BRYStON BDA-1

vegasdave · « **Reply #60 on:** 8 Oct 2008, 09:45 pm »

Cool. Thanks again. Did you use the upsampling feature on the BDA-1?

tfroncek · « **Reply #61 on:** 8 Oct 2008, 11:27 pm »

James,

How is the upsample implemented? Is it a linear interpolation or something else? Is it all done with a fixed logic design in a PAL or something similar? In other words, no DSP?

Thanks,

Tim

ian.ameline · « **Reply #62 on:** 9 Oct 2008, 12:22 am »

There's no way they're going with linear interpolation -- that's pretty much the worst way to do it. Their upsampling is restricted to integer multiples -- this is good -- keeps the math simpler. The short (but counter-intuitive) answer is that you stuff the extra samples with 0s and then feed the resulting signal through a finite impulse response filter -- this correctly fills in the intermediate values. See http://en.wikipedia.org/wiki/Upsampling for a simple treatment of the subject, or http://ccrma.stanford.edu/~jos/resample/ for a more in-depth treatment. (The best treatment you'll probably find on the net is at http://dspguru.org/info/faqs/multrate/interp.htm)

Because the samples have been stuffed with 0s, the hardware to implement the FIR is somewhat simpler (requires fewer multipliers) -- The co-efficients for the FIR filter are pre-computed based on the window size and the characteristics of the low-pass filter you're looking for (rolloff rate etc). Now the guys at bryston probably didn't design and implement their own upsampler -- these are available in hardware, and is probably in the re-clocking chip they use -- there are usually a small selection of filters (2 to 4) available on these. I'm curious to know the characteristics of the one Bryston chose for the BDA-1 -- James? Care to ask Chris Russel for me?

vegasdave · « **Reply #63 on:** 9 Oct 2008, 03:59 am »

I'm more interested in how the upsampling sounds!

konut · « **Reply #64 on:** 15 Oct 2008, 12:33 pm »

What is the output impedance of the BDA-1? Is it possible to use a XLR to RCA adapter cable on the balanced outs to take advantage of the higher voltage output for single ended use? I have a passive volume control switching pre is why I ask.

konut · « **Reply #65 on:** 17 Oct 2008, 12:10 am »

Quote from: konut on 15 Oct 2008, 12:33 pm

What is the output impedance of the BDA-1? Is it possible to use a XLR to RCA adapter cable on the balanced outs to take advantage of the higher voltage output for single ended use? I have a passive volume control switching pre is why I ask.

Maybe this was overlooked?

James Tanner · « **Reply #66 on:** 17 Oct 2008, 12:20 am »

Quote from: konut on 17 Oct 2008, 12:10 am

Quote from: konut on 15 Oct 2008, 12:33 pm
What is the output impedance of the BDA-1? Is it possible to use a XLR to RCA adapter cable on the balanced outs to take advantage of the higher voltage output for single ended use? I have a passive volume control switching pre is why I ask.

Maybe this was overlooked?

Sorry,I missed this. The output impedance is 50 Ohms and once the system becomes unbalanced (as in adapter cable) the gain is 2 volts instead of 4 volts.

james

konut · « **Reply #67 on:** 17 Oct 2008, 12:23 pm »

Thanks James!

ian.ameline · « **Reply #68 on:** 26 Oct 2008, 04:34 am »

For those looking for more details on the innards of the bda-1, I have some nice pics for you (hosted at image shack). Yes -- the first thing I did was attack it with a set of precision torx drivers and my digital camera

. What can I say -- I'm a bit of a signal processing and electronics nerd -- and now I have created the nerd porn for the rest of you

(I just took the lid off and took pics -- didn't actually touch anything inside.)

For those wondering about the upsampling, they're using the TI (Burr-Brown) SRC4392 for the sample rate conversion -- while it can do any rate conversion from 1:16 to 16:1, they're restricting it to 2x and 4x upsampling. (This is likely wise -- non integer multiples need alot more math done on the signal, and it's very hard to completely avoid aliasing and other problems that can crop up). For those wanting all the gory details on how the re sampling works, Have a look at the datasheets for this chip at;

http://www.ti.com/lit/gpn/src4392

Or if you're really adventurous, have a look at the patent covering their technique at;
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=7,262,716.PN.&OS=PN/7,262,716&RS=PN/7,262,716

If you look at the pics, you can clearly see how they have separated the digital and analog ground planes -- most signal traces are surrounded by ground traces. (Look to the right of the dacs for the analog signal traces for an example of this.)

Oh -- I almost forgot -- it sounds *amazingly* good. Fantastic precision, detail and control.

(It's connected via balanced cables (canaire 4 star) to a BP-25 w MPS-1, and then with balanced cables to a 4B-ST-Pro. The speakers are PSB Stratus Gold-i, bi-wired with 10 gauge belden speaker wire.) Source is from a Mac Mini, toslink fibre -- digital output on the mini set to 44.1khz -- their available output rates are 44.1, 48 and 96 khz -- the latter two require non integer upsampling and the software that does that on the mac (in OSX 10.5.5) is not up to my standards. The upsampling on the BDA-1 is very very good -- The difference is very subtle -- with it on, the soundstage seems slightly laid back -- with it off, the sound stage feels a bit more in-your-face, and perhaps I'm imagining it, but I also might hear a tiny bit of "graininess" that is not there at all when the upsampling is on -- I'm not sure whether I like it on or off better -- and I can't tell with alot of source material. Clearly I am going to have to do alot more listening

The source material is ripped from CD, and stored with apple loss-less compression.

(for those of you with a mac, go to "Audio Midi Setup" in Applications>Utilities, and set the output sample rate to match our source material -- 44.1/16 for ripped CDs, and 48/24 for almost every dvd. -- I can definitely hear their upsampling when playing through the FrontRow software -- and I don't like it.)

Ok -- here are the pics -- click on them to embiggen

vegasdave · « **Reply #69 on:** 26 Oct 2008, 07:21 am »

Thank you very much for your review. Nice system by the way.

john1970 · « **Reply #70 on:** 26 Oct 2008, 10:57 am »

Ian,

Nice review and I enjoyed the pictures. Nice to know how Byrston did the upsampling. I currently have my BDA-1 on order and expect it to arrive by mid-November. I can't wait to have it in my system. The rest of my front end is very similar to yours with the identical preamp and a Bryston 4B SST amp.

Cheers,

John

ian.ameline · « **Reply #71 on:** 26 Oct 2008, 05:36 pm »

John,

I think you'll like it alot - you're a more patient man than I to be able to hold out until mid November

For those considering it, if you can, you should find a place locally where you can listen -- it sounds great, and as with everything else bryston, it's built like a tank -- I'm very happy with mine. (Picked it up at Whitby Audio -- they gave a good price, and the guy there I bought it from, Mark, is very knowledgeable - I recommend them.)

Hey James, who is "DM"? (saw his initials in a stylized logo in the corner of the board -- see the first image in my previous post -- bottom right corner near the analog output op-amps.)

Cheers,
Ian.

James Tanner · « **Reply #72 on:** 26 Oct 2008, 05:45 pm »

Quote from: ian.ameline on 26 Oct 2008, 05:36 pm

John,

I think you'll like it alot - you're a more patient man than I to be able to hold out until mid November For those considering it, if you can, you should find a place locally where you can listen -- it sounds great, and as with everything else bryston, it's built like a tank -- I'm very happy with mine. (Picked it up at Whitby Audio -- they gave a good price, and the guy there I bought it from, Mark, is very knowledgeable - I recommend them.)

Hey James, who is "DM"? (saw his initials in a stylized logo in the corner of the board -- see the first image in my previous post -- bottom right corner near the analog output op-amps.)

Cheers,
Ian.

Hi Ian,

Bryston always trys to give our engineers recognition for their design efforts. Sometimes it is in the name of the product - like "ST" for Stuart Taylor on the amplifiers, Mike Pickett - for "MP" on the MPS-2 Power Supply, and of course Dan Marynissen "DM" on the CD Player and the External DAC.

james

vegasdave · « **Reply #73 on:** 26 Oct 2008, 09:25 pm »

That's a very nice touch, James.

What does the extra S stand for in regards to SST?

alexone · « **Reply #74 on:** 26 Oct 2008, 09:43 pm »

...it means 'super' when i am informed correctly. so it is 'super stuart taylor'.

al.

b5pt9 · « **Reply #75 on:** 26 Oct 2008, 09:58 pm »

Quiz - where does the name "Bryston" come from??

ian.ameline · « **Reply #76 on:** 27 Oct 2008, 02:00 am »

Your google-fu is weak -- learn from a master :-)search for 'origin of bryston audio' (no quotes) and you'll find;

http://www.soundstagelive.com/factorytours/bryston/

And I quote;

"when Bryston started in 1962, the company was based in the US and had nothing to do with audio. Bryston’s three founders, Tony Bower, Stan Rybb, and John Stoneborough (their last names form the acronym from which Bryston takes its name), made blood-analysis equipment. This continued until 1968, when NASA engineer John Russell, Sr. bought the company. John had worked with NASA during the 1960s, but found himself out of work following the layoffs that accompanied termination of the Apollo missions later that decade. At this time, John moved his family to Canada and re-launched the company there. Once his son Chris had finished college, John hired him to work for Bryston, and Chris set to work designing the first Bryston amplifier.

This amplifier was completed in 1973...."

john1970 · « **Reply #77 on:** 31 Oct 2008, 01:29 am »

Ian,

Looks like I won't be waiting until mid-November. I've just received the FedEx tracking information and I should have the BDA-1 delivered on Election Day! I can't wait to hear it in my system.

Cheers,

John

ian.ameline · « **Reply #78 on:** 2 Nov 2008, 09:28 pm »

John, I'm sure you're going to love it. I've found that it has given me a new appreciation for much of my music library.

James, please pass along my kudos and thanks to Dan Marynissen and the rest of the team at Bryston. The BDA-1 has "completed" my system -- the missing piece is missing no longer! The BDA-1/BP-25/4B-ST/PSB-Stratus Gold-i all Canadian combination sounds incredible, and is giving me many, many hours of enjoyment.

James Tanner · « **Reply #79 on:** 2 Nov 2008, 10:05 pm »

Quote from: ian.ameline on 2 Nov 2008, 09:28 pm

John, I'm sure you're going to love it. I've found that it has given me a new appreciation for much of my music library.

James, please pass along my kudos and thanks to Dan Marynissen and the rest of the team at Bryston. The BDA-1 has "completed" my system -- the missing piece is missing no longer! The BDA-1/BP-25/4B-ST/PSB-Stratus Gold-i all Canadian combination sounds incredible, and is giving me many, many hours of enjoyment.

Great to hear Ian - I will certainly let Dan know you appreciate his efforts.

james