Class A or AB

[Rafa]

I was wondering is there any audible difference between solid state Class A and Class AB amps??
I havent seen much class A amps around so I was wondering which type to use in the small amp Im building. I thought that class A would sound better but I don know...

Any idea suggestion, sound clips would be great

I really apreciate your help
Thanksssssssssssssssssssssssssssssssssssss

[grapefruit]

Class A amps are rarely used because of their poor efficiency. You won't notice the difference between a class A and well designed class AB amplifier.

What power amplifier do you want? The best/easist way to do it would be with an IC amplifier. Depending on the power you want there are many choices. For 50W the LM3886 is a good choice. If you only want about 7W into 8 ohms the LM4950 is a good choice. It will deliver this power from a 12V supply.

Regards,
Stew.

[Rafa]

Thaksssss a lo t Grape
I told you about class A becuase I found this:                     at http://www.oliveaudio.com/index.php?page=3

``Compared to the chip based amps, the amplifiers circuits displayed here will give more power, better sound quality, more audio bandwidth, and more versatility to play with´´

So I want it around 20 watts so chips will do fine?? tda 2040??
So chips souds like transistor in poweramps??

[grapefruit]

Yeah the TDA chip or LM1875 would do fine. If you're not designing a PCB it might be best to get a kit. If it's for a guitar amp I really don't think you'll notice the difference between a chip or discrete amp. The chip amps sound a lot better than some discrete designs, and all the hard work is done for you.

Regards,
Stew.

[Thomas P.]

For that matter you should consider reading articles from www.aikenamps.com (in the Tech info section)

For example:
"Last Word on Class A" and
"Is the VOX AC30 really class A?"

But there are a lot of other grat papers there!!!

[brett]

Hi
my valve amps are all class AB or class B.  The class AB can be a pain to get biased.  Although this isn't so much of a problem with solid state components, a mis-biased AB amp shows what poor AB sounds like.  Bad.

Also, as well as the class A vs class AB thing, you might want to consider some of the other limitations of various solid-state devices.  For example, some of the amp chips have thermal protection.  It saves the chip but you can't use such an amp in public in case it gets hot and decides to shut down for 10 minutes in the middle of a tune.

Also, the distortion characteristics vary a lot.  The little 386 has quite nice distortion, and a Ruby or Dual Ruby makes a good practice amp.  Some people don't like them, but I like some MOSFET power amps.  With a decent heatsink, you can run a simple pre-amp straight through a BJT (MJE3055) or MOSFET (MTP3055) voltage follower and get good results in the 5W region.
Have fun with your amp project

[Rafa]

Thanksssss for helping me
I think Ill go for a chip Class AB poweramp
Maybe Il build first a little gem to see if I like it

[d95err]

For tube amps, there is a lot of mareketing mumbo-jumbo and hype about class A. Most of the time, "Class A" marketed amps are really just regular class AB with cathode bias (e.g. Vox AC30). If we disregard obscure boutique amps, the only commercial class A tube amps available are those that are single ended, i.e with only one power tube.

For Hifi, class A will be better, since there is no crossover distortion. For guitar, distortion is part of the sound. So, class A would not necessarily be better, just different.

[Rafa]

Tomboy thanks for the help

I found this:                                             at http://www.aikenamps.com/

no rejection of even order harmonics (a great advantage to guitar players!), and generally asymmetrical limiting on overloads which further emphasizes even order harmonics (which are more pleasing to the ear than odd order harmonics

Tlaking about single ended amps (ClassA)

Now Im not sure what to do? 

[Rafa]

Does it exist Single ended and push pull solid state amps or is it only used for tubes
How can I know if a SS Class A amp is Single ended or push pull
Sorry for being so ignorant 

What type is this amp:




Thankssssss a lot

[Thomas P.]

I believe a simple common emitter setup would be "single ended"

[grapefruit]

That looks like a single supply push pull amp.

In my opinion, generally you don't want to drive a solid state amp into clipping. You have pedals for that.
It really depends what you want the amp for. If it's just a practice amp I still recommend the LM4950. I haven't used it for guitar, but when doing power tests on it, I found that it clips fairly smoothly and assymetrically. It's good for 7 watts into 8 ohms in bridge mode.

If you need more power, and as Brett said you dont want it muting on you, go for the LM3886. It's used in heaps of commercial designs. Your power supply will determine the power you can get from it. It's pretty much bullet proof. One mistake with a discrete power amp and you'll have a loud bang, and smoke will come out. And you can't put the smoke back in!

http://cache.national.com/ds/LM/LM3886.pdf

I'm not sure where you live but you should be able to find a kit using the LM3886 or 3876.

Stew.

[idlechatterbox]

There's usually pretty good discussion of your options in the low- to medium-watt SS amps at

http://www.ssguitar.com/


A lot of people over there (and here too of course) have done some pretty amazing things with the Ruby and similar practice amps. Good luck 

[Rafa]

Thanksssssssssssssssssssss

[brett]

Hi
here's a link to a very simple, very rugged 40W amp using cheap parts.
I built a similar one many (30) years ago.
http://sound.westhost.com/project12a.htm
cheers

[Rafa]

Thanks a lot brett
I just wnated to know does it sound good??
Did you used it for a guitar amplifier??

[brett]

Hi
I used it for a hi-fi amplifier.
Not very Hi-fi by today's standards, but ok back then.
You'd need a high-output pedal to drive it, as it needs about 1V input.  Or maybe a boooster, like the beginners project.
cheers