The beginning engineer can be overwhelmed with the number of preamps out on the market, however, understanding the role of the preamp in the signal path is important and so is understanding what one preamp will do (or not do) to your source. Also, a future sound engineer needs to be familiar with classics as they serve as references to other sound engineers. The Neve 1073 is a classic preamp, classic enough that Vintech Audio (amongst others) makes a clone of the original 1970’s design. This clone, the x73i, is one of the preamps available to students at Musitechnic. Last time we put the original 1073 in context and shared some of legendary designer Rupert Neve’s thoughts, this time we’ll hear how the X73i sounds and compares to a basic preamp from a Mackie 24-8 mixer.
The set-up
For the following preamp test sessions I setup a microphone in a booth, facing a loudspeaker. As you can see in the picture below, the distance between the microphone and the loudspeaker is about a foot.
For this session, the microphone used was a Shure KSM44, cardio. The microphone signal was split with a Y cable (as a consequence, when the signal gets to the preamp it is 6dBs lower than if there had not been a Y cable) so as to be sent to both the microphone inputs of the X73i and the Mackie 24-8 channel 1 preamp.
Calibration
For calibration I played a sine wave into the loudspeaker, picked up the signal with the microphone and adjusted the gain of the two preamps on test so their levels matched.
Here is a spectral profile of the recorded sine signals:
The distortion was clearly audible coming out of the loudspeaker
Mackie preamp
Vintech Audio X73i preamp
Here are the recorded signals :
I could not hear a difference between the two. I played both channels back simultaneously and the level increased by the expected 6dB (doubling of the level). I then flipped the phase on one of the channels as they both played. The level decreased drastically, about 34dBs, which made the distortion inaudible. The sine wave does not entirely disappear so the signals are different enough to not cancel out completely. Any slight difference in level between the two preamps is enough to account for some of the signal not canceling out. However hard I tried to have identical levels coming out of the preamps, I was limited by the accuracy of the monitoring tools I was using in my DAW.
Here is the audio of the combined preamp signals with one channel phase inverted :
Here is a spectral profile of the combined recorded signals with one channel phase inverted:
Combined preamp signals with one channel phase inverted: the level decreased by 34dBs
Combined preamp signals with one channel phase inverted and Master fader at +12dB: the distortion is audible again.
Pink Noise
I also used a complex signal that resembles music somewhat: pink noise. The complex pink noise signal reveals that the difference between the two preamps is all over the frequency spectrum. Something the 1kHz sine wave could not have shown us as well. What the spectral profiles below tell us is that when combined with one of the signals phase inversed, the resulting spectral envelope is not only lower in level (which is to be expected) but its frequency distribution is not the same at all: most phase cancellation occurs roughly between 200Hz and 2kHz. This can be interpreted by saying that, the differences between both preamps probably lies in the low and high frequencies.
Here is a spectral profile of the recorded signals :
Both preamp signals combined in phase (left) and both preamp signals combined with one channel out of phase (right).
Here is the audio of the combined preamp signals with pink noise :
I personally was not able to hear clear differences between the two preamp signals..
Drums
The next step was to play some percussive content. I played a drum audio file (normalized at 0dBFS) into both preamps. The first thing I noticed was the loudspeaker having a hard time dealing with the kick drum, you can hear the distortion it generates. For our tests we can consider the distortion as part of the source, it does not come from the preamps.
I was able to hear more brightness from the x73i. The hi-hat for example seems brighter to me in the x73i. Even the kick drum sounded ‘cleaner’ in the x73i, it seems to rip and tear in the Mackie preamp, sounding like a digital-bit crusher whereas the x73i seems to handle that ‘overload’ better. Listen for yourselves.
Here are the recordings of the individual preamp signals with the drums
“Minimum-color” tests
Acoustic guitar
The next source I used to test the preamps had both a percussive content and rich harmonics: an acoustic rhythm guitar.
This time I tried to minimize the ‘color’ of the X73i preamp on the signal by setting the (theoretically neutral) output pot to maximum and pre-amplifying the incoming guitar signal with just enough gain to match the recorded level of the Mackie preamp. In the previous blog I mentioned that the output pot of the X73i plays the same role as the fader on a console and as such, should be pretty neutral. By doing this I tried to get as little ‘Neve’ sound as possible in my recorded signal to see if I could still hear a difference between the two preamps. Flipping the phase on one channel gave the same result as with the pink noise: the mids disappeared and the resulting signal was comprised mostly of lows and highs.
Here is the audio :
Guitar 2
Guitar 3
I’m not going to tell you which is which, but I’ll put you on the track so you can test your critical listening skills!
One of the audio files is the combined preamps with one out of phase with the other. Because the level was so low (phase cancellation), I boosted it 20dBs. One of the files is the Mackie preamp and one of the files is the Vintech X73i in ‘neutral’ mode as explained above.
What should you listen for :
The out-of-phase-combined signal has lost mostly mids (as we noticed with the pink noise) so it should sound pretty bad (or cheap!). I’ll tell you what I heard (results may vary!). One of the preamps has lows that are kind of wild, like a resonance (on certain chords) that just stays, like a low note drone. I would not call this a positive point as the lows seem slightly exaggerated. This same signal also has bright highs. At first they seem bright and clear but then they start feeling aggressive and brittle, they too seem a little exaggerated maybe especially when compared. Finally, the other signal also has that low note drone that I mentioned but it is much more controlled, more restrained and by consequence more pleasant to listen to. The highs in this signal are present but not overrepresented. If all this sounds too technical, just use a ‘Cheap Vs Luscious’ scale. Which guitar track sounds cheap to you? Which guitar track sounds luscious and professional to you? Ultimately, when you are recording music, that’s what counts! Remember the ‘Neve’ sound is sometimes described as warm, not necessarily high fidelity but musically pleasant. The ‘cheapest’ sounding guitar should be the combined out-of-phase preamps. In theory the ‘cheap’ sounding guitar should be the Mackie and the ‘professional’ sounding preamp should be the Vintech X73i. The out-of-phase-combined signal seems to just emphasize the unpleasant characteristics of the Mackie preamp.
Cowbell
Transients are notable for putting amplifiers to the test. Using percussions as a source helps us hear the difference between these two preamps. In the audio files bellow it is relatively easy to hear how abrasive the attack of the cowbell sounds with the Mackie preamp. Because both preamps take a toll with the attack, I’m assuming the microphone is responsible for the clipping. Regardless, clipping can occur in a real life situation so it is interesting to hear how both preamps deal with it.
Hear the audio here :
The most obvious difference is in the low end. The Mackie gives a thumping sound not unlike a vocal plosive (like the letters p and b for example) whereas the Vintech Audio seems to handle it much better.
Here are two snapshots of the visible differences between the two preamps dealing with a cowbell attack. Notice how more jagged the Mackie waveforms are at the larger transients.
Notice how different the attack transients are on both preamps:
Voice
With a singing voice it is not the low end that caught my attention but rather the high mids. The high mids seemed to be more aggressive in the Mackie preamp. Is it me or the buzzing sound in the voice seems slightly attenuated (a good thing) in the Vintech Audio preamp? You can hear for yourself. Remember the Vintech Audio is set for minimum coloration.
Hear the audio here :
“Maximum-color” test
Gabriel Boucher, a teacher at Musitechnic and an electronics aficionado, was quick to remind me of the well-documented way in which engineers use this type of preamp: they crank the preamp to get the ‘color’ and attenuate the output with the post preamp gain control (essentially a fader). This is what I set out to do with this third series of tests. To calibrate the signals I sent a sine wave to a loudspeaker placed in front of the microphone (a U87 this time) in a recording booth. I pushed the Mackie and Vintech Audio X73i preamps to the max. I adjusted the X73i output to match that of the Mackie preamp (within a tenth of a dB) with the X73i’s post preamp gain control (labeled ‘Output’ on the X73i). It had so much more gain than the Mackie preamp that I had to really trim the output of the X73i.
Tones and noises
Once the calibration was done, I changed my calibrating signal to various tones and noises. Here is where differences became more obvious.
With a square wave, the Mackie preamp was 2.8dB hotter than the X73i
Hear the sounds
With white noise, the Mackie preamp was 6.5dB hotter than the X73i
Hear the sounds
With pink noise, the Mackie preamp was 3.5dB hotter than the X73i
Hear the sounds
I have no clue why the Mackie preamp gave that result but looking at the actual recorded waveforms something else becomes obvious: the Mackie signal tends to be more erratic in terms of level. In other words, for a given signal the X73i would be more stable in level than the Mackie preamp. If you take a look at the white noise and pink noise recorded waveforms (the last two audio segments) in the snapshot below, you will see what I mean.
I do not have the technical knowledge necessary to explain what is happening but can only speculate that the Mackie preamp is pretty linear with simple signals but is less controlled with very complex signals (pink and white noise). Which leads me to ask, how would the Mackie preamp act with a complex wave form like a snare or a cymbal? What about a distorted electric guitar? Another question: is there erratic behavior only when the gain is pushed to the max?
More gain
At this point I wanted to know how much more gain the X73i had.
Hear the sounds
The X73i has about 20dB more gain than the Mackie preamp. The signal stays very clean as you can hear. While we are on the subject of gain, bear in mind that we are splitting the signal at the microphone so there is 6dB less gain at the input of the preamps.
I also recorded the sound of both preamps set to maximum. They are both noisy at this point but the X73i is still cleaner. Radio frequencies are clearly audible in both signals but one of the preamps is more aggressive in the higher frequencies. I adjusted the recorded signals so that their playback levels match.
Hear the audio here :
The human voice is probably the most recorded audio source so here is a recording of the voice with a U87 and both preamps on maximum.
To take advantage of the load impedance options of the X73i I tried a R121 ribbon microphone with an acoustic guitar. I set the load impedance of the X73i to 1.2kΩ. Both preamps are at maximum. Do you feel the X73i has more low-end?
And to finish this test, here is a voice with the ribbon R121 microphone and both preamps set to maximum gain. Notice the background noise (hiss) is more audible with the Mackie preamp
Conclusions
To recap on the results of this test, here are a few comments that can be made :
- I was expecting to hear the color of the X73i but what the Mackie’s noise and erratic behavior is what stuck out most.
- Way more gain. You may not care too much about that if you are recording loud hip-hop vocals but if you use ribbon microphones, 20dB more gain is awesome. If you record soft sounds (Foley for example) or ambiances and room tones, 20dB more gain is always welcome.
- The X73 is generally less noisy than the Mackie preamps.
- The audible differences between the two preamps depend on the source. With some sources (like an acoustic guitar) the differences are more clearly audible than with other sources (triangle for example).
- I have only presented the preamp, many X73i users rave about the EQ section that I did not even touch for this test as it was the preamp I was really interested in comparing. So bear in mind that the Vintech Audio X73i is more than a just preamp.
- Is the Vintech Audio X73i worth it? Is it overpriced? It depends, if you make a living as a sound engineer or if you are studying sound engineering, you probably won’t obtain the same answer. I believe that with the Mackie 24-8 preamp you get 90% of the performance for 10% of the price of the Vintech Audio X73i. However if you want 100% of the performance Vintech Audio, you have to pay 100% of the price. This is also the difference between consumer/semi-pro gear and professional gear.
Regardless of your opinion of the X73i, I hope about you were able to hear some differences in the sounds of the two preamps I compared. If you cannot hear a difference, I suppose it means you do not need this external preamplifier.
Questions and comments : k.blondy@musitechnic.net
