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Guitar amp plans

Started by lliw, June 04, 2006, 09:03:09 AM

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el mo

you need speakers rated for the right performance, rating does indeed not depend on the size of the speaker. a new jensen10" 25W one should probably cost some 40-50 bucks.

if you can find a defective combo (preferably w/ a working speaker) you should get that and gut it- it can save you the bother of building the cab and the chassis (12 hours of work)and you can concentrate on the electronics. furthermore you get the switches, knobs, etc almost for free, possibly even a suitable transformer.

teemuk

If you want a "quiet" practice amplifier it's better to use a speaker with low SPL rating. The power rating of the amplifer itself really isn't that important - it's all about the speakers. In my opinion, you'd better build a 60 - 100W amplifier instead of low power one. Why? Because you probably end up needing one after few years anyway. If it's solid state, you can (without loss of tone) make this amp as quiet as any amp from 5 - 25 W range just by adjusting the volume knob. Remember the speaker thing: When you need more volume just plug it into a high SPL rated speaker system and have lot more headroom than 5 - 25 W amplifers can provide. Just make sure the speaker can handle the power: The tone of voice coils deformed by excessive heat is not very pleasing. By the way, when coupled with ordinary guitar speakers even 5W amps are too loud for apartment use. I practice with a 1/2 watt amp (it has a 3" speaker") or with a 12W amp (8" speaker) with the volume knob at one or two. As a recording amp, I crank the latter to 5. If I'd want to play with a metal drummer both amps would be insufficient. Quiet practice amps would really need less efficient speakers, such as hifi speakers. Unfortunately hifi speakers have a very flat frequency response while guitar speakers roll-off at 5kHz.

Is this a price issue? If you think you can DIY cheaper you are probably wrong. You can, of course, but it means that you have to salvage parts from equipment thrown to trash cans etc. This is actually pretty fun and I've done few great discoveries this way lately. If you are able to get the heatsink, mains transformer and perhaps even the speaker for free then damn right it will be cheaper. If you buy them the price is perhaps even higher than buying an amplifier.

Chip - Discrete? Chip amps are easier to build and requirement for parts is smaller. They have built-in protection circuits and thermal compensation. Their power ratings are also smaller, perhaps even bloated, since the smaller die area can not get rid of the excessive heat as quickly as the larger die area of few transistors can. I'd choose discrete because it's much more educative to learn how the circuit works, how to thermally compensate the bias, how to layout a PCB etc. After acquiring such knowledge you have a lot more options in tweaking or expanding the design than you have with chip amps. This can take years though, and if you want to quickly build something that actually has a good chance to work on the first powering up then build a chip-amp. Nice alternative for LM series chips is the TDA series. Most of them show a PCB layout for the application circuit in the datasheet too. I recall that a TDA7294 was about 100 watts.

joecool85

#17
You could use a LM4780 which would give you 120watts.

And for an easy to build, great sounding stompbox, try my 5th Gear Overdrive.  It goes from a middle overdrive sound to a pretty decent distortion.
http://wiki.ssguitar.com/index.php?title=5th_Gear_Overdrive
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