How hot is hot enough?
I recently bought a Rode NT1-A condenser mic, an ART MP tube pre-amp and an Audiophile 2496. With this gear I’m pretty happy with my signal chain. However, when I plug it all in I find that I have to wind the gain up quite a lot on the preamp to get a “reasonable” signal. To record my accoustic guitar I need to have my input gain at about +40 to +50db (just before I overdive the preamp) and the output gain at the max +10db to get a wave file that peaks at about -20db…not too bad I suppose?
But with that level of gain on the preamp I get enough noise to make my 24 bit sound card amost redundant as far as dynamic range is concerned. I’m just wondering if this is normal for a condenser mic to require so much gain, or have I bought a dodgy preamp (it was second hand). Of course my guitar is not very close to the mic (maybe 20 cm pointed at the 15th fret) but any cloesr I get distortion (mic distotion maybe?). So the main question is, how hot a signal can you expect from your condenser mic?
Any help on this matter would be really appreciated.
You should have quite healthy level from NT-1. It’s by no means extremely hot and you need some gain. Hotter than dynamic mic thou.
Actually 20 cm is not far away if you talking about miking an acoustic guitar with it. The distance might as well be one meter and you should be able to do ok. On the other hand, NT1 itself shoudn’t distort no matter close to the guitar you move it, that’s for sure.
Try plugging something else to it to check if the rode is ok. Electric guitar for example.
Are the output levels good? Try less input gain and more output gain.
What about the levels is you soundcard? There should be a way to adjust that too in software (althou I’m not familiar with the soundcard you have)
Thanks varakeef for your thoughts. The sound card settings are right up and I had the same situation when I ran the setup into my SBLive so I’m pretty sure it’s not the sound card settings. I’ve run my electric guitar throught the preamp and it sounds fine. Although, again I did have more gain wound up on the preamp than I would have though necessary…but that’s a subjective judgement I suppose.
Problem is I don’t have another mic or preamp to check mine against. Might be the only solution I suppose.
In the control panel of the 2496, you can also set the sensitivity from -4 to +10 bd. Maybe this brings an a bit extra.
I don’t see that? I have consumer versus -10dBV output level adjustments. Is that in the lastest driver/software update?
Hm - slightly different then.
I use the drivers that were on the CD, and they show -10, consumer, +4
I messed up the numbers in the previous mail
Unless you’re doign somethign strange, I’d say your mic or your pre is knackered. One thing which might be worth checking is the phantom power output voltage on your preamp while the mic is connected. Should be 48V or thereabouts.
I’m thinking we’ve got slightly different software/ driver versions which is probably no biggy. Also, I think that the output levels aren’t going to affect the microphone input (line in) levels. Thanks for your thoughts though.
Thanks for your reply. The thing is I get a really nice sound when I follow the conditions I set out in the opening post. It’s just I was curious as to what could be expected as far as signal strength is concerned going into the soundcard/ntrack.
I should have said that the preamp had a tube replaced by the guy I bought it off before he sent it to me (I bought it over the internet). I was surprised by this as he said it was a year old, but he replied that it was because he’d used it as a guitar preamp to sweeten his sound. This burns out the filaments quicker…makes sense. Now I’m thinking perhaps the preamp had other problems or maybe he’d got a bum tube or maybe who ever put it in did an average job…I’m very much thinking I need another mic preamp to compare
You should be able to very easily drive the inputs on your sound card to clipping - especially as they are -10 level (which is lower than pro line level). If you’ve got the gain all the way up and you’re only making -20db on the input meters then something’s wrong somewhere.
You might want to check that tube, as well. If it’s a lower-gain tube like a 12AT7 or a 12AU7, instead of the specified 12AX7, that could be why the output is so low. Or, the tube might just be a defective one…
Sounds like a phantom power issue to me assuming everything else is set correctly.
Thanks all for your feedback
You’ve convinced me that I have a problem somewhere which is what I wanted to confirm from this post, so cheers for that. I talked to a guy in the shop I bought the mic from and he’s given me a technician’s phone number so I’ll try that. I’d place a small bet on the trouble being as Tim outlined that it has something to do with a low gain tube being used instead of the correct one (I think the correct one is a 12AX7a). I’ll let you all know how the situation pans out.
Bubba might be on the right track. Try different mic cables. A faulty cable might work for audio and stillnot get the phantom power to the mic. Double check the phantom voltage at the mic end of the cable as well, and compare it to what the preamp puts out…in other words rule out phantom supply problems first.
Sounds like a good idea. I’ll get my multi-meter out and see what I can find out.
Just a little update to my microphone preamp saga. I talked to a tech today on the phone and amongst many other things he suggested I have a look at the current rating on the power supply and compare it to the ART tube MP specs. The power supply the guy gave me when he sold me the preamp is rated 600mA. Specs for the preamp say 9VAC@700mA.
Looks to me like there’s not enough juice getting to the preamp. As Bubba/Phoo suggested I also took a look at the phanton power. I had two different voltmeters reading 45.2 V at both the preamp and the end of the mic cable. This is not 48V…is it? I mean to ask, is this close enough to 48V to not affect the performance of the mic?
I’ve got a 9VAC 1A adaptor for my GNX1 that i’m so tempted to plug in but have been warned of the possibility of polarity differences causing small puffs of smoke and funny smells That along with the fact it’s 1A and not 700mA.
The story looks like it will continue…
Hi, If the adapters are AC you can’t have any polarity problems and the 1 amp current rating of the other supply is not a problem as the preamp will only take as much current as it needs.So plug it in and give it a try, (although I doubt it will fix your problem).
If you’re putting out 45V then that’s close enough to not be an issue. An audiobuddy puts out half that but still works okay. Was this open circuit or while loaded though? You want to check this with the mic connected.
As far as power supplies goes, your preamp will draw the same current from both. The larger current rating one would be preferable as it will not run so hot, and is less likely to give up the ghost.
45v should be enough, but the measurment needs to be taken under load – with the mic plugged in. A nearly dead battery wil read 1.5 volts with no load, as will faulty power supplies (depending on the problem they have). Mics don’t have much load, but they might have enough to bog down a fault power supply. See if the volts falls much when the mic is plugged in. It may fall just a little. I don’t thing it should fall much, but even if it falls just a little it could point out a potential problem, and is it drops to only a few volts then you found it…sort of…It could be a near short in the mic loading it down.
(I’m making a big assumption you checked the DC volts with a VOM at the mic cable and no mic.)