Have a problem with my Cdt 100
The left channel has suddenly become about 30% lower in volume than the
Right channel ? On both outputs both Tube & s/state ?
Everything works ok just low volume on L channel
Digital out to DAC is working fine .
I tried exchanging all the op amps ( easy as they are socketed ) but no change
So I bypassed all the analog section & tube section by wiring the Dac outputs
Direct to my preamp , works ok but still the same problem ?
Low output from L channel ?
As this uses 2 DACs in parellell for each channel is this a bad Dac ?
Hard just to replace them as they are SOP , very small
Anybody have any ideas about this ?
The left channel has suddenly become about 30% lower in volume than the
Right channel ? On both outputs both Tube & s/state ?
Everything works ok just low volume on L channel
Digital out to DAC is working fine .
I tried exchanging all the op amps ( easy as they are socketed ) but no change
So I bypassed all the analog section & tube section by wiring the Dac outputs
Direct to my preamp , works ok but still the same problem ?
Low output from L channel ?
As this uses 2 DACs in parellell for each channel is this a bad Dac ?
Hard just to replace them as they are SOP , very small
Anybody have any ideas about this ?
You've done a fair bit of deductive work yourself, which is really good.
I would use a frequency sweep recorded on a CD. If one of the channels outputs 30% lower signal at all frequencies, especially high (20kHz), then you most likely have a semiconductor / IC failure. However, if the reduction in amplitude varies with the frequency, then you probably have a faulty passive component - a capacitor most likely... This is a long shot...
Another way to check this is to trace the signal from either the input (laser), or from the output (and you have already come half way up yourself), and then find the section/point that has equal signal amplitudes. Get the circuit diagram. I would also use a higher frequency signal for this, at least 15kHz sinewave recorded on a CD.
You'll need an oscilloscope as well (50Mhz for those digital IC's...)
Nick
Would you actually be able to 'scope anything at '1'?
This is the Current out (IOUT) of the DAC IC's and therefore most 'scopes wouldn't show anything. Or am I missing something?
P.
This is the Current out (IOUT) of the DAC IC's and therefore most 'scopes wouldn't show anything. Or am I missing something?
P.
I'm not so sure that is a reliable technique tbh.
Different opamp parameters will see a massive variation in the signal level seen at 'point 1' even though the signal seen at the opamp output would be the same.
For a device like the OPA2604 you might be looking at just a few 10's of microvolts of signal, for a 741 it could be a few millivolts. Both would generate the same level at the opamp output.
Checking the output of the first opamp is definitely valid though.
Different opamp parameters will see a massive variation in the signal level seen at 'point 1' even though the signal seen at the opamp output would be the same.
For a device like the OPA2604 you might be looking at just a few 10's of microvolts of signal, for a 741 it could be a few millivolts. Both would generate the same level at the opamp output.
Checking the output of the first opamp is definitely valid though.
Mooly just made me remember how I scoped the dac/s outputs.
All the opamps are socketed in this Shanling, I pulled both L&R I/V opamps, and inserted a 1kohm resistor between the input and ground this enabled me to scope the output of the dac/s
Cheers George
All the opamps are socketed in this Shanling, I pulled both L&R I/V opamps, and inserted a 1kohm resistor between the input and ground this enabled me to scope the output of the dac/s
Cheers George
that would work.- Status
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