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

[X.G.]

http://www.hifidiy.net/dispbbs.asp?boardID=2&ID=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?boardID=2&replyID=170525&ID=16858&skin=0

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

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.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[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.

 

[jan.didden]

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]

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

 

[jan.didden]

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.]

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.....

 

[Lyra]

Seems interesting....have anyone tried to build this I/V ?

What is the original DAC inside the KRELL ?

To X.G. : Have You had more time to recheck the drawing ?

To tvi: where do you get the drawing in your attachment...is it based on the hand-drawed scetch posted by X.G. ?

Lyra

 

[X.G.]

hi, Lyra

the DAC IC is 2 pieces of PCM58P-K

the DAC is not on my hand now.I had re-checked the schematic...it just has a little mistake which is in the relay circuit.

 

[Leolabs]

"xiao di zhen de pei fu ning"

Anyway,anyone know how to get rid of that phase shifter and build it with a single-ended output only???

 

[cac liu]

up !
¶¥!½­ÃÅ.

 

[Leolabs]

"luan ma,kan bu dao"

 

[Elso Kwak]

"xiao di zhen de pei fu ning"

Anyway,anyone know how to get rid of that phase shifter and build it with a single-ended output only???

Just omit the phase shifter and use 1 output amp.
The used coupling caps are shrill Harry Haller reported a long time ago, or was it Fred? I would try to omit the caps too as much as possible.

 

[rfbrw]

Think Krell KSA50 without the output transistors.

 

[chokh]

Hi X.G.

Do you have redraw the Krell SBP-32X's digital part? My friend has the same Krell DAC and always unlock.He had been asked the Hong Kong agent for repairment but they seems can not fixing the problem.Does your DAC has the unlock problem.What kind of CD transport you are using now?Thanks.

 

[X.G.]

hi,chokh.

I can't re-draw the digital sch,cause the digital PCB is 4 layers or even more....

this DAC still have a little unlock problem: when switch the other equiment on/off at home,it may unlock by accident.but before deal with it ,the unlock problem is serious than before.

the method of deal with it is : add a 10n cap between the 'ground' terminal of the digital in(or analoge out,i fogot.....my frinend did by my advice ) and the 'ground' of box nearby.

wish it can help you.

X.G.

 

[chokh]

Hi X.G.,
Thanks your infromation and advice.Yes,my friend told me also the same problem about switches other equtment will cause unlock. I can see the photo of your DAC's digital input and output connection without a digital transformer.Right?I think it may has insulation problem between digital signal and grounding. Adding a digital transformer may help for unlock.