Hi all, this is my first post. I've been lurking for a couple days now. I am interested in building my own guitar amp (obviously). I am wondering what is a good starter project?
Ideally, I would like to have a 100W amp with a killer distortion channel similar to a Randall RH100 or better (warhead perhaps), but I do realize it's best to start small.
I have lots of experience in soldering and a fair amount of knowledge of electronics, but I'm by far not an expert. I'm a technician in a Honda dealership, so I do see my fair share of wires.
All input greatly appreciated.
Start by building a Randall preamp.
Search this forum.
Mensur built an excellent one, just listen to his posted MP3s, he drives a TDA7294.
Siund is impressive.
it does sound quite good. should i get a power amp circuit from chipamp, or do I need something more for that kind of power? I've looked into the LM3886 a little bit but I don't see what it's total power rating would be. Or does you're wattage rating come from the preamp? I guess I'm newer at this than I thought.
On another note, is an Opamp just an integrated circuit? Or is there more to them than that. Are they made specifically for amp design, or can I pull one out of say, a cars PCM?
just curious.
Chipamps are good, but best of all is that they come in kits with everything needed, they are relatively simple, and since many have built them successfully, there's a pool of knowledge and help available around here.
They usually supply 50/60W each; a stereo Kit gives you 100/120W; if you become power hungry you can later build a powered box and add speakers and power indefinitely.
An Op Amp is an integrated circuit.
The excellent TL072 costs less than 1$; just buy a few and experiment.
That Randall preamp uses Fets, they are also inexpensive.
at the risk of asking a "dumb" question, what do you mean by a powered box?
When I look at a schematic and see four diode symbols making a diamond shape, is that just four diodes, or something I've not seen before?
Should I trust myself to use perf board to build a preamp like this, or should I look harder for a PCB?
thank you
The diamond shape is a bridge rectifier which comes as a single component. It is made up of diodes internally though, hence the appearance.
Hi heineken.
A powered box is simply a cabinet with a speaker, say a 12", and a power amp built-in, say a 50/70W chipamp and its power supply.
It only has a couple input jacks , an (optional) volume control, a power switch, a power cable, and little else .
The idea is this: we usually encourage members to build a not-too-complex 15W (TDA2030) to a somewhat more complex 50/70W amp, (LM3886/TDA7294), to ensure success.
Many say: good!, it sounds great!, but now I need more power/speakers.
Instead of throwing everything overboard and starting from scratch, I suggest building powered boxes, when and if needed, which allow you to go real power crazy if you want.
They are driven from the preamp output of your original amp, the parallel input jacks allow for easy daisy chaining, everybody is happy (except your neighbours).
Just imagine your original 15W amp (homemade or store bought) driving 4 70W/12" (or 15" or 2x10") boxes.
Woodstock anybody? ;)
EDIT: forgot this:
You can use perfboard; if available use Veroboard (stripboard) which allows easier designs and neater boards.
Download the excellent DIY Layout Creator.
Use the original Windows version (unless you are a Linux/Mac guy) because there are already a lot of excellent projects there; the new Java (universal) version is not compatible with them.
Study other guy's layouts to learn.
It's good to start by building preamps on solderless protoboards; only after that you build them on permanent boards.
Good luck.
EDIT2: just an example of what can be made with DIY Layout Creator on stripboard (they also offer PCB and Perfboard options):
(http://i47.tinypic.com/r295d2.jpg)
That's really cool. I'm going to go find that program now and play around a bit.
thanks for all the advice guys I really appreciate it. and look forward to lots more! lol
will it show you how everything hooks up on the bottom side, or do you just figure it out from the schematic?
Hi Neken ;D (sorry, couldn't resist)
Start with something relatively simple, say a Screaming Bird or LPB1 or similar, just to practice.
Draw the regular schematic on a sheet of paper, then try to deploy it on "veroboard", which is simulated by square gridded paper.
Use pencil and rubber to correct layout until you like it.
Consider horizontal lines as uninterrupted horizontal tracks, joining everything soldered to them unless specifically cut somewhere.
Join tracks vertically with short pieces of wire, also draw components as long as needed to reach whatever they have to.
That's to say, the actual design is *not* automated, but brains, pencil and rubber on a sheet of paper.
Play some music you like, work preferably at night or in a quiet moment (you don't want wife/boss/kids/mother/customers/teacher/etc. interrupting ) and draw, correct, redraw, etc.
The program lets you confirm relative sizes and draw it neatly, both for you and to publish in the Net, as the above example.
Step by step draw more complex ones.
so when you buy the LM3886 stereo kit, you end up building you're power amp, and a clean channel preamp? is that right, or am I still confused?
thanks for all you're advice, everything is coming along nicely in my head so far.
Hi heineken.
Almost there.
Your stereo power amp kit means you get *two* 50W LM3886 amps, don't know if on two separate boards or a single stereo one, plus a power supply board, ask the kitmaker for details.
The power transformer can either be sourced fom him or somewhere else you prefer , or pulled from some dead guitar amp.
You will have to build a preamp which will drive one or more power amps.
okay... so, if I were to build an amp with a clean channel, and footswitchable distortion channel, would I need two separate power amps?
what do you think of this as a power amp??
http://www.a1parts.com/newkits/amplifiers_kits.htm#DISCRETE POWER AMPLIFIER 200W-K8060
this guy has a lot of stuff to pick from on his website, and I just discovered it today, so there is probably somethng better on there. I figured if I can source my parts within the country, than at least I can save money on duty and exchange
that link is actually supposed to go directly to a heading of: DISCRETE POWER AMPLIFIER 200W-K8060
you have to scroll down the page about 1/3 of the way
I had seen it a couple months ago, looks good, although somewhat more complex.
If you dare ..... go on.
I'd rather build *just one* more 3886-class chip amp before getting into the next step, a higher power, full discrete power amp, but of course, it's your project.
Good luck.
Good point, sometimes I get excited and try to jump in balls deep.
I'll start with the 3886
what are the main differences between the LM3886 and the TDA7294? is one more reliable than the other?
CAn you use any old power transformer, or is there specific ones that work with specific circuits? I have a dead head out of an old Samick 60W amp, where the transformer seems in good shape. there's also a lot of good parts in there I can use I think, like the circuit for the effects loop, and I may even just grind the chassis down and paint it to use in my project.
Hello heineken,
LM3886 is 50Watt cont output into 8Ohms. 135W instantaneous power
Using 35/35VDC rails.
TDA7294 is 60Watt cont output into 8Ohms. 100W instantaneous power
Using 38/38VDC rails.
Edit; In answer to the reliability, it's not really an issue with most of these chips.
I'm not the expert but LM3886 is proly the better one.
Re, the POWER AMPLIFIER 200W-K8060
There is one thing that those starting out should bear in mind when hunting for power ratings.
I'll use that K8060 as a good example.
You read 200Watts and you get all excited BUT?? hang on look carefully at the real power.
It's only really a 70 Watt Amp. (I quote from page,,,70W rms power @ 8 ohm load)
Not so flash in the real world,, only just above average. 8|
If we hung a 2 Ohm load off the output we could make it look like a *killer watty*
You would likely get over 300Watts @ 2Ohms and the thing would also blow up in a faily short time. :'(
It's always wise to convert any *Whatty* numbers into 8 Ohm Loads as 8 Ohms is generally the ideal load for such things.
Always look for x amount of Watts RMS @ 8 Ohms ,, that will give you a fairly good idea of real power.
Get those *Peak music power* rating out of your mind they always make things look better.
Even worse when you see PMPO ratings. :duh
If you want more power than 50/60 ish Watts then IMO forget chip Amps and go dicrete components for power Amps.
This means big Transformers, big filter caps and a serious heat sink.
The *Samick 60 Watt* you mentioned is likely a chip amp so at a guess the PSU inside is only capable of 50 ish Watts,, any more and you just waste money.
Yes you could drop a great big poweramp inside it but it will only deliver 50 ish watts as the transformer is not designed to give what it has not got. You would likely fry the trans windings anyway.
Cheers, Phil.
okay. sourcing a new transformer as we speak.
If I wanted to have a clean channel as well as a gain channel, can I do this with one LM3886 Stereo kit? Seems like I should be able to, but I've been wrong before.
and I believe I've read before you could take most overdrive/distortion pedal schematics and turn them into a preamp? I was thinking either a Krank distortus maximus or the Dr. Boogey as my high gain channel, both of which I've found the schematics and veroboard layouts. do you need to make any major adjustments to them? I'm sure it's probably already been covered somewhere in this forum, I hate coming along late in the game.
Quote from: heineken on March 25, 2010, 09:11:13 PM
okay. sourcing a new transformer as we speak.
If I wanted to have a clean channel as well as a gain channel, can I do this with one LM3886 Stereo kit? Seems like I should be able to, but I've been wrong before.
and I believe I've read before you could take most overdrive/distortion pedal schematics and turn them into a preamp? I was thinking either a Krank distortus maximus or the Dr. Boogey as my high gain channel, both of which I've found the schematics and veroboard layouts. do you need to make any major adjustments to them? I'm sure it's probably already been covered somewhere in this forum, I hate coming along late in the game.
Hi heineken,
You can have multiple preamps with only 1 Poweramp, You just have to sort out how you want to switch between the channels.
Unless you are a relay building guru building such circuits can really slow progress.
IME, it's a lot easier to have a totally seperate unit for preamp/s as that can be a self contained floor unit seperate from PowerAmp.
My reasoning is simple, any channel switching can be done with direct (mechanical) switching which makes design simple.
(Of all the amps I've repaired more than 50% of issues are in relay type circuits that switch something via a remote pedal.
This fancy relay circuitry is only needed because ALL the controls are in the Amp,,,
Soooo if all the preamps are on the floor unit and most poweramp unit don't need any controllers then why make life hard.
Just build all the preamps and switching arrangements inside one dedicated floor unit.
Yes a lot of pedal circuits can/are built into a preamp circuitry But I strongly advise you to Bread board test it all first.
It took me a few years of frustration and failed circuits before I caught onto the realisation that no matter how simple some of these
mix an match may look,,,,.a LOT them will no doubt be a waste of solder and time. Hint trust me I've been doing this for over 30 years.
Of all the stuff I've built (seemed like a fantastic to good to be true circuit at the time) only about 5 circuits have been seriously useful.
Does that make Me a bad designer,, or am I just refusing to except crap circuits? LOL
Poweramps (especially chip ones) there is not much to tweak and most of them don't colour the tone greatly
BUT with all Preamps there are just so many different ways to effect a change to Tone/ Dist/ OD/ Crunch.
So when you read the blab on some of these sites with schematics and build instructions be warned you are taking on someone else's opinion
of what constitutes a fantastic sound.
And will it work with your Guitar /Amp / Speaker /musical style.
In my experience ,,it's a big gamble to etch a board,, build it ,,,and have it all magically come together.
but it's possible no doubt.
I've got a whole bottom draw chock full of dud PCB's that will end up as land fill no doubt.
It's rewarding long term but you do need to have the patience when things don't go as planed.
Phil.