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Passive bass into Active/passive input?

Ezmar

Ezmar

Jul 8, 2010
837
46
#1
Quick question, I plug my bass into the Active input, even though it's a passive J. I find that the Active input gives a softer, less "amplified" tone. I also recently ran into a problem with a speaker cone, and it needs to be replaced. Could that have anything to do with what input I use, or is that as ridiculous a theory as I think it is? What exactly is the difference between the active and passive input?

Again, I don't really think there's an issue there, but it never hurts to understand your electronic equipment a little better.
 
#2
Active inputs generally have a -6dB cut to the signal, which is why you're detecting a softer tone. You could get the same effect by rolling down the gain on your amp in the 0dB loss slot.

Your speaker blowing has more to do with the amp pushing too much to the speaker. That's where the Master Volume control comes into play. Regardless of what load your guitar is giving to the amp, the master controls how much load is fed to the speakers.
 
#3
"Active" and "passive" labels are often misleading. They do not usually refer to differences of input impedance, but rather, differences of nominal signal level. That being said, there is no inherent difference in voltage between active and passive basses. The difference is the nature of their output impedance.

In any case, the active input of most amps is usually nothing more than a padded version of the passive input.
 
#4
I'm no electronics whiz, but an active input is designed for hotter basses with active electronics, so the signal is reduced so the amp is not overdriven by the input signal. As such, plugging a passive bass into an active input will give you a softer tone, but to no real gain I can see. It shouldn't adversely affect the speakers either.
 
#5
awilkie84 said:
Your speaker blowing has more to do with the amp pushing too much to the speaker. That's where the Master Volume control comes into play. Regardless of what load your guitar is giving to the amp, the master controls how much load is fed to the speakers.
Click to expand...

Yeah, that's where I'm kind of confused, because the Master volume hasn't been set above 3, ever, and it's almost always been below 1. I also am a college student and I keep my amp at home, so I've barely even played it, much less cranked it at all. Ah well. That's life, innit? Might have something to do with the fact that I'm using an old Hartke 3500 amp, that thing is apparently famous for how much power it pushes.
 
#6
Active input is the same as the passive one, except that it has a "pad" which lowers the input level, usually by about 10 decibels. This is useful if your bass has an extremely hot output, which really has nothing to do with it being active or passive.

In other words, the only reason to use an Active input is if your bass' output is so hot that you're overdriving the input stage of your amp too easily, with out turning the gain knob up very much at all. Hope that helps.

And I don't think your input level has anything to do with blowing your speakers, but some people here might say it does. I think blowing speakers is more an issue of how you set the master volume.
 
#7
Ezmar said:
Yeah, that's where I'm kind of confused, because the Master volume hasn't been set above 3, ever, and it's almost always been below 1. I also am a college student and I keep my amp at home, so I've barely even played it, much less cranked it at all. Ah well. That's life, innit? Might have something to do with the fact that I'm using an old Hartke 3500 amp, that thing is apparently famous for how much power it pushes.
Click to expand...

By 3, do you mean 3 o'clock?
 
#9
Ezmar said:
By "3" I mean 8 O'Clock.

Or whatever it would be, I don't have my amp here, I don't know exactly where it is. Volume level 3, anyway.
Click to expand...

OK. Then it shouldn't be any user error that caused your speaker to fail, unless you used an instrument cable to connect your amp to the cabinet. Or maybe your cabinet isn't rated to handle all the power from your amp? In either case, your choice of input didn't harm your speaker.
 
#10
matante said:
OK. Then it shouldn't be any user error that caused your speaker to fail, unless you used an instrument cable to connect your amp to the cabinet. Or maybe your cabinet isn't rated to handle all the power from your amp? In either case, your choice of input didn't harm your speaker.
Click to expand...

Yeah, I didn't do anything stupid like that, It should be rated to handle it, it's probably just a cheaper speaker, it was one of the new Acoustic cabs.
 
#14
matante said:
OK. Then it shouldn't be any user error that caused your speaker to fail, unless you used an instrument cable to connect your amp to the cabinet. Or maybe your cabinet isn't rated to handle all the power from your amp? In either case, your choice of input didn't harm your speaker.
Click to expand...

This would blow the amp before the cab, as the lower resistance rating would potentially be too much for the amp to handle.
 
#15
awilkie84 said:
This would blow the amp before the cab, as the lower resistance rating would potentially be too much for the amp to handle.
Click to expand...

Not necessarily. Exceeding the current rating of a gauge of wire will cause a lot of thermal dissipation until you fry the wire like a fuse. How that affects the output stage of an amp depends on how it is engineered. A solid state amp runs comfortably at an infinite output impedance, but if the impedance drops too close to zero, the current through that resistance will destroy some components. Conversely, if you are dealing with a vacuum tube-based output stage, there is a transformer there to lower output impedance and provide inductive coupling to block DC from the tubes, before reaching the speakers, so that transformer will provide a 100% reactance at a zero-Ohm load, but an infinite impedance load would damage the tubes.
 

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