Portable class D Bass Guitar amp/speaker design

SEclassA

Member
2010-12-07 1:50 am
Hi,

I have been on this site for a while but am at work and cannot remember my username (also hotmail is blocked so I cannot retrieve it)

Anyway, A friend of mine has been asking about a light portable bass amp that he can lug with him and use for around 4 hours.

So far I have come up with the following:

Using 4x 60W/hr 6 cell notebook batteries for the supply
Using 1x 60W/hr 6 cell notebook battery as a reserve supply (switchable)
Using a 45-55 litre max fibreglass enclosure with a 10" driver and 4" mid
Using 2x 41hz.com Amp 11 (60w [email protected]) (one for a switchable backup with a 2 ohm resistor in series with the speaker as a "limp mode" backup).

I know this will not blow the house down, but with a speaker around 92db 1w 1m am I safe to assume it will be quite loud? Also it has to have bass extension to 41.2hz.

Can anyone suggest a suitable speaker? Is there anything that screams failure in this project?

Are the 41hz amplifiers up to this task, if someone unplugs a guitar and it makes a high level pop sound will the ampifier take it? Should I add input protection (such as 2 lots of opposed polarity banks of 3x diodes in series to clamp the input level)

Thank you for your help with this.
 
Seriously, I would use a more sensitive speaker , 92db isn"t especially sensitive , a 95db would be twice as loud , a 98db would be 4 times as loud and a 101db would be 8 times as loud ... I use 101db"s with my guitar amp.. A more sensitive speaker would mean you would need a less powerfull amp for the same volume and use less batteries ......

To get a good sounding bass amp you need to focus more on the Preamp cuz that is where a good bass sound comes from and a good eq section .....
 

res07njc

Member
2005-05-11 3:05 pm
FL
To get a good sounding bass amp (now this is just my opinion) you can't make a class D amp.

Could you elaborate on that statement a little? Do you mean as a simple power section, conjoined to any preamp feeding it? I know there are numerous schools-of-thought, and even more tastes concerning sound flavors... e.g. 'grind', old-school round boominess, hifi, etc..

The class D, as a power section, would seem to easily reproduce what its being fed.. without imparting its own sound. Then again, maybe that is the problem? A number of commercial mfrs. don't think so (with some level of acclaim as well..).

Being a portable rig, the efficiency of class D practically seems necessary. Sorry i can't help impliment it, but I second a super-efficient speaker... I think the Eminence kappalite series go up to 100dB, and a couple may even work in small enclosures. Lightweight too..
 
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To get a good sounding bass amp (now this is just my opinion) you can't make a class D amp.

Thats not true at all , many of the newer high powered Bass amps use Class D , they are simply way more efficient and actually perform very well at low frequencies ..... The bass player for my band has a 800w Bass amp that is class D and fits in a 1u rack space and sounds great .....
 
To get a good sounding bass amp (now this is just my opinion) you can't make a class D amp.

I think your opinion is incorrect - there's no reason you can't use class-D for bass, most PA amps (where most of the bass goes anyway) are class-D. Plus many specific bass guitar amps and combos are now class-D - it's the way of the future, bigger amps, less weight, and less waste :D
 
I don't think an opinion can be incorrect. I am not saying that you should agree with me or that there is anything unfunctional about a class D amp. Just that in my opinion the many advantages of a class D amp are at the expense of top notch audio quality. You can only get top notch audio quality from a class A amp but class AB is more functional and probably good enough for most situations but still not top notch. They don't build those class D bass amps because they sound the best. They build them because of the weight and the efficiency etc.. They also run cooler. That class D bass amp needs to be 800 watts to compete with 2 and 4 hundred watt bass amps that are class AB.

There are plenty of class D PA amps but to say most PA amps are class D is just not true. It may be true for new ones but I don't know. I do know that I wouldn't use one and I am not the only one. When I see a PA amp for sale if I pick it up and it is not heavy as hell I put it down and move on. I don't even need to hear it because I know it is class D. I had a Peavey CS 1200 in my possession recently and I don't really know for sure but it was likely class D (and likely had MOSFETs in it but I didn't look inside) because it was very lightweight and it was not as loud as the 600 watt JBL amp I had that was class AB with BJT's. To be specific when I say 1200 or 600 watts I am talking about bridged into 4 ohms.


I am a musician and not much of a tech so I try to stay out of the technical discussions you guys have and only throw in my 2 cents in order to give you the perspective of a musician who judges the stuff only by the sound of it. I learn a lot from you guys about DIY'ing and building amps and stuff like that but sometimes I think some of you don't always let your ears be the final judge. The only reason I made a comment about the class D is so you would know that some of us think they are sonically inferior. I was not trying to say that you should think that. I am not articulating this very well and it seems like the more I say the worse I am getting my point across but I did not intend to be argumentative or anything. I just thought you might gain something from being aware that there are people with my point of view (besides me even) in case you didn't already know that.
 
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I don't think an opinion can be incorrect. I am not saying that you should agree with me or that there is anything unfunctional about a class D amp. Just that in my opinion the many advantages of a class D amp are at the expense of top notch audio quality. You can only get top notch audio quality from a class A amp but class AB is more functional and probably good enough for most situations but still not top notch. They don't build those class D bass amps because they sound the best. They build them because of the weight and the efficiency etc.. They also run cooler. That class D bass amp needs to be 800 watts to compete with 2 and 4 hundred watt bass amps that are class AB.

Everyone is entitled to their opinions :D

However, you seem to understand VERY little about amplifiers.

For a start, top class audio quality is available from ALL amplifier classes, and class-D as much as any other. Certainly class A is pretty well pointless, particularly for PA or guitar use. Many top-flight HiFi amps are now using class-D - like I said before, it's the way of the future.

Amplifiers of the same power are obviously the same volume, if a 200W AB amp sounds louder, it's because you're over driving it, creating massive distortion, and distorted sound is louder than clean sound. This is why valve amps sound louder than transistors ones, distortion means louder sound.

Class D amplifiers commonly have protection to prevent over driving, these keeps the sound high quality at all times - Fender guitar amps often tend to
do the same as well.

Incidently, it's interesting to stick a scope on the output of guitar and PA amps, you'd be amazed how much of the time your 'high quality' amplifier spends overdriven and clipping.
 
My definition of top notch audio quality is the output is exactly the same as the input only louder. It is true I don't know nearly as much about amplifiers as far as building them (but more than you seem to think) but I know a whole lot about them as far as using them and what they sound like. Probably a lot more than most around here. Tube amps sound louder whether you overdrive them or not and so do class AB amps. BJT amps sound louder than MOSFETs without either one being overdriven and the only way you could not be aware of that is by using meters to judge and not your ears. But I do know that only class A can produce an output that is exactly the same as the input only louder. I also completely agree that they are unfunctional for real life purposes as I already said.

You should know better than to say
Amplifiers of the same power are obviously the same volume, if a 200W AB amp sounds louder, it's because you're over driving it, creating massive distortion, and distorted sound is louder than clean sound.
because once you drive an amp into clipping (a SS amp that is) it does not get any louder no matter how much more you turn it up. If it did the tops would not be squared off (clipped). Even using a meter to judge. It only gets more distorted. Not much more though. A SS amp will distort horribly as soon as you pass the point of clipping. It is not gradual increase like it is with a tube amp.

But even with a meter and without even using your ears at all a class D amp will distort more and NOBODY builds one because they love the sound so much. They build them for other reasons. I have seen people here agree with that but not in so many words. A female DJ whos name I can't remember was talking some months ago about how she could use class D amps and make her life a lot easier but she doesn't and the reason why she doesn't is because of the sound.
 
Some people do think class D amps sound just as good as class AB amps. Many people do not. I don't know of anybody who thinks they sound better.

But then again some people do not think tube amps sound any different than solid state amps. But I think it is clear to anybody who listens closely that they do. I think anybody who really listens can clearly hear the difference. They might prefer the sound of solid state amps or they might prefer the sound of tube amps but they should be able to hear that there is a difference.

Just out of curiosity here is a question for everybody. Is there any legitimate reason why you, actually I should say anybody, would NOT want to use a switching (some call them switch mode) power supply in audio equipment? I mean there are a lot of advantages to using them but will it affect the sound quality and if so will it degrade or enhance it?
 

tinitus

diyAudio Moderator R.I.P.
2005-11-24 1:47 am
Anyway, A friend of mine has been asking about a light portable bass amp that he can lug with him and use for around 4 hours.

maybe your friend is asking a bit much of you
and we have still no idea how your friend intend to use this "portable combo"

are you aware that you may also need a special preamp/buffer stage, with very high impedance
tho I think there are some smaller ones with battery

Maybe take a look at Phil Jones Bass Buddy BB1 Micro

well, my thought yesterday was some small T-amp modules running balanced
41hz have some for single 12V
I even think there are stereo modules with onboard supply
I dont know if they will be tough enough for a balanced amp
I dont know if balanced is even possible with single 12V

hmm, I have seen a switchmode supply with a battery security mode
not sure how that works
 

tinitus

diyAudio Moderator R.I.P.
2005-11-24 1:47 am
if someone unplugs a guitar and it makes a high level pop sound will the ampifier take it? Should I add input protection

I expect your friend is used to turn down volume knob on his instrument before doing anything like switching off amp, or unplugging

btw, you may better forget about anything below 100hz, and go for optimal sensitivity above that, maybe even a use a genuine 100db driver peaking to 110db
 
Almost every bass player would lust after one of these...
[IMGHTTPDEAD]http://www.fclefbasses.com/upload/walter_woods_f_450.jpg[/IMGHTTPDEAD]

And they have since day one had switching power supplies, and I think the newest power amp designs are of switching type too.

Bass amp not sounding good because of it being a class-D design... Sorry, but that's just prejudicios bollocks.

A SS amp will distort horribly as soon as you pass the point of clipping. It is not gradual increase like it is with a tube amp.
For the record, many solid-state instrument amps these days have soft clipping circuits to get that gradual clipping. Those kinds of designs have been known for a few decades already. And for another record, many of the generic tube amps do not really have such a gradual soft clipping as people commonly think they do. Stick a scope to them and see for yourself. For example, this is a scope capture of a tube "Trainwreck" clone amp.
[IMGHTTPDEAD]http://home.polstra.com/amps/wreck1/scope/IMG_0688.jpg[/IMGHTTPDEAD]
People hype up the sound of Trainwreck amps but the supposed soft clipping of tubes apparently has nothing to do with that.
 
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I am not familiar with Walter Wood amps but one of the most popular ones among bass players I know are the Galen Kruegers. I don't know what class they are. Ampegs are very popular too. I will ask some bass players though. Any bass player who prefers a noisy amp probably would kill for one though.

I already mentioned using PA amps that I believe were class D but did not open up and look inside to see for sure. The reason I believe they were class D is because they were extremely lightweight and ran very cool. I did not like them.

I was just wondering whether you base your judgements on what you HEAR or not. Switching power supplies are very noisy. I don't even say IMO there because as far as I know there are no recording engineers anywhere who do not agree with that. I record using a MOTU 24i which is digital recording using a computer. I would much rather record with analog equipment but it is so much more expensive there is no way I could afford it. I am always trying to find ways to get the computer farther away from the recording equipment (which is hard when the computer is part of the recording equipment) and especially the mics because of the noise created by the switching power supply in the computer. I have never seen a computer that didn't have a switching power supply but if they exist I would like to have one.

Switching supplies are very noisy but if you judge them without your ears they are better in every other way.

Bass amp not sounding good because of it being a class-D design... Sorry, but that's just prejudicios bollocks.

If they sound good enough to you that is all that matters but I assure you that I have no agenda to promote the idea that class D amps do not sound good. To me they just really don't sound good. I wish they did. There are many advantages to using them. I wish all of my competition used them.

For the record, many solid-state instrument amps these days have soft clipping circuits to get that gradual clipping.

Yes they do. Mostly guitar amps but also some bass amps. It is artificial clipping though. The reason that is done is because of exactly what I said and that you quoted me saying.

A SS amp will distort horribly as soon as you pass the point of clipping. It is not gradual increase like it is with a tube amp.

I mean the clipping is real in that the signal is definitely clipped but it is not created by overdriving the amplifier until it clips which would sound terrible in any solid state amp. Marshall JCM 900s are tube amps but they have diode clipping. I can't stand them. In my opinion they are not really tube amps because of the diode clipping. It is very similar to the way solid state amps create their artificial distortion. Some people would not consider the amps I use tube amps either because they have solid state rectifiers but I would not go that far. Amps exactly the same as mine only with tube rectifiers are worth more money than any other amps in the world. They call them Plexi's. You will not see one for under 3 grand probably and usually about 5 grand. That is for the head only. To me the difference in sound is slight and not worth that kind of money but the rectifier is all the solid state I can handle in a guitar amp. If it were practical I would not use solid state PA amps either but you have no choice really. It has been so long since they sold tube PA amps.