Em-brace your case
Hi Thorsten
Good idea!
If the external approach is adopted, what is the best means of connecting the clock and I2S between the two units, ie. what type of cables, etc. should be used?
Would you recommend re-clocking of the I2S as it enters the external case?
One last capacitor question:- Are Os-Cons any good for decoupling on the analogue side of the DAC?
Hi Rotellian
It would be great if Bernhard (or anyone else with experience of this) could confirm it for us.
Is your CD62 the same as Bricolo's? How do you think the build quality compares to the Rotel 965?
Hi Bricolo
Relief!
It seems like you have the best of both worlds - a nice metal case, aluminium front panel and the internal plastic bracing. I would call it a metal case too
- jumped to the wrong conclusion when I saw the bracing.
Where will you place the new DAC? Will you remove the existing DAC or run a two-DAC setup like Carlos?
I'm in the same situation - so any improvement will seem good, without something better to comare.
Hi Thorsten
Good idea!
If the external approach is adopted, what is the best means of connecting the clock and I2S between the two units, ie. what type of cables, etc. should be used?
Would you recommend re-clocking of the I2S as it enters the external case?
One last capacitor question:- Are Os-Cons any good for decoupling on the analogue side of the DAC?
Hi Rotellian
Originally posted by Rotellian
I imagine that a ceramic cap across the motors terminals and then possibly same again from each terminal to gnd would help. But i could be wrong
It would be great if Bernhard (or anyone else with experience of this) could confirm it for us.
Is your CD62 the same as Bricolo's? How do you think the build quality compares to the Rotel 965?
Hi Bricolo
Originally posted by Bricolo
No problem, Fin
Relief!
It seems like you have the best of both worlds - a nice metal case, aluminium front panel and the internal plastic bracing. I would call it a metal case too
- jumped to the wrong conclusion when I saw the bracing. Originally posted by Bricolo
Yes I'm planning to change the DAc, for the momment I'm trying to get Rudolf's super pair IV to work
I have a +3V DC offset on the output, whatever I do with the pot.
Where will you place the new DAC? Will you remove the existing DAC or run a two-DAC setup like Carlos?
I'm in the same situation - so any improvement will seem good, without something better to comare.
OK so I modded my CD723 - and it's getting better
On my route to the CD723 KYW-SE Signature LE OSE I am currently at about the "S" stage (actually 1b on the plan below). It already sounds quite respectable!
Modification Sequence (intended to address the biggest problems first, so that later mods can be properly judged):
1. Upgrade PSUs
a) +/- 15V for I/V stage
b) +5.4V for DAC (gives 4.9V on DAC after 100R/220uF filter)
c) +12V for Servos
d) +5V for VAM1201 signal processing
e) +5V for clock
2. Modify circuits
a) Fit Tent Clock
b) Adjust for 2mA FSC
c) Change o/p filter from CF to KYW circuit
d) Try AD812
e) Output null circuit to remove o/p caps
3. Upgrade components
a) BG NX Hi-Q for Vref
b) Silmic decoupling caps for I/V
4. Mechanical Mods
Further updates in due course.
On my route to the CD723 KYW-SE Signature LE OSE I am currently at about the "S" stage (actually 1b on the plan below). It already sounds quite respectable!
Modification Sequence (intended to address the biggest problems first, so that later mods can be properly judged):
1. Upgrade PSUs
a) +/- 15V for I/V stage
b) +5.4V for DAC (gives 4.9V on DAC after 100R/220uF filter)
c) +12V for Servos
d) +5V for VAM1201 signal processing
e) +5V for clock
2. Modify circuits
a) Fit Tent Clock
b) Adjust for 2mA FSC
c) Change o/p filter from CF to KYW circuit
d) Try AD812
e) Output null circuit to remove o/p caps
3. Upgrade components
a) BG NX Hi-Q for Vref
b) Silmic decoupling caps for I/V
4. Mechanical Mods
Further updates in due course.
LM317 (National, unknown vintage, previously used) - everything else pretty much as KYW recommends. All caps PanaFC except the 2200u Rubycon YXFs (no particular reason, just had them in the bitbox). 3R3 and 10R are wirewound ceramic cased 3W.
Here are my notes:
----------------------------
Implementation
1a and b) 20VA 0-15, 0-15 Avel Toroid with electrostatic screen. 11DQ090 rectifiers generating 2 identical rails with 3R3 – 470uF (FC) – 10R – 2,200uF (YXF) – connector to local reg board which contains 3 X LM317. Each LM 317 set for 46mA quiescent with 220uF FC to decouple each ref pin. Still using decoupling on audio board, 220uF 25V FC for I/V, 470uF 25V FC for DAC, 39uF 35V FC for DAC Vref.
Listening
1a) More detail and noticeably cleaner sounding (compared to 7815/7915 Audionics PSU). Still somewhat thin and sibilant but good separation between instruments.
1b) Much of the thinness has gone, the sound has much more body and greatly improved tonality and texture of voices and instruments. Increased detail and tunefulness on bass, treble seems less distinct however percussion sounds tighter and more realistic. Slightly mechanical quality to the music. Could well be better than the Arcam at this stage!
Note: Concerned about sharing of OV line for +5 and +15 V lines which means that the DAC supply current (5mA) returns through approx 3cms of shared CAT5 wire. This will impact regulation of the +15V supply.
---------------------
I might need to re-visit the shared OV wire aspect, but will probably leave this until other mods are done so it's easier to hear the difference.
The main reason I think the results are better this time is because I am taking much more care over really tight layouts and grounding (even though I have learned time and time again, with power amps, that the grounding is ultra critical). KYW's enhancements (preload and CRC on the vregs) also seem to be very worthwhile. I also suspect that the KC-7 either radiates or picks up lots of vhf - I had it right under the VAM1201 pcb and the data sheet recommends a screening can here.
Re: Em-brace your case
Konnichiwa,
IMHO? Analogue style connections on twisted pair or Coax. For example, a LM6171 per line could drive backterminated 75 Ohm Coax Cables on BNC or SMB connectors using high speed micro coax (RG-316DT comes to mind). This makes for 4 pcs of very thin and rugged coaxial connections with a bandwidth > 100MHz, making for a reliable transmission of the clock to the transport and the I2S signals to the DAC. Probably overkill and no doubt purely digital transmission methodes can be made to work as well, but my original background is more analog and I generall treat "digital" signal as analog, makes me more confortable.... ;-)
Absolutely. Clock local and direct next to the DAC circuitry and send to the transport as "sync". reclock all signals just as they enter the DAC Chip (if a digital filter is used re-clock after the filter) and use really fast, low noise logic for the reclocker too, plus possibly the trick of having two flip flops in series (need to look at that more in detail).
Of course, you can also fit a USB input and a normal S/P-DIF and an AES/EBU port to your DAC, making it even more versitale.
Depends, if the signal is truely analog (eg no switched component), usually no, if there is switching involved, especially with a lot of gates, yes, it is usefull. The problem is that the defintion of "Analog Supply" varies from chip maker to chip maker. It may be the supply for an Op-Amp or for a bunch of buffer gates and a switched capacitor filter and often the Datasheets are not specific enough for modern DAC's to allow this to be worked out on the green table. Empirical research may be required.
Sayonara
Konnichiwa,
Fin said:
IMHO? Analogue style connections on twisted pair or Coax. For example, a LM6171 per line could drive backterminated 75 Ohm Coax Cables on BNC or SMB connectors using high speed micro coax (RG-316DT comes to mind). This makes for 4 pcs of very thin and rugged coaxial connections with a bandwidth > 100MHz, making for a reliable transmission of the clock to the transport and the I2S signals to the DAC. Probably overkill and no doubt purely digital transmission methodes can be made to work as well, but my original background is more analog and I generall treat "digital" signal as analog, makes me more confortable.... ;-)
Fin said:
Absolutely. Clock local and direct next to the DAC circuitry and send to the transport as "sync". reclock all signals just as they enter the DAC Chip (if a digital filter is used re-clock after the filter) and use really fast, low noise logic for the reclocker too, plus possibly the trick of having two flip flops in series (need to look at that more in detail).
Of course, you can also fit a USB input and a normal S/P-DIF and an AES/EBU port to your DAC, making it even more versitale.
Fin said:
Depends, if the signal is truely analog (eg no switched component), usually no, if there is switching involved, especially with a lot of gates, yes, it is usefull. The problem is that the defintion of "Analog Supply" varies from chip maker to chip maker. It may be the supply for an Op-Amp or for a bunch of buffer gates and a switched capacitor filter and often the Datasheets are not specific enough for modern DAC's to allow this to be worked out on the green table. Empirical research may be required.
Sayonara
Hi Dave
Excellent report, Dave - it really helps to hear how someone has implemented what we have been told.
Hi Thorsten
I really like this I2S direct approach, with feeding the clock back to the transport. Even though I might not take on something like this for some time yet, this information helps to ensure that future flexability is built in now - while everything is apart.
The guy who upgraded his QED Digit in the following thread:-
QED Digit upgrade
used Os-Cons on all supplies to the SAA7323 Bitstream DAC (similar to my SAA7321). I thought that this might give a clue to the nature of the supply pins but then realised that he also used Os-Cons for the supply to the Op-Amp!
Not wanting to spend a fortune on this particular DAC (in light of your comments), I've narrowed the choice of decoupling capacitors down to Os-Con SA or Black Gate STD (based on price, size and availability). Do you think that this is a reasonably safe approach?
Excellent report, Dave - it really helps to hear how someone has implemented what we have been told.
Hi Thorsten
I really like this I2S direct approach, with feeding the clock back to the transport. Even though I might not take on something like this for some time yet, this information helps to ensure that future flexability is built in now - while everything is apart.
The guy who upgraded his QED Digit in the following thread:-
QED Digit upgrade
used Os-Cons on all supplies to the SAA7323 Bitstream DAC (similar to my SAA7321). I thought that this might give a clue to the nature of the supply pins but then realised that he also used Os-Cons for the supply to the Op-Amp!
Not wanting to spend a fortune on this particular DAC (in light of your comments), I've narrowed the choice of decoupling capacitors down to Os-Con SA or Black Gate STD (based on price, size and availability). Do you think that this is a reasonably safe approach?
Nichicon Muse
Hi Rotellian
The Nichicons are available at Percyaudio.com in the US. Not sure if they will seem cheap to you - but compared to the prices I would pay locally for Panasonics, they seem attractive. Shipping costs are reasonable too. They also have BGs, which, to me seem cheap at about 60% of the Ozzie prices. Might be worth a look!
Just noticed that someone is selling bags of 50 * 470uF Muse KZ for US$24. http://www.diyaudio.com/forums/showthread.php?postid=422666#post422666
Hi Rotellian
The Nichicons are available at Percyaudio.com in the US. Not sure if they will seem cheap to you - but compared to the prices I would pay locally for Panasonics, they seem attractive. Shipping costs are reasonable too. They also have BGs, which, to me seem cheap at about 60% of the Ozzie prices. Might be worth a look!
Just noticed that someone is selling bags of 50 * 470uF Muse KZ for US$24. http://www.diyaudio.com/forums/showthread.php?postid=422666#post422666
More on capacitors
Hi All
After reading Dave's report on his progress so far, I'm now a bit curious about various filtering approaches used between the rectifier and the regulator.
Thorsten recommended the following arrangement:-
However, Dave implemented the following setup:-
Does the change from the 4,700uF to the 2,200uF capacitor make a big difference?
Also, I have seen some examples where something like: 2,200uF - 10R - 2,200uF - Reg. have been used. What difference does this type of arrangement make?
Also, Thorsten spoke of using 100uF at the regulator pins - Dave has used 220uF. Is this significant?
For the power supplies to the servos, Thorstem suggests capacitors with about 10,000uF before and after the regulators:-
It looks like I may have to compromise on something here, due to availability. So I'm wondering what is most important - capacitor size or quality?
A transformer with 12Vac secondaries produces about 17Vdc. I assume that a 25V capacitor is required here as 16V is probably a bit risky - even allowing for voltage drop across the diodes. In quality capacitors like Panasonic FC or Rubycon YXF, the largest value in 25V is 4,700uF. In Nichicon Muse, there is 6,800uF. Cheaper brands like Jamicon, make a 10,000uF.
Any suggestions???????
Hi All
After reading Dave's report on his progress so far, I'm now a bit curious about various filtering approaches used between the rectifier and the regulator.
Thorsten recommended the following arrangement:-
However, Dave implemented the following setup:-
Does the change from the 4,700uF to the 2,200uF capacitor make a big difference?
Also, I have seen some examples where something like: 2,200uF - 10R - 2,200uF - Reg. have been used. What difference does this type of arrangement make?
Also, Thorsten spoke of using 100uF at the regulator pins - Dave has used 220uF. Is this significant?
For the power supplies to the servos, Thorstem suggests capacitors with about 10,000uF before and after the regulators:-
It looks like I may have to compromise on something here, due to availability. So I'm wondering what is most important - capacitor size or quality?
A transformer with 12Vac secondaries produces about 17Vdc. I assume that a 25V capacitor is required here as 16V is probably a bit risky - even allowing for voltage drop across the diodes. In quality capacitors like Panasonic FC or Rubycon YXF, the largest value in 25V is 4,700uF. In Nichicon Muse, there is 6,800uF. Cheaper brands like Jamicon, make a 10,000uF.
Any suggestions???????
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