Custom Bass Amp (not your normal thread)

[mrabassist]

Though I've used dozens of bass amps through out the time I've been playing, I have to say I've been most pleased, as can be expected, with the Fender Bassman 300t, the Ampeg SVT-CL, and a reallly old Silvertone Bass Amp (1954).

So, like any bored bass player does, I'm teaming up with my good friend Danny Morris, a great electrical engineer based out of Columbia, South Carolina, and a few other amp techs that I've worked with along the way to build a completly custom hybrid of these three amps.

Essentially, I'm stealing the preamps of all three, making it a three channel amp, inserting built in compression, and running to a power section that models the Bassman (it's a lot more efficient then the other two)

So I thought, hey, someone out in recordingreviewland might be interested in this, I'll post a lot of stuff about us building it, maybe it will inspire someone.

It is completely new territory for me but, given that people show interest, I want to take in suggestions and or give out suggestions during this experiance. I've played through Danny's customs before and they have a pheonomial tone, better than anything I've heard or worked with in my thousands of shows i've played, listened to, and recorded (usually, we started out with a few duds haha)

anywho i do have one request
if anyone has an old empty amp head (im open to whatever it is, obviously it has to be as roomy as the old tweed bassman heads or the old ampegs) i am currently without one. I came across an ampeg empty that i loved but lost it in a house fire (along with my rickenbaker, thank god for insurance) but yea, if anyone knows of a good place to find them, has seen them lurking in their local music stores, or has one lying around, i'm very willing and eager to buy

i'll keep you guys updated with sound previews and everything.

[kyle barton]

i think this is a great idea. you'll be getting exactly what you want, assuming that the new circuits are close to the original tones of the original amps.

i love the modular preamp into separate poweramp approach. i use an egnater modular guitar preamp into a VHT stereo poweramp.

assuming that the bassman style pre into bassman style powerstage still sounds like a bassman, are you sure that the silvertone and ampeg preamps will still sound right going through the bassman powerstage? that's the compromise with my guitar rig. the different preamp stages all get the EL34 color on the powerstage (which is a nice color to be sure) but doesn't match perfectly with all the tones. ie, they sound great in their own right, but don't sound exactly like fenders twins or voxac30s or bassmans, etc.

keep us posted, and give us pictures after you get started

[mrabassist]

we thought about that problem and really, we arent worried about it

when you look through the three schematics, the power sections have very similar makeups, of course preamps are where 90 percent of where the tone is,but there is also a similar 5 percent in the power sections.what we decided to fix this to save us from making three power sections, which would be insane haha, i might as well just run three rigs, we are probably going to make three dedicated driver sections too to cover up 3 percent of that remaining 5.of course its all trial and error, you never know.

i will definatly keep this updated though

[kyle barton]

your gonna love your rig.
i'm gonna love reading about it while you build it.
makes me wish i was better with a soldering iron

[mrabassist]

haha trust me, our arms are covered in burn marks and it hasn't gone without sparks.

[brandondrury]

of course preamps are where 90 percent of where the tone is

I guess maybe in bass land. I've not found this to be true in guitar land.

i'm gonna love reading about it while you build it.

I'm VERY excited to see how this turns out.

Brandon

[mrabassist]

Brandon

The preamp section contains the initial tube source, the eq, and the drivers for your tubes

so naturally, its where most of the amps tone comes from. of course theres a lot factored in from the player and his or her bass, but when it comes to amp tone, the preamp is what decides how the power amp is going to translate the signal. thats why, generally, an ampeg preamp played through an svt classic power section and a crown power amp should sound fairly similar. notice i say fairly.

what may have you thinking the power amp section devlops the tone is what is driving those tubes, which is generally considered in either stage one, the preamp, or stage two, the invertors.

[mrabassist]

UPDATE NUMBER ONE (its short)

Decisions

So, of course, the best part about building a custom amp is that it gets to be....custom! That means I get to cut out a bunch of unnecessary crap and add in a lot more necessary crap. So here is what I have decided so far:

1. I am only going to push 200 watts in the power section. Yea, its cool to write on forums that you never push your bass amp above 5 on the master volume, but honestly I don't care to brag about that. ... ... OK I'm lying. I'd love to say that, but in all practicality, I want to be cost efficient. By the time I honestly need to be pushing a full 300 watts of tube power, I'll be able to buy that and not think about it. Here is what drove me to do this: 1) I get to subtract 2 tubes from my power section, taking it down to 4 6550's, which means a longer lasting power section, less purchases, easier replacements, and more efficient biasing. 2) The way ampeg and fender figure, you need a 600 v transformer to power those 6 tubes to be rated at 300 watts of output (thats the input transformer, I don't quite remember the output transformer's rating but its considerably less of course.) Whats the big deal? Somewhere above 450 v the price shoots up about 100 dollars. So basically, to add two tubes, which isn't that expensive, it becomes a nearly 300 dollar ordeal. IF ANYONE knows a way around that, we are still a ways from building.
2. Single inputs. Not a big deal, I just don't see the need in the constant passive and active inputs, it's a way for companies to use cheaper, worse sounding parts by offering a quieter alternative right on the amp.
3. Ultra-high and ultra-low switches. This is a feature of the ampeg in the EQ section that the amp is famed for. And it is important, i think, for people who have changing tones. Not for me though. I know what my amp needs to sound like, which is a blessing. I will probably build these tones into my EQ section so that there are no switches.
4. Removing my previous idea for a compressor. I'm just going to build an outboard pedal. I know exactly, and have finished, the compression section for the amp but I'd rather keep that separate. Not cause i might regret the tone later, or because i think its cool to have pedals, but because heaven forbid something go wrong in the compressor, it could shoot out a bigger section of the amp that I'd rather preserve.
5. Stageable preamps. This is something I'm pretty sure has never been done before. Who knows, maybe I'll become famous. Here is going to be the setup on the chassis


Stage Gain EQ EQ EQ EQ EQ Master

Very simple right? But what, you might ask, is that stage knob for? I am putting multiple preamps into my amp, however, most of them build off of eachother. The Silvertone model is a much simpler, less tube involved type, which will then lead into the Ampeg which is more complex, using more tubes, which will then move into a Fender/Orange copy which, if anyone has ever used the amp, knows that the preamp uses a TON of tubes and complex settings. So think of this stage knob has a easy control preamp bias. As i move it, it will open up more power and gain from the next level of preamp. It's a very advanced type of amp modeler, in simple terms. I know that may go over some heads, I will be posting a ton in detail later.


OK i think that's all I have right now. We are still looking for a good casing if anyone has suggestions.
Please, submit ideas and thoughts and anythings and everythings.

[brandondrury]

Thanks for the update, dude! I need to mention this in the next newsletter!

Brandon

[mrabassist]

Eh, ok. Update Numbro 2

I scratched the stage idea. If i ever care for another preamp section, I can rewire for under 30 dollars.

This is going to be really quick-and impressive, i think

I purchased every single component to the amp minus the case for the head and the tubes for 250 dollars.

This includes the chassis, alll the hardware, all the wire, electronics, tolex, switches, bulbs, special VU meters. Everything.

I'm siked.