Wednesday, June 23, 2010

New Feature on the Mission Chicago Amp

Bruce Collins has added an interesting new feature to the Mission Chicago Harp Amp – but it bears a little explanation:

It is a Cathode Bias Bypass switch, but you can think of it as a FAT or BOOST switch. It switches on or off a circuit that regulates the power to the preamp tube, a 12AX7.

In the ON position the amp has the same circuit as in my prototype version of this amp: The tone is tweaked for what Bruce calls a ‘chunky-modern” tone. In the OFF position the bypass is disabled, giving what Bruce calls a “politely vintage” tone.

When the switch is ON the amp cranks out more gain; say 6db more. I played an amp with this new feature at our blues jam at Ziggies in Denver last Sunday, and the tone difference was distinct. With the switch OFF, the tone was warmer, fatter, um... wider. It lost a bit of volume but took on a sound that reminded me of my 1953 MASCO ME-18 amp.

The switch is a small toggle on the underside of the chassis next to the preamp tube socket. It is not hard to reach when you know where it is. You can reach behind your amp and flick it and hear the tonal change immediately.

The Mission Chicago Amp must be the most versatile harp amp on the planet. Look at the unique controls:

-Switchable from Fixed Bias to Cathode Bias (punchy to crunchy)
-DEEP switch (changes the tone stack curve for surprisingly low growl from a mid-sized 1x12 amp)
-and now, this new Cathode Bias Bypass switch (it needs a new name)

Along with the separate bass and treble controls, these switches make the amp infinitely adjustable to your taste. Nobody else is making harp amps like this.

NOTE: I played my Mission Chicago Amp at a private party in the huge backyard of a VERY swanky mansion last Saturday. We were on a deck facing the yard (more than an acre), pool, gardens, etc. I had the amp up to 7 (out of 12) and the volume was more than enough to keep up with two loud guitars and the rest of a rocking blues band. The host loved our sound and paid us twice the agreed upon fee.


Anonymous said...

Glad to have an update and hear a new clip. Cant wait to try mine out!

Anonymous said...

Dang - this amp keeps getting more interesting... I've got to try one soon!!