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Making a guitar amp... ( Using a Rack?)

Discussion in 'Guitars' started by rohr, Feb 1, 2010.

  1. rohr

    rohr Guest

    Okay, so I am wanting to make a guitar amp, but not with a DIY kit. I just want to buy, for instance the top of a combo amp (Idk what it is called), a speaker, and make a housing for it all and put som finish on the housing. My friend has done this, and he got away with it for about $50 and it is an amazing amp.

    Does anyone know how this is done? Do you know a good site to get me going because I cannot find anything.

    What is the top of a combo amp called? (where all the controls are)

    What is a guitar preamp all about? (The ones that go in a rack and have a variety of adjustments) Would this be usable to put inside the housing (i would think not)? Is there any components im missing? What does this do?

    Could I take a guitar preamp and plug it into a cabinet with a few speakers in it and run my guitar off that? Would this hurt sound quality?

  2. tmarkov1

    tmarkov1 Active Member

    you basically are looking to repackage the contents of a guitar amp in your own case, it sounds like. that top part is the amp! Those are usually original equipment with amplifiers and unless you go with a custom manufacturer, your only bet is to find an amplifier on ebay that maybe just has a blown out speaker. You would have to design the casing for the amp and the speaker and if you wanted to customize it with a 19" rack mount space, you could rackmount an ART or Marshall preamp in it. The alternative is finding a straight up tube amp or solid state amp (much like PA or Live Sound Amps) and then you would design those to fit in the 19" rack and run your preamp into that amp. That would make the most sense to me. Anyone else?
  3. dvdhawk

    dvdhawk Well-Known Member

    It's called a "Head". Your buddy has an amazing sound amp, because it was an amazing sound amp before he started - all he built was the box around it.
    You'll need woodworking tools / skills and a head that already sounds good.

    This is how the pros do it, might give you some ideas.
  4. rohr

    rohr Guest

    I have a good amount of woodworking skill. Any suggestions or is it just personal preference?

  5. dvdhawk

    dvdhawk Well-Known Member

    100% personal perference. If you love the way your buddy's amp sounds, I'd start looking there. Don't forget to ask what kind of speaker he's driving with it. The speaker is an equally important part of the sound he's getting. [and the guitar, and the strings, and the pedals, and the technique]

    Every amp has it's own charms. [That's why some of us have a Mesa, and a Marshall, and a couple Fenders, .... etc.]

    And don't rule out a combo amp (amp and speaker in one cabinet). Down there in the Daytona area, you should be able to check out lots of music stores, pawn shops until you find something you like the sound of.
  6. Kapt.Krunch

    Kapt.Krunch Well-Known Member

    1) He may have done that with $50 worth of material to build the cabinet. He must have already had the amp. Parts to build the circuity of a guitar amp of any kind that puts out any kind of power and "sounds amazing" will cost much more than $50...even if you have a separate preamp. The power amp portion is generally the more expensive section, especially if it's a tube amp.

    2) A combo amp is an amp that has the "chassis" (preamp and power amp sections) and the speaker(s) in one cabinet.The part with the controls is called the "chassis", and usually contains the preamp and power amp sections, unless the pre- and power sections are separate, as some older amps were (pre on top, power amp on bottom, etc.) Then, they are called the preamp chassis and power amp chassis.

    3) A "preamp" is the circuitry that receives the input signal (guitar) takes it from a VERY low signal and boosts it somewhat, through the preamp gain (or simply volume) to the levels at which tone controls, reverb/tremolo/vibrato, etc. circuits can work with the signal to then pass it on to the power amp section, where it boosts it much, much more to drive the speaker(s).

    4) No. A preamp is designed to output low signal to be boosted by the power amp. There is not enough coming out of the preamp to drive a speaker. You need a power amp.

    You could use a rack-mount (Marshall, etc) or a POD-type device to run into a power amp to drive a speaker. A lot of those modelling amps, say a Line 6 Spider, are basically just a POD hardwired to a power amp driving a speaker, in one convenient box.

    Now, there are some things you can do to make a cheap, good-sounding amp. I've done it, and there was a series of articles in Vintage Guitar last year about it. Old tube amps from old organs, radios or hi-fi equipment can be salvaged and turned into pretty cool little guitar amps. But, you have to know what you're doing. Because a lot of what you need is there, all those need is connections changed, some values of components changed, some OLD capacitors changed, etc. BUT, you HAVE to know what you are doing. You can kill yourself messing around inside high-voltage, high current tube amps.

    It sounds like you just want to find a good deal on a decent-sounding combo amp, and make youself a fun little project by building your own cab, and popping a speaker in it, right? You'll have to decide how much power you want the amp to be. 1-5 watt bedroom loud? 15W small gig, low practice loud? 20-35W club, good volume for garage band loud? 40-100W blow-your-face-out loud? You have to find the appropriate power amp and make sure the speaker(s) is up to whatever you throw at it.

    Do you already HAVE an amp that you are thinking of doing this with? If so, what is it?

    One more thing. SAFETY WARNING!. IF you have a tube amp that you are going to use, AND you are removing it from an existing cabinet, be careful about not touching any internal components, ESPECIALLY if it has been turned on very recently. Those big capacitors can store quite a wallop even after it's been unplugged and turned off for while. Trust me on that! We use a large bleeder resistor to ground the positive ends of the electrolytic caps to discharge them before touching anything inside. Shorting with an insulated-handled screwdriver may work OK in a pinch, except it may create sparks and burn marks, and it's not really the best thing for caps to discharge that quickly. It's better to drain them down slowly. IF you are going to do that, and IF you don't know what I am talking about, leave the amp off and unplugged for a week, and then remove it from the chassis, still being careful to not touch anything inside. Or, have a friend over who knows what I mean.


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