Linkwitz "Transform" Circuit Help

The schematic shows that the filter is running off +/-15V lines, so the so-called 'ground' is really the 0V of the amplifier. If you're putting this into a seperate box then the 'ground' of the circuit will be connected to the shield (outer) of the RCA plug.

How are you intending to power this circuit? You probably don't want the mains Ground/Earth to be connected to the 0V at this point to avoid injecting hum into the following power amp.


2007-06-30 6:01 am
Yes, I've used the spreadsheet. In fact, everythings already put together it's just not working, thus the troubleshooting aspect right now which is driving me up the wall needless to say.

For C1 and C3 I have polarized electrolytics in place (shame on me). I need to know if they would somehow break the circuit though since it's showing the use of nonpolarised, because I've gone over everything else and it's the only thing I didn't really follow.
C1 & C3 are shown in figs 2 & 3 as non polarised.
I would use a film cap for these. But I don't know what value you are using. non polarised electrolytics could be substituted but may reduce performance. I doubt that the signal levels on the polarised electros would cause them to break that quickly, but if you've used Tantalum then maybe they have failed quite quickly.

The input ground goes to signal shield. You must return the input signal from whence it came.
The output ground and the 10uF decoupling cap go to the power supply return. Again you must close that loop for current to flow.

The ground triangle symbol under the input is confusing, but I would take that to your audio ground star. If you do this, you must break the link between the GND symbols or you will create a hum loop.
It's the usual problem of calling everything "ground" when they all have a different purpose.


2007-06-30 6:01 am
Hello, I'm back again.

Well, now I have a PSU made and working. What I did was I bought a higher powered DC supply and modified a cmoy PSU section to split it into a bipolar with virtual ground.

It seems to be working, however I'm getting a rather nasty hum out of it. I'm curious as to what Andrew was saying about the hum loop, and where I need to break the ground at.

Thanks for being patient with me guys, I'm still doing my best to learn this. :)


When I attach the virtual ground to the signal ground with the others the hum's reduced to nothing, and it still works though the output seems to be slightly lower. Is this how I was supposed to connect it?