Guitar Amplifiers
Oct 7, 2006 at 8:57 AM Thread Starter Post #1 of 10

xelion

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Well I've just gotten in to DIY audio type things, made a cmoy, got a second one in the process(just needs an opamp) for my friend. And I was wondering if there are any good cheap amplifiers that would work with a speaker so I could use it with my guitar.

I guess my real question is, what is the difference between a headphone amp, and a speaker amp, and if there are any good schematics for good amps.

Thanks.
 
Oct 8, 2006 at 7:32 PM Post #2 of 10

bperboy

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I'd also be interested in any kind of amp, not for a guitar, but for a violin! I play the violin, and have a passive pickup, but no amp that's less than 30 years old. I was vaguely thinking about DIYing one, but I really don't have any ideas for an amp/speaker combo.
 
Oct 8, 2006 at 9:29 PM Post #3 of 10

Minion

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If you want to build a cheap but powerfull Guitar amp or power amp for pretty much any source you might take a Look at the LM3886 Type power amp IC"s....

They can deliver up to 68w into 4 ohms from a single chip with only a few external components and are very clean sounding....

If building one for a High impedance source like a Guitar ,Bass, Violin then you might want to have a Preamp before the power amp stage as the LM3886 expects a Line input at about 10k ohms and a Guitar can be over 1m ohms so a preamp to buffer the signal is a good idea Pluss the preamp also adds your EQ and Gain controlls.....

I am right now designing a Guitar amp useing the LM3886 Chip for the Power amp and a OPA2134 for the Preamp stage, It has a pots for preamp Volume, Gain, Low, Mid, High, and has a Bright switch for a Trebble boost and also has a Mute switch and a Master Volume on the Power amp stage and also has switchable Hi and Low gain inputs....and all of this Fits on a PCB smaller than 4in x 4in....The heatsink for the LM3886 is bigger than the PCB (Minus the Power supply)....

the Power supply has +/-15v regulated for the Preamp and +/-22v Unregulated for the Power amp IC running off of a 18v-0v-18v 100vA Toroidal Transformer but the transformer could be bigger.....

The LM3886 can also be Bridged with multiple other LM3886 chips to give power rateins above 250w into 4 or 8 Ohms....

These chips also have Overheating protections so you won"t burn out a chip if you mistakenly don"t put a big enough heatsink on it.....

Right now my design is Just a prototype that isn"t completed yet as I am waiting for some LM3886"s to show up in the mail but I"m 99% sure it will work well as the Idea is taken from the Data sheet and other working designs.....

If you would like a schematic and/Or PCB design then PM me with your e-mail and I"ll send it to you.....

Cheers
 
Oct 8, 2006 at 9:58 PM Post #4 of 10

NiceCans

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Wow, great thread! My son is in need of a new guitar amp, and a DIY would be sweet. Knowing him though he'd want to gang 2 to 4 of these to increase the output. I'll keep an eye on this and see what turns up.
 
Oct 8, 2006 at 10:19 PM Post #5 of 10

blip

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Hey good topic! I've always been fascinated with guitar gear... though I haven't built any because I don't play... I'm just fascinated by gear that is designed to sound cool not nescessarily be transparent or blah, blah, blah. Anyway, I have some familiarity with the designs out there... so lets get thinking!

First thing to do is to set up your specifications:
A) How efficient is the speaker you are using?
B) How loud do you need it? (Take these two together to figure out the wattage you need)
C) Tubes/Solid State?
D) Is there any signature sound you are looking for?
E) How portable does it need to be?
F) How much do you want to spend
G) Any other things that it needs to have?

As minion said, the LM3875 or LM3886 is a great place to start for any amplification project. The common circuit that these are used in is called a GainClone (or some derrivation thereof) and is quite a nice performer. (These chips used to sit at the heart of VERY expensive Japanese equipment). If you need a moderate 50w or so they are a decent, cheap (maybe $50) way to go. They can also be bridged for more power if you like. The only disadvantages really are that they throw a fair amount of heat which can cause problems and unless they are bridged they do have power limitations.

If you need very low power... think about going class D. There are quite a few 10-25 watt class D kits out there for cheap. But you will need an efficient cabinet (hey that could be a fun project to!). Big advantage is that they generate next to no heat. You can even run them from batteries! Plus they sound pretty nice.

If you want tubes there are tons of designs out there... lots of schematics of vintage amps are floating around as well.

And if you want power there is always this: http://sound.westhost.com/project117.htm
 
Oct 10, 2006 at 1:35 AM Post #6 of 10

xelion

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Quote:

Originally Posted by blip
First thing to do is to set up your specifications:
A) How efficient is the speaker you are using?
I don't have a speaker yet, so suggest one.
B) How loud do you need it? (Take these two together to figure out the wattage you need)
loud.
cool.gif

C) Tubes/Solid State?
I would really love to have a tube amp. Though solid state would be cool too, just not as cool.
D) Is there any signature sound you are looking for?
not really, something clean.
E) How portable does it need to be?
not very.
F) How much do you want to spend
Well the amp I was planning on buying was about $500-$600, so if I could make a comparable amp for the same price, I'd take it.
G) Any other things that it needs to have?
Just the basics really, bass, mid, treble, volume. Some built in distortion would be cool, but not manditory.

And if you want power there is always this: http://sound.westhost.com/project117.htm



That is also the most badass metal thing I think I have ever seen.

So yeah, I really don't know anything about designing circuits, as I said I'm pretty new to all of it. I've only made 1 1/2 cmoy(my second one doens't have left channel
frown.gif
I think it's the input jack though) And planning on a SOHA in about a month when I get my PCB.

And as for the tube amps out there already, yeah, but it'd be sweeter to design my own(with lots of help from you guys *wink wink*)
 
Oct 10, 2006 at 4:43 AM Post #8 of 10

blip

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Yeah that ESP amp is just truly unnescessary! I wonder if anyone has ever built it... and for what?

I tend to be more of a solid state guy... Though all those pretty glowy things tempt me too! But here is a website I ran across a while ago which looks like a great place to start. They have several designs that seem very well documented and might fit your requirements neatly: http://www.ax84.com/ .

One struck me as particularly well documented and interesting: http://www.ax84.com/index.php?pg=pro..._id=p1-extreme . It might be a little underpowered but it looks like a great simple amp that could be put together for a reasonable price without having to spend days searching for parts.

Another option is to try to build a very clean solid state amp and supplement it with an amp simulator. At least one guitar player I know swears by this approach... of course he has enough dough for a pretty schweet simulator.
 
Oct 10, 2006 at 3:32 PM Post #9 of 10

Minion

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With my Latest Guitar amp Project I am useing the Guitar preamp found here in Figure #1:

http://sound.westhost.com/project27.htm

accept I am useing the OPA2134 instead of the TL072 for the preamp.....

then I am takeing the output from the preamp in to the input of the Basic gainclone configuration useing a LM3886.....

I have allready designed and etched a PCB with both pre and Power amp modules on it and it is only about 4in x 4in square.....

I don"t know what I will use as a speaker but maybe if I can"t find something good for cheap I will maybe try out a few better quality midrange Car speakers and see how they sound.......

I won"t know for probably a couple weeks to a month if this project is a true success but will let you guys know and will post a PCB design for you so you can build your own....


Cheers
 

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