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JoeBob 5th November 2001 06:04 AM

Alright, I'm new to this board, seems as though it's got alot of people who could possibly help me out ;) I'm new to building home audio parts, started off when I saw skeaper components at my local electronics store, and I built a pair of LARGE speakers, rather well I might add. Now my amp (silly little sony amp (100w x 5 channels) pumps nowhere near the power my speakers can handle well over 500w RMS, but an amp that would put out 500w or 600w would be perfect for me... So I recently thought about DIY amps... If someone could point me in the direction of a project for me to take on which could suit my needs I'd greatly apreciate it.

Now I haven't done too much electronics, but a enough, but I pick things up quickly and I know a couple of pros (they build multi-milion dollar projects and such) whom I can always turn to for help, so what I'm trying to say is even if it's my first time trying to make an amp, I'm sure I can do a good job (with a little help if needed ;).

Where should I start? Should I go with tube or solid-state? I'd obviously like to do so without it costing me too much. I don't know much about what is better then what, but idealy I'd like something in the rage of 600w for a pair (stereo only, obviously) of speakers. Maybe even a pre-amp/amp combo if needed, I'm not sure what is needed. Hell, I don't even know the difference between A amps and AB amps or whatever else there is, but I'm hoping to learn a little bit, I'm not an audiophile, just a guy that like big loud things :). I hope someone can help me and I hope I'm not asking to much...

[Edited by JoeBob on 11-05-2001 at 12:20 AM]

AudioFreak 5th November 2001 09:15 AM

Ok here goes..........

Class A amps waste alot of power as heat so that the output devices are always 'on' this avoids switch on/off delays and the like...... Class B is basicly the oposite .... the output devices are off all the time unless puting sound into your speakers. Class AB are in the middle they use a very small amount of power most of the time in the output devices which is disipated as heat .... this is better than B but not as good as A with similar benifits when in the 'on' state.

For 500W RMS ..... yeah thats doable it's gonna be solid state (cause of efficiency and distortion) and Class AB (unless you wanna quaduple your house wiring capacity :) ).... i would suggest 2 mono amps operating in semi balanced mode (where the input can be balanced or single ended and the output is balanced ie. their is no ground pin at the outputs there is a +ve and a -ve then each half only has to do half the work) as this is the easiest way of getting this kinda power and unless you think you are ever gonna need more than 500W this design will suit you well.

Your gonna be using transistors not mosfets for the output devices cause mosfets are not linear enough in Class AB.

You could consider Class A with mosfet outputs but you would want to idle (ie. waste as heat about 300 watts per channel all the time) Think heat ...... lots of heat ...... then think about 10 times worse than that :) this would ensure Class A except for when driving the amp very hard or into a low impedance speaker.

offer some good starting points.

Oh and think simple. 3 gain stages MAX! with as little feedback as possible.

I just have a few questions for you. how efficient are your speakers? what is their nominal impedance? do you value your hearing?

But seriously, 500W/channel stereo is insane and will quickly send you deaf unless your listening room is the size of most peoples houses.

Hope this helps.

[Edited by AudioFreak on 11-05-2001 at 07:30 AM]

AudioFreak 5th November 2001 01:28 PM

i think i may have misinterpreted your posting ..... do you mean 500-600W/channel stereo or 250-300W/channel stereo totalling 600W for the 2 channels?

If it is the latter, all my comments stand except the following 2...........

250W/channel is still insane although it will take a little longer to permanently deafen you.

The Class A disipation could be halved but you would benefit from leaving at the higher figure.

paulb 5th November 2001 02:01 PM

Check out:

JoeBob 5th November 2001 06:02 PM

500-600w a channel I mean't, sorry for not being clear. And yes I know it's insane and probably damaging to my ears in the smallish space which it'll be in (a room in the house). But I'll probably won't ever listen to them at that much, it's just so that I can, and who knows maybe someday I will play them that loud for some strange reason. And yes I do value my hearing, and my speakers have a nominal impedence of 4ohms. Hope that helps...

swede 5th November 2001 09:45 PM


One reason for beginning with a lot smaller amplifier is that if you are a newbie, and even if you're not, things go wrong and the bigger amplifier you ruin, the more expensive it'll get.

Start out with a Leach-amp or something like it to get your clothes warm, and continue from there.

BIG amp = mucho dollares
SMALL amp = a lot of dollars, but not mucho


Super 6th November 2001 02:06 AM

I'm assuming your Sony amp is an integrated receiver? When it says 100 wpc, thats not the continuous power. Rather, you'll be lucky if your continuous power is even a third of that, and I'm assuming it can drive your speakers to a normal listening level? Very few speakers are going to need 600 watts continuous, no matter what the size. Odds are you dont really need any more than 200 wpc. Can we have some info on the speakers you built, drivers in particular? Theres a very good chance they wouldn't even be able to handle 600 watts before ruining every driver.

JoeBob 6th November 2001 02:38 AM

Yup, integrated reciever, and I didn't know about it pumping out power continuously and that being less, I guess that explains why alot of the high end amps are 50wpc and 60wpc. And I'm going to listen to swede's advice and build a leach amp first, looks like a good place to start, not something excessively easy, but not something that I won't use when something better comes along. The total of my speakers RMS power comes to above 600wpc (can't tell you the exact drivers because it's sealed up and I can't remember where I put my list of drivers, maybe I'll dig it up later). But if the RMS power is above 600wpc, would 600wpc continous be damaging to it? I'd like to eventually build something that would power them to their full potential, not that I need something that loud, but just so that I can. I don't know if you understand, but I'm the kind of guy that puts nitro in their car, just because I can, I may use it very very infrequently, but I know I can.

AudioFreak 6th November 2001 03:42 PM

Just a little advice.........

If you get 600W RMS from adding the ratings of each of the drivers in the enclosure, it doesn't mean that you will actually be able to run 600W RMS thru the speaker ....... this depends on the crossover setup ..... generally speaking, the only way of getting anywhere near this calculated RMS value is to remove all the crossovers and run each frequency range off separate amplifiers (ie. in a 2 way speaker, run the woofers off one amp and the tweeters off another amp ..... just scale this for the number of frequency bands in your enclosure) and use an active crossover between the preamp and the amps.

If and when you decide you are ready to build a bigger amp, I would be glad to give advice or help where ever it may be required (where possible of coarse).

Super 6th November 2001 04:07 PM

AudioFreak is correct. The enclosure can also play a factor when determining power handling as well (sealed vs ported).

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