MDAC First Listen (Part 00101010)
- Thread starter jirij
- Start date
- Status
This may come as a surprise, Usher BE718s
They're relatively inefficient,
http://www.stereophile.com/content/usher-audio-technology-be-718-loudspeaker-specifications
so as with any amplifier you use with them it will depend on what distance you sit and what volume you listen at.
http://www.stageaccompany.com/support/calculator.html
According to Wiki ''The project has been officially kicked off on September 5th, 2013''
So about 2 years.... CD-transport to mention just a few extra dimensions). John should be doing listening tests around xmas I expect.
Any chance we could go with a bluray drive instead of CD ? I'll rarely use an optical drive but Bluray would be handier..
JohnW
pfm member
@JohmW
Sorry for the offtopic: John I have the 8200dq protoyype you sent me for the... let's say lost dacapo board. Well the analog preamp part works but the if I use the digital inputs, they only output one channel. The headphone outputs both the two channels ( at least it worked this way until the headphone connector broke inside muting the 8200 and I had to remove the headphone board).
What should I check?
Sorry for the offtopic: John I have the 8200dq protoyype you sent me for the... let's say lost dacapo board. Well the analog preamp part works but the if I use the digital inputs, they only output one channel. The headphone outputs both the two channels ( at least it worked this way until the headphone connector broke inside muting the 8200 and I had to remove the headphone board).
What should I check?
JohnW
pfm member
Dear Mr. Westlake:
A while back you mentioned your $18K purchase of a used analyzer system from the USA that sold new for about $100K.
Although we are considering adding to Mr. Swenson's already full test bench with the purchase of an APx525 (with ultra-high bandwidth BW52 option for 1.2 million FFT and 24-bit resolution), we would be interested to learn what sort of system you procured to extend your measurement capabilities--and what the capabilities of that new system bring beyond what you were able to do previously.
So would you mind sharing the make and model of your tool with us?
And have you published any measures from it yet?
Respectfully,
Alex Crespi
UpTone Audio LLC
A while back you mentioned your $18K purchase of a used analyzer system from the USA that sold new for about $100K.
Although we are considering adding to Mr. Swenson's already full test bench with the purchase of an APx525 (with ultra-high bandwidth BW52 option for 1.2 million FFT and 24-bit resolution), we would be interested to learn what sort of system you procured to extend your measurement capabilities--and what the capabilities of that new system bring beyond what you were able to do previously.
So would you mind sharing the make and model of your tool with us?
And have you published any measures from it yet?
Respectfully,
Alex Crespi
UpTone Audio LLC
JohnW
pfm member
Alex,
I'm not a big fan of the AP systems - I have 4 of them in my lab, and I cannot think when I last powered one up. They are OK for production line testing but I find them pretty useless for bench R&D work - what I find most useful is a High Resolution wide bandwidth FFT system - I personally use Audio analyzers from Rohde & Schwarz which are far better for "real time" bench work.
I recently purchased a fully loaded Vector Signal Analyaser system from Agilent / Keysight. The VSA is basically an RF BW FFT system. This allows "real time" FFT analyses across a wide BW so I can observe the spread spectrum clock modulation etc.
The VSA is useful for the spread spectrum clock circuit development but its still not ideal for the realtime 500MHz BW required for the USB2.0 signal as its limited to a RT BW of 85MHz or some such.... Still I'm very happy as it arrived just in time for the Detox clock circuit development.
Its a real challenge to measure across such a wide BW with high dynamic range - I use various signal source / integrity analyzers from Keysight and Wavecrest.
The first thing you need to buy is a differential probe (atleast 1.7GHz) - this will set you back around US5K (although I think my probes are 6GHz or some such).
The problem is that nobody really cares about the signal content of the USB datastream at such a critical level - and I'm not aware of any system that has the required dynamic range at a realtime 500MHz BW... so you have to either perform indirect measurements or limited BW measurements. Its always a trade of between Dynamic range or Bandwidth even at these silly prices.
A decent FFT analyzer + high performance scope with Diff probe is a good place to start.
Next, try and arrange a demo of a real time spectrum analyzer from Tek such as there RSA6000 Spectrum Analyzer to see if you can capture the USB data with a usable dynamic range...
I'm not a big fan of the AP systems - I have 4 of them in my lab, and I cannot think when I last powered one up. They are OK for production line testing but I find them pretty useless for bench R&D work - what I find most useful is a High Resolution wide bandwidth FFT system - I personally use Audio analyzers from Rohde & Schwarz which are far better for "real time" bench work.
I recently purchased a fully loaded Vector Signal Analyaser system from Agilent / Keysight. The VSA is basically an RF BW FFT system. This allows "real time" FFT analyses across a wide BW so I can observe the spread spectrum clock modulation etc.
The VSA is useful for the spread spectrum clock circuit development but its still not ideal for the realtime 500MHz BW required for the USB2.0 signal as its limited to a RT BW of 85MHz or some such.... Still I'm very happy as it arrived just in time for the Detox clock circuit development.
Its a real challenge to measure across such a wide BW with high dynamic range - I use various signal source / integrity analyzers from Keysight and Wavecrest.
The first thing you need to buy is a differential probe (atleast 1.7GHz) - this will set you back around US5K (although I think my probes are 6GHz or some such).
The problem is that nobody really cares about the signal content of the USB datastream at such a critical level - and I'm not aware of any system that has the required dynamic range at a realtime 500MHz BW... so you have to either perform indirect measurements or limited BW measurements. Its always a trade of between Dynamic range or Bandwidth even at these silly prices.
A decent FFT analyzer + high performance scope with Diff probe is a good place to start.
Next, try and arrange a demo of a real time spectrum analyzer from Tek such as there RSA6000 Spectrum Analyzer to see if you can capture the USB data with a usable dynamic range...
Hi John:
Many, many thanks for your detailed reply. I will forward your comments to John Swenson. He does already have an expensive set of differential probes, a wide-band scope, and a decent RT spectrum analyzer.
But we have not the budget (and perhaps not the need) to venture into the really high dollar ($40K plus range) of test gear. I have seen some used Wavecrest DTS units at fair prices, but again, that my not be our priority at this point.
Best regards,
ALEX
JohnW
pfm member
Alex,
The Wavecrest DTS units are nothing more then glorified time interval counters and useless for the Johns needs - I use a SIA4000 and ScopemaX units. The SIA4000 has quite poor LF noise performance (the SIA3000 which are quite common are even worst), but the ScopemaX is much better.
http://02d354b.netsolhost.com/technical/pdf/ScopemaX CTA vs. E5052B.pdf
Wavecrest is sadly now out of business, I guess there units where just too expensive.
That's what he told me too.
Yes, now that Wavecrest/Gigamax are OOB, I've been watching for a used ScopemaX for our John (Swenson).
Many thanks again.
--Alex
P.S. I must say, my heart had a bit of its own jitter event when I saw the $79K starting price of the Tek RSA6000 you mentioned. Maybe we are all in the wrong business!
beammeup
pfm Member
OK interesting, also interesting reading your advice on a valve/tube amps opening up the sound stage - and of course the possibility of introducing a TDAC.
John, what is it about the valve as an electronic component in the design of audio that can noticeably improve the delivery of sound? I'm interested from an engineers perspective. Is it just generally a superior 'component' to put in a circuit offset by the fact that it generally requires more maintenance and consideration from the user (thus putting people off)?
Related to the tubes discussion, I have been playing with a small hybrid tube headphone amp (with SS output stage) and I can assert that the soundstage seems wider than in some other SS amps that I have used. Arguably there is harmonic distortion, but in a very pleasant way
But I am sure John's design will have a great soundstage, I am looking so forward to gettin the FDAC!
But I am sure John's design will have a great soundstage, I am looking so forward to gettin the FDAC!
- Status