[joensd]

Hi there!

I always wanted to build a class a amplifier but don´t want it too complicate.
I thought about a good opamp followed by transistors,fets working in class a and am still looking for a schematic.
Anyone seen and tried such a thing (maybe some links etc.)?
A regulated power supply like from the known JLH-amp and that should be it.

thanks in anticipation

 

[JMT]

Chu just published Kevin Gilmore's new Class A amp design on HeadWize, looks very interesting. Here is a link for you.

 

[joensd]

thanks JMT
looks real interesting
BUT:
i tend to forget i´m cruising in headphone forums
what i forgot to say was that i wanted something around 20w per channel to drive loudspeakers and maybe separate stage for headphones
i got inspired by the designs for headphones that use an opamp followed by transistor/fet stage, why not use this for loudspeakers as well, it´s simple,straight,good sounding !?!
if anyone got a cool schem for that;great
if not i´ll just try and maybe burn something

 

[joensd]

btw found something i was looking for at:
http://sound.westhost.com/project76.htm[/URL]

 

[Possum]

Kevin Gilmore's amp for dynamic headphones was old (not OLD old), but just hasn't been posted in the HeadWize project libraries. The info and schematics for this amp has been available on Kevin's website. aos and hsnam (h-something? sorry

) have built these. I'd really like to try one sometime, but already having a class A Szekeres makes me want to try something completely different first, like a tube amp.

Speaking of Szekeres...
joensd, if the Kevin Gilmore amp looks too complicated, check out the Szekeres amp variations with an op amp gain stage in the project library. It ends up being pretty simple if done properly:

http://headwize.com/projects/szeke1_prj.htm

 

[Apheared]

possum, he said 20w... he doesn't want a headamp, wants a speakeramp...

Hmm, simple, class A, rock solid, tried and tweaked boards available, and dirt cheap build for incredible sound... http://www.passlabs.com/tech.htm

 

[Possum]

Yeah, I should read the rest of a thread sometimes before I reply. Amps here are usually for headphones, so I guess I didn't expect a speaker amp. Hey, I was rushing to get to a class

 

[Tomo]

Hello,

How far do you intend to go? How far you can go to obtain good sound? I can suggest if I know your needs.

Class-A speaker amplifiers are very hard to design and to build. Unlike headphone amplifiers, these will consume extraordinary amount of power to keep running. The efficiency for Class-A amplifiers is about 10 percent. That means you will have to be able to supply more than 200 Watt to each channel. Pass amps and other class-A designs look very simple and realistic. However, in truth, they always end up extremely large, heavy and hot. Hot enough to cause a lot of problems. Due to high current requirement, you cannot use wimpy regulator designs. In fact, voltage regulators should NOT be used since they are not efficient and simply heat up. Capacitive PSU will be more realistic. Note here that many components will not be able to handle the heat emitted. So heatsinking is extremely important.

Class-AB could be a better solution. Chances are you will hear less noise and distortions from speakers than from headphones for going Class-A probably makes very little perhaps too little difference.

The Easiest and perhaps very affordable way is to use high power opamps like LM3886 and TDA1552. I know TDA1552 has gotten very good reviews. Many speaker amp DIYers consider TDA1552 as a standard of comparisons. It requires very little wiring and external parts. Only thing to care about is to heatsink the chips well because they heat up. This is rated class-B or class-AB. This is a solid performer although it ain't perform like 1000 dollar amps.

Tomo

 

[joensd]

wow somebody replied
i forgot to click the email notification
yeah you´re right apheared some people have lack of patience
(but myself sometimes as well)
yeah i know about power requirements
was just about to experiment around (never can stop really)
maybe just check out one channel and then decide if it´s worth building
i´ve seen the projects at passlabs but thought they´re too heavy in price etc.
thought about the jlh class a amplifier which looked simpler to me(forgot the site, probably you know)
but you´re right maybe i should think more economical
by the way : i just finished a stereo amp with lm3886´s and i was really impressed what integrated stuff can sound like
i only got some 2K/W heatsinks per channel which is not enough too be prepared for some party but enough for a lil room
with bigger heatsinked case i could even think about replacing my standard marantz amp with this ; it was a real cheap project as well
thanks for wise comments, will thinks about it
there are days where i just think i need to build something

 

[Possum]

You might want to check out the forums of www.diyaudio.com. There are most likely many more users there that build speaker amplifiers rather than headphone amps.

If you have lack of patience, DIY might not be for you. I've found from experience that patience is required in the planning and building stages, otherwise you can end up with a project that could require much troubleshooting and may give less than the desired results.

 

[joensd]

yeah possum you´re right with that
patience is of the essence
actually i am; i just wrote that there are days...
i´m more or less understanding all the circuits but not so far with my experience that i design/calculate them myself
i just take schems that look cool and modify here and there
that´s why i really love the forums here cause there are real cool circuits and a lot of people with massive knowledge
it´s a real good chance to learn and get into serious audio design
BTW:hopefully i learned to repair stuff so troubleshooting is some hobby of myself
thanks for the link
bye

 

[Tomo]

Hello,

Class-A speaker amplifiers tend to be cumbersome to build with small or very small improvement from recent Class-AB speaker amplifiers.

If you do not have experience dealing with power tool and processing massive metals, you shouldn't be jump starting with Class-A speaker amplifiers. Class-A speaker amps will require massive heatsinks and powerful power supplies. It ain't for sissys like me. You really can burn yourself. (Or, you can use it as electric heater or electric cooking pad.)

I would be content with Class-AB designs. Smaller irons and much less heat. Also, this type of designs are widely available since many commercial amps use this type. Also, now you can have One Chip modules that can output 22W per ch and some of these are very high quality if you build with prestine parts. (Note that since only thing you have to add is some resistors, caps, and PSU, you can really spend bucks on those components.)

Believe it or not, couple of these ONE CHIP module has made it to the ranks of Japanese Audiophiles. That is quite impressive considering that most of Japanese Audiophiles will not accept nothing but super high quality tube amps. (Note SONY is NOT Japanese Audiophile. It is preying on gimpy innocent ppl.)

Please also note that speaker amplifers have larger margines of performances than headphone amps. You can have higher noise and distortion levels. Yet, since the speakers are NOT right at the ears, you will not hear the difference. (Dynamic capability of the amps becames far more important. But I won't get in there yet.)

I understand that tweeking and modifying sophisticated designs can give you higher performance. But then some solutions are right at our feet and we don't notice it. Class-A does not always mean better especially when you are building speaker amps. So you should not restrict your search on Class-A amps.

Tomo

 

[jteef]

I would also direct you to the Death of Zen at www.sound.au.com > project's. He's got boards for sale for it and its very simple.

As others have said, speaker amplifiers can get pretty expensive. I recently built the Leach Amp, Class AB design, pretty complicated though. And spent about 400 dollars. This was with relatively cheap parts and did NOT include the chassis that my friend built me which would have cost another 500 bucks.

big heatsinks, chassis', power toroids, and filter capacitors are going to be where the major bulk of your money goes in a power amp. (150-200 dollars at least)

jt

 

[paulb]

Also check out the famous JLH Class A amp and others at:
http://www.gmweb.btinternet.co.uk/index.htm
There's headphone amps here too, btw.

 

[joensd]

hi
was wented for a few days
many thanks for links
had a look at the jlh amp before
looks simple but´s supposed to be a proofed design
will have to save some bucks and thinks about class a in general before building and heating (winter´s gonna come up soon)
bye