Acoustic VSI June 2007

HiFi, LoFi, Tubes, Transistors, ICs, Commercial, DIY

Postby pseddon » Wed Oct 10, 2007 12:00 am

Is there anyone else out there building this?

I have a couple of questions to which I cannot find the asnwer.

1. What do the JP1 to JP4 do - I assume they set the speed value but which is which?
2. What should R2 be set to - is the same as the output of IC4D - the virtual earth?

My transmitter is working but the reciver has a fault with IC3A which is at maximum output. I have changed the IC but no change. The input with no signal is 0v but the output remains stuck at near supply voltage. As the full tarck layout is not shown in the article I am not sure if there might be a track fault?

regards Peter
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Postby pseddon » Fri Oct 19, 2007 12:00 am

So looks like no one else is building this - or maybe their's are all working. The problem with IC3A that I mentioned in my first post seems to be a design fault. I put the chip on a breadboard and simulated the input. You need at least +1.4v before the output comes out of postive saturation and it doesn't start acting as a proper voltage follower 'til the input reaches +1.6v. So looks like it will never work. Anyone else got any suggestions?

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Postby sarma » Sat Oct 20, 2007 12:00 am

Hi Peter,

While I have not assembled the project myself, a study thro the article makes me feel that the network of 10K resistors and followed by jumpers JP1 to 4 is mostly for variable reference voltahe for the ADconversion. The author may clarify.

You are perfectly correct , that the R2 (Adjustable) is for bringing 2.5V Virtual earth to a close limit of 1mV as desired in the article. It is like expansion of the range around mid point .

As reggards the minimum of 1.4V for IC3B I am yet to study.

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