UniVibe sounds better pre gain… there, I said it. Now, I know this is a subjective statement, but you know, the VAST majority of the people I know and have spoken to consider the UniVibe style circuit to be perfectly placed pre gain stages. Of course, there is going to be someone who is already googling for their favourite picture of Jimi with a FuzzFace into a Vibe into his Marshall’s… of course, the main issue here is that Jimi’s amps were always cooking, so the UniVibe WAS going into dirt, just it also had some going into it as well – the thing to remember here is that the last thing in the chain, in the case of Jimi and Trower, their amps are on pretty well full tilt so that is what is deciding the overall tone. Now, if they were going into very clean amps…
Why does this happen? What changes does an effect like a UniVibe make to the signal that makes it SO picky about signal chain placement. Most effects can sit happily either pre or post (although they will sound different) I can’t think of one that is so very different dependent on placement. To my ears, pre gain the Vibe sounds fat and exciting, and post gain is sounds thin and weedy. I know that, once again, it’s just my opinion, but that appears to be the general consensus. So much so, I broke out my trusty Helix Native and used the same riff to show the difference. So, same riff, just moving the vibe from front of gain (amp is a basic Mashall model going into 2x 4×12”, one with a 57 and the other a 411). I recorded the opening riff of a great little song called “Mystery Song” by the mighty Status Quo and sliced it down the middle to separate the tracks and put the UniVibe in a different place – the only change in the chain is that the second part of the riff has the UniVibe moved from first in chain to behind the amp and before the speakers.
To explain this, the best thing to do is to go into the mechanics of a UniVibe style effect to understand why it works in the different positions. Basically, a UniVibe is a 4 stage filter that creates 2 notches that are moving around each other (worth noting here, the UniVibe is more of a filter effect, it’s kinda misplaced as a modulation, but…). The Q on these notches is quite narrow so the human ear is hearing the emphasis on the space between the notches. When the LFO (low frequency oscillator, the thing that gives the movement sound, the ‘sweep’) is moving up and down, we ‘pick up’ that space between and inadvertently concentrate on that. As the range of the sweep isn’t the complete, it cuts off and comes back the other direction. Because of the two notches, this is what creates that out of phase/wet sound we’ve all come to love.
The reason it gives the impression of being more comfortable pre gain, is because as the filters are moving around, it excites the harmonics in the dirt that emphasises them in a way that is pleasing to the ear, when it is post dirt, those harmonics are in place before so the notches are removing them in specific places, and the main section in the middle that we hear is sounding flat. When that hump hits the dirt and clips (overdrives), the dirt pedal/amp gets all excited and makes it pleasing to the ear, also, a good dirt stage (and most not so good ones) will compress the signal somewhat as well, so it’s bringing in all those pleasant frequencies into a nicer sound and focusing our ears to the sounds, once the ‘compression’ is before it, everything is flying freely around and there is no focus. In order to make UniVibe sound the way we perceive it should sound, it needs the compression of the gain stages (whether it be the dirt pedals or driven amp) to bring it back into control, not allow the top end to run around freely and be “the UniVibe” – when it goes behind, it almost turns into another effect that maybe should have a different name? What should it be called?
OK, so – my dodgy sound example – Hopefully you’ll notice that when the riff moves to track 2, the sound does become instantly weaker and more leaning towards the top end – it starts to sound very filtered (which is what the effect is doing) – this is because the filter in the UniVibe now has free reign over the tone and the parts it’s emphasising are there for you to hear – when it goes pre gain the gain stages are flattening everything out, compressing it all and bringing it all under control. You can see with the EQ graph (although it’s quite subtle, but it’s there) how those frequencies are allowed to be more prominent.
For this recording I have increased the gain element and made the vibe more prominent, just to emphasise the effect – it’s not designed to be a soundalike!