Using more than one input at the same time.

[Lizooki]

I have an Acoustic B100 Combo from that I bought new from GC years ago.
It has two front inputs ... active and passive.
Would it hurt anything to use both at the same time?
Not that I would need to .... I don't own a playable active bass.
Just always wondered about that.

 

[JRA]

...and you know: a car has so many 'inputs' for liquid stuff --- why not put gasoline in all of them...vrrroooom....!

 

[mmbongo]

No, only use one at a time.

 

[Crater]

No, only use one at a time.

Complete nonsense. It's perfectly safe to use both inputs at once.

Back in the bad old days, bands would play and sing through the same amplifier.

When in doubt, read the manual. ( I didn't see any warning against using both inputs at once)

 

[Redbrangus]

Technically, there is only one input; it has two input jacks, one of which employs a resistive 'pad' to help prevent overloading the input stage with a 'hot' signal, like that which may occur with an active bass. So there is only one channel with one level control. Yes, you can plug a device into either or both of these input jacks, but there is only that one level control, so the relative volume of devices plugged into that one input will depend on the volume controls of the devices themselves. A real-world application of this concept might be to plug your passive bass into it's usual input and use the second jack as an input for your phone or MP3 device (utilizing an appropriate adaptor) which will have a relatively hot output (as compared to your bass)--so will benefit from the internal pad on the 'active' input--and has it's own output level control, so that can be used to control the balance between bass and playback. This is an acceptable work-around for an amp lacking an external input for CD or MP3 playback. However, when you input multiple sources through one, relatively unsophisticated amp and speaker system, overall system performance suffers somewhat from products of the intermodulation between the various inputs. For this reason, I advise only doing this in a personal practice or rehearsal situation, not for performance, except in very low volume environments.

 

[lz4005]

I have an Acoustic B100 Combo from that I bought new from GC years ago.
It has two front inputs ... active and passive.
Would it hurt anything to use both at the same time?
Not that I would need to .... I don't own a playable active bass.
Just always wondered about that.

Those labels are lies. There is no direct correlation between presence of a battery in your bass with output level.

Always try the 'passive' input first with every bass. Only use the 'active' input if you get unwanted distortion with the 'passive' one.

 

[agedhorse]

It depends on the design of the amp. There are 5 or 6 common ways to implement the 2 input jacks with active/passive circuitry. Some disable one of the jacks, some do not. Some alter the input impedance and some do not. Since this feature is predicated on using only one input at a time, that's what I recommend to avoid adverse performance.

 

[Redbrangus]

According to the block diagram that I found for that particular amp, both inputs could be used simultaneously, but that information is somewhat suspect, given that it also shows both the 'active' and 'passive' input jacks as being routed through the -10dB pad. At any rate, I defer to @agedhorse's recommendation to use only one input jack at a time.

As to whether the labeling could be called 'lies': that seems a bit extreme. I think most folks understand an input on a bass amp that's labeled 'active' as opposed to 'passive' to be one which employs an input pad. I agree that it could be more accurately labeled, but then, they are products designed to be used by bass players.... @lz4005's advice to only use the so-called active input jack if the passive one is too hot (has too much gain) is valid.

 

[chaosMK]

I use an old Mesa 400 that has two inputs. You can run them simultaneously, it's fine if anything thickens it up a little, but I prefer using just the hotter Input2 with my active bass. I use an A/B switch to basically get a clean/dirty channel out of it and run a distortion pedal (Boneshaker + Noise Gate) into softer Input1. I like being able to control the gain after a dirt pedal since they tend to end up louder than my clean tone.

 

[Pings Bass]

I remember as a teenager with a Kustom 200 doubling as a guitar amp and vocal PA. Sounded like hot garbage.

But for people who like that kind of thing, that's the kind of thing they like.

 

[ihaveaquestion]

They did it on these demos:

 

[Gravedigger Dav]

It depends on the design of the amp. There are 5 or 6 common ways to implement the 2 input jacks with active/passive circuitry. Some disable one of the jacks, some do not. Some alter the input impedance and some do not. Since this feature is predicated on using only one input at a time, that's what I recommend to avoid adverse performance.

I've been to a few adverse performances and consequently, try to avoid them. For example, this year's Super Bowl halftime show was an adverse performance.

 

[micguy]

Many of the amps that have two input jacks, if you use both simultaneously, it connects the two source to each other in parallel. A couple things that'll do:

1) If one of the instruments is active, the other one (a passive instrument with a higher impedance) will be attenuated A LOT - you won't hear much of it at all.

2) If both instruments are passive, you might get way with it, but know that they will interact - if, for example, one of them has a standard volume control (a P bass, for example), and you turn it off, it will turn off both instruments. Turning it down, similar effects will happen. Switching from 1 pickup to 2 (in parallel), the other instrument (because your instrument now has a lower impedance) will get quieter.

In short, its not likely to cause the end of the world, and if your band is a few teenagers in the basement with nobody listening (intentionally - Mom and Dad probably can't help but hear you), then maybe it's OK, but it isn't something to consider in live performance - until the day one of your amps blows and you have no choice.

OH, and by the way, two guitars playing through the same amp, with tremolo - that's kind of a neat effect. But I wouldn't do it for more than one song, or the audience will get seasick.

 

[Eddie LeBlanc]

 

[nilorius]

Active and passive doesn't work together, so you must choose.

 

[yberwaffe]

You can't break anything so you might as well try.

 

[PaulCISSA]

Current issue Fender Bassman and Super Bassman have a pad (IIRC -6db) on input 2, but you can use both inputs together per the manual. Both inputs are rendered -6db when in use together. I guess the point there is that there are many ways to implement an input circuit and YMMV.

 

[StatesideRambler]

Default to plugging just one instrument into an amp. If the amp has two preamps, two channels if you like, into one power amp then an instrument into each is fine. They won’t interact and each can be separately controlled by its preamp.

 

[agedhorse]

Current issue Fender Bassman and Super Bassman have a pad (IIRC -6db) on input 2, but you can use both inputs together per the manual. Both inputs are rendered -6db when in use together. I guess the point there is that there are many ways to implement an input circuit and YMMV.

There are many ways, that's why "it depends"

 

[jdh3000]

I have an Acoustic B100 Combo from that I bought new from GC years ago.
It has two front inputs ... active and passive.
Would it hurt anything to use both at the same time?
Not that I would need to .... I don't own a playable active bass.
Just always wondered about that.

It's been my experience with any amp with two inputs that one is padded for a hot signal like an active pup or using pedals, while the other is for passive.

When you plug something in both sides simultaneously, they are both then padded.

I use my Hartke as a practice amp plugging my bass in one side and my phone, computer or mp3 in the other...when I plug in the mp3 or whatever my bass volume drops. But I play along with the audio and it doesn't hurt it.

The only other way I could see using both sides would be keep two basses plugged in, like for swapping.