What is the best Bassman design for bass

[Danelectron]

Any opinions on the best Bassman design to build for actually playing bass through? Are these good for bass or are there better tube designs out there? I want to build a bass amp for my brother for his birthday. 50 watts is plenty of power for his / our use which is why I am looking at a Bassman. Thanks, Dan

[imaradiostar]

A tweed (5f6a) bassman circuit with 6550's and 100 watt transformers (for added bass) would be pretty cool. I'd probably go with some additional power supply filtering as well. You'll need a really efficient cabinet to make that work though!

jamie

[JoeM]

Always seemed like bassmans made decent guitar amps. I saw a band where the guitar player used a blonde bassman, and the bass player used a Dual Showman.

[Chuck H]

50 watts is plenty of power for his / our use which is why I am looking at a Bassman.

Fifty watts can be a lot of power for guitar. But for good clean bass reproduction even at lowish volumes you need an amp with more than enough power. I wouldn't use a fifty watt bass amp for anything bigger than a coffee house gig. Well, unless I wanted a that slightly atonal distorted sound that the smaller amps get for bass. It's not a bad thing. Just sort of a one trick pony.

LF demands a lot of current so a really ample power supply is a big plus. If you really only need a small amp then the suggestion of a Bassman with 100 watt iron, really solid tubes and bigger filters is a good idea. I might add that a diode rectifier is a "should" for any tube bass amp.

Will this be a head or combo type amp? I ask because with a low power bass amp a good sealed or ported cabined will really enhance performance. So that's a head most of the time. If absolute portability is the goal and you want this to be a combo amp you might consider a custom cabinet for the project that isolates the amp from the speaker cab.

If I were building a small bass amp I'd probably do a pair of 6550's at around 500 volts, choke between the plates and screens, big iron and big filters. I wouldn't build a Bassman topology only because I think a bass amp needs more EQ control.

[imaradiostar]

I agree with chuck- more EQ is a good idea. I just like the sound of the 5f6a bassman/marshall cathode follower on bass- it seems like it has a positive effect on the tone of a bass but that's subjective. I think it's part of what I like about the sound of an SVT as well.

Here's a though- build the 5f6a circuit but use a bax or james type tone circuit (treble bass only) which allows a more or less totally flat tonal response. Add an extra buffer and the "mid cut" tone circuit from Merlin's book to achieve a more "modern" bass sound when needed. It allows a mid scoop somewhere around 500-1000 hz and could easily be tuned by having a center off DPDT to change the capacitor values. I'd use a simple mosfet based buffer after the bax/james stack to drive the mid cut circuit.

jamie

[Danelectron]

HE will only be using this in the house for practice and he has some cop calling neighbors so I'm sure 50 watts will get him in enough trouble.

Chuck, this will be a head unit. He has a Trace Elliot cabinet and some kind of peavy cabinet with a 15" speaker that he will be able to utilize.

So the 5F6A would be a good place to start? I want to do the basic design first and then maybe work in some mods. I don't have a lot of experience with tweaks, so I'm shooting for a functional amp that has a decent sound from the start.

I will review the schematic and post back with any questions I may have. Thanks for the suggestions. Dan

[imaradiostar]

I also suppose you wouldn't go wrong with an Ampeg B15 circuit.

jamie

[txstrat]

I also suppose you wouldn't go wrong with an Ampeg B15 circuit. jamie

OH YES. The sound of a B-15N can make addicted. I am...

[J M Fahey]

Silverface Bassman135, definitely the best of Bassmans, by a long shot.
The absolute killer was the one with two JBL D140F (or E140) but that might get pricey.
The 4x12" Bassman cabinet, with the funky "inverted pyramid" front panel was a killer too.
Tweed style amps break up too early and are too buzzy/crunchy for Bass; obviously are killer for guitar.
The tweeds were not useful for bass, even when there was nothing else available !!, that's why everybody preferred Ampegs !!! The Black/Silverfaces yes, they did deliver.
There will not be a big $$$$ difference between a 4x6L6 powered one, and a 2x6L6 one, and the effort will be practically the same.
You can't go wrong with an Ampeg either.
(Except for a B25, huge, heavy and lousy)

[mac1amps]

Most Bassman's, contrary to their name, are much more appropriate for guitars (unless you're going for a "crunchy" bass sound). As far as Fenders go, the Showman's make excellent bass rigs due to their "modest" gain preamps. That is, unless you're "competing" with Marshall stacks, in which case you'll need more power...........What was Leo thinking when he named these BASSmans?? I own (4) Bassman heads, but I wouldn't even consider plugging one of my basses into them (that's what my Showman's are for).

[imaradiostar]

OK, I guess I'm the odd man out. I think (at moderate volume) the tweed bassman/marshall circuit sounds great for bass. I guess I like the slight distortion added by the marshall preamp and cathode follower but maybe I'm in the minority.

If I were building a tube bass amp today it'd probably look more like a Hiwatt with only one input channel and some sort of very large 150-200 watt tube output section.

One of "The Ultimate Tone" books lists a simplified SVT. That could be an excellent starting point and by planning your chassis a little oversized you could build it with a pair of 6L6's and swap to bigger tubes and transformers later if needed.

jamie

[J M Fahey]

Fully agree and add: the specific Bassman 135 I was suggesting *is* a Dual Showman with no effects.
The "Bass" channel is muddy; the "Normal " one is good.
It's no by chance that it's "Showman like".
The 2x15"JBL version holds its own against a Marshall; others probably not.
I used to have a 2xEVM15L one, which was *very* loud too..

[Danelectron]

Thanks for your suggestions!

I think I'll try the Bassman 135 design. He doesn't need effects and I suppose the extra power might get utilized at some point. He has been impressed with the small guitar amps I have put together so I thought it might be a nice gift to build him something he can mess with. Thanks all! Dan

[J M Fahey]

Just one caveat: those "135" (there were also Twin/DualShowman/PA versions) used special ordered 6L6 , which aren't available today (yea, I know, there's a "reissue", probably quite good but doubt they match the old ones), so to play it safe lower slightly +B to around +450V (the old ones went over 500).
You do not need to build both channels either, specially because the "good" one is the "normal" one.
The "bass" one was not too clear. Good luck.

[Chuck H]

Or just change the bias arrangement and use 6550's. That's really not rocket science, anyone can do it, and the actual usefulness for bass would probably actually improve.