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Real Amps Cranked

Only published comments... May 04 2012, 12:00 AM by Chris Townsend

If you’re reading this blog, then most likely you love the sound of a cranked guitar amp pushed into that sweet spot of power tube distortion and speaker breakup. At least I sure do! When I started working on the Eleven amp models, it was very enlightening to hear the isolated raw sounds from actual vintage guitar amps, because I was mostly used to hearing the mixed and processed guitar sounds on records. Sure I owned a Boogie Studio .22 combo amp, but even those measly 20-something watts were plenty loud to get the neighbors or police banging on my door, so rarely did I venture beyond preamp distortion territory.


I found that much of lore surrounding these vintages tube amps is true. They actually do have ghost notes, swirl, speaker breakup, sag, and various other “grungies”, which are not necessarily obvious when listening to the produced sound on a record. When listened to in isolation it’s amazing how much more grunge is actually audible.  But I would say all of this contributes greatly to the character of these amps.  I also spent quite a bit of time listening to raw guitar tracks extracted from Guitar Hero-type video games. When listening to the isolated tracks sometimes I thought the sound was a bit harsh and thin, but I was often blown away by how awesome the tone was when I unmuted the backing tracks. It’s amazing what a difference context makes.



I would guess that these days, many guitarists have never heard the raw unadulterated sound of a cranked vintage tube amp, so I thought it would be helpful to post some audio clips of our vintage amp collection. At our Avid offices, we have a pretty good studio setup with excellent sound proofing, so cranking amps is no problem. Keep in mind that these clips have the amps mostly set to 10 for maximum distortion, and no attempt was made to dial in “good tone”. Unless you are Eddie Van Halen and like everything on ten, these clips more illustrate how not to set your amp. :) But they really do show off quite clearly what these amps are capable of. Also, these clips don’t use exactly the same mic positions we used for the Eleven modeling, so if you do a comparison with Eleven it’ll be a bit apples-to-oranges. Maybe in a future blog we will do some real A/B tests, but that takes a little more work to set up.  All of the following clips are as straight as they come—guitar signal into amp into mic with no effects or other processing applied.


I’ll start out with our AC30. This amp was a former coworker’s who, over the years, owned six AC30s. This one was his favorite. You can definitely hear the speaker breakup in these clips. And in the first clip especially, you can hear what is often referred to as “swirl”, which is a phasey, fuzzy distortion for lack of a better description. Also, another good example of a massively overdriven AC30 is Sex Type Thing by Stone Temple Pilots.  If you get a chance to listen to the isolated tracks (from the Rock Band video game), you can even hear the amp "drop out" a couple times, apparently due to power supply sag.






In this clip, we really tortured a poor old Tweed Bassman. Not sure I would ever want to drive this amp so hard, but we had fun trying. The amount of speaker breakup, swirl and just plain grunge is over the top. I added another version with less gain, which maybe is a little more realistic use case.





Next up is a Blackface Deluxe. The first track really shows off swirl and speaker breakup. For the rhythm guitar track, I added another version with less gain for comparison.  






These Plexi tracks have it all going on. You can hear ghost notes in the lead guitar track (especially at 2 seconds). Ghost notes sound like an out-of-tune note mixed in at a low level. This is caused by modulation from the power supply’s 50/60 cycle hum. Also, listen for sag, swirl, and speaker breakup. Other obvious examples of heavily overdriven Plexi amps are AC/DC's Let There Be Rock (available as isolated tracks on the Rock Band video game), and of course Guitar Hero Van Halen edition has tons of great examples.  Pearl Jam’s Alive (available on Rock Band) is also another amazing example.





Being a more modern amp, the JCM800 has a lot less in the way of speaker breakup, sag, and ghost notes. Very interesting to compare with the Plexi.





In this Tweed Deluxe clip, I mainly hear speaker breakup.  Neil Young’s Rockin' in The Free World is great example of a heavily distorted Tweed Deluxe.



And now for one last clip, which is of a Blackface Twin. This amp has a lot more headroom than most amps of its day, so it doesn’t distort nearly as much though it's set to 10.






PS: The audio samples in this post are available to download as .WAV files for the highest sound quality.


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About Chris Townsend

I am the Lead Guitar Products Architect at Avid.  I created most of the amp and FX algorithms in Eleven Rack and the Eleven Plug-In.  On a typical day I can be found coding algorithms while simultaneously strumming the guitar.  My wife discovered I was a true engineering geek when she saw I was reading Inside the Vacuum Tube while on vacation.

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