Home made audio multiplexer (switch) using 4051 or 4052? (74HC...)???

[pekinin]

I am interested in building a audio inputs switch (audio selector). I have experience in digital circuits, but not much in analog circuits, but I am passionate about audio. So I need a little help.

Had thought of using a pair of 4051 with 8 inputs each, and also a small micro controller (atmel avr or microchip pic). It would be better to use the 4052? (I prefer to have 8 stereo inputs with two 4051, one for each channel)

Someone can recommend me any design or schematic?

I have to put a "audio buffer" or preamp? in the output? in the input? in two places? (if so, could use a NE5532?)

Any information is welcome: schematics, designs, tips, ideas... (I need help especially in the analog audio part (input or output preamplifier, buffer...)

Thanks you very much for everything!

PS: The 4051 has an acceptable quality? or make noise in the audio?

Thanks! bye!

[dangus]

I'm not sure about the quality of the old CMOS muxes. There's newer and more expensive muxes available from mfgrs like Maxim and Analog Devices.

ADG508FBN from Analog Devices is one that I've used in data acquisition applications. The specs are pretty good, and it has the sometimes useful feature of going high-impedance on the inputs when unpowered. The dual 4:1 version would be more useful, the ADG509F, since one chip is all you need for a stereo four-input switch.

Maxim's versions are the MAX4708 and MAX4709, if those are more available. Just beware of chips from vendors in China that are used non-faultprotected MUX chips that have been removed from boards and re-marked. I nearly got stung with 100s of those, buying through a broker.

[pekinin]

I am interested in the classical CMOS 4051 or 4052, for two reasons: they are very cheap and easily found at any electronics shop. Thanks for your answer, all help are welcome!

Regards!

[Steerpike]

4051 and 4052 work very well if they are buffered on the input (before) and output (after).

[mlloyd1]

go to the hafler web site and look for the manual for the 915 preamp.
this design will have some useful tips for you.

mlloyd1

[pekinin]

What is the best way to buffering the in and out of 4051 (and 4052). Using the NE5532 operational (or other)? discrete design with transistors?

You have a drawing of the buffering circuit?

One question, could I use the output buffer to send the signal to more than one output (i.e: amplifier, REC output, VCR ...)?

[AuroraB]

4051 and the likes have a resistance that varies with the applied signal voltage. If you don't object to phase inverson, - using an opamp as an inverting amp- try to use the mux part inside a summing/current amp - mux output directly couples to the - input, and choose series and feedback resistors to match your impedance and gain demands.

The SSM-2402 is a fundamentally better part for the task - albeit quite more expensive. This app.note might give some ideas....
http://www.analog.com/static/importe...50192AN121.pdf

[pekinin]

Hello, like AuroraB said, I've been looking schematic of pre-amplifier Hafler.

I have seen the 4051, has connected the audio input directly, without any input buffer. In the output it has a buffer, a FET Follower (is the correct name?).

I modified the schematic to suit what I want to do, is attached. Is that correct? If I build like this, works ok?

As I said I do not know much about analog signals. I can connect "Audio amp output to" to more than one input line of various device at the same time (without loss of signal)?

Another question, a 2SK163 replacement easy to find? I asked in my usual electronics but they don't have it.

Thanks a lot!

[pekinin]

Originally posted by Steerpike
4051 and 4052 work very well if they are buffered on the input (before) and output (after).

Steerpike, can you give me more info about how to buffering the input and outputs of 4051 (or 4052)? Thanks!

[porkyc]

Please bear in mind that these chips are NOT silent switching. By their very nature, there is an artifact at the time of switching. The Analog Devices purpose built mux/switches are better.
Also, put the switch at the virtual earth point of the output buffer amp so you are switching current, not volts.