Archive for July, 2015

I e-mailed Mesa Engineering awhile back about the loop mod for the 3 Channel DR parallel fx loop to make it serial.  I received the same schematic that I now know everyone else gets.  I can see the appeal for someone who doesn’t want their signal to be “tainted” by a pair of jfets, but they aren’t amplifying, only opening to allow the signal through.  It’s no different than having any other quality part in the path.

More recently, I saw that a company is advertising their bench fee for a different mod and the loop retains some of the functionality afterward.  I thought to myself, what would do that?  One thing that came to mind while off on one tangent is the idea to pinch the dry channel off. Then the light bulb flashed and blew up over the idea I’m writing.  This is not only easier than adding a part or bypassing the jfets, it is entirely reversible.  Here’s how to mod the fx loop and gain a killswitch:


DR and H400aSo…  got bored and threw in a Harmony H400a to my setup.  When I would split my signal from the guitar and send it to both, the Recto would hum from a ground loop.  I expected the same here, but there was not any hum at all.  It won’t work for Metal, but for some good ol’ Classic Rock, Blues, or whatever isn’t brootuhl, it’s fun.  The Mesa EQ actually sounds pretty good through the Harmony, but it’s very “middy” from the lack of lowest lows and highest highs due to an 8 inch speaker.  At the right balance, it sounds great and provides some nice stereo sounds.  If I were to ever get around to making the doodad to run the Harmony to a speaker cabinet, this would be awesome.  If you have similar gear, it doesn’t hurt to try something and see if it makes a decent sound.

This is a pretty awesome video.  It lines up with some of the ideas I’ve been exploring and he is a very good guitar player.  Enjoy.

His cab is different from mine and his amp is the “Reborn” Recto, but most of our ideas are very similar.  For anyone trying to do the same kind of sound sculpting, remember to factor in the cab and don’t be too anal.

Before we begin, I’d like to note that Dual Rectifiers produce much more low boost in their preamp and the use of 6L6 will also produce a much more “round” bottom.  Beyond the bass boosting, there is not a massive difference in pre-EQ, preamp frequencies from a Marshall.

Another consideration is that frequencies below 70 Hz will make speakers rumble and fart.  Frequencies over 6 kHz become attenuated by the speakers.  Frequencies close to 2 kHz are part of the Rectifier presence circuit, which is not represented by this calculator.  Because the Rectifier has SO much low end, judicious use of the bass control is recommended for anything other than Modern Channel 3 (Solo) or Channel 4 (Roadster/Road King).

Some users may find it difficult to dial in their sound when switching over from a Marshall or an amp that follows the basic Marshall design or may want to get somewhere closer to a Marshall for any reason.  Here are some examples of settings by matching the EQ according to it’s approximate equal shape, or a shape that will get a person to similar sound.  I’m using Duncan’s Tone Stack Calculator to do this.  For all comparisons, the Marshall tone stack is: Bass-5, Mid-6, Treble-7.  This may not be a setting a person might be using, but using the calculator will enable one to experiment with settings they like to get “in the ballpark” with the Dual Rectifier.  Just remember: these are simulations are kind of a rough guide; in the end, your ears are the most important tool.