Entschuldigung, ich habe mich vertippt. Ich meinte den Spannungsregler LT3045. Für den ZD3 benötigt man drei Dual-Operationsverstärker.
https://a.aliexpress.com/_EwGk07C
https://a.aliexpress.com/_EwGk07C
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Got the DAC in the mail, popped in SS3602s, looks much better now! 🙌
Now, I am curious about C30,C32 and C70,C72 caps - they are in series with what seems to be feedback resistors. These are usually calculated for specific opamp, but since DAC was designed with swappable opamps in mind, I wonder if caps were oversized to have extra safety margin?
Now, I am curious about C30,C32 and C70,C72 caps - they are in series with what seems to be feedback resistors. These are usually calculated for specific opamp, but since DAC was designed with swappable opamps in mind, I wonder if caps were oversized to have extra safety margin?
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The 330pF are noise suppression capacitors and are not directly in the signal path, but C30 and C32, as well as C70 and C74, are. They could be bridged, provided the subsequent amplifier has a coupling capacitor at the input.
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That a manufacturer knows his products and their implementation quite good. For each product and their specific implementation. It seems unlikely that they mix up stuff.
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Normally - manufacturer provide examples (in datasheets and app. notes), just to work.
But these examples are not always the best implementation.
Alex,
What about the PS of the op amps? And its decoupling caps?
Might be wise to know before swapping op amps... or in order to find improvement paths?
In short:
1- It is advertised by Fosi that the op amps are fed by "isolated power supplies". This marketing talk sounds promising. But if so, what is it exactly? It would IMHO be Interesting to find out what route they went to raise the voltage (BTW, what rail voltage do they use?) and regulate it to feed the op amps as that can be quite critical for the sonic results.
2- What are the PS decoupling caps (numerotation/identification, values and also "quality" /C0G etc.) at their op amps PS output? So directly at the output of the OP amps PS and of course also directly at the OP amps +V and -V inputs to avoid oscillations etc.
Looking into that (on top of the usual SMPS filtering or whatever other external PS, and possibly a pair of OPA1612 and 1x OPA1656 or so) might help finding interesting tuning potential.
Anyone to reverse engineer this unit to answer 1 and 2?
Have fun
Claude
Might be wise to know before swapping op amps... or in order to find improvement paths?
In short:
1- It is advertised by Fosi that the op amps are fed by "isolated power supplies". This marketing talk sounds promising. But if so, what is it exactly? It would IMHO be Interesting to find out what route they went to raise the voltage (BTW, what rail voltage do they use?) and regulate it to feed the op amps as that can be quite critical for the sonic results.
2- What are the PS decoupling caps (numerotation/identification, values and also "quality" /C0G etc.) at their op amps PS output? So directly at the output of the OP amps PS and of course also directly at the OP amps +V and -V inputs to avoid oscillations etc.
Looking into that (on top of the usual SMPS filtering or whatever other external PS, and possibly a pair of OPA1612 and 1x OPA1656 or so) might help finding interesting tuning potential.
Anyone to reverse engineer this unit to answer 1 and 2?
Have fun
Claude
Desoldered C30,C32 and C70,C72 and measured 100pF each
C15,C16 and C33,C34 are 10nF
R93, R84, R3, R36 all are 500 ohms
R95, R87, R32, R37 all are 100 ohms
Attached is also ess recommended schematics in full
C15,C16 and C33,C34 are 10nF
R93, R84, R3, R36 all are 500 ohms
R95, R87, R32, R37 all are 100 ohms
Attached is also ess recommended schematics in full
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Unfortunately high frequencies don’t sound good - there seems to be some funny business going go with the schematics. Tried replacing some caps but still no improvement. Will try tinkering with bypass caps later.
Mmmm, what would have been their purpose? It seems worthwhile to follow PCB tracks and make a drawing.
+1 on drawing Op Amp's PS
Perhaps easier if starting at the OPA's +V and -V pins and trying to find out where they come from, or whatever...
For example, the first thing you should notice starting from the OPA's PS pins is a cap to ground, the last (and important) decoupling cap, should be very next to the OPA...
Perhaps easier if starting at the OPA's +V and -V pins and trying to find out where they come from, or whatever...
For example, the first thing you should notice starting from the OPA's PS pins is a cap to ground, the last (and important) decoupling cap, should be very next to the OPA...
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