Voodoo Lab

Hi there,

What's the GCX buffer out impedance ?
I think having guessed the input impedance is 1M, since 2 x 2M resistors (R2 + R5) are connected in parallel, right

Thanks

The input impedance is about 1M, but I will admit to not memorizing the actual output impedance as it has never been necessary to know other than to know that it is a typical low impedance output. Are you having some sort of trouble with the using the buffer?

Thank you. I actually have no particular problems with the buffer.

Yet, I use to use 3 x #GCX + a dual stereo line mixer, & planned to use soon 2 in 3 buffers as line drivers in a stereo setup, almost at the very end of my FXs chain, just before line isolation boxes (Palmer PLI-01 ; Lehle P-Split II for instance).

Simply I wanted to know if the GCX buffer was appropriate as a line driver in such a path.

Subsidiary question : I've built several TL071 buffers (see below), & have encountered issues as regards their placement. Indeed, when they're placed @ the end of my FXs chain,& if I switch on/off any electrical device connected to the household mains supply, then my buffers start to react oddly. In one word, they produce a huge white noise while amplifying the signal in the same time. Nonetheless, that strangeness doesn't occur anywhere in the FX chain, any ideas ?

archaos wrote:Thank you. I actually have no particular problems with the buffer.

Yet, I use to use 3 x #GCX + a dual stereo line mixer, & planned to use soon 2 in 3 buffers as line drivers in a stereo setup, almost at the very end of my FXs chain, just before line isolation boxes (Palmer PLI-01 ; Lehle P-Split II for instance).

Simply I wanted to know if the GCX buffer was appropriate as a line driver in such a path.

The GCX buffer should be fine for this if you do in fact need to run additional buffers here. Is this at the end of an effects chain running to the front of an amp or is this for effects that are at line level after a preamp section?

archaos wrote:Subsidiary question : I've built several TL071 buffers (see below), & have encountered issues as regards their placement. Indeed, when they're placed @ the end of my FXs chain,& if I switch on/off any electrical device connected to the household mains supply, then my buffers start to react oddly. In one word, they produce a huge white noise while amplifying the signal in the same time. Nonetheless, that strangeness doesn't occur anywhere in the FX chain, any ideas ?

The first thing I would suspect in that case is the power supply section of your buffer circuits. Try experimenting with different grounding scenarios or increase any filtering and check any regulation or rectifier circuits for problems.

Is this at the end of an effects chain running to the front of an amp or is this for effects that are at line level after a preamp section?

At the end of the chain in front of an amp actually.

The first thing I would suspect in that case is the power supply section of your buffer circuits. Try experimenting with different grounding scenarios or increase any filtering and check any regulation or rectifier circuits for problems.

You mean to install a bridge rectifier like in the GCX ? Did they opt @ DMC for installing a brige rectifier in the GCX to avoid problems I'm currently encountering by using DC ?

Well I assume you are using DC power in some form... we use the bridge rectifier because our initial power source is AC and we need DC to power the audio circuit and the logic circuits.

Likely is that you need to isolate the power for the buffer circuits from each other and/or any other devices that might be sharing the same power source.

Thanx for the tips.

Homework done.
I've finally managed to get rid of that boring noise caused when switching electrical devices.
Indeed, I've put the lowest resistor in value : 150R, to keep the lowest impedance possible, & in serie right @ the output of the IC. Now everything is fine, no more white noise occurs.