Can I switch between two input receivers?

How do I do this? A new diy twin tda1541a dac is on the way (partially assembled tube-lover's kit). His design makes use of cs8412 digital receiver. In addition to a spdif BNC input, I want to modify this dac to add a USB interface using pcm2706 digital receiver. This IC is capable of receiving USB (and spdif) and outputing I2S to the twin tda1541a IC's (which are capable of accepting i2s input).

I would build a small daughterboard with the 2706 interface with separate battery power supply so that it is not bus powered (total of about 7 parts for this board). This interface has been built by other diy'r.

So if I want both BNC spdif input socket and usb input socket on DAC, how do I best accomplish this? Here are possible options

a) Only use the 2706 digital receiver; both for spdif input and usb input. It would send i2s to the tda1541a's. But I would need some type of switch to do this? Also, would I have to de-solder the cs8412 IC that comes installed on the dac pcb?

b) Use both the cs8412 (for spdif interface) and the 2706 board (only for usb). How would I do this if I want both 8412 and 2706 to send i2s signal to tda1541a's? Can tda1541a receive two I2s signals? If this configuration is possible, how do I switch between spdif and usb inputs?

I am concerned about taking the cs8412 out of the design: (1) because most of these tda1541 dacs use this receiver; and they must use it for good reason and (2) I am paying for the part and attendent caps, power supply etc.

How best can I accomplish my goal of adding the usb interface?

Here's photo of dac pcb...



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Hi Doede, Like This....?

I've heard wonderful things about your impressive dddac. As a novice DIY, I would appreciate any feedback on whether I am on the right path in terms of your recommendation for using a sub mini relay. I found this one:

Magnecraft PC Board Relays DPDT SUBMINIATURE 6V

Do the i2s outs of both the 8412 and pcm2706 DIR's terminate into this subminiature relay, which then passes the i2s signal onto the dac i2s input?

Also, does this subminirelay require a manual switch, or does it just auto detect which DIR has current flowing through it and then pass the I2s out from the "active" DIR?

Any input is much appreciated!


Paid Member
2003-07-02 10:10 pm
I am not sure HOW critical it all is, but these relais seems ok to me... I am using similar ones I can get locally ...

Basically both receivers work in parallel and "terminate" in the relais. I do the switching by hand between both inputs with a 1 pole switch on the front panel. The position which normally would be used most, is that the position were the relais is in rest and current flows. Of course, you could look for some clever circuit, based on the USB receiver or so, that indicates which one is "on air"...

good luck !
Me, I've got a more complicated scheme: I want to switch signals from 3 inputs with independant selection modes.(3 different EIAJ, MUX OB/TWC, SPDIF...) You should look at the PNG to understand what I mean. I also want to remotely switch inputs, so a mechanical switch is not an option.

Note: In the PNG, I don't repeat the complete EIAJtoI2S and SPDIF converter each times, that's why I need to switch off inputs, in case one input uses the same mode as an other.

Relays would have been a good option in this case but the only problem is that if I need 5x 1$ DPDT relay for each inputs I will end with 15$ of relays, which is a bit too much.

I just found a post talking about using a 74F157. Is there a better choice? Will it affect jitter? Is there an other 74 series(HC,F...) I should use?


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2001-10-26 11:51 pm
With all the switching going on, it will be a lot cheaper to use IC's but for ultimate isolation T switches would be best. BTW, unless you are using one of the earlier digtal filters i.e the DF1700/SM5813 and before, you will have to convert the output of the filter into OB from TWC.