Microphone Noise - Help

[StubaJohnston]

Hi Folks,

Newbie here Apologies if this question has been asked before - I'm currently suffering "googleitis" from all my searching!

I've recently purchased a Rode K2 microphone to help kickstart my venture into computer audio recording. At the moment I'm in the process of investigating what audio interface/pre-amp to buy, so in the meantime I am trying to record my Rode K2 using a Presonus Inspire 1394. The Inspire 1394 works perfectly for the guitar line in but my problem is that I encounter a loud hissing/hum when I'm using the K2 in the mic input.

FYI - Here are the "givens":

• This hum increases when i increase the gain on the pre and reduces when i reduce the gain on the pre.
• This hum is only present when the mic is connected
• This hum is still there even after letting the K2 "****-up" for more than 60 minutes

These have been my troubleshooting tasks thus far:

• I've isolated the K2 and it's power supply to a seperate room - Hum is still there!
• I've tried both of the "ground" options on the K2 Power Supply - Hum is still there!
• Tried recording vox with the pres gain turned low but was unable to record a strong enough signal to work with
• Removed mic jack from Inspire box whilst hearing the hum - The hum disappeared instantly.
• As the Inspire has two mic inputs (with inbuilt pres) I've tried the microphone on both inputs and experience the same problem with both inputs.

Now I'm quite confident the problem is not with the microphone itself (I'll add here that I had a friend test the K2 on his set-up and he got a great sound with no apparent noise.) I think the problem is to do with the Inspire pres giving a dirty sound but I'd hate to think that there are users out there "living" with these dirty pres in their day to day recording. I'm hoping there are some other tips or troubleshooting tasks that I can do to help fix or minimise the noise.

Also, before anyone mentions that it's because I'm using a low entry point audio interface with built in pres and that I need to upgrade to a better quality interface with better pres to get a better sound!! Rest assured.. I'm currently investigating my options and reading reviews after reviews

I just can't believe that the hum that I'm experiencing with the Inpsire 1394 is a "out of box", "live with it" kind of issue?

Any help or tips/tricks would be greatly appreciated!

Thanks for listening,

Stu

P.s - I'm using Cubase LE4 - Is there anything in Cubase that can help remove the Hum? Although the hum is apparent with or without cubase open.

[Cursed Lemon]

I'm having problems with the recording quality of my Mbox so I understand the frustration.

How exactly are you hooking up the guitar, now? As opposed to how you're hooking the mic up, that is.

[StubaJohnston]

Hey Cursed,

Thanks for the response.

I should have clarified. The guitar is my acoustic Fat Lady (Cole Clarke) with in-built pre connected to the Inspire 1/4" instrument input.

Cheers,
Stu

[Cursed Lemon]

If you're confident that it isn't the mic, then it may be that the mic pre may be defective on its own. Which would be strange considering that the 1/4" input and the mic input would both be using the same pre...I would try plugging another microphone into it just to make absolutely sure.

Do both mic pres have the same problem?

[Audio~Geek]

I just noticed that w.a.r.m. is a bad word here! :lol:

I'll give my honest opinion that the sound you're hearing is from the interface. It's an entry level interface, it gets sound into the computer, but being an inexpensive interface, compromises needed to be made and it's not built of the highest quality parts.

Got another mic cable to try? Got another mic to try?

What about when you unplug the mic but leave the cable plugged in?


You want to get rid of the Hum from the source, figure out if it's from the mic, the cable, or the interface.

If those steps don't get it sorted post a clip so we can hear what you're hearing.

[StubaJohnston]

Thanks folks for the replies.

I will try the suggestions and relay my findings. Unfortunately I'm at work at the moment.

I realise it may be the interface but I really struggle to understand how anyone could use it if they too are experiencing the same noise.

By chance, are there any Inspire 1394 users floating around that can vouch for the pres?

Thanks again folks,

Cheers,
Stu

[StubaJohnston]

Just thinking - My K2 has been tube modded and now has a custom vintage AMPEREX BUGLE BOY 6DJ8 ECC88. How long should one of these tubes take to w.a.r.m up?

Could it be the tube w.a.r.ming up that I am hearing? I've left it to w.a.r.m up for 60 minutes. Do you think I need to let it w.a.r.m up for longer? If so, how long?

Does anyone else have this modded tube config in the Rode K2?

Thanks again folks,

Cheers,
Stu

P.S - Anyone know why the word "w.a.r.m" is always replaced with *'s? Hmmm curious!

[Audio~Geek]

its a dirty buzz word!

the mic shouldn't hum at all.

I'd say 10 minutes is sufficient for a tube mic.

[hugo_zair]

Does the "hum" continue if you shut down the software control panel of the inspire?

Edit: I've now re-read your observations more carefully and see that your friend's test has effectively eliminated the mic. But, by pulling out the "jack" the hum disappears. That would tend to clear the Presonus. Which leaves the cable. Is it literally a jack? ie are you using an unbalanced lead. Did your friend use the same lead when he checked it? It must be connected with an XLR to XLR. If it is try another one.

Now some general stuff from an ex owner. I do groan when I see forum posts denouncing certain gear as c**p on the basis of one example but I did buy an Inspire from Dolphin Music a couple of months ago and was not happy. To my surprise (and their credit:-) my buyer's review was actually posted and is currently the latest one on the Inspire ad page. maybe I was just unlucky.

basically my feelings are these. The Inspire preamps do not have a lot of gain and I suspect that's because there's so much digital noise going on in that small box that, at that price point, they can't screen it out. The pres are probably not actually noisy but they can't keep the digital whine out of them. So they settle for what appears to be about 40db (before "booost"). As well as hiss/whine, there is a "motorboating" sound (that I've read about on other forums) that is caused by the software control panel running..digital cross talk somewhere.

The boost button, as far as I can learn from the internet, is not true "gain" but a digital process within the AD. Perhaps a bit like enlarging a section of a digital photo and seeing the resolution go down. Anyway, on my example, it was a joke - the digital noise that came up made it unusable.

As an experiment I bought a 24bit soundblaster live USB (just £11.50 from an Ebay dealer) and hooked it up with an Audio Buddy pre (now £55ish) and that combination far exceeded the Presonus. My Inspire was returned pronto.

The Inspire price has leapt from £98 to £155 at sometime in the last few months. Perhaps it's a re-design?? or perhaps it's just a price hike to make it appear more desirable :-)

But digital noise is something to look out for with firewire interfaces..I later bought an NRV10 and was disapointed with the noise performance of that also...but that's another story..

edit (Aug 2009) debate on the terrible NRV10 preamps here : NRV-10 input gain issue - Page 5 - The Official M-Audio User Forums ...read b4 you buy!

[millett513]

have you tried recording with the volume up just to see if the hissing goes through or not... my guess is it will but it still might be worth a try... if it doesn't, it still sounds like a problem but not as big of one