Linkwitz "Transform" Circuit Help

[Shike]

Hey guys, I've been trying to build a linkwitz transform circuit and had a quick question. Are the grounds shown supposed to be connected to the RCA ground, a chasis ground, floating, or virtual?

Thanks for your time in advance,

-Andrew

[Shike]

Hey guys, sorry for the bump, but I really need to know what I'm doing wrong with this circuit.

The schematic can be found at:

ESP Project 71

Thanks

[Ouroboros]

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.

[Shike]

So far I am hooking the grounds to the RCA outer jacket and power with a regulated 15v wallwart.

Here's another question, would having a polarized C1 and C3 cause the circuit to break?

[Ouroboros]

I wouldn't advise the use of non-polarised electrolytics in these positions. Have you downloaded John Murphy's Linkwitx Transform Excel spreadsheet from the True Audio site? This will allow you to play with scaling the values so you should be able to use ordinary film capacitors.

[Shike]

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.

[AndrewT]

Hi,
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.

[Frank Berry]

You're using a regulated 15 volt Wall Wart?
Is it a Bipolar supply?
The circuit needs + 15 volts and - 15 volts.
A single +15 volt supply won't work with this circuit.

[Shike]

Originally posted by Frank Berry
You're using a regulated 15 volt Wall Wart?
Is it a Bipolar supply?
The circuit needs + 15 volts and - 15 volts.
A single +15 volt supply won't work with this circuit.

Well, seems I probably just found my largest problem.

What the cheapest way about going to make a 15V Bipolar supply?

[AndrewT]

go back to ESP and read