CD 300 with CDM-0 and dual 1540

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#24
Now something where its all about: last night, neighbours where having a party, and my wive went for a visit...
After a half an hour the CD300 took off and gave some fine tunes. Have Played otherwise "sharp" sounding disks (Tears fo Fears, Elemental): not so on this :tons: 14 bit "downsampling" machine!!
Didn't know what my amp & speakers where capable of.
 
#26
now with jpeg
 

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#27
tubee said:
now with jpeg
Click to expand...

I assume you are still using an op-amp based i/v converter behind the tda1540 DACs. I have a philips CD-104 which is practically the same but i have pulled out the op-amps and replaced this with a 4 transistor output stage which gave an enormous improvement in the sound quality. After measurements it was clear why. Before, a 20 khz sinus wave was a triangle shaped signal (Nyquist) but now it's almost a sinus.
 
#28
Hello MidiMaze

Yes use the standard opamps NE5532, the machine isn't touched by anyone and is completely original. Sounds really good, even when its only 14 bit, but also because of good cdm. Had several thougts about how sound can improve with a good opamp, or better a simple I/V like yours, or something like Jocko's I/V. When doing this i don't want to change much in the CD-300 and keep it original as possible. A additional small pcb wil do, carefully mounted.
MidiMaze can you explain more your 4 transitor-scheme, or are you even willing to share a schematic with us?
 
#30
MidiMaze wrote:
have pulled out the op-amps and replaced this with a 4 transistor output stage which gave an enormous improvement in the sound quality.
Click to expand...

How do you compare performance in the bass-region of this 4 transistor I/V? I ask because i don't want to loose the very nice bass (with ML-TQWT) It has a little attenuation on the deep bass, but no booming at all, very tight and controlled, my "reference" bass performer overhere in my home.
But nevertheless still curious about the schematic, i will wait right here...
 
#32
tubee said:
MidiMaze wrote:
How do you compare performance in the bass-region of this 4 transistor I/V? I ask because i don't want to loose the very nice bass (with ML-TQWT) It has a little attenuation on the deep bass, but no booming at all, very tight and controlled, my "reference" bass performer overhere in my home.
But nevertheless still curious about the schematic, i will wait right here...
Click to expand...
The bass response is a lot quicker than with the original op-amps in place. The highs are much clearer, it's just as if you take a blanket away laid over your speakers.
I use a CD-371 for testing circuits, and if i'm pleased with it, i build it in my Marantz CD-50. The CD-104 i have is still being modified. But take a look at the pictures of my CD-50.
Marantz CD-50 modified
 
#34
The bass response is a lot quicker than with the original op-amps in place.
Click to expand...
So its worth a try then.

Nice mods on Marantz, i see you applied the original Tent PS- scheme for the XO, i did on a CD640 non os also, but later i changed the PS for the XO in this one:

http://home-4.worldonline.nl/~t708955/schem/xoschema.jpg

Music is not so laid back anymore and because of smaller caps (mounted tantalium also) more "rhitmic" sound, i like it above Tents PS which emphasise the high bass a little, but this is matter of taste.
 
#36
tubee said:

Nice mods on Marantz, i see you applied the original Tent PS- scheme for the XO, i did on a CD640 non os also, but later i changed the PS for the XO in this one:
http://home-4.worldonline.nl/~t708955/schem/xoschema.jpg
Click to expand...
Ehhm, this a different supply scheme. I do'n use Guido's scheme because the voltage regulator he uses generates a lot of HF crap. The good old 7805 only produces a spike at 78 Khz, but the 100nf caps take that away, buffer it with about 1000uf and you have a pretty clean supply.
In my humble oppinion a good outputstage gives a far better result than a new XO, mesured and listend...
 
#37
drews said:
What about simple resistor for doing the I/V converter instead op-amp??
Click to expand...
It seems that when you only use a resistor the internal current sources of the DAC won't switch at the same time due to a high load impedance. You may gues what happens to the signal comming out of the DAC. The DAC is a current source which should be loaded with the lowes impedance as possible. That's why my 4 transistor scheme uses a BJT with a high bias current to get the impdance low.
 
#38
the voltage regulator he uses generates a lot of HF ****
Click to expand...

Guido uses that good old 7805 also..... And what is ment by the four asterisks?

But when it produces much HF, its no miracle why the XO-PS with a TL431 sounds better. Kwak version 7 uses TL431 also.

For the CD300 indeed is no need for a better clock i think, the standard I/V is the weakest point.
 
#39
tubee said:

Guido uses that good old 7805 also..... And what is ment by the four asterisks?
But when it produces much HF, its no miracle why the XO-PS with a TL431 sounds better. Kwak version 7 uses TL431 also.
Click to expand...
A certain word was moderated, sorry for that.
But the TL431 is much worse in HF than the 7805, i'll see if i can make some pictures of the spectrum. I would reccomend a 7805.
 
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