Help chosing first Bass Amp Build

[skypn]

I'm back with a whole different set of questions.
I guess I would like my first full amp project to a 15-30w practice amp, of which I would get lot's of use. I could learn about the circuit, practice soldering, case building (I am a woodworker), etc.
My first build was a stand alone pre amp, posted here:

http://www.madbeanpedals.com/forum/index.php?topic=28666.0

I mistakenly thought the only difference between Guitar and Bass amps was the value of the coupling cap, something I have learned here is not the case. The first forum I joined was a "pedals" forum, and it seemed that was the case with them.

What are your amp suggestions?

I know I can learn a lot about building amps here, but is there a "Bass Builder's" forum that anyone would recommend as good starting point?

Thank You In Advance

 

[sds1]

Cool preamp, what's that SMPS putting out VDC?

I don't know alot of about tube bass amps, but in general it's a different set of requirements as you're amping lower frequencies with max clean headroom in mind. For these reasons solid state amplifiers make more sense for bass, and the tube amps designed for bass tend to be 100W+.

However there's also the Fender Bassman, a nice small 50W head. A single channel Bassman head would be a fairly straightforward project, I just don't know what bass players would say about playing though one of these. Do these make good bass amps?

I also think the speaker cab design and configuration is of much higher consideration than in a typical guitar amp application.

One other thought, every gig I play the bass player is always running DI. Is DI a must-have for a bass amp?

I'm following out of same curiosities.

 

[Wally]

I would suggest building an AB165 Bassman if you think you are up to it. The only change from the schematic that I would suggest is to use 2 x 220mfds in series in place of the stock 2 x 70 mfd caps in the first filter stage. This will firm up the low end and make for a punchy amp. This amp would suffice for gigging with low output guitar amps and a sensible drummer. Get a good EV speaker for it....build with an appropriate OT. Oh...and add an adjustment for the bias voltage. I like having the bias balance that is stock as long as the voltage is also adjustable. One can run mismatched tubes if wanted/needed and also set bias as desired.

https://schematicheaven.net/fenderamps/bassman_ab165_schem.pdf

An advantage of this circuit is that there is also a hot guitar preamp in that Normal channel.

 

[Paul-T]

Surely, the B-15 is the most coveted small bass amp.

Such a shame this is so pricey.
There's good info on a B-15 build here.

and the best source I can see, with layout etc, is here. (But sadly, not finished afaik).

 

[sds1]

An advantage of this circuit is that there is also a hot guitar preamp in that Normal channel.

And a great guitar amp it does make!

 

[skypn]

sds1---185VDC

I want to build my own amp, because frankly, building the Banny I was just a whole lot of fun! I'm not even considering building a "gigging" amp, at least for now. When I do get to gig (not often) I run my pre amp through a SS power amp via effects return. Also, I have a nice Eminence 8" just sitting in a box *shrugs*. Then again, letting the speaker decide...

Let me put it this way...if the 5F1 was a Bassamp at 15w 8ohms I'd be happy.

I had thought of building 5F1 anyway, and let my 6-string buddies try it out, then scrap it for parts, but that might just be chasing my tail.

TIA

 

[skypn]

Wow! You're replying faster than I can. Maybe the B15 would be a better second or third build.
Again, thank for all the help guys

 

[Paul-T]

Wow! You're replying faster than I can. Maybe the B15 would be a better second or third build.
Again, thank for all the help guys

You are right. There aren't really any fully-documented builds. At some point, we need someone here to do a simplified version, with one channel and maybe diode rectification. It's really the last classic that doesn't seem to have been addressed here in full.(there's one unfinished build, here).

Plus in these days of improved monitoring a 50W bassman is far more practical than used to be the case.

 

[skypn]

sds1---185VDC

I want to build my own amp, because frankly, building the Banny I was just a whole lot of fun! I'm not even considering building a "gigging" amp, at least for now. When I do get to gig (not often) I run my pre amp through a SS power amp via effects return. Also, I have a nice Eminence 8" just sitting in a box *shrugs*. Then again, letting the speaker decide...

Let me put it this way...if the 5F1 was a Bassamp at 15w 8ohms I'd be happy.

I had thought of building 5F1 anyway, and let my 6-string buddies try it out, then scrap it for parts, but that might just be chasing my tail.

TIA

 

[Nickfl]

If you built a 6l6 version of the 5f1 with large transformers running at a higher voltage and used a solid state rectifier and bigger filter caps, I think you could have a pretty decent practice amp suitable for bass putting out 10-12W. The lack of tone control seems like a downside for bass (I think it is for guitar too) but maybe if you play a bass with an active preamp on board it wouldn't be? Then again a 5f2a is almost as simple a build with the added advantage of a tone control.

The thing is, the added transformer cost and complexity of modifying a small single ended practice amp to be suitable for bass negates a lot of the cost savings and simplicity that makes them common first build recommendations, so it might be just as well to jump into something more complicated like B-15 or a AB165...

 

[jhundt]

I was thinking about building a bass amp myself a while ago. I liked the idea of an Ampeg Portaflex, but with some proper power in it for real-life bass gigs.

I was thinking about using this preamp, from RunOffGroove. It is based on the old SB12 Ampeg flip-top:

http://runoffgroove.com/ginger.html

for a power amp, I was researching this possibility, since these days every bass player I know has switched to these massively-powerful but tiny little Class-D amps:

https://www.parts-express.com/sure-...0320X1568179Xc30bc7a088844d0d268097d41e80c007

I never got past the research stage - too many other things going on. But the idea is still swimming around in the salty sea of my subconcious mind.

 

[jhundt]

Surely, the B-15 is the most coveted small bass amp.

Such a shame this is so pricey.
There's good info on a B-15 build here.

and the best source I can see, with layout etc, is here. (But sadly, not finished afaik).

good stuff, but I am inclined to thing they are all going crazy with copying an old amp. Those parts packages were most definitely frightening!

I don't know any bass player any more who really wants to play on a tube amp. The touring bass-players I know are all pretty annoyed when the get an SVT or another tube amp as back-line. So they all carry these tiny class-D amps in their gig bag. Tubes just don't mean as much to bass players as they do to guitar players.

 

[Mr Ridesglide]

With a lot of help from my friends (Billllllllllly Sheeeears!) in this forum I put together a Bass Channel only AA165. I was lucky and used transformers from a Twin that was in a auto accident. I did it with 4 output tubes, 6L6, and it really is pretty nice with two 10's.
The fella that plays bass with me most of the time uses it at my home for rehearsals and on the last gigs on the stage with us. It held up rather well but nearly did get to the point of no more room left before a bit of mushiness.

 

[Wally]

With a lot of help from my friends (Billllllllllly Sheeeears!) in this forum I put together a Bass Channel only AA165. I was lucky and used transformers from a Twin that was in a auto accident. I did it with 4 output tubes, 6L6, and it really is pretty nice with two 10's.
The fella that plays bass with me most of the time uses it at my home for rehearsals and on the last gigs on the stage with us. It held up rather well but nearly did get to the point of no more room left before a bit of mushiness.

Mr. Ridesglide, what filtering did you use in the first stage? With 2x220’s there is a lot of room before things get mushy. Big punch..great articulation.

 

[Phrygian77]

I mistakenly thought the only difference between Guitar and Bass amps was the value of the coupling cap, something I have learned here is not the case.

Well, the classic Alembic F-2B is just an AB763 preamp with 50uf cathode bypass caps (instead of 25uf), and a .1uF output coupling cap.

 

[Phrygian77]

And you could pair that preamp with half of a Dynaco ST-70 output, and I imagine it would work well as a 30W practice bass amp.

 

[Mr Ridesglide]

Mr. Ridesglide, what filtering did you use in the first stage? With 2x220’s there is a lot of room before things get mushy. Big punch..great articulation.

I used 2 x 100uf in series. You may remember it as I was using the transformers from a twin amp that I ended up needing voltage doubling -

 

[Wally]

Rides, 2x100 is Series yields a 50mfd cap, which is approximately a 50% increase. There is a discernible but not huge difference from the 35mfd cap arrangement of the stock circuit. If you are ever there again and want to get some punch and low end firmness, put 2 x 220’s there. It will become a much more giggable small bass amp, ime.

 

[Silverface]

Wow! You're replying faster than I can. Maybe the B15 would be a better second or third build.
Again, thank for all the help guys

How much electronics experience do you have?

The preamp you built is a printed circuit board, one-tube, VERY simple "assembly project". You are getting suggestions for modified versions of various bass amp circuits that I don't think you truly understand. To do anything like that you''d need a solid understanding of basic electronics, the ability to read schematics - and re-draw them to adapt the changes - and understand WHAT the different parts specifically do so you know WHAT you're building.

Even the complete kit sets rarely contain "instructions" beyond those similar to a plastic model set - i.e. where to place and solder specific parts. Few even contain testing procedures, and almost all imply that you should assemble the entire amp first - THEN - in some cases - do a couple of very basic tests.

But they expect you to bring ALL electronics knowledge with you.

High-end kits include electronics instruction and the best use "phased" construction, starting with the power suppt - and full testing at each phase.

Mojotone is the only one I'm aware of that offers a 50-watt bass amp head (FWIW the 5F6-A Fender is a much better guitar amp than bass amp, and the AB763 extremely complicated for aa beginner). BUT - they include only the most basic assembly instructions, so if you don't understand electronics it would be a poor choice IMO. It's also expensive.

If you are looking for a 15 watt amp kit that will make a good bass amp without having to modify it in ways you don't understand - they don't exist.

 

[skypn]

The preamp you built is a printed circuit board, one-tube, VERY simple "assembly project". You are getting suggestions for modified versions of various bass amp circuits that I don't think you truly understand. To do anything like that you''d need a solid understanding of basic electronics, the ability to read schematics - and re-draw them to adapt the changes - and understand WHAT the different parts specifically do so you know WHAT you're building.

Silverface. You are correct on all counts. I understand Ohm's Law, how some of the parts work, but some, not what they are doing specifically. I do NOT know enough to do my own mods*shrugs*. I can read a schematics, recognize the symbols, but just enough to realize I don't know everything that's going on.
I am not looking to build "kits", but to actually learn how to build Bass amps. I have come to realize that there is no 15w bass amp out there for me. Or any "shortcuts".
My plan is to lurk here awhile, study basic electronics (high school was in the 70's), until the fog lifts. When I do, I plan to follow Phrygain77 suggestion. I've looked at the schematic for the Dynaco ST-70, and understand enough to know it's a little over my head. That is if I don't change my mind on what to do when I know better.
I am lost when it comes to power supplies.
I will defiantly post any schematic I have re-drawn here, before I try a build.
I believe eventually I will get there, for I have learned so much just by reading RobRob's website. I will not let my lack of knowledge hold me back for long.

Thank You for your sage advice.