Output level control on Aguilar OBP-3?

[mmbongo]

It it possible to add an output level trim pot to an OBP-3 that will allow level adjustment without altering the tone? Seems to be about the only feature this preamp is missing.

[line6man]

You can put a trim pot at the output.

[Clark Dark]

line6man what ohmage would you recommend for the trimpot?

[line6man]

Originally Posted by Clark Dark

line6man what ohmage would you recommend for the trimpot?

Same as for a regular post-preamp volume pot. I'd say 25k or 50k.

[mmbongo]

Anybody have a diagram on how to do this?

There is no tone loss by doing this?

My volume pots are 500k.

[line6man]

Originally Posted by mmbongo

Anybody have a diagram on how to do this?

There is no tone loss by doing this?

My volume pots are 500k.

The output of the preamp goes to the first terminal, the output jack's tip terminal goes to the wiper terminal, and the third terminal is grounded.

If you have an active/passive switch, then the "preamp output" connection of the switch goes to the wiper.

There will be losses, as you are decreasing output impedance with a resistive load.

[mmbongo]

Originally Posted by line6man

There will be losses, as you are decreasing output impedance with a resistive load.

Is this true with preamps that come with a trimpot already installed? Lakland, Bart, Nordy...

[line6man]

Originally Posted by mmbongo

Is this true with preamps that come with a trimpot already installed? Lakland, Bart, Nordy...

Any time you add pots parallel to a circuit, there are resistive loads.

AFAIK, preamps tend to have gain pots, rather than volume controls, however. The trim pots control the gain of the ICs or transistors, not attenuate output.

[mystic38]

many preamps are really active eq, not amplifiers with gain and personally i dont think its a great idea to add anything to the output of a preamp..you are completely changing its output impedance and drive characteristics.

if you are researching and considering purchasing this preamp..simply go for the vol/blend option ... that does exactly what you want

[mmbongo]

Originally Posted by mystic38

if you are researching and considering purchasing this preamp..simply go for the vol/blend option ... that does exactly what you want

Yeah I've already got that, but it's not as precise as a trim pot, plus it's easily moved without me knowing it.

Sounds like I need to stick with preamps that have trimpots built in.