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simple help.. Making a simple amplifier. pls help urgent.

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paulbostaph

New Member
Hey there. im a drummer but Im planning to create a guitar tone that i had in mind. I have created a bulldog simulator which can be look at as a normal guitar gadget and preamp. The sound im searching for is purely in the state it is without amplication now ie. if i record it directly.

So here is the newbie question i wanna ask you. How do i create an amplifier that provides alot of amplication and gain without making any significant difference to the tonal qualities of the original signal. sortof a HiFi amp or a DC-powered headphone amp (not enough gain).

I really want to create one amp with high wattage through an AC supply. Is such an amp simple to make. Can you please suggest a simple way of making such an amp. It is pretty urgent as we want to play it out as soon as possible. thank you for any feedback at all.
 

Skyknight

New Member
Please, tell us more. How many watts do you want? 0.5? 10? 20? 100?

Apart form this, what's a guitar tone? Is it an effects board? I wasn't able to understand you well. Where are you getting the signal from? Where do you want to input it?

If you want to make a Marshall yourself I can tell is much much cheapier to buy it wherever you live. And you don't want distorsion, isn't it?
 

hamfiles

New Member
The easiest one off the top of my head is a simple class A, using a
MOSFET, like the proliferated, IRF 510.



There is one configuration here:

http://www.rason.org/Projects/transaud/transaud.htm

You can't get much easier than the schematic for the MOSFET amp. The input potentiometer is biased for 1/2 of supply voltage with no input connected. This allows for maximum voltage swing, so that your signal is not clipped. It also allows for a wide range of voltages.

There are tons of amplifier circuits on the net. It really depends on how much power you want. The above amp will probobly be OK for a guitar amp.

Also, IC's like the LM 383 are pretty simple. The 383 is an 8 watt amp, that also uses minimal components.

National semiconductor has the data sheet for it with a couple of schematics here:

http://www.electro-tech-online.com/custompdfs/2003/05/LM383.pdf


You can order one at www.jameco.com, and most electronics component stores can get you one.
 

paulbostaph

New Member
first off thank you for all your replies, been very helpful.

As for more specifications, i want build an amp unlike a Marshalls (or other guitar amps) as these amps normall have a "non-flat" voltage/frequency graph and the sound will break-up (distort) as you crank up the amplifier. This is what we are paying it for as it makes it sound good but thats not what i want. I want a simple amp that has insignificant distortion even when you crank it up and also with a flat "voltage gain/frequency" graph. one that simply amplify the sound flat. the source that im looking to amplify is a at "line level".

i have found the links given to me quite helpful but is there schmatics for simple amps that can operate at 90< watts? i really found everything here useful, thank you for the feedback so far. I would prefer the simple schematics for this higher wattage amps (like the ones you have been giving me so far).
 

Scubasteve

New Member
Hey,

I have really no idea what you want by your description. First you say that you want a hi-fi amplifier, now you say that you don't care about original signal quality. I do not understand the voltage gain/frequency reference, which makes me think of a bass/treble control (amplifies differently for different frequency bands).

This is the design process you should consider.. First, start with a small audio signal. Then, you add distortion or filter it out the way you want, add effects, etc. After that process, you will have the audio signal wanted. You need to amplify that to optimally drive your specific speakers. This will obviously require an amplifier, which amplifies the original signal without giving it unwanted distortion and a linear operation.

Please explain exactly what you want if you want our support.

Steve
 

paulbostaph

New Member
i didn't say i don't care about the original signal quality. The original signal quality is all i want to achieve to reproduce after the amplification. I want an amplifier that does not distort the amplified (such as in guitar amplifiers) signal or alter it in anyway even when cranked up. And i would want a simplest method to this at 90<W. To put it bluntly, The "line level" signal i have now is PERFECTLY the sound i want and i would want minimal alterations to it during amplification. Guitar amps have charatersitics such as warmth is the mids or brightness in the high freq. or breaking up at higher volume.etc which i don't want. i really thought i made it clear, sorry.
 

hamfiles

New Member
By 90<W, do you mean under 90 watts?

Elliot sound products has some good hi-fi amps, at

http://sound.westhost.com/

I believe they sell amps, but they also have a lot of schematics for DIY projects. You can click on the projects link to see them.

All of their amps that I have seen posted reportedly have a flat frequency response, with very low THD.

About distortion at higher volume, when an amp is turned up, it will clip the signal when the AC signal has a higher peak to peak voltage than the supply voltage of the amp.

Check the level of the input signal, probably about 1/2 to 1 volt peak to peak for line level. Then look at the voltage gain of the amp you are considering. Whatever the voltage gain, multiply this number by the input signal level. The supply voltage has to be a little higher than this or the amp will clip at maximum volume.

Example: input signal at 1 volt p-p. Using a power amp with a gain of 20, 1 volt x 20 equals an output signal of 20 volts peak to peak at max volume. If the supply voltage of the amp is 18 volts, whenever the volume cranked over the 18 volt threshold, the ac sign wave will be cut off, or clipped, at the top and bottom, and it will sound like many cheap amps do at high volume.

Also, no amp can convert all of the supply voltage to an ac signal. Some of the voltage is lost when passing thru the transisitors. An amp with a gain of 20, used with an input of 1 volt, should have at least about a 24 volt supply voltage to ensure no clipping of the signal.

I don't think you will find any simple designs for hi-fi power amps. The closet thing would probably be some of the integrated circuit chips from National semiconductor. They have a couple of high performance amp chips that can work from different supply voltages, from about 20 to 60 volts.

They have a section called overture power amplifiers that list them here.
http://www.national.com/parametric/0,1850,811,00.html
 

Skyknight

New Member
If I didn't understand wrong you want something OVER 90W. So, really you want a "clean Marshall" . It doesn't matter if you want it clean or not. You need 90w (that's what I wanted to say with "a Marshall"). So, I encourage you to buy a power stage because the quality of the sound will be greater than the one you could build and the price would be probably minor. Anyway, I've found what I think is a very good solution for your problem:

http://www.electro-tech-online.com/custompdfs/2003/05/TDA8927_2.pdf

This is an amp, which can give 80W (stereo) or up to 150W (mono bridged). I think you'll get good sound (almost no distortion) if you make the bridge arrangement and you set it to not more than 60% (about 90W). All the curves about the output and the input are in this pdf file (well it's the datasheet), you'll see too how to arrange the circuit and the recomendations of the firm (philips) for using the product. Be sure about the power supply you'll give it to it. It should be able to supply about 130% or more (better more, about 160%) the amp you are building (or you'll get distortion much sooner, about the 40% of the amp range if you supply just with 150W). A mean, you'll need to be able to give 1.3*150W= 200W [minimum] That's not a joke. If you buy this philips chip, I really don't know, but I think it will be reasonably cheap. So don't save a sole € in the power supply and the cooling system or you and your band will end burned in the local hospital. :!:

This is not the subject now but I also wanted to say that, if you get a very good and powerfull signal you should input it into a very good speaker. Don't forget the speaker must be able to manage aprox 200 or 220% of the input signal. This means about 350W (RMS of course, forget about the "ghost measures" of the PC speakers, I can grab mines with a hand and its supposed they can manage 200W :lol: ).
 

paulbostaph

New Member
I have decided to attempt this schematic upon one of your suggestions http://sound.westhost.com/project3a.htm . I would really want to thank all of you for your explanations and clarifications that i could use. Now this is the last question i have to ask, using this schematic, whats the voltage i have to supply if i want it to operate at 90W. any other suggestions, further clarifications or anything notable is appreciated. Sorry to be borthering you guys upon the same matter but i have to get it done. thanks again.
 

Scubasteve

New Member
Hey,

It says that you need to use a maximum of +/- 42V for it to produce the most output power. I would use this or something a bit lower, and make adjustments. Just because the amplifier can do 100W, doesn't mean you have to push it to that limit.

Steve
 

Gene

New Member
A high wattage amp with low distortion is not simple to make. The circuits provided are good ones but there are factors involved with creating clean amplification besides hooking up the parts. Do you know how to build a minus (-) 42 volt supply? Since you mentioned that you are a drummer and presumably in a band, is it possible for you to feed your device into an AUX input on one of the guitarist's amps rather than build your own? What about buying a used amp - maybe one that has the reverb blown out?
 

Scubasteve

New Member
I agree with Gene.. Designing and building a quality amp is a science!
Making the actual schematic and doing all of the calculations is only half of the battle. A poor PCB design could lead to disaster, and in some cases, it will not even work.

My teacher at school designs tube amps and he said it took two years for him to figure out how to do a proper PCB design..

Steve
 

hamfiles

New Member
Hey, paulbostaph. I don't know if you noticed or not:

1) Phil Elliot sells PCB's for his project 3a

2) Data box in the link shows 100 watts, with 35 volts into 4 ohms.

3) Near the top of the web page there is a link to a very detailed construction guide that a reader made.

I agree with Gene and Scubasteve, building such an Amp is complicated. The double sided supply this amp needs is equivalent to a single supply of 75 volts, using + and - 35 volts, so that equals alot of headroom, massive volgage swing available. If you do build this, please be careful with the power supply.

Basically, a double-sided power supply with equal plus minus values is equivalent to two supplies in series, like 2 batteries, with all ground connections made where the plus and minus connect the 2 supplies together.

Plus lead here------{+ _ }---{+_ }---------minus lead here
/
/
/
ground lead here

The most common way to construct this is to use a step down transformer with a center tap on the secondary side. The 2 outside secondary output leads go to a full bridge rectifier and are the positive and negative connections, and the center tap directly from the transformer is the ground.

The project does show the supply wired properly, but I believe there is a typo under the transformer in the schematic. It is labeled: 25-0-25, it should read: should be 35-0-35.
 

paulbostaph

New Member
you guyz and gals are really nice pple to warn me about all these shortcomings. Really appreciate it. I'll ask my friend who study's electronics to see whether he can help me make this one. But i'll put this making of the amp as my last resort due to your suggestions. I'll check out the price of new and used amps first. The only problem is getting the prices of hi-fi amps as i don't even know who sells them. But anyway i'll get it solved. I need this hifi amp not only for the drums but i want to try it for guitars for some reasons. Thanks again for all your concerns and warnings.
 

Scubasteve

New Member
Hey paulbostaph,

The funny thing about making your own stuff in electronics is that it usually costs more then just going out and buying it commercially.

The only advantages that we can get, is that we can make it better or more specific to what we need. In the case of an amplifier, commercially available amplifiers are much cheaper. Even buying the nice shiny aluminum extruded cases directly from the manufacturer in small quantity will probably superseed the cost of a finished unit! I would know, I have looked into building a nice amp for my car.

Steve
 

paulbostaph

New Member
the more the reason for me to buy it off the rack. around how much would such an amp be (90W). Im not looking high end here as it might just not work for me. Oh yeah, i don't think i need a real hiFi amp as long as the signal is not changed in characteristics too much. I know im not being specific here but i hope you have the idea. Any estimations will do i wont quote you on it even if its far off :wink: .
 
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