Best Mic Preamp vs $

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I got a chance to listen to a CD recently that compared a lot of the different mic pres, and I have to be honest: I was pretty surprized by the results. The CD basically goes through a bunch of different sound samples from various instruments through all of the preamps, one by one. I listened to all the samples blind, and put smiley faces next to the ones I liked, straight-faces next to the average ones and so on.

Here are just a few random thoughts:

Focusrite Red - Disappointment. I was fully expecting this one to be one of my favorites, but as it turns out, too many straight faces, a few smileys, and a few frowns. Nothing special.

Presonus - Another disappointment. Not bad, but nothing special here either. One too many frown faces.

Grace Design - Undecided. I liked this one on all of the "weird instruments" and percusssion that were tested. I also gave it the highest marks, hands down, on things like woodwind and brass instruments. As far as drums, guitar, and other more traditional pop instruments, it was just okay. Conclusion: probably great for classical, folk, or jazz, but a little too vanilla for pop/rock and definitely too plain-jane for metal or punk.

The surprize of the bunch: DBX. I don't recall which model it was, but I remember it was one of their Silver series. Surprizingly clean sounding, contrary to what I have heard from other users. I found this one to be more of a jack-of-all. A few smiley faces, a lot of plain faces, but I don't recall any frowns. It just sounds "pretty good" on just about everything.
 
Any other pre's with voltage problems?

Harvey,

Are the results of the tests you mentioned posted anywhere that we could see them? Now I'm wondering if any other pre's, budget or otherwise, have a similar problem. Anyone know for sure? Do the pre's in any of the popular mixers have this problem? It would sure be nice to know.
 
Here's David Satz' complete post:

Date: 2001-01-15 07:14:27 PST
<roccoflores@my-deja.com> wrote:

It´s incredible they can sell a product with such a big problem.

Unfortunately, U.S.-designed mike preamps in the lower price category often have circuitry that can't possibly work well with high-quality, transformerless condenser microphones. The phantom powering circuit is often just plain wrong, and the preamps overload far too easily.

I always check these two parameters plus the function of the "clip" indicator, before trying out a preamp on live music. Just for fun, here are some notes that I've kept over the past few months. The issues here are:

[1] Input overload voltage (0 dBu = 775 mV, which would be a decent spec to aim for; 6-10 dB higher would be better, but 0 dBu is OK _if there is a reliable overload indicator_)

[2] adequacy of the phantom power supply for a microphone that needs ca. 4 to 5 mA (for two such mikes, if the preamp is a stereo unit)

[3] if an "overload" indicator is present, at what level relative to actual overload does it light? (Note: I measure this only as a steady-state voltage, not as an impulse--but both behaviors are quite important.)

==============================================

Siemens V 72 overloads at -15 dBu in (no phantom powering, no overload indicator)

Symetrix SX202 overloads at +2 dBu in (4 above LED on); phantom powering OK

dbx 760X overloads at around +3 dBu in (5 above LED on); phantom powering OK if extraneous resistor feeding the two 6.8 kOhm phantom resistors per channel is reduced in value (modification approved by dbx technician)

Beyer MV 100 overloads at ca. -5 dBu in (6 or 7 above LED on); phantom powering OK; overload point decreases as batteries wear down, but "clip" LED seems to track this behavior.

PreSonus "Blue Tube" (fails 48 V phantom test) overloads ca. -14 dBu in

Midiman "Audio Buddy" (fails 48 V phantom test) overloads ca. -17 dBu in (LED lights exactly where output distortion is audible, but can miss input overload) David said it only put out 30 volts -HG

JoeMeek VC3 (fails 48V phantom test) does NOT overload with +6 dBu in! (original model, not the current model VC3Q)

Aphex 107 "Tubessence" (marginally fails 48V phantom test with odd results; Aphex tech support described a fairly strange circuit with non-standard voltages and resistor values, claiming that it met the "AES" standard for phantom powering, which does not exist) overloads ca. +4 dBu (ca. 7 dB above LED on, but the LED interacts w/low cut filter also-try -4 dBu in at 500 Hz,)

Event EMP-1 does NOT clip at + 6 dBu in (though clip LED comes on 9 dB before!); phantom power OK

ART Dual MP (squeaks by on 48V phantom test) normal setting does NOT clip at + 6 dBu in; LED lights exactly where input distortion is audible at higher gains. At +20 input gain, clips at about -8 or -7 dBu.

Nakamichi MX-100 "mixer" (3 in, 2 out): No phantom power; does NOT clip at +6 dBu in; no overload indicator

M Audio DMP2 (original model): Phantom power OK if only one channel loaded (open circuit voltage on other channel drops to +44.6 V); input clips ca. 75 mA (ca. -20 dBu); LED reflects output clipping only (lights ca. 2 dB below that).
 
I guess thats why M-Audio doesn't make any voltage claim on the Audio buddy's phantom power.I've never had a problem with my mics,so I guess I've been lucky.Probably anyone thinking of getting one should make sure it can power whatever mic(s) they want to use with it.

I haven't read many post complaining of underpowering with the Audio buddy and there seems to be a good many users,does that mean that many mics today that are listed as needing 48v can run on much less?I have an AT 3525 that is supposed to need 48v and it runs as smooth as glass through the Audio Buddy.The thing I guess I don't understand is how everyone that uses it raves on how quiet it sounds(it is very quiet),is it that many of the popular low to mid budget mics are electret?
 
An electret mic (like the AT4033) won't really care about that, since electrets don't need phantom power to polarize their capsules....But, an externally polarized capsule will not get its full charge from preamps that starve the phantom power
Click to expand...



Hey Harvey, generally speaking, whats an "electret mic" and what's an "externally polarized capsule?" How can you tell which one you have?
 
To amend my earlier post where I said that I have not read many post complaining of problems because of under powering mics with the Audio Buddy,the truth is that I have never read a single post where someone was having any trouble powering their mics.

Every post I have read on the Buddy has commented on how dead quiet it is,noise is never a problem(which matches my experience).I can only guess that most people must be using electret mics by accident or design.I just read the spec sheet for my AT3525 and it says that it is a fixed-charge back plate permanently polarized condenser.That sounds like a electret to me.Thing that confuses me is it says that it requires 48v(+ or - 4v)for power.If it's electret why would it require 48v?Being electret would explain why it works so well for me but I still don't understand why it would require 48v.Oh well back to reading the big mic thread for me I guess.

Harvey,a little off topic but I was wondering if you've used the AT3525 and your opinions on it if you have.I'm especially interested in how it compares to other mics like the V67 or the C-1 as I'm interested in one of these mics and I have no way to hear them locally.I paid $150 for the 3525 and they are still available at that price so I guess another 3525 giving me a pair of them is another option.
 
Maybe the problem is that most of us have no idea what an underpowered microphone would sound like! I mean, only having a couple preamps and mics at my disposal, I might run into a situation in which I've got an underpowered mic that *could* sound better. Would I know it?

Slackmaster 2000
 
I just posted something about this to the wrong thread. Oh well.

Harvey, can you give some insight as to why it seems to be so difficult for certain manufacturers to derive 48V from a 12V power supply? It doesn't seem like it would be too difficult to at least get within a few volts. Where exactly are they skimping? Are seperate transformers required; one for phantom power and one for the preamp circuit? Maybe this is one of those technical things that we don't need to know, but I'm somewhat interested.

Slackmaster 2000
 
Randy Yell said:
To amend my earlier post where I said that I have not read many post complaining of problems because of under powering mics with the Audio Buddy,the truth is that I have never read a single post where someone was having any trouble powering their mics.
Click to expand...

I just put the Audio Buddy through my new multimeter, which measured 41.4 volts of phantom power.

I've never had any problems powering a mic with one but I'm wondering a few different things...

1. How it would sound with an auxilliary phantom power supply that is 48v?

2. I'm going to have my old electronics guy look at it to see if he can get it to w/i 2v of 48v.
 
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Out of curiosity, I just measured the phantom power voltage of both my ART Tube MP and my Symetrix SX202.

The ART Tube MP put out 47.5V.

The SX202 put out 45.1V on both channels.

Slackmaster 2000
 
A poster at Harmony Central forum (Ozraves) today reported going into Guitar Center with a digital VOM and measuring the phantom voltage of the AudioBuddy at 44.1 volts,which is within posted specs of plus or minus 4 volts of the standard 48v.
Tom
 
Maybe m-Audio is resolving the problem.

It seems that the farther you go back, the lower the reports are.

Slackmaster 2000
 
Tom Hicks said:
A poster at Harmony Central forum (Ozraves) today reported going into Guitar Center with a digital VOM and measuring the phantom voltage of the AudioBuddy at 44.1 volts,which is within posted specs of plus or minus 4 volts of the standard 48v.
Tom
Click to expand...

actually, the audio buddy, which i own, tested at 41.4v.

the rolls phantom power supply at gc tested at 44v to 44.3v. i tested two of them.

i tested a dbx unit b/c it was conveniently available at gc. it tested at 47.5.

i probably should have asked them to pull out an audio buddy to test to see what they are doing today.
 
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