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Double Bass AMT S25 Bass Mic

#101
I'm blending the AMT with the Dyn-B nowadays and loving it to death.

Regarding the gooseneck - I got the gooseneck for my tailpiece mount made quite long so it would reach almost to the fingerboard. I don't have any problems with any sound from it although sometimes when I do have buzzes, I think it may be the mic but then discover it to be something else like the corner of the bow quiver or the quiver ties vibrating against the top table or sometimes even the leather bib I have on the right shoulder.
 
#102
Chris Fitzgerald said:
I'm loving the AMT to death for the sound - nothing I've tried has even come close. But I've found another weird design thing: certain frequencies seem make a rattle sound in the gooseneck. Depending on where I mount it, different pitches make this strange "springing" sound. Thankfully, it doesn't make it through into the amplified tone, but it's annoying acoustically. Anybody else experience this?
Click to expand...

YES. And it did come though the amp, too. It is the sound of the wires rattling inside the goose-neck.

The DIY fix is to try putting as much bend as possible in the goose-neck. The REAL fix is to send it back to AMT: They will install a Teflon sleeve in the goose-neck which stops the rattle cold.

Props again to Marty at AMT for round-the-clock service. He treats everyone as if he or she was the most important customer the company ever will have.
 
#103
Chris, I am having a similar problem but I have not yet determined it is the AMT. Mine is most bothersome on second octave Bb. The sound I get is more of a "rattle" than a "springing." For the longest time I thought it was my end pin rattling but that doesn't seem to be it. It is very hard to figure out on my own. One time I had my wife help me for a few minutes and she made it stop by holding the AMT but I wasn't convinced that is it. Since you are having a similar problem, I will get my wife to help me out agian and let you know.
 
#104
KUNG FU SHERRY said:
YES. And it did come though the amp, too. It is the sound of the wires rattling inside the goose-neck.

The DIY fix is to try putting as much bend as possible in the goose-neck. The REAL fix is to send it back to AMT: They will install a Teflon sleeve in the goose-neck which stops the rattle cold.

Props again to Marty at AMT for round-the-clock service. He treats everyone as if he or she was the most important customer the company ever will have.
Click to expand...

Damn, I was hoping there would be an easier way to fix it than that. Still, thanks for the heads up, and I may end up sending it away. I just can't stand to part with the damn thing now that I've found the sound! Maybe off topic, but does anyone know what the little set screw right on top of the mounting bracket shaft is for?
 
#105
Hello guys,

I was a happy owner of an AMT for a couple of days, unfortunately my microphone made strange popping sounds. I talked to Marty at AMT and he advised me to send it back to them. That I did, and waited for 4 weeks.

I contacted Marty and asked him what was going on. He started talking about their thorough testing methods of their microphone. This long story ended in the fact that they had found nothing wrong with the mic and that this is classified as a user error. He claims I have used it in the "wrong" way and caused those sounds in some way.

I'm just curious, how do you use your mics? Like what type of cables, mic preamps and amplifiers. Is it necesary to have an additional preamp before the mixer? (except for the AMT preamp of course) Doesn't make sense to me.

I've tried several combinations of cables, mixers and amplifiers: from my DJ mixer at home to the big mixer in the rehearsing room. I just can't realise how this can be a user error.

Another thing, the ground lift switch on the preamp worked as a lowpass filter for me. When using only battery power, the switch killed all treble set in one position, while sounding perfectly clear in the other (with the popping sounds though). Does this make sense?

Any answers appreciated. Thanks a lot
 
#106
The AMT preamp is not really a preamp but just a power supply and signal processor. You need to go from that into a mic preamp. If you're going into the mixer then it has preamps built-in.

I don't believe you should need the ground lift switch at all when using battery power. The whole point of a ground lift switch is to break the ground loop caused by two ground connections. In your case, you have only one.

I'm sorry you had a bad experience especially after all the research you did. I would be pretty confident that AMT did test your unit extensively. If you've tried changing every component in the signal chain - including the bass, the power source, etc. I'm not sure what else you can do.
 
#107
Exactly what I thought. Would it be a necessity to use an XLR->XLR cable into the mixer? or would it work fine with a XLR->instrument jack cable as well?

Does your ground lift switch act like a lowpass filter as well? When using battery power that is. Doesn't it seem strange?

I've tried to replace everything in the chain. The same popping sounds are heard from the mic.

AMT has agreed to send me a new mic, but according to them it won't work better or worse since there was nothing wrong with the old one I sent in.
 
#108
I think where possible, you should always try and go for the XLR. For one thing, I'm not sure that all 1/4" mixer inputs are balanced. They are higher impedance and the sometimes the gain control works differently. From I understand from speaking to Marty, the whole idea of the AMT preamp is that it creates a signal similar to an SM58 in terms of output and impedance. The theory being that since that is such a widely used mic, it will work with most setups.

I'm not sure about the ground lift switch with the battery but Marty should be able to say why it does that. In any case, without two power sources, you should never have to use it.

I don't have the ground lift switch as I have the super preamp and it has three outputs (two XLRs and one 1/4") and one of the XLRs is ground isolated.

If you're going into a mixer, also make sure phantom power is not on - although most mixers only have a global option so if it's needed for other mics, you may have no choice. The presence of phantom may make a ground loop more likely but it depends on your setup. I can't remember how many outputs the standard preamp has - just one XLR?

I don't use the battery (although if I recall, the standard preamp only has the battery option) because I don't want to deal with the hassles of worrying about whether the battery will go flat or not at a critical time. Even though I know the battery might be quieter.

Tell us how you go with the new mic.
 
#109
I had a similar but slightly different problem with the standard preamp and switching to the super preamp solved it. First, I was going from the XLR out of the std pre to my walter woods instrument input. With that set up, the gain of the mic was too low and caused me to have to crank up the gain on the WW causing noise. Going through a simple mic pre solved the problem but increasing the gain and properly converting the impeadance therefore allowing me to lower the gain on the WW. But I didn't want to have to use an additional box so I switched to the super pre which has a 1/4 output with 40db more gain.

I think what you have to do is use an XLR out from the std pre to a mic pre using its XLR in (whether it is in a board or mixer or an independent unit) then go from there.

See if that works.
 
#110
The Jazz Lawyer said:
I think what you have to do is use an XLR out from the std pre to a mic pre using its XLR in (whether it is in a board or mixer or an independent unit) then go from there.
Click to expand...

Exactly. That's the way it is designed to be used. As I keep saying, the term "preamp" is a bit of a misnomer for the AMT box. You have to essentially pretend the box is not there - it's purpose is to just to make the AMT look like any "regular" mic which you still need to plug into a preamp.

At the very least, if you're going to convert to a 1/4", use one of those inline transformers to setup the impedance.

All that said, using a simple outboard mic pre should work fine into most amps.
 
#112
Chris Fitzgerald said:
Interestingly, the output of the AMT XLR signal is hotter than the Full Circle signal when I'm mixing the two signals in the Focus 2 preamp. Since I like more mic signal than pickup signal when blending, this works out perfectly.
Click to expand...

Chris, are you using the Acoustic Image Focus 2 now? If so, how does it compare to your EA iAmp? Are you still using just a single VL-208? How is the headroom? I have always been suspect of AI gear as their power statements are a bit misleading. The Clarus is rated at 300 watts but that is into 2 ohms - who runs 2 ohms - it is actually +/-150 at 8 ohms. The Focus 2 is rated at 600 watts at 4ohms and 300 watts at 8 ohms. Tell us what you think.

PS the mic input on the Focus 2 is rated at 600 ohms which may provide more gain to the mic input compared to the instrument input which is a switchable 1meg or 10meg hence the "hotter" appearance of the mic.
 
#113
The Jazz Lawyer said:
Chris, are you using the Acoustic Image Focus 2 now? If so, how does it compare to your EA iAmp? Are you still using just a single VL-208? How is the headroom? I have always been suspect of AI gear as their power statements are a bit misleading. The Clarus is rated at 300 watts but that is into 2 ohms - who runs 2 ohms - it is actually +/-150 at 8 ohms. The Focus 2 is rated at 600 watts at 4ohms and 300 watts at 8 ohms. Tell us what you think.
Click to expand...


So far, I love it because the Focus 2-channel pre is a bit cleaner than the Raven Labs PMB II, and because the XLR input allows better tone from the mic. I'll give a power comparison after this weekend's gigs.
 
#115
Chris Fitzgerald said:
...I've found another weird design thing: certain frequencies seem make a rattle sound in the gooseneck. Depending on where I mount it, different pitches make this strange "springing" sound. Anybody else experience this?
Click to expand...

Chris, I took a good listen to my bass for the rattling sound and have at least determined that it is not the AMT. I have focused my suspicions once again on the end pin. So I can't give any advice on your problem.
 
#116
Sam Sherry said:
The DIY fix is to try putting as much bend as possible in the goose-neck.
Click to expand...

Sam, I owe you lunch! I found a way to put a double bend in the gooseneck that all but eliminates the rattle. I may also try adding some kind of weighted wrap to some portion of the arm to see if that may also help, kinda like a wolf eliminator kinda thang, but for now, I'm good. Thanks again!
 
#117
I got my new AMT S25B yesterday and based on my limited trials, I think it is a keeper. As several others have mentioned, I am experiencing the wires rattling inside the gooseneck. I haven't had time to experiment with bending the gooseneck to eliminate or minimize the rattle. I'm more concerned right now with finding that sweet spot so that I'll be able to get the tailpiece conversion.

My first impression is that the sound is very natural. Not as good as a pro studio mic like a Neumann U67 (my favorite), but far superior to any pickup I've ever used. Like Chris, the output from the mic is quite a bit hotter than either my PUTW or Realist pickups. This particular unit was made in May of this year and if there is a trimmer inside the pre box, I couldn't find it. I would actually like to reduce the output a bit. I'm using the S25B with a AT CP8201 matching transformer into my AI Contra amp. The only micophone cable I had handy was 25 feet long, but the output signal was apparently unharmed. I am going to have a shorter cord made ASAP. The level of volume without feedback (with the bass about 3 or 4 feet in front of the amp) absolutely amazed me. I've tried other mics in the past and had to discard them because of feedback. I'll be watching this weekend to see how much drums and crowd noise gets picked up when on an actual job.

My thanks to Sam Sherry, Ray Parker and Adrian Cho for their helpful email advice that led me to purchase the AMT S25B. The place where I bought it offers a 45 day right to return, but I doubt if I'll be sending it back now that I've tried it.
 
#118
The trim pot is on the deluxe preamp only. It only affects the output of the 1/4" send. If you're using a mic cable than, yuh, there's no trim but you shouldn't need one.

The beauty of using a mic cable is that it because it's low-impedence you can use a long one without signal deterioration (unlike a high-impedence guitar cord). I was able to get a 10' mic cord at the local chain musical outlet.

Let us know how you make out . . .
 
#119
After a week or so of trial and error, the best spot I've found for the mic on my bass is on the centerline about 4-5" above the bridge and about 1/4" above the table. While I'm anxious to get the tailpiece upgrade, I would like to hear where others have found that elusive sweet spot is on their basses.

While I haven't have a chance to use it on a job that was loud or noisy, I have not noticed any degree of bleeding from the drums or other instruments. I find that the mic is not as sensive as my PUTW pickup and I tend to dig in more with the mic (getting my fingers caught up in the strings occationally!). Oh, but I love the natural bass sound!
 
#120
If I'm reading your message correctly, that's about where I have mine. I think it ends up being a inch or two below the end of the fingerboard. The only time I really noticed any bleed from other instruments was at a rehearsal where we were sort of in a semicircle and the trumpet player was basically facing me at 90 deg. He was basically blowing across my mic and I could hear it coming through my amp.

The tailpiece upgrade does make for less hassle but as I'm starting to play more chamber music with my bass (I only have one), I do wonder whether anybody thinks that the mic on the bass is weird. The Dyn-B is on there all the time too but it's usually not as noticeable especially since I have it directly under the bridge.
 

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