| stef1777 |
Hi folk!
I'm looking to implement a better circuit to replace a CD4053BCM (Farchild) between a DAC output and a volume control inside an equipment. The 4053 is a 16-pins SOIC version.
I'm not familiar with analog switch.
Can we source a better reference than the Farchild version using other suppliers?
Can we found another IC to replace it using the same pinout and logic control?
Thanks in advance.
Stef...
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| davidsrsb |
There are many 4053 makers.
Your circuit is a simple change over that suffers from poor crosstalk. |
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| stef1777 |
| quote: | Originally posted by davidsrsb
There are many 4053 makers.
Your circuit is a simple change over that suffers from poor crosstalk. |
Yes, crosstalk and THD...
I tried to compare Maxim MAX4053A and Fairchild CD4053BCM specs but they do not use the same ref to calculate crosstalk. I'm lost.
The diagram posted previously do not show all components. Just the one used by the analog signals. At input, its an AKM DAC, at output an CS3310 (replaced by a PGA2311).
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| davidsrsb |
THD will be negligible with a high impedance load as long as the signal stays between the supply rails.
Crosstalk is hard to compare as some of the data sheets use very unrealistic 50R input and OUTPUT resistances. The series source resistor has a bad effect on crosstalk. The best way to kill crosstalk is to use a "T" arrangement of switches arranged ON-OFF-ON or OFF-ON-OFF. Take care to filter the power supplies well - easy enough as current drain is tiny.
Fancy switch chips mostly just have very low ON resistance, which has little effect in this sort of circuit. |
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| clem_o |
Hi!
How about replacing the thing with a DPDT 5V relay... zero distortion, bw better than any electronic analog switch at a reasonable cost...
:-)
cheers |
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| stef1777 |
| quote: | Originally posted by davidsrsb
Crosstalk is hard to compare as some of the data sheets use very unrealistic 50R input and OUTPUT resistances. |
I am sure that they do it purposely. Unfortunaly, I'm so bad with maths...
| quote: | Originally posted by clem_o
How about replacing the thing with a DPDT 5V relay... zero distortion, bw better than any electronic analog switch at a reasonable cost... |
Relay will produce clic and ploc...
Another solution will be to use circuit as Analog Device SSM2404. But this is not pin-out compatible and will need a new design plugged in place of the existing soic16 CD4053. Not a five minutes work!
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| timmoss |
| Don't know of a pin for pin replacement , but a few circuit mods can improve matters. Biasing teh inputs to around half supply voltage and using DC blocking caps will lower distortion (bias with 510k resistors and use a potentia; divider to derive 1/2 supply volts. Alternatively use them at the virtual earth point of an op-amp , one in series and one to ground driven by an inverter, this give excellent distortion and cut-off but obviously requires a rebuilt. incidentaly the virtual earth system was and possibly still is used by Harrison in their well regarded high end recording consoles,and if i rememer correctly by Rupert Neve in his consoles. |
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