Ampeg query

[Andy Thomas]

Dear fellow bass players,

Can anyone help with the following:

Just bought an Ampeg BA 115T Combo-salesman slightly uncertain about whether 0db or -15 db inputs should be used for active/passive bass settings?

Not very tech. minded so simple laymans language would be helpful if anyone has any ideas.

Thanks

Andy Thomas

[Dood]

Hi Andy,

The -15dB input is designed to 'pad' or reduce the input volume from a particularly hot signal to stop it from distorting the preamplifer (the first section of the bass amplifier signal chain). Now, it is usually expected that active basses have a much higher signal output than that of passive pickups - and thus, if the signal is too strong it will indeed cause the preamp' to distort. If a nice clean sound is what you are after then, plugging a hotter signalled instrument in to the -15dB input will help to reduce any chances of distortion.

so that's the theory out the way! In practice.. it's usually a little different!

There are passive pickups on the market that I have found to have a much higher output than some active basses!! So, what do you do??!! Well.. it kinda confuses matters.. as you may not actually *know* if your instrument has a high output or not.. Well, Andy.. it will be a case of trusting your ears. Try both inputs.. play nice and loudly and see which sounds best. Does one distort more than the other?

Obviously, you may *want* your amplifer preamp to distort and sound all dirty, in which case, using the 0dB input will help to raise the gain in to overdrive. (unpadded input).



Now unfortunately, I cant see a 'signal clipping' LED so I wont be able to give you a quick tutorial on setting up the gain control using one!.. so, I would suggest starting with the gain control at zero and slowly turning it up as you play until you hear the signal distort through the speaker (you will be able to hear this even with the master at lower volumes) , now, back the gain down again until the loudest notes you play still give you a nice clean signal. IF the signal distorts even with the gain control low, then use the -15dB input and start the process again. Conversely, if you can wind the gain all the way up and you dont get any distorting at all, then probably best to use the odB input, as the bass may have a low(ish) output.

Hope this helps!

What basses are you plugging in to your nice new shiny amp? ;o)