VOX | Discussion Forums » VOX Amplifiers » AC30 AC15, Custom Series & Custom Classic
I love my sturdy little loud-as-hell AC15CC1, but my newest project requires a higher-gain sound than my previous. I've driven the amp to distortion with a Boss OD-2, but I'd like to get more natural overdrive out of the amp, and, as you all know, these amps (stock) just don't overdrive or break up very easily. They're Voxes, so they're expected to be that way!
Any suggestions about getting more gain out of this little tank of an amp? I am going to switch out the driver 12AX7 tube to a higher gain tube, for starters.
Any favored overdrive or distortion pedals that you folks really like in combo with this amp? I'm looking for something closer to a Marshall sound... after all, the 60's plexis had an almost identical tube compliment!
Thanks!
Hi jkinatl - if you're after a higher gain Marshall tone, I recommend you check out the following pedals: -
Marshall Guvnor II (I use one of these myself, great sounding & inexpensive)
Marshall Jackhammer - as above, but even more gain
MI Audio Crunch box - Superb (I'd like one of these myself - fabulous Marshall tone)
Box of Rock - about the best pedal out there for an authentic overdriven JTM45 tone
Good luck, & let us know how you get on
Rich
If you are good with a soldering Iron (and don't mind voiding your warranty), I modded mine recently and can get CRAZY amounts of gain just using a clean boost pedal.
All I did was change R6 from a 100k resistor to a 220K resistor. I clipped out the bright cap as well - which seems to make it a little more pedal friendly.
If I use an electro harmonix lpb2 (I built one with a kit from www.generalguitargadgets.com) I get a LOT - and I do mean A LOT of gain from the amp at gig volumes. Mine rivals a mesa boogie, but turn off the boost and the whole amp cleans up... It's great!
I would just use a clean boost. My personal favorite is the Catalin Bread Serrano Picaso. Its small, easy to use, ability to use power supply, and for a boutique pedal is not expensive.
Hughesp wrote: All I did was change R6 from a 100k resistor to a 220K resistor. I clipped out the bright cap as well - which seems to make it a little more pedal friendly.
I was wondering what you mean by the bright cap. I have the The AC30CC and the schematic so could you tell me what it is labeled on it. I know it is a different amp but still the same design. I am fairly new to tube amp mods but I have done some and I do feel comfortable with minor mods. I have heard people say that they have clipped the Bright cap but I am not sure what it is.
Any help would be appreciated.
Peace and Great Tone to All, Rob
Rob. Generally the bright cap is a capacitor that has a small value usually measured in picofarads that is soldered on the outside lugs of the volume pot. As the resistance increases on the pot, high frequencies see the capacitor as a short and choose to take that path instead. Small value capacitors tend to pass more high end frequency. Also as you turn the amp up, the effect of the bright cap is slightly reduced. Personally I would replace it with a different value rather than clip it. And rather than change R6 which is a plate resistor, I would of changed the cathode bias resistor. The relationship between the plate and cathode would still change resulting in more gain but allow for the same voltage from the power capacitors to reach the plate of the 12ax7.
Interesting idea changing the cathode bias resistor... I went with the plate resistor because that is what vox typically did in the old AC30 top boost pre-amps - which are pretty similar to this pre-amp. So your idea would probably work to get more gain, but it strays more from what the classic top boost pre-amp does.
I can certainly see changing the value of the bright cap, but I'm quite happy having just taken it out all together.
If you want to hear my amp in action (with a clean boost pedal), check out this video of my band playing live:
http://www.youtube.com/watch?v=kDcqVQdkvxk
There is quite a bit gain there for my tastes.
