Audio Buddy phantom power issues

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crazydoc

crazydoc

Master Baiter
I emailed the following to Midiman tech support several weeks ago:

"The Problem:I got an audio buddy mic preamp as a christmas gift. I got a large diaphragm condensor mic recently to use with it, and have been somewhat disappointed in its performance. I measured the phantom power voltage of the audio buddy with a vtvm (essentially no load on the circuit). Open circuit voltage is 35 volts, and voltage with one mic in the circuit is 27 volts. I haven't measured it with two mics, but suppose it to be even lower. Phantom power is supposed to be 48 volts. I believe I have a defective unit, and would like it repaired or replaced. Advise me how I can have this done. Thanks."

After a week of no respose to three posts, I called on the phone and after being shunted around a few times, spoke to someone who allowed that the voltage "seemed a little low." He told me I could send it to them and have it looked at and repaired.

I was reluctant to do this as it's my only preamp and I'd be unable to record while it was away (for an indefinite time period.) I took it back to GC where I had bought it, and even though this was now some 4+ months later, they agreed to replace it. I exchanged it for what appeared to be a new unit in a shrink wrapped box, but when I got home and opened it, it was obviously a return from someone else.

I tested the voltages of this unit, which were 40 volts open and 31 volts with a one mic load.

The audio buddy specs simply say "phantom power" and list no voltage or current values, so I'm probably SOL in insisting on 48+/-4 volts. My gut feeling is that it uses a low current voltage trippler or quadrupler which is poorly/cheaply designed and unable to provide the proper voltage in any of their units.

My burning question is this:

Does anyone know what type of signal degradation occurs as phantom voltage decreases, in a typical condensor mic circuit? If it's just a decrease in output voltage/volume I can live with that, but if it changes the mic's tone/frequency response that's another matter. Although the change could be for the better, in my experience random changes in life are always for the worse.
 
For most modern, low cost mics, 40/31V should be plenty.

The signal degradation you'd see if you were running a mic that needed more than it was getting would be a fairly significant loss of headroom, rolled off highs, and some low-end weirdness as well. Basically, if this was happening, you wouldn't have to ask...you'd know. ;)

What mics are you running off the Audio Buddy?
 
I believe this topic has been discussed before, and it's a known fact the the Audio Buddy is a bit shy on phantom power voltage.

To my knowledge, having less than optimal voltage for a mic that requires it's voltage to be within the 48V + or - 4V spec, may cause several properties of the mic to change...including frequency response differences, lower maximum SPL, lower output, distortion, etc.

However, there are many, many people who are using the Audio Buddy with mics that claim to require the voltage be within 4V of the 48V spec, and have not reported any noticable signal degradation...although it's possible without another preamp to reference to, these types of differences would not be evident.

Maybe someone else who has done a comparison can chime in with some more information.
 
I have one and haven't HEARD any degradation,but I'm no golden-eared one.Steve (Ozraves) did an in-store test at GC at 44 volts I believe.
 
Thanks for your input.

I remember this being discussed before, but I don't remember that any definite conclusion was reached.

I don't have (yet) another pre with known 48v voltage to A/B compare to, nor the experience to hear subtle (or even obvious) signal degradation.

I can't trust my ears due to high frequency loss, and sometimes I think that some connections have come loose between my eardrums and auditory cortex - but that's another issue.

It would be interesting if someone who has the capability to measure a mic's frequency response could do it as a function of phantom power voltage - but I guess it would be an individual characteristic for each model or brand.

The mics I use with the audio buddy are mxl 603, mxl 67, and Behringer B1, all of which sound an order of magnitude better for voice and acoustic guitar than the sm58 I was using before. Now my music, instead of sounding like muddy shit, sounds like clear and crisp shit.
 
I have a dmp2 that I use strictly on my Behringer ecm8000's. Those along with others like the AT 4045 are exempt from the need to have all 48 volts.

I forget. Is it because they're electrets? :)
 
I read on another post that someone who e-mailed M-Audio about the voltage of the Audio Buddy actually received a reply and they claimed 40v.That correlates with what Oz measured his at which was 41.4v I think.As people have mentioned that is enough for many if not most mics especially the mics within the homewrecker's usual budget.A lot of these mics are electret in design so they can run perfectly with much less than even the 40v the buddy supplies.I have an Audio Technica 3525 which claims to need 48v but works perfectly with my AB.A closer inspection of the specifications revealed that it is indeed an electret mic.I have an Mxl 2001p(boo!boo!hiss!)that is externally charged according to its specs but I have never tried it on the Buddy.I don't see how starving the 2001p of a few volts would hurt the sound of the 2001p,it already sounds like shit.Shit in shit out.

Crazydoc,I think the first unit you had was indeed defective.Now you say that your mics sound like clear and crisp shit instead of muddy shit.If it's clear and crisp than I wouldn't guess the mics being underpowered to be your problem.From what I understand a higher noise floor would be one of the results of insufficient phantom power and if your mics sound clear and crisp it doesn't sound like you have a noise problem.Although there could be other symptons of low power I guess.

I guess I don't really understand what you mean by "clear and crisp shit".Are you getting some high end artifacts that you think is caused by the preamp?If the signal is clear and crisp it sounds like it is plenty strong although I wouldn't trust the metering on the Audio Buddy when setting levels,I use my ears instead.I've noticed the clip light sometimes is a little slow to light even when I hear audible distortion and that the signal light is not much more responsive.
 
Randy - The signal sounds fine to me - I just don't have the experience to know if it should be even better if the proper voltage were used.

The reference to the shit, muddy, clear or crisp, was tongue in cheek to my recordings (singing, playing, music), not the quality of the signal. Sorry for the confusion.

It sounds like the audio buddy I have has what they consider their nominal voltage, though it would be nice if they would include it in their specs so the customer would know this before the fact. Other than this, I like the unit - it's quiet and seems to give a faithful uncolored amplification of the signal.
 
Cool Crazydoc,if it is noise free and has a hot enough signal then it's probably doing it's job.I like my Buddy and it works just fine with my mics but I'm sure that there might be some externally charged condensors that might have trouble with 40v.I haven't heard of anyone with problems with specific mics but that problem could exist.

I agree M-Audio should be more forthcoming with information.It is kind of like Audio Technica,I have a 3525 and no where do they state diaphragm size.I believe it is 5/8 in but I'm still not sure(not that it matters I guess).No company should withhold pertinent specs,it ain't quite lying but it is a sin of ommission.Funny thing is that I really like both products.
 
I've never noticed slight decreases in quality due to phantom problems. It usually either works fine or sounds like absolute crap.
 
Fortionately the ecm8000 pair I use with mine only really need 15v to work properly. My PZM mics use the same electret and work on 1.5 even though I modded them to use 9v.
 
i can' t find my own audio buddy around here to check it yet again.

i think it was something like 42v or maybe 41.4v. in any event, it was over 41v and less than 45v.

the power should be the same no matter if you have a mic drawing power on one channel. it should be the same on both of the power outs on each plug.

you need a very high impedance multimeter, digital preferably. if you don't have this then you are not going to get an accurate reading.

it sounds to me like you ran into a situation where somebody on the manufacturing line was screwing up and it didn't get caught. you should take the unit back and get one that meets the criteria i've posted above.
 
And just when I thought my li'l buddy was ok.

ozraves -
I'm using a VTVM with 1meg input impedence to measure the voltage, so this is not a factor. Even so, when I plug in a VOM with 20Kohms impedence with the VTVM hooked up, the voltage only drops a few tenths. Also, if you are correct that plugging in a mic shouldn't load the circuit enough to drop the voltage, then it wouldn't matter what kind of voltmeter was used - it too should have no effect on the circuit.

However, mics_do_ load this circuit - a lot. The LDC's (v67 and B1) drop the voltage to 29 volts (from 37 I am measuring now) and the mxl603 down to 27 volts.

If you get a chance, (and find your audio buddy) measure the open circuit voltage on one channel, and then with the meter still hooked up, plug a mic into the other channel and see if the voltage drops significantly.

I can't easily measure the voltage with two mics hooked up (without taking it apart and probably voiding the warranty), but I'll bet there is a further drop with the second mic, down another 10-15%.

I'm afraid the circuit just can't put out enough current (which doesn't need to be more than 10 or 20ma I think) to drive the mic circuits at a reasonable voltage.

I guess the good news is that it sounds ok to me. However, if ozraves' unit does _not_ show a voltage drop when a mic is plugged in, then mine is definitely defective and I'll send it in for replacement/repair.

Thanks for everyone's input and help.
 
My Shuresm58 mic sounded pretty good with my audio buddy, but I wanted a crisper more 'out there' sound, and after reading many posts re condensor mics decided to buy an Audio Technica 3525 on ebay. The signal is weak and I'm not sure how to rectify that. I have to turn the speakers way up to hear myself when I play it back.

I've been reading about 48 V of phantom power, but I read here in the audio buddy manual: "9 Volt AC Power Jack. The rear panel power jack of the Audio Buddy accepts a 9 volt 500 milliamp acc power adapter. Does that have anything to do with the voltage being drained? Or whatever? Someone of you will probably know what I'm talking about. Thanks.
 
Joan said:
I read here in the audio buddy manual: "9 Volt AC Power Jack. The rear panel power jack of the Audio Buddy accepts a 9 volt 500 milliamp acc power adapter. Does that have anything to do with the voltage being drained?
Click to expand...

No, it doesn't. You're fine. You either forgot to turn your phantom power switch on, or you have the gain too low. How, in God's creation, did this thread get dug back up? :D
 
Actually, I often use a pair of Oktava MC012's into a Behrenger MXB1002, which provides only 21v nominal phantom power when plugged in, 18v on batteries. This goes into a KORG PXR4 Pandora. Gosh, I lose a little headroom, and paradoxically, I find it works better with the pads installed in the Oktavas, especially for loud sources, and I boost the gain at the board. Try the Audio Buddy with another condenser mic, if you have another or know someone who does. Not happy with the results? Maybe you just don't like that mic.-Richie
 
How high should knob be turned up on audio buddy

You're going to hate me for revisiting this topic, but I need to know - how far up should I turn the knob on my audio buddy to get volume? It's almost all the way around to get a strong sound. Otherwise, volume is too weak. I'm using an audio technica 3525 mic. Phantom power is turned on. Thanks so much guys. Joan
 
To each mic its own, I guess. My V67 needed just a little, probably at about 9 o'clock. My Nt1 from rode needed a little more, around 10-12 o'clock. What are you sending to and what type of cabling are you using?

Pete
 
Joan

If your SM58 sounds ok thru the audiobuddy, but the AT is weak, then the problem is probably either the mic or the phantom voltage. Find another (known good) preamp to plug into - if the mic sounds ok, the problem is the audiobuddy phantom power. If the mic still sounds weak, the problem is the mic.

I seldom ever have to turn the audiobuddy gain past 12 o'clock with any condenser mic.
 
As others have mentioned, it seems to depend on the mic being used.
Some are fussier about phantom than others.
Neumann mics usually won't operate well without 48v.
A friend had lots of problems getting his U89 to work properly with an audiobuddy.
It was picking up RF and sounding crappy.
Used with another pre that provided 48v, using the same cables, the mic performed up to spec with no trace of RF.
 
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