Mesa Bass 400+

BillJarrett · #1 07-25-2010, 06:54 PM

I did a brief search on the topic, but could not find anything I was searching for so...

Does anyone know of any mods I could try out on my Mesa Bass 400+?

I did see a bias control mod, but I was hoping maybe someone had tinkered a bit more and could at least point me in the right direction.

RickenBoogie · #2 07-25-2010, 07:25 PM

What are you looking to change?, or, are you just wanting to mess around with a perfectly good amp?

BillJarrett · #3 07-25-2010, 07:28 PM

A little of both, actually.

I love the amp, although specifically I would like to know if theres a way to change the "pull" frequencies on the EQ, or perhaps something along the lines of even added a mid shift pull also.

Mr. Foxen · #4 07-25-2010, 07:45 PM

If you can't figure it from the schematic, you might want to learn tinkering on a slightly less massive and expensive and prone you electrocute you piece of equipment.

Selta · #5 07-25-2010, 07:46 PM

Quote:

Originally Posted by Mr. Foxen

If you can't figure it from the schematic, you might want to learn tinkering on a slightly less massive and expensive and prone you electrocute you piece of equipment.

This.

marklaforest · #6 07-25-2010, 07:53 PM

I can see where you're coming from on this one - I've got a 400 and I love it, but I find I've got to really tweak the EQ on it to get it sounding the way I want it to. Once it's there it's monstrous but it takes some serious knob twisting. Maybe just re-tubing would be a good place to start? Or playing around with some preamps or something?

BillJarrett · #7 07-25-2010, 07:58 PM

Quote:

Originally Posted by Mr. Foxen

If you can't figure it from the schematic, you might want to learn tinkering on a slightly less massive and expensive and prone you electrocute you piece of equipment.

Sound advice.

I was just hoping for some guidance from anyone who has experience in tinkering with these things. I can read the schematic, and have done small repairs on some older amps in the past, but didn't want to get into brainstorming the "how and where" if someone had already tried a few things.

JonPol · #8 07-25-2010, 08:45 PM

I've heard of a 12au7 mod that increases some headroom, that's about all I know about it though. Hopefully someone will chime in and educate us both on it.

twinfallsbass · #9 07-25-2010, 09:10 PM

I'm not sure if you know this or not, but flat for " Mids " is all the way to 10, it's a cut only for Mids. I owned this amp for a LONG time before I found this out, once I set the Mids knob to 10, holy crap, that amp OPENED UP. I mean honestly, unless you knew, who would turn the Mids knob all the way up?

BillJarrett · #10 07-25-2010, 10:06 PM

Quote:

Originally Posted by twinfallsbass

I'm not sure if you know this or not, but flat for " Mids " is all the way to 10, it's a cut only for Mids. I owned this amp for a LONG time before I found this out, once I set the Mids knob to 10, holy crap, that amp OPENED UP. I mean honestly, unless you knew, who would turn the Mids knob all the way up?

I was completely unaware! I will crank it up first thing and the morning and do some testing.

Maybe I should find a custom 0 to -10 knob for it?

BurningSkies · #11 07-25-2010, 10:23 PM

Quote:

Originally Posted by BillJarrett

I was completely unaware! I will crank it up first thing and the morning and do some testing.

Maybe I should find a custom 0 to -10 knob for it?

Then you may also not know that flat on the treble and bass controls is around 2.

Sartori · #12 07-25-2010, 10:25 PM

Quote:

Originally Posted by twinfallsbass

I'm not sure if you know this or not, but flat for " Mids " is all the way to 10, it's a cut only for Mids. I owned this amp for a LONG time before I found this out, once I set the Mids knob to 10, holy crap, that amp OPENED UP. I mean honestly, unless you knew, who would turn the Mids knob all the way up?

Yeah, thankfully I read a D-180 manual before mine arrived, so I knew. I boost the mids all the way up, and the graphic EQ right now is functioning mainly as a mid boost.

Seriously, I know it's a historical and popular tone stack and all (especially for guitar), but for my purposes, it's pretty useless. What's the point of a knob that has to be cranked all the way to be flat? It's like it was made for mid-scooping.

BillJarrett · #13 07-25-2010, 10:35 PM

I run my bass setting around 4-6 depending on the bass, mids are at 6 (which is scooped i guess!) and treble is at 4 or less, depending on the bass/stage @ the venue. EQ is on with a bump in the low end and very slight mid boost.

I'm going to spend some time tomorrow tweaking after learning about that mid knob. I may completely change all of this in 8 hours.

Sartori · #14 07-26-2010, 12:25 AM

Yeah, for my D-180, the bass knob is pulled out to center on the lower frequencies, and I have that dialed back just a tad. Mids are dimed. The high knob I have pulled out cause that changes the sound a bit and that's up to 5 for extra nasty.

Calaverasgrande · #15 07-26-2010, 02:38 AM

Honestly there are a number of tones that amp makes without mods.
First off input 1 is very vintage and bassy. Kind of like a bassman. The second input is much brighter and if hit hard enough will go into some nice distortion (a stingray will drive it pretty hard).
If you have an active bass you can play through the effect return which bypasses the preamp, but still goes through the graphic EQ.
So also keep in mind that the graphic is the last thing your tone sees before the power amp.
Switching out the first tube (the one closest to the input jack) pretty much alters the entire tone of the amp. I like old RCA's or JJ Teslas in the first pre slot. Actually pretty much anything except a Mesa tube is awesome in that socket!
Also the EQ is super powerful and interactive. It takes a bit of getting used to. For example, not only is the eq flat at bass 2, mid 10, treble 2. But if you turn the bass or treble up past 6 or 7 it will start to take over more of the signal. So turning up the treble all the way will actually make less bass come thru. I had my amp busted with the treble stuck on 8 for a whole tour once. Pure hell!
Oh yeah, and be wary of the bass knob pull out. It sounds good at first, but quickly becomes mud city.

PS. Like Ampeg SVTs these amps are best played hard with the gain up!

Grantini · #16 07-30-2010, 09:29 PM

I can't even imagine why you would want to modify it. The great thing about this amp is it's simplicity. It's like adding mods to a Fender Reverb chassis... if you want all that stuff buy an amp made that way. Stock is best, and mods break. The 400+ is a tank, leave it stock...

Mingo Sanders · #17 07-30-2010, 10:05 PM

I know next to nothing, but I think the fastest smart way to find a sound you're looking for is to try your stock 400+ with a variety of cabinets. I'm a believer that cabinets have divese sounds, not amps, or at least not as much as cabinets.

Mostly I'm jealous. And yes, I know there's probably one in the classifieds calling my name. Enjoy.

Randall · #18 07-31-2010, 02:15 AM

Rather than modify your amp why not try another preamp with a different "voice" through your 400. This will allow you to change the character of the mesa without attempting some mods that require a lot of technical knowledge. If if run my Trace Elliot preamp or my Aguilar agro through my D-180 it changes the tone character a lot.

ridgeback · #19 07-31-2010, 02:24 AM

dont know if you have this or not..
http://www.mesaboogie.com/manuals/Bass%20400%20Plus.pdf