Portable class D Bass Guitar amp/speaker design - diyAudio
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Old 7th December 2010, 01:38 AM   #1
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Smile Portable class D Bass Guitar amp/speaker design

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 RMS@32V) (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.
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Old 8th December 2010, 11:44 PM   #2
Minion is offline Minion  Canada
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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 .....
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Old 10th December 2010, 02:56 AM   #3
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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.
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Old 11th December 2010, 11:45 AM   #4
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Quote:
Originally Posted by Peckerwood View Post
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..

Last edited by res07njc; 11th December 2010 at 12:14 PM.
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Old 11th December 2010, 12:34 PM   #5
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Just thinking too.. were you planning to plug the bass into an amp module? Are the impedances going to work with that? You might need a preamp if this thing is going to sound good... especially for a bass.
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Old 11th December 2010, 07:07 PM   #6
Minion is offline Minion  Canada
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Quote:
Originally Posted by Peckerwood View Post
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 .....
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Old 11th December 2010, 07:41 PM   #7
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Originally Posted by Peckerwood View Post
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
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Old 12th December 2010, 07:34 AM   #8
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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.

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.

Last edited by Peckerwood; 12th December 2010 at 07:52 AM.
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Old 12th December 2010, 02:45 PM   #9
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Originally Posted by Peckerwood View Post
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

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.
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Old 13th December 2010, 11:57 PM   #10
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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
Quote:
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.
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