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Audio Input / Source Selctors

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quad

Well-Known Member
Joined
Feb 14, 2008
Messages
855
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Location
Hyderabad
I hope U1 is not a 89S2051 type.
The ATTiny/Atmega are much better and easier to
program too.
Suds, if possible, keep a small footprint for
the PCB. Maybe by breaking them into two stacked
ones... makes it easier to fit into an old amp.

Cranky, how about an intermediate step to ground
while changing sources? Is that better?
He is using a dual pole relay per channel, so he is
switching the ground too.

About the power cycle, the newer atmels should have
enough internal eeprom space to save the settings.
Don't remember if the old 89s ones have eeproms.
 

suds

New Member
Joined
May 23, 2009
Messages
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Location
Bangalore, India
I hope U1 is not a 89S2051 type.
This design is around 89c2051, but this can be changed..

also I am working on one more version, using rotary switch, instead of micro controller.

Does it drop back to input 1 when the power is cycled, like Brit amplifiers?

Yes, on power recycle it drops to input 1.


And is the ground not switched along with the signal?
Its designed for unbalanced input, where ground is common.

if possible, keep a small footprint for
the PCB. Maybe by breaking them into two stacked
ones... makes it easier to fit into an old amp.

Sure this can be done, but will increase the over all cost of pcb, due to setup charges.



IMO in high-end equipment it is preferred to separate the grounds by using a second set of relays to switch the ground. This is very easy to implement with two relays in parallel for each set of inputs, one for signal and the other fro ground. This would help prevent ground loops and contamination of clean signal paths (such as from CDPs, phonostages and DACs) by dirty paths (such as PC, iPods etc.


yes, but this will increase the PCB size and components, thus increasing cost of project..

To prevent pop and click-free operation, it may be desirable to introduce make-before-break operation. If it is not embedded in the logic of the chip

This can be included in micro controller version,need to write codes for it.

Steps are as follows : IN1 -> Mute -> change to IN2 -> un-mute, by design other inputs which are not used are muted, (input tied to ground).

to make it remember previous input state. EEPROM with micro controller can be used to store the data, can read upon power on, I am new to embedded programming, it will be complicated for me to write the codes.
 

quad

Well-Known Member
Joined
Feb 14, 2008
Messages
855
Points
93
Location
Hyderabad
Some sources may have issues with shorted outputs

Sure. Just thinking out aloud here - what if the
ground connection can is through a suitable resistor
to protect the source from a shorted output?
Perhaps the mute relay can go to ground through a resistor.
Then the process would be to Mute-Break-Make-Unmute. ?

In MBM, could there be any possibility of
damage/other issue (to the sources) if you connect
two sources simultaneously to the input?

You need three poles per channel to switch the ground. L/R/G. I can see dual-pole relays.

My bad! Must have been half asleep while seeing
the schematic.

Suds, the alternative controllers are nearly pin
compatible with the 89s2051, but bring plenty
other useful features (incl eeprom).
 

suds

New Member
Joined
May 23, 2009
Messages
72
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Location
Bangalore, India
I Have Completed the rotary Switch version,
One rotary switch for source select, one push button (push to on ) switch for mute
 

viki_v2

Member
Joined
Mar 4, 2009
Messages
96
Points
18
Location
Dombivli
I Have Completed the rotary Switch version,
One rotary switch for source select, one push button (push to on ) switch for mute

Hello,
the link for Pdf file is broken, can you give Pcb files for Source Selsction with rotary Encoder.

Thank You
 
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