Hiya / help with a portable bass amp

[JungleVip]

Hi I am a newbie on here so please forgive any schoolboy errors. I am looking to build a bass amp for busking, camping and small gatherings.

I have the idea to construct this from components and would appreciate any help. I was thinking of using this for an amp: Amp

And these as speakers (one per channel): Speakers

Would there be any problems with getting a reasonable sound from this kit as a backbone. Any help appreciated

[Steve Conner]

Sure, I guess it'll sound as good as any bass amp with 40W and 5.25" speakers with plastic cones ever would.

You will need some sort of preamp, a hi-fi amp doesn't have the right input impedance. Except if you have an active bass, then you might be able to plug it straight in. The preamp could be as simple as a bass compressor stompbox, you might have one already.

If it were me, I'd look for speakers with higher sensitivity and real paper cones. But maybe low cost and small size is more important to you. Not to mention, plastic cones are more water resistant, which could be important for busking.

[J M Fahey]

Will this run on batteries?

[Steve Conner]

The amp runs off 12V, so I guess it will.

[JungleVip]

Thank you. I have been told that a the signal from a bass guitar would blow the speakers and the output stage of the amplifier. Being a software bod not hardware(much to my regret) I dont really understand any of this and am not sure if there is any truth in it anyway. Could someone please explain this to me?

[Steve Conner]

There is some truth to that. Slap bass has a huge dynamic range. I've tried playing bass through my hi-fi a few times, and it was easy to make the woofer cones flap alarmingly, not to mention trigger the protection on the power amp, even when it didn't seem all that loud. However, it was certainly loud enough for a practice amp, and the hi-fi did not explode instantly as some people seem to think.

The amp you're looking at is so low-powered, I doubt it could blow speakers. And being a Class-D amp, it should be fairly immune from overheating and blow-out itself. (Class-D amps are very efficient, so they don't generate much heat to overheat themselves with.)

What sort of software do you do? I'm currently doing industrial DSP programming.

[JungleVip]

Many thanks again for the reply. I did for a long time Delphi/SQL server mainly enterprise business applications(yawn) I have done java as have part of my studies and server side apps for ftp and what not. I'd like to do some low level stuff but it means starting again.

[JungleVip]

Sure, I guess it'll sound as good as any bass amp with 40W and 5.25" speakers with plastic cones ever would.

You will need some sort of preamp, a hi-fi amp doesn't have the right input impedance. Except if you have an active bass, then you might be able to plug it straight in. The preamp could be as simple as a bass compressor stompbox, you might have one already.

If it were me, I'd look for speakers with higher sensitivity and real paper cones. But maybe low cost and small size is more important to you. Not to mention, plastic cones are more water resistant, which could be important for busking.

I am getting closer thanks to the help. I am thinking about going with this Speaker because of the sensitivity as Steve C. Suggested. but the low frequency is 100hz and the low E on a bass guitar is about 40hz will this be a good compromise?
All help appreciated...

[MarkusBass]

The idea is very good (and several companies are offering such amps). But the details are not. You have to know that for guitars and bass guitars there are special speakers manufacured. And what you want to buy is a home Hi-Fi speaker. Go to e.g. Celestion and select a smallest speaker(100W). You may find smaller speakers from other manufacturers (I would buy 30-50W speaker) but definitely you cannot use a Hi-Fi speaker. Using a class-D amp for a bass guitar is already implemented by many manufacturers (e.g Phil Jones, Ampeg, Eden) but these amps are different than a Hi-Fi amp you think of. The difference in mainly in the preamp (for a bass guitar you need different frequencies and a different sensitivity).

Mark

[J M Fahey]

Been reading carefully and only now can answer with some precision.
1) It may work for what you want, between certain limits.
2) The power will be more than enough to practice at home, alone or with friends playing acoustic instruments , or will match up to, say, a guitar player using a 10/15W amplifier and a *light* handed drummer.
3) The amp is stereo, you will need *two* speakers (which still may share the same enclosure).
Each speaker must be 4 ohms impedance.
Rather than that Celestion , which is not bad, but only available in 8 or 16 ohms AFAIK, I would suggest the Jensen Mod:
Jensen Mod 8-20 4 ohms, U$24 . or
Jensen Mod 10-50 , U$43 , U$ 43. <-- this one is quite good and actually recommended for bass.
4) The real power available is 16W per channel.
If you can do with the bare minimum, you *can* use only 1 channel, 1 speaker, you'll have 16 real watts available.
That will be enough to play at home, in a (very) quiet Church, inside a shop with a basically acoustic band, etc.
With 2 speakers, specially the better ones, you may play in a Subway station, or in the street or at a quiet Park.
You will need at least one of those 12V 7AH Lead Acid Gel batteries (the kind often used in alarms or emergency lighting) or the regular ones , used in motorcycles.
You can get a full afternoon of music from them.
5) As you see, the main problems for Bass are acoustic, on the speaker and efficiency side, because Bass is a "difficult" instrument.
This small amp and the relatively inexpensive speakers suggested *will* do , your Bass will be heard, but of course will not shake walls or have deep bass.
It will be quite usable though, similar to what a 15W practice amp, with an 8" or 10" will do.
The Hi Fi equalization is similar to what a Polytone sounds: warm sound, not much effect on highs.
The 200mV sensitivity is fine for an active Bass, somewhat poor for a Passive one.
Just try it: if enough (with your Bass), fine; if not, you can somewhat boost it with a clean preamp , some Bass multi-effects or processor, a compressor pedal, etc.
The compressor is recommended anyway to better use your limited power but avoid farting.
Good luck.

[JungleVip]

Thanks all all of you! I have bought the Tripath anyway and can start my testing in a couple of weeks when it arrives. Much appreciation to all!

[JungleVip]

I have checked the other threads but I am still not sure about cabinet design; I thought I'd ask here before staring a new thread

For the cabinet I thought a closed back design with each speaker in a separate compartment. Would the size(s) of the cab make much of a difference with a small amp such as this? To the speakers have to be aligned horiz/vert or on a diagonal? and would each compartment have to be a specific size to match the speaker etc.?

Some of the talk on this subject confused me somewhat