re-draw the I/V sch of Krell SBP-32X DAC

[X.G.]

http://www.hifidiy.net/dispbbs.asp?b...D=18222&skin=0

I compare the krell DAC and my TDA1541 NOS DAC with steep LPF.

the rezult is:

soudstage, danamic and the brightness of piano,the krell is better

the smooth and vocal,my DAC is better

my DAC is on here:

http://www.hifidiy.net/dispbbs.asp?b...D=16858&skin=0









the DSP IC is motolora KSP56001,the anolog power(+/-12V) is 7818/7918 +MC1468(maybe mc1486)with MJ15030/15031,the digital power is 7808+7805.and the PCB of digital part is 4 layer.

[geekay]

waiting reply
^_^

[wwwblue]

up

[tvi]

Have you traced out the power supply?

[X.G.]

I traced all digital power supply,and I found that it is so simple and standard,so I didn't traced all details of analogue power supply.


the DAC is in my friend hands. if you want to know all about the PS,I will ask him to help.

thanks for your hard work....the sch is just my sketch which I draw while I traced...I had no more time to re-check it.

[janneman]

Hi X.G,

That is an interesting I/V. What I wonder about is why they used those coupling caps. With a bit of ingenuity they could have avoided that, especially as it appears they have an offset pot in the driver stage at the end. What do you think?

Jan Didden

[X.G.]

hi,Mr. janneman

before I draw the SCH,I guess that the analogue circuit is discrete IV +positve discrete OPA +negative discrete OPA.but you now can see that,the discrete OPA all are positve,and arrange a BJT as splitter phase stage.the BJT splitter phase stage is very simple and effective,but have much offset,so they used two 10U coupling cap.

for the input coulpling 10U cap of splitter phase stage....I didn't try PCM58,but I have tried my TDA1541 NOS DAC,the coulpling cap is necessary,because the offset of temperature...In the ML DAC which show in ML website,you can see the heat couple of the PCM1702(PCM1704?) and the NTC(PTC?) resistor.maybe the ML DAC tell me why.

X.G.

[Jay]

Originally posted by X.G.
soudstage, danamic and the brightness of piano,the krell is better

the smooth and vocal,my DAC is better

Sounds like you're comparing higher bit DAC with lower bit one. I would prefer the higher one, Krell I suppose in this case, and workout the vocal quality through caps replacement or speaker design

[janneman]

Originally posted by X.G.
hi,Mr. janneman

before I draw the SCH,I guess that the analogue circuit is discrete IV +positve discrete OPA +negative discrete OPA.but you now can see that,the discrete OPA all are positve,and arrange a BJT as splitter phase stage.the BJT splitter phase stage is very simple and effective,but have much offset,so they used two 10U coupling cap.

for the input coulpling 10U cap of splitter phase stage....I didn't try PCM58,but I have tried my TDA1541 NOS DAC,the coulpling cap is necessary,because the offset of temperature...In the ML DAC which show in ML website,you can see the heat couple of the PCM1702(PCM1704?) and the NTC(PTC?) resistor.maybe the ML DAC tell me why.

X.G.

Yes I see that, but all the voltages on those coupling caps are all very close to zero. A simple servo would take care of any residual temp drift. Now with the coupling caps, the temp drift is no longer seen at the output but it is of course still there, it moves the operating point of the stages around.
But then again, many people prefer coupling caps over servo's, so maybe that's the reason behind as well.

Jan Didden

[X.G.]

Originally posted by janneman

But then again, many people prefer coupling caps over servo's, so maybe that's the reason behind as well.

Jan Didden

yes.I am one of them.

for my experience,I get the relax sound more easily in coupling caps than in servo's.

to Jay:

what I said is in speaker.in the headphone,the whole sound of my NOS DAC is better than Krell...

yesterday,I compare my NOS DAC with the PS audio's digital Link II...the sound of my DAC is much better,more relax,more focus,more smooth,deeper soundstage.....