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Double Bass AMT into GK MB150-112

N

Nathan Parker

Oct 10, 2008
698
14
Seattle, WA
#1
Okay, so I looked into this, and I think I'm on to something, but I just wanted to be sure. I just bought an AMT 25SBXBBQ whatever-the-devil-its-called. It's the C-clamp model without the super pre-amp. I'm trying to run it through my GK amp, and there is just not that much output.

The impression that I got is that I should be using a microphone pre-amp as well. Is that the case, or is this just the reality of the mic through an amp? It sounds good, but I have to turn the gain and volume well past 50% to get an audible sound. With my full circle, I hardly have to turn up at all before I start getting a sound. Just want to make sure I'm doing the right thing before I slap down some more money on a microphone pre-amp.
 
#2
When you move the mic over the f hole does it get a whole lot louder? If it does, it's ok. If it doesn't, you might have a problem.

That said, assuming it is working properly, the mic will start feeding back before you get to even moderately loud pickup volumes when used through an amp. I have to blend mine with a pickup to get regular bandstand volumes out of the amp.

mark
 
#3
How are you connecting the mic to your amp? Since the AMT S25B without the super preamp only has an XLR output, you'll need a matching transformer such as a Invalid Link Removed to connect the mic's balanced 150-ohm output to the GK amp's un-balanced high impedance input. The matching transformer also provides some gain (24 dB for the Shure A85). This should help quite a bit (if you're not already using a matching transformer).
 
#4
Ahhh, that might be the problem, Robgrow. I'm just using a cable that has XLR on one end, and 1/4inch on the other. No converters or pre-amps or anything of that nature.

And yes, Mark, it does get louder over the F-Hole. It worked fine through a PA on a gig the other night. Just trying to fine tune it with my amp, is all.
 
#5
I have never successfully used an AMT through an amp.

There are those here who have.

I quit trying.

I use an old Sennheiser Dynamic through the amp with the pickup and it kicks the AMT's ass.
 
#6
Nathan Parker said:
Ahhh, that might be the problem, Robgrow. I'm just using a cable that has XLR on one end, and 1/4inch on the other. No converters or pre-amps or anything of that nature.

And yes, Mark, it does get louder over the F-Hole. It worked fine through a PA on a gig the other night. Just trying to fine tune it with my amp, is all.
Click to expand...
As an alternate possibility, if you have one you can also use a small mixer to 'interpret' the mic signal for your amp.
 
#7
Uncletoad said:
I have never successfully used an AMT through an amp.

There are those here who have.

I quit trying.

I use an old Sennheiser Dynamic through the amp with the pickup and it kicks the AMT's ass.
Click to expand...

It took me YEARS to get it to work. When I first got it, I put it on and it sounded like warmed over dog doo. I worked with it for about an hour and gave up. It went on the shelf. A year or two later, I tried it again. No luck; back on the shelf. It was either the 3rd or 4th time that I tried it, I started to get something useable. After that it worked and continues to work great. I really don't know what I did differently this last time. Maybe I just found the right balance of pickup and microphone.

Before I got the AMT to work, the only microphone I could get anything useable out of was an EV RE 20 (and boy did it sound good). But it was too big for the C-clamp so I had to haul a mic stand to the gig and the mic itself comes in a small suitcase. It was just too much work to haul all of that stuff. Plus I was always nervous someone would bump into the mic stand and launch the fairly heavy RE-20 through the front of my bass.

mark
 
#8
Nathan, I could never get any sound from the AMT out of my GK MB150 either. Then somewhere I heard or read an interview with an AMT engineer who said the mic wasn't designed to work with combo amps, it was designed to work with separate amp heads and cabinets. Since I only had a combo amp, I put the AMT away and forgot about it for a few yearss.

Recently I bought a separate amp head and cabinet rig. Just for yuks, I tried the AMT mic on it, and it works well. It still won't give you a whole lot of volume before feedback, so you can't use it for loud gigs, but it's usable and has a nice sound.

(That said, on mic-worthy gigs I use a Sennheiser e609 mic, which does work with combo amps as well as separate mic/cab rigs.)
 
#10
robgrow said:
How are you connecting the mic to your amp? Since the AMT S25B without the super preamp only has an XLR output, you'll need a matching transformer such as a Invalid Link Removed to connect the mic's balanced 150-ohm output to the GK amp's un-balanced high impedance input. The matching transformer also provides some gain (around 10dB or so). This should help quite a bit (if you're not already using a matching transformer).
Click to expand...

RobGrow has the answer here. The AMT is a low impedance microphone, and you need to convert it to high impedance to run it through your GK—either with the little converter plug that Rob recommends, or with some kind of mixer pre-amp.

That being said, it will be louder, but it still might not sound that great through your amp. You might check the "Ask Lynn Seaton" thread because he has a lot of experience with mics through amps.
 
#11
Thanks for all the answers. I've always been a lamer when it comes to understanding mics/amps/pickups and all that other stuff. I am just now trying to work with and understand these pesky electronics, and it is daunting. I have a newfound respect for sound engineers and those types that deal with this on a daily basis.
 
#13
Why not use the 1/4 output on the Super Pre to the amp as opposed to the XLR?

I like my AMT going into a PA and the Realist to give me some monitor via an amp if necessary although my preference is AMT only for my main gig with Light of East.

Question: I've had situations where the mic going through a PA is massive and other times where the sound man just shrugs and says he can't get anything out of the Pre. This is using the XLR out put. Can anyone explain what might be happening here.

As an aside, I've done two gigs this week without mic or amp and that was a real treat to do.

EDIT: Just noticed that you said you don't have the Super Pre. My sense of detail working overtime again.
 
#14
The soundguy has to give you phantom power for the AMT, right? Or else you are using a battery in the box? I've had situations where I ask for phantom power from the board and they say "sure." But then they come back in a minute saying they don't have a signal from my mic (because they did not hit the phantom power switch on my channel).
 
#15
Nathan Parker said:
It worked fine through a PA on a gig the other night. Just trying to fine tune it with my amp, is all.
Click to expand...
Uncletoad said:
I have never successfully used an AMT through an amp.

There are those here who have.

...

I use an old Sennheiser Dynamic through the amp with the pickup and it kicks the AMT's ass.
Click to expand...
bassbuddie said:
AMT trough the amp was not very successful to me. SM58 worked better. But the AMT through a PA was successful.
Click to expand...
Very important point, and sometimes it's hard for me to tell from a given post where the mic signal is going.

I am a die hard now for running a mic (blended with a pickup if needed) thru my amp. It does present a number of challenges, the mic feeding back being first and foremost for me. But sending a mic to the PA is just a different ball of wax. I always think it's important to note which context we're in.

And I think that's in part (maybe?) what the folks at AMT were driving at. Their mics are not designed first and foremost to run into a "typical" bass amp sitting behind you on stage. While that can be made to work within certain limits, that's probably not what it was primarily designed for. There are a couple of good threads on why some people prefer dynamic mics for this type of app.
 
#17
Yea Steve I forgot about that, it's worth moving over here.

Lynn Seaton said:
I usually use an Acoustic Image with the Shure Beta 56 microphone. I place it on the floor behind me and slightly to one side. For feed back control, don't stand directly in front of the amp. If I am using a pickup only through the amp for louder gigs, I will elevate it, but place it the same. I would still like to have my mike in the house PA whenever possible. For louder gigs, I use the Realist pickup through a Walter Woods amp and a 15" JBL K 140 in a custom built cabinet or a Bag's End 15" cabinet.
Feedback is not usually a problem if the volume is reasonable. Protect your hearing folks. Unfortunately, the volume on the bandstand has gotten out of control in recent years. I like to play with a balanced group sound based on the volume of the acoustic piano on the bandstand without monitors. Engineer the balance of the band on the stand. Play like a well mixed recording. If everyone sets up close, then it should sound like a good mix to everyone. If everyone on the stand plays their volume level appropriately, it will be well balanced like a great recording. During a shout chorus or the peak of a hard hitting solo , the bass may be "felt but not heard". In other words, you will not hear every note you play as distinctly as if you were playing alone by yourself. That is normal.
With the ability to listen to recordings at any volume we choose, we can lose touch with what is a real volume level in performances. The compression on many recordings makes for a limited dynamic range as well. In live performances, dynamics should range from a whisper to a roar. Too many people play at one monotone volume the whole tune and the whole night- loud! The inclination to turn up everything to be heard is a losing battle with no winners. Talk to your bandmates about going the other direction and playing softer to start. Sometimes, it is GOOD to play so soft you can hear yourself breathe. Yes, it is fine to get louder, but people get tired of "being screamed at" from the bandstand all the time.
Click to expand...
 

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