OK so I modded my CD723 - but it's still mediocre - Page 3 - diyAudio
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Old 2nd June 2004, 10:25 PM   #21
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Quote:
Originally posted by Kuei Yang Wang

no capacitor in the feedback loop
Just tried that in my 880, no change.
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Old 3rd June 2004, 02:27 AM   #22
Fin is offline Fin
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Quote:
Originally posted by carlosfm
Of course it was.
And I have two independent RCA outs on the player, I can even A/B.
There's no comparison between a bitstream Dac, the better that it may be, and a good multibit Dac.
Yes, the TDA1543 is good.
Forget the specs, well done it's very good.

Bitstream Dacs always sound undynamic to me.

Thanks Carlos - it's good to hear from someone who has given both types of DAC a fair go. I will probably end up doing something similar to you - ie. take the SAA7321 in the CD624 to it's max, and then do a good multibit dac for comparisson. The idea of being able to A/B two DACs in one CDP is great. Do you run them off the same Tent Clock at the same time?
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Old 3rd June 2004, 03:04 AM   #23
Fin is offline Fin
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Default Absolute fact!

Quote:
Originally posted by sreten
Hmmm......

I don't know why I'm being given a hard time for trying to answer
the original question, and after all these are my opinions, not
statements of absolute fact.

If you think differently fine, they are my considered opinions.

That's fine Sreten - everyone is entitled to their opinion. However, you did challenge almost every DIYer on the Digital forum. Your statements telling us that we are all wrong were presented as "absolute fact".

Quote:
Originally posted by sreten
You can't turn a cheap CD player into a giant killer.
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Old 3rd June 2004, 08:51 AM   #24
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Quote:
Originally posted by Fin

Do you run them off the same Tent Clock at the same time?
Yes, it feeds the 7310, the digital filter, and the bitstream dac separately.
The TDA1543 gets (NOS) I2S from the 7310.
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Old 3rd June 2004, 09:12 AM   #25
Dave S is offline Dave S  United Kingdom
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Default Thanks for all the replies...

They have given me some more things to try.

I will try some of the KYW mods in the not too distant future.
I note with interest his comment about the C Found mods as I also had some doubts e.g. CF recommends changing the -11V PSU cap from 3,300u to 4,700u to match the +11V, (quote) "this balances the loading of the mains transformer windings and allows for a slightly higher current dissipation". Impressive stuff!!!!

The KC-7 is built on Elso's pcb and fitted <5cms from the signal processor - maybe I should connect it to BCK at the DAC as well (do I need to disconnect the original BCK i.e pin 48 of the SAA7378 from BCK input, pin 1 of the TDA1545?).

Elso - thanks for the OP275 recommendation. I replaced the OPA627s I/V in my Arcam with a pair of OP176s and was surprised to get a worthwhile improvement. The OPA627 is better than the OP176 in the o/p filter but it seems to be the other way round in the I/V. I will try an OP275 next time I open up the CD723.

My approach with the CD723 is in line with the points made by Fin and Jean-Paul - it's a bit of cheap, clean entertainment to see what can be achieved. Better to peel a few tracks off this pcb than a Wadia! Expectations are low so if it turns out good then that's just fine with me.

On another point - discrete I/V stages - I'm sure many will recommend this. However I had a bad experience with the LC audio ZAPfilter. The minimal instructions are wrong and eventually LC more or less agreed that the thing cannot accomodate unipolar current output without an external bias current.
Anyway, I ran the thing as a line stage to see how it sounds and was unimpressed, it's some way behind an OPA604 run off even the most basic of power supplies!
Might be tempted by KYW's OPA660 I/V circuit if I can find a decent pcb to accommodate it (haven't got time to design one 'cos I need to finish quite a number of projects).

Cheers

Dave
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Old 3rd June 2004, 09:55 AM   #26
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Try the LM6172 for I/V.
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Old 3rd June 2004, 10:10 AM   #27
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Default Re: Thanks for all the replies...

Hi,

Quote:
Originally posted by Dave S
I note with interest his comment about the C Found mods
I happen to know the gentleman, nuff said.

Quote:
Originally posted by Dave S
The KC-7 is built on Elso's pcb and fitted <5cms from the signal processor
Seperate (galvanically) PSU with low earth leakage for that?

Quote:
Originally posted by Dave S
maybe I should connect it to BCK at the DAC as well
No, don't.

Quote:
Originally posted by Dave S
I will try an OP275 next time I open up the CD723.
Try an LM6182 please. No reactive components in the feedback loop, just one resistor and adjust teh values for 2mA 0dbf on the TDA1545 (see datasheet).

Sayonara
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Old 3rd June 2004, 10:34 AM   #28
Dave S is offline Dave S  United Kingdom
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Quote: "Seperate (galvanically) PSU with low earth leakage for that?"

1) Elso recommends using the digital +/-10V rails, not a separate PSU.
2) Given that Elso may be fallible, how do I get low earth leakage? Do I need an E-I core transformer rather than a toroid?

I added an IEC mains input, which means I have the possibility to earth the chassis - is this worthwhile?

Dave
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Old 3rd June 2004, 12:30 PM   #29
Dave S is offline Dave S  United Kingdom
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LM6182 is discontinued, not sure if I can find NOS. Can I use AD812 in the same way?

Other duals in my bitbox: OP275, RC4227, NE5532, AD8620 (SO8) - any of these worth a try?

LM6172 looks viable if I can find one (not listed in Farnell, RS or Digikey), OTOH the feedback resistor, 3K3, seems a bit high for such a fast amp.

Should I change the o/p circuit from CF's, which is:
3K3 feedback resistor with 470pF polystyrene in parallel
47uF pana FC // with10nF Wima on opamp output (you aready told me to change this)
1K series resistor and 470uH and 820pF in shunt (after the coupling caps).

Thanks
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Old 3rd June 2004, 03:20 PM   #30
jkeny is offline jkeny  Ireland
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What about Peufeu's claim that Philips CD723 is not bit accurate -
http://peufeu.free.fr/audio/extremist_dac/bit_accuracy/

can the player ever get beyond mediocre?

John
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