Bass combo line out level to low for altec power amp.

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cbdb

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#1
Want to use an Altec power amp 9444B driven by an Asdown bass combo line out to drive the combo speakers. Problem is not enough level. At least 10db lower than the combo power amp. Any easy fix, or do I need additional electronics? Do bass amps generally have that much more input sensitivity? I have tried a direct connection ( the one going into the power amp pcb ) same problem.
 
#2
Pardon me for asking two obvious questions.

Question one: Were the gain knobs on the back of the Altec turned to maximum?

Question two: Many pro-audio devices have some sort of switch that toggles them between -10 dBv (consumer level) and +4 dBu (pro-audio level) signals. Does your Ashdown have such a switch, and if so, is it set to the +4 dBu setting? (It should be.)

-Gnobuddy
 
#3
Everything is turn up max. I've never seen a instrument amp with a level switch on the line output. I tried another 300 watt amp it's closer to the original level. Looks like a input sensitivity thing and/or pro/comercial mismatch. Does anyone know if instrument amps line outs have a "level" like pro stuff is +4dbu commercial is -10dbm.
 
#6
cbdb said:
Does anyone know if instrument amps line outs have a "level" like pro stuff is +4dbu commercial is -10dbm.
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I haven't seen much evidence of a standard, but typically 1/4" jack instrument amp line-outs will be "instrument level", often around 100 mV. This is actually considerably lower than both the -10 dBv and the +4 dBu standards.

In those cases where there is a proper balanced line-out, usually via XLR interface, there is more chance of finding a consumer/pro-audio level switch, and corresponding signal levels (316 mV / 1228 mV). But still no guarantees - my Mackie mixer has XLR main outputs, with a switch that sets them to either "mic level" or "line level", with no indication of what either of those actually means in terms of millivolts RMS!

Some years ago, I ran across the same problem you describe when I tried to run the line-out from a bass guitar preamp into a dbx rack compressor, which was designed for a +4 dBu input level. That particular dbx model has no pre-gain knob ahead of the compression, so you have to feed it the right signal level, otherwise it doesn't work at all.

I ended up plugging my bass guitar direct into a little ART preamp, which has very flexible gain settings, and using that to feed the compressor.

-Gnobuddy
 
#9
Looks liken the line level out is too low for non instrument amps. The preamp has 15 volt rails so I though it would put out a decent level. The pre has a meter for level and that's what I use to set the pre gain. I guess the aim was to have huge headroom, bass guitar dynamics can be large.
 
#10
You have something stupid going on. The amplifier should produce full power with less than a volt input. Are there input transformers on the back and if not are there jumpers? On the back input barrier strip is the "LO" jumped to the ground? Are you trying dual mode or bridged mono?
 
#11
Yes the ground of the guitar cable from the pre is cone ted to - and ground on the in of the amp. The amp
Is dual mono not bridged. Didn't want the potential of putting 600 watts into a 250 watt cab. Guess it's time to get the scope out. I think the bass pre just doesn't put out a lot of level. The eq has 18db of gain so they probably gain staged the pre to handle players that "turn it up to 11". I also tried the direct feed to the combo power amp but no level difference.
 
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