New DIY modular bass amp

For you Bob Villa types that modify modules

Moderator: Jaded Faith

Jules15
RM20
Posts: 1
Joined: Thu Feb 27, 2020 2:25 pm

Re: New DIY modular bass amp

Post by Jules15 » Wed Mar 04, 2020 2:08 pm

Emperor-TK wrote:
Thu May 14, 2015 12:17 pm
I'm approaching the finish of my DIY modular bass amp and I thought that some here might be interested in the project (if not here, then where else? ;) )

At first, I was just going to use an RM4 with a big solid state power amp, but I really wanted a couple of features that rig couldn't provide. That combo was too big, actually being wider than my 18" wide bass cabinet. Also, I would never need four modules for bass, but I wanted to use dual channel modules. This led me to whip up the following amp.

The amp uses a pretty typical RM4 type front end with a few minor changes. I don't really care for the switching on my MOD50, with a switch for each channel. Instead, I wanted A/B switches, one for the module, and one for the channel. Now I can use only a dual footswitch to control a double module dual channel amp. I don't need midi on the amp, so I went with basic relay switching for the logic signals to the modules. The relays are controlled by a programmable logic chip using momentary switches to change states. This way I could have redundant switches on the front of the amp and on a foot pedal like the original.

For the power amp, I went with a 500W ICEpower/Bang and Olufsen Class D amp that has been showing up in a bunch of commercial products these days. I used the 200W version in another build, and I'm pretty happy with the performance.

There's still a couple things left to do. I need to upgrade my 12V transformer because I ran out of juice (hence the lack of tubes in module 2). I have one on order that has roughly the same footprint. I also want to add a DI out and a built in tuner. The three LED holes on the front are for the tuner, and I have a relay installed to switch the input signal between the tuner and amp. I hacked up an old Sabine and it works, but the clock is injecting digital noise into the circuit that I need to suss out. I removed it from the amp in the mean time.

Anyway, I used it at rehearsal last night, but the Vox module doesn't have quite enough low end for me. Bass-centric modules are next on my list, starting with the Fender Dual-Showman/Alembic F2B circuit that I used in my last build. That sucker has a nice fat low end.

For years I used a '73 Marshall as my bass amp, sometimes with an extra Ampeg V4B to round out the bottom. I plan on doing some bass modules for myself based on guitar amps, but with blend knobs to blend in the clean sound for deeper lows. However, the one thing that everyone gets wrong with blend knobs on bass overdrives IMHO is that they blend in the full frequency clean sound. This never sounds good to me. It's a clean sound disconnected from an unrelated over-driven sound. I'm going to do a low pass clean sound for the blend so that the clean just fattens up the overdrive a bit without adding any real timbre to it.

Simulation Regroupement de prêt
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Tell me how you make your own low pass sound?

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