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Old 18th July 2006, 07:24 PM   #621
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ecdesigns ,

also ... can you calculate the amount of negative feedback in the output stage?


thanks
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Old 18th July 2006, 10:22 PM   #622
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Default clock buffers

Hi tubee,

Thanks for your reply [post#618]

In the test setup I didn't use differential drivers yet, as the DAC is located close to the CD player. I synchronously reclocked the I2S signals from the servo chip and used a 7 BCK delay for WS, and inverted it to adjust the sony format so it will work with the TDA1543. This setup uses a timing chain with 6BCK intervals of course.

For the octal D-I DAC I still use the DS8922 (Dual RS422 driver / receiver) as it produces better results. But I am already looking for better ones. I also used self made stranded wire twisted pair cable of about 2.5 meters long to reduce cable induced jitter. I am testing long wires to transport differential I2S because I need it later when using the mac. When only using the CD changer, I could use much shorter I2S interlinks.

As I said, the schematic diagram is a rough setup, the 74LS164 should be a 74HC(T)164 of course (the LS indication is fixed in the schematic capture program, so I have to edit this each time). Inverters.... yes I get your point, the only ones that could cause jitter are the BCK buffers for the TDA1543 clock. Both WS and DATA may contain jitter as they are not directly determining the initiation of the conversion process in the TDA1543. The timing chain only output's both delayed WS and DATA. So only the TDA1543 BCK is critical for jitter. Well then let's try a dedicated clock driver for BCK like the CDC208 or IDT74FCT807BT.
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Old 19th July 2006, 07:18 AM   #623
tubee is offline tubee  Netherlands
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Default clock

Thanks for comments John.
Quote:
try a dedicated clock driver for BCK like the CDC208 or IDT74FCT807BT.
With a Tent XO or something like that?
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Old 19th July 2006, 10:45 AM   #624
a333bt is offline a333bt  Slovenia
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Hi Ecdesign,

can be this something useful (putting op-amp into Class A)?

http://www.audioasylum.com/audio/twe...es/130847.html

I am already confused, what DAC to make for CD-PRO2 (48fs).

Would you later can give more details about Sonic resonators?

Till now i have best results with Klangfilm fieldcoil 8" speakers in open baflle filled with fine sand. No need tweeter, crossover. Still i plan to try also Plasma tweeters.
I tried speakers with same construction alnico and field coil (elektromagnet).
It makes very big difference in sound: much clean, details, more natural, faster...
Friend will convert Lowther speakers to field coil soon, it could be interested to hear.

All the best. Bostjan
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Old 19th July 2006, 02:30 PM   #625
Art is offline Art
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Default 64 bit Shift Register HFE4517

Hi ecdesigns and all,
Nice to meet you, ecdesigns. I think dual 64 bit shift register HFE4517/MC14517 will help this great job more simple. Please consider the schematic below.

You can add more MC14517 and connect to Q1-Q7 of 8 bit shift register 74HC164 for more step. For example, if connect MC14517 to output Q4 of 74HC164, you will get FS/SD20, FS/SD36, FS/SD52, FS/SD68.

How do you think?
Regards,
Monsan S.
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Old 19th July 2006, 07:30 PM   #626
tubee is offline tubee  Netherlands
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Default pulling a opamp in class A

Audio.nl gave such tips. I did it once, after different results i never tried it again. But is worth a try.

http://audio.nl/articlepic/fig4.JPG

More tips: http://audio.nl/tips.htm
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Old 19th July 2006, 08:02 PM   #627
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Default 8 X TDA1541A / 32 X TDA1543 ?

Hi tubee,

Thanks for your reply [post#623]

The clock buffer is intended to keep BCK jitter low, it can be used for both the master clock oscillator and the synchronously reclocked BCK. Every gate (inverter) adds jitter to the input signal. I have been very busy today testing all kind of buffers. The 74...08 types seem to produce the cleanest signal. Speed: LS08 / 17nS, HCT08 / 11nS, HC08 / 7ns, F08 / 4.2ns, VHC08 / 4.3ns. So the fastest types have around 4ns propagation delay, the fastest types also seem to produce the lowest jitter.

Oh yes, I also completed the 32 X TDA1543 D-I setup, I will post a photo later. My aim was to see if it could catch-up with the octal D-I DAC, using more chip's. Even with 32 chip's the Direct Interpolation works fine. It will work with 64 chip's as well, no doubt. That's about the limit as we run out of taps.

Comparison to the octal D-I DAC using the TDA1541A showed the octal D-I DAC still sounds more beautiful, especially the warm midrange and crystal clear details and lower overall distortion. So both the tube output stage (mixed mode) and low distortion DAC's are important (TDA1543 has about 10 times higher distortion when compared to the TDA1541A). It's doubtful if the low distortion of the octal TDA1541A setup can be obtained with lot's of TDA1543's in parallell. Then there is the problem of DEM clock synchronizing, this is not possible with the TDA1543.

So after a lot of experimenting and listening, the octal D-I DAC using the TDA1541A still has the best sound quality.

Now I need to get BCK jitter as low as possible AFTER the interlink. The way this is achieved will determine how the I2S interface will be constructed. Since there is no real standard for I2S connections, I plan to use a 8 way metal DIN connector / socket with screw locking mechanism and gold plated contacts. This connector can carry 4 differential signals, BCK, WS, DATA and a addittional clock signal (MCK) and has a screen connection. The quality is better than the plastic RJ45 connectors and different types of twisted pair cable (stranded wire) can be used.
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Old 19th July 2006, 08:06 PM   #628
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Default Selecting the DAC setup

Thanks for your tip [post#624]

I will do some experiments with putting op-amps in class A.

As noted in the previous post, the octal D-I DAC is better compared to the TDA1543 D-I setup. So I will use the existing setup with 8 X TDA1541A.

When using CD-PRO2 (48fs), there are 2 possible solutions:

1) Use a sony format timing chain module in the octal D-I DAC, the CD-PRO2 can now be directly connected to the octal D-I DAC.

2) Use the universal I2S interface, and feed the derived philips format directly to the octal D-I DAC using a philips format timing chain. The universal I2S output signals are already synchronously reclocked with the master clock, so they have low jitter.

> I think it's best to put some more information about the sonic resonators in a new thread (loudspeakers / ESLs, planars, alternative technologies section) as soon as I have got some more time. The sonic resonators are full 360 degree omnidirectional radiators with a spherical pattern, meaning there is no sweet spot as we know it, sound impression will stay exactly the same, no matter where you listen, so the "sweet spot" is all around you and even beyond the listening room. Volume can be turned all the way up without sound colouring. Distortion is so low (due to corrective mechanism), you could loose sense of volume setting, you only notice they are playing really loud when you try to talk to someone next to you and discover you have to shout so they can hear you.
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Old 19th July 2006, 08:15 PM   #629
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Default Timing chain setups

Hi Art,

Thanks for your tip [post#625]

Smart setup, yes this would be a super solution for the timing chain. But when I looked trough the HEF4517 datasheet, it turned out maximum advised clock frequency is only 1.5...2 MHz at 5V. BCK is about 2.8 MHz, maximum propagation delay must be well within 177ns. So the HEF4517 (220-440ns @5V) is basically too slow, it might just work, but it remains very critical. Have you already tested it ? The HEF4517 power supply voltage could be raised to 15V (60-120ns) but then 19 fast level translators would be needed.


Regards,

John
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Old 20th July 2006, 02:56 AM   #630
MGH is offline MGH  United States
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Hi EC,

Well, I have to wonder as your Octal D-I DAC nears completion how much it will end up costing as a DIY kit. Given the amount of machining you are putting into the chassis alone - BTW, it is very professional and clean looking - plus the number of parts involved in the digital and analogue sections, I'm hoping the kit price won't sky rocket - at least by DIY standards. Could you give an estimate of what this kit is going to cost for us mortals?
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