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  #1  
Old 02-14-2018, 11:32 AM
Jimi2 Jimi2 is offline
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Default Acoustic amplifier - type of input question

Hey guys, so I知 looking to pick up an inexpensive, relatively compact acoustic amp, and am looking at the Behringer ultracoustic acx450 and the Acoustic A40. Both on sale at GC for around $200. These two look appealing in large part because they both offer dual inputs with separate volume controls, and I知 planning, at least some of the time, to run a clean signal as well as a split signal with effects at the same time. They both offer separate volume controls for each input, but the Behringer has separate eq and effects, whereas the Acoustic has the same eq and effects for each channel. So I知 thinking the Behringer looks better, BUT the write up specified that input 1 is for a guitar while input two is for a line-level source. I know this typically includes keyboards, etc. but my question is whether it will work satisfactorily for a guitar signal with effects. Sorry if it痴 a dumb question!
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Old 02-14-2018, 11:57 AM
cmac cmac is offline
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The first input is high impedance, and is intended for plugging in a guitar directly, e.g. the signal from an electric guitar would work well here. The same electric guitar won't work well in the line input socket because the impedance of the unit is too low.

If the guitar goes via a preamp, which also includes effects pedals, then it can go into line level or instrument inputs. The difference is now in the expected signal strength - the line level input is set up to work with a stronger signal then the instrument input, but you can adapt to these by adjusting the output level from your effects unit / preamp.

So to answer your question, the line input should work fine with the output of an effects unit.
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Old 02-14-2018, 12:59 PM
Jimi2 Jimi2 is offline
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Great, thank you. Sounds like the Behringer will be preferable then. The only other thing (sound considerations aside) that might bias my choice toward the Acoustic is that it has a direct output, which I gather is better for sending a signal to a PA. I知 working on some new material that値l probably be played at coffee houses and open mics initially. Without a direct out, am I looking at micing the amp? How big of a deal is this? More dumb questions, I know. I知 just getting back into this after a number of years away from it.
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Old 02-14-2018, 03:17 PM
cmac cmac is offline
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You're describing using the amp as a monitor, i.e. it's your personal amp and it feeds the house PA. This is a perfectly normal way to use such an amp, but the Behringer is no good for that because it has no signal output at all. Micing the amp isn't really a good option for this.

If this is important then you have a couple of choices:

1. Ignore the Behringer. Or at least ignore the ACX450 - the ACX900 has stereo DI outputs that will be perfect for the job of feeding a PA. But many other amps have an output that will do the job.

2. Get the ACX450, but also get a small mixer for the coffee house scenario where the mixer can be configured to send the main output to the PA and a monitor / control room output to the ACX450.
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Old 02-14-2018, 03:54 PM
varmonter varmonter is offline
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Now please take this with a grain of salt.
but i run the other way when i hear the word
Behringer. I would look for a used fishman
loudbox mini on reverb or ebay. it might
be 50 bucks more but in the long run it's
money well spent.
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Old 02-14-2018, 05:05 PM
Jimi2 Jimi2 is offline
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Quote:
Originally Posted by varmonter View Post
Now please take this with a grain of salt.
but i run the other way when i hear the word
Behringer. I would look for a used fishman
loudbox mini on reverb or ebay. it might
be 50 bucks more but in the long run it's
money well spent.
Yeah, Behringer def doesn稚 have the reputation of Fishman, and I was actually looking at the loudbix mini. But it appears the second input is an xlr, and I really need a second instrument input for the FX I知 running. I知 doing some weird stuff and would like to avoid setting up two amps. The Behringer actually gets some really good reviews....so I thought that might be the way to go.
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Old 02-14-2018, 05:08 PM
Jimi2 Jimi2 is offline
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Quote:
Originally Posted by cmac View Post
You're describing using the amp as a monitor, i.e. it's your personal amp and it feeds the house PA. This is a perfectly normal way to use such an amp, but the Behringer is no good for that because it has no signal output at all. Micing the amp isn't really a good option for this.

If this is important then you have a couple of choices:

1. Ignore the Behringer. Or at least ignore the ACX450 - the ACX900 has stereo DI outputs that will be perfect for the job of feeding a PA. But many other amps have an output that will do the job.

2. Get the ACX450, but also get a small mixer for the coffee house scenario where the mixer can be configured to send the main output to the PA and a monitor / control room output to the ACX450.
Why is micing not a good option?
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Old 02-14-2018, 05:38 PM
cmac cmac is offline
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Quote:
Originally Posted by Jimi2 View Post
Why is micing not a good option?
Conventionally (and I'll come back to this at the end) the signal being sent to the PA should be as 'clean' as possible, which is to say it should be as close as you can get to your desired sound. The PA's job is to reproduce the input but louder, and the only correction should be for room acoustics.

When you mic an amp you introduce two stages of changes to the sound. First, the amp's output from the speakers is non-linear, especially a cheaper amp, so some frequencies will be boosted while others are reduced. Second, the microphone's sensitivity is non-linear, since it will respond better to some frequencies than others. Even with a first rate amp and microphone, the sound is affected by mid placement in front of the amp, the difference in tone from different parts of the speaker, and the acoustics of the environment around the amp.

By contrast, electric guitars are miked via an amp all the time, but that's because electric guitar amps deliberately colour the tone to get a characteristic sound, and that's part of the package the player is looking for. Also the dynamic frequency range from an electric guitar isn't as wide as an acoustic, so the microphone is not such a limiting factor.

Now, you said that you are 'doing some weird stuff', and what I've written here is presuming that the signal being sent to the amp's power stage should be the same one that goes to the PA. But maybe the sound you are aiming for means that the distortions introduced by miking the amp are irrelevant, in which case give it a go and see how it works out. But conventional wisdom with acoustics is to have the signal chain from guitar to PA as pure as possible to retain the essential tone of the instrument.
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Old 02-14-2018, 08:24 PM
Jimi2 Jimi2 is offline
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Makes sense. Thanks. With at least some of the stuff I知 working on, I知 actually combining an effects heavy signal chain with a separate clean signal for some acoustic/ambient-ish stuff. The 田lean signal will probably even have some reverb on it, so technically even that wouldn稚 be clean I suppose. An amp痴 direct out will be before any effects, right? So maybe it does make sense to mic it.
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Old 02-14-2018, 08:57 PM
BT55 BT55 is offline
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I would recommend looking for a used Fishman Loudbox Artist. That has 2 instrument\Mike inputs and a connection for the house sound system. Yes it is more than your budget but think of it as an investment which will have a much higher value than your other options when upgrading.
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Last edited by BT55; 02-14-2018 at 09:51 PM.
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  #11  
Old 02-15-2018, 02:42 AM
cmac cmac is offline
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Quote:
Originally Posted by Jimi2 View Post
Makes sense. Thanks. With at least some of the stuff I知 working on, I知 actually combining an effects heavy signal chain with a separate clean signal for some acoustic/ambient-ish stuff. The 田lean signal will probably even have some reverb on it, so technically even that wouldn稚 be clean I suppose. An amp痴 direct out will be before any effects, right? So maybe it does make sense to mic it.
I'd expect the amp's DI output to include any built-in effects, but it depends on the amp. Ideally you'd have the choice to take the output from pre-effects or post-effects.

To be honest, having lots of effects in an amp is quite gimmicky and will almost certainly turn out to be inflexible and difficult to use. I think you will likely end up looking for a multi-effects stomp box at some stage and just using the amp purely as an amp.
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Old 02-15-2018, 03:05 PM
Jimi2 Jimi2 is offline
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Quote:
Originally Posted by BT55 View Post
I would recommend looking for a used Fishman Loudbox Artist. That has 2 instrument\Mike inputs and a connection for the house sound system. Yes it is more than your budget but think of it as an investment which will have a much higher value than your other options when upgrading.
Yeah, good point - that looks perfect, except for price. I may have to go with something cheaper and look at upgrading later.
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Old 02-15-2018, 03:07 PM
Jimi2 Jimi2 is offline
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Quote:
Originally Posted by cmac View Post
I'd expect the amp's DI output to include any built-in effects, but it depends on the amp. Ideally you'd have the choice to take the output from pre-effects or post-effects.

To be honest, having lots of effects in an amp is quite gimmicky and will almost certainly turn out to be inflexible and difficult to use. I think you will likely end up looking for a multi-effects stomp box at some stage and just using the amp purely as an amp.
Yeah, I致e found most in-amp effects to be crappy, especially on cheap units. I致e got a bunch of stomp boxes on my pedal board that I知 using primarily; it might be nice to have reverb in the amp if it痴 decent though.
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  #14  
Old 02-15-2018, 03:18 PM
Jimi2 Jimi2 is offline
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Thanks for all your help guys, I am still learning!
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