformer (and thus the 26 grid), which is connected to the 26 control grid.

 

All signal wires in the DAC/preamp are solid core silver in teflon. The PS wiring is 16gauge silver coated copper in teflon for the + leg and Cardas copper litz 15.5gauge for the - leg.

 

I should be receiving my 50mm u.fl cables today, then I can hook up the USB board to the DAC, but I really don't have a source of USB music at this point. That's the next project...but I'm very happy with standard CDs now through this setup! How much better could high-rez be?

 

Pictures:

 

First is of the DAC section of the preamp at the completion of construction.

 

Second is the back panel showing the USB and BNC connectors and the two switches. The top switch changes between S/PDIF and I2S on the DAC (for changing between S/PDIF and USB inputs), and the lower switch turns the DAC OSF on and off. Running S/PDIF, both switches go toward the BNC jack, running USB PCM both switches go toward the USB jack, running USB DSD, top switch goes toward the USB and the bottom goes toward the BNC (because the BUFFIIIse needs the OSF on to process DSD).

 

Third is of the completed DAC with the lid off during the initial testing. Pretty cool light show...

[Jabs1542]

Very impressive, good quality craftsmanship and it works too! Well done

[barrows]

Sweet build mags. I am looking forward to hearing how it sounds via USB. The ESS SPDIF is pretty good, but USB in my DAC is far superior to SPDIF. I am very happy with the two Reflektors powering the digital side of my DAC as well.

[Mags]

Sweet build mags. I am looking forward to hearing how it sounds via USB. The ESS SPDIF is pretty good, but USB in my DAC is far superior to SPDIF. I am very happy with the two Reflektors powering the digital side of my DAC as well.

 

Well, I downloaded the Sonore drivers on my laptop tonight and bought a USB cable at Radio Shack so I could check out the USB functioning. I played a couple songs that came with my PC in the media player (guess they are MP3s) and it works! Ninja Tuna didn't sound bad at all, actually!

 

Right now I'm downloading the free sampler from HD Tracks to check out HD via the USB. I'll listen to it after dinner and report back.

[Mags]

OK, so I downloaded Foobar and played the HD Tracks sampler. The tracks were 96kHz, not the highest resolution, but they did sound very good through the USB interface. One of the songs was Sonny Rolllins' St. Thomas, which I also have on my CD/hard drive player in 44.1, so I listened to it from the computer via USB and from the player via S/PDIF. The CD player/SPDIF sounded more in-your-face, with more intense highs than did the computer/USB. Bass on the computer/USB was stronger, to the point of being a bit too strong in some cases.

 

Interesting, but I don't know what it means re: computer audio, since I doubt my Dell Inspiron laptop with whatever sound card comes standard is representative of the state of the art. I have a friend coming by next week who is more experienced in computer audio, bringing his setup - we'll do some listening and that will probably give me a better idea of the potential.

[Mags]

In case anyone is interested, here's the rest of my system.

 

The amps are DIY SET monoblocks using the 833C DHT (directly heated triode) tube, good for 200WPC using a plate voltage of 2.3kV. Driver tube is the excellent Russian 6E5P tetrode, in triode mode.

 

The speakers are Infinity RSIIb, circa 1985, completely gutted and rebuilt with external passive crossovers and new midrange diaphragms from Apogee Acoustics. Second pic was taken during the audio get-together mentioned in the first post.