Hi all,
Based on some discussons here, I recently tried to reclock the SPDIF output of my Rotel 855 cd player (used as a transport) using 74HC74 fed from a 66MHz clock (asynchronous)
In stock form, the Rotel uses a 74HCT08 buffer and I placed the 74hc74 between the oversampling chip and the 74HCT08.
I have noticed very small pops occasionally coming through when music is playing.
Couple of questions:
1. Is the 74HC74 in the right place, i.e. should it be AFTER the '08?
2. Transformers on digital out appear attractive because of the comon mode impedance provided. Could I place a transformer after the '08 or should I try '74 after '08, with '74 feeding the output transformer?
Thanks for any help!
Ryan
Based on some discussons here, I recently tried to reclock the SPDIF output of my Rotel 855 cd player (used as a transport) using 74HC74 fed from a 66MHz clock (asynchronous)
In stock form, the Rotel uses a 74HCT08 buffer and I placed the 74hc74 between the oversampling chip and the 74HCT08.
I have noticed very small pops occasionally coming through when music is playing.
Couple of questions:
1. Is the 74HC74 in the right place, i.e. should it be AFTER the '08?
2. Transformers on digital out appear attractive because of the comon mode impedance provided. Could I place a transformer after the '08 or should I try '74 after '08, with '74 feeding the output transformer?
Thanks for any help!
Ryan
Stupid question time.......
Why async, instead of sync?
See if the forum search function turns up any SPDIF circuits with my name. But if it doesn't:
Don't use the Q and Q_bar to make a differential signal.
Jocko
Why async, instead of sync?
See if the forum search function turns up any SPDIF circuits with my name. But if it doesn't:
Don't use the Q and Q_bar to make a differential signal.
Jocko
Hi Jocko,
Can you explain your comment about not using qbar and q to make a differential signal - this is exactly what the PS Audio lambda drive does on both spdif out and aes/ebu via an output transformer.
Can you explain your comment about not using qbar and q to make a differential signal - this is exactly what the PS Audio lambda drive does on both spdif out and aes/ebu via an output transformer.
That is what I suspected, although the differences are very small compared to the period of the actual waveform. I am not sure that a high bandwidth differential driver would be much better in this regard due to delays. I think it is questionable whether most cmos logic would drive AES/EBU or even spdif well single ended (roughly 220 ohms total with series and back termination resistors on AES/EBU) through a transformer with a ratio of 1.4:1 which is why the Lambda uses differential drive with a ratio of about 3.3:1 or 4:1 .
Perhaps paralleling a couple of gates for higher output current would work somewhat better..
When the lambda worked it sounded good, few transports at or above the price surpassed it let alone equalled it.
Kevin
Edits to fix embarrassing typos.. LOL
Perhaps paralleling a couple of gates for higher output current would work somewhat better..
When the lambda worked it sounded good, few transports at or above the price surpassed it let alone equalled it.
Kevin
Edits to fix embarrassing typos.. LOL
SPDIF, Jocko
Jocko,
Have not seen any schematics with that search, only offers of a board and some pics of a completed circuit posted by someone. Do you have a schematic you can post here?
Thanks
Ryan
Jocko,
Have not seen any schematics with that search, only offers of a board and some pics of a completed circuit posted by someone. Do you have a schematic you can post here?
Thanks
Ryan
If you asynchronously reclock the SPDIF datastream, I'll wager a pound to a penny that the propagation delay between q and qbar will be the least of your worries.
My question had absolutely nothing to do with the asynchronous clocking question, but rather Jocko's assertion that driving a spdif output transformer with the Q and Q_bar outputs of a flip-flop was a bad idea. I understand in theory why this is not the best thing to do, but NO one so far has furnished evidence of a superior way of accomplishing this task. Every approach has its pitfalls.
The Lambda Drive I own commits just this faux pas, and demonstrably sounds better than almost anything I have yet heard except for some very expensive teac/esoteric drives.
Kevin
The Lambda Drive I own commits just this faux pas, and demonstrably sounds better than almost anything I have yet heard except for some very expensive teac/esoteric drives.
Kevin
kevinkr said:
Perhaps a re-reading of the title of this thread, not to mention the first post, is in order.
(Asynchronous) reclocking should be done after the DIR and also after the digital filter if present IMO.
Hi RFBW,
Yes I know what the title of the first post was and the initial subject of the thread - I was an early participant, but as I stated earlier my question was aimed at a specific assertion that Jocko made in regards to generating the spdif output - which was admittedly an aside to the general topic of the thread, but appeared in this thread. My question was seeking clarification of that assertion only, and I intended no offense in my response.
I was actually hoping Jocko would reply in person, as you may note in my post the question was directed solely at him. I can think of several reasons why this might not be the optimum approach, but as he is regarded as something of a guru on such issues I really wanted to hear his response.
Also as previously noted many theta and all PS Audio transports drive their aes/ebu and spdif transformers directly off of the Q and Q_bar flipflop outputs, and sound good doing it.
🙂 🙂
Kevin
Yes I know what the title of the first post was and the initial subject of the thread - I was an early participant, but as I stated earlier my question was aimed at a specific assertion that Jocko made in regards to generating the spdif output - which was admittedly an aside to the general topic of the thread, but appeared in this thread. My question was seeking clarification of that assertion only, and I intended no offense in my response.
I was actually hoping Jocko would reply in person, as you may note in my post the question was directed solely at him. I can think of several reasons why this might not be the optimum approach, but as he is regarded as something of a guru on such issues I really wanted to hear his response.
Also as previously noted many theta and all PS Audio transports drive their aes/ebu and spdif transformers directly off of the Q and Q_bar flipflop outputs, and sound good doing it.
🙂 🙂
Kevin
I have answered that question the other day on another forum. Rather than advertise the fact, I let the others say the same thing. But if you are enterprising you may be able to find the answer.
Anyway.............as rfbrw points out, that will be the least of your problems. But go ahead............try it anyway. You'll find out the hard way. Two bad ideas combined can make for some really rotten sound.
(But if you put Wadia on the front panel, no one will know! Amazing how many people can hear dreck, and think it is hot snot just because it costs $8K.)
Jocko
Anyway.............as rfbrw points out, that will be the least of your problems. But go ahead............try it anyway. You'll find out the hard way. Two bad ideas combined can make for some really rotten sound.
(But if you put Wadia on the front panel, no one will know! Amazing how many people can hear dreck, and think it is hot snot just because it costs $8K.)
Jocko
I've absolutely no doubt at all that asynchronously clocking spdif is the wrong way to go, I was just curious about the flip flop issue. Jocko, I will look for your posting on the other thread.
I can't talk to the Wadia issue, the last one I heard was at least 10 yrs ago, and for whatever reason, price and label on the front panel aside, I didn't like it.
Kevin
I can't talk to the Wadia issue, the last one I heard was at least 10 yrs ago, and for whatever reason, price and label on the front panel aside, I didn't like it.
Kevin
Hi Dr. H,
Check this (excellent!) link. It explains a lot and will help you make your own decision. Try making it synchronous and see if the clicks disappear.
http://www.lessloss.com/types.html
Cheers,
Extreme_Boky
Check this (excellent!) link. It explains a lot and will help you make your own decision. Try making it synchronous and see if the clicks disappear.
http://www.lessloss.com/types.html
Cheers,
Extreme_Boky
Thanks everyone,
I will try the following and report back:
Feeding 74hc74 with the cd players clock (synchronous reclock)
Reclocking with '74 AFTER 74HCT08
Jocko, any info on the SPDIF circuit you allueded to? Any diagrams perhaps?
Thanks
Ryan
I will try the following and report back:
Feeding 74hc74 with the cd players clock (synchronous reclock)
Reclocking with '74 AFTER 74HCT08
Jocko, any info on the SPDIF circuit you allueded to? Any diagrams perhaps?
Thanks
Ryan
Extreme_Boky said:
The clicks are probably due to the metastability effect. Try my ASR with two flip-flops in series and that problem will be solved.
HI Elso,
Thanks, I meant to include that option as well. I noticed on Pedja Rogic's website that he uses the 74 in this way, i.e. d1 clocked to q1 which is input to d2 and clocked to q2, both lcocking processes using the same (asynchrocnous) clock.
Will report back
Thanks, I meant to include that option as well. I noticed on Pedja Rogic's website that he uses the 74 in this way, i.e. d1 clocked to q1 which is input to d2 and clocked to q2, both lcocking processes using the same (asynchrocnous) clock.
Will report back
I have built Pedja's DAC + reclocker.
I listened to basic DAC for 3-4 weeks and played with different capacitors and grounding topology. Once I was very happy with the basic DAC, I added Pedja's reclocker with EXCELENT result.
I will post my findings about different stages of my tuning and impressions about this DAC in general.
Just to add, this DAC & reclocker together with Audiomeca Memphisto II transport produced truly amazing results. I don't think there's any "digital" combination / stand-alone player out there that approaches analog closer than this combination.
Regards,
Extreme_Boky
I listened to basic DAC for 3-4 weeks and played with different capacitors and grounding topology. Once I was very happy with the basic DAC, I added Pedja's reclocker with EXCELENT result.
I will post my findings about different stages of my tuning and impressions about this DAC in general.
Just to add, this DAC & reclocker together with Audiomeca Memphisto II transport produced truly amazing results. I don't think there's any "digital" combination / stand-alone player out there that approaches analog closer than this combination.
Regards,
Extreme_Boky
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