#1
Im building a solid state amp out of e-waste. I have a nice cab scavenged from an old record player box and some kia door speakers. It sounds really good for guitar. Now i need suggestions on parts to look for to make a guitar amp. The volume i need is something just above talking level. The budget is 0. I have a whole junk yard of e-waste. So phones, radios, computers, tvs, antennae amplifiers... is there any old, post 80's, technology that can easily be hacked to make a guitar preamp? If i can produce a line level, an old stereo or radio can be the power amp.
#2
Open up the radios and antennae amplifiers (pc sound cards?) - look for discrete transistors/resistors and op-amp IC chips. You also want the capacitors and diodes for effects (simple cutting distortion switch). Capacitors should be grounded (they will spark) to remove charge before you start dis-assembly. I assume you have a power supply taken from one of these things that already goes ac-dc and drops the voltage.

Once you have a gauge on what components you have (check component numbers online) you should be able create a pre-amp from a circuit diagram (search google images for something like "solid state pre-amp schematic").

For further reading check out "Art of Electronics" book- a very comprehensive guide.

If you can tell me more about what components you actually have i can design you a circuit and offer more advice.
#3
Thanks for the info. Im fairly novice at electrical engineering. It does seem like building a circuit would be fun and these designs are fairly simple. It will take me awhile to study up on the components. I wouldn't at this point know exactly kind of parts to tell you about but thanks for the offer. I do have several sound cards from old 90s computers, an old pa amp. Several stereos and component stereos, some defunct record players. But i dont know much about the components yet.
#4
The PA amp and the stereos will contain a pre-amp stage you could remove, or you could use the whole thing if it still works. Though it may be a touch noisy compared to a dedicated pre-amp. If you tell me what resistors and transistors you have I can knock out a quick amp design for you, be careful when using online pre-made schematics as they will not necessarily be designed for the components you have and can cause problems.
#5
I'd start walking around your junkyard and start grabbing all the transformers. Those are the number one thing worth salvaging in old amps. I've never messed around with using the preamp section of a hi-fi amp for guitar, I'd rather scrap the components and build something new. Check for old tubes too, even those can go for a bit of money if they're operational. I've bought an oscilloscope recently, it has a really old nice sounding 12AX7 in it. Put it in my amp and it really cleared up the glassiness and ice picking that I was getting.

Some PC sound cards will have Gold Capacitors in them, these are probably worth salvaging. I've heard of people scrapping the gold plated connectors as well.
Small PC heatsinks are worth keeping.

I guess really when scrapping, the imagination's the limit provided your junkyard is big enough. If you happen to find a Yamaha CA-610 let me know, mine recently committed suicide.... Could use a few parts.
..I was watching my death.
#6
The only tubes i have are from a 60s knight star roamer but i want to get that going again as it looks like a really cool radio but it doesnt work. It makes a really strange noise. Almost no sound comes out of it but i can tell the speaker is on as it makes a very low volume hum and some crackle but when i power it off it makes a noise like a pure tone that raises in pitch until it cant be heard any more. Cool sound but not a working type sound
Last edited by geo-rage at May 25, 2016,
#7
So found some transistors, they start with a funny f and are numbered 2n4356 b38
2n43568 846
848
2n5133 b44
2n513 843
844
Whats it all mean?
Also found a cool looking canister labeled 50uf40v- and 50mfd40v-
#8
The 'canisters' are capacitors rated at 50 microFarad 40 volts, and 50 milliFarad 40 volts. The numbers on the transistors indicate the type, you've got two 2n4356s, a 2n5138 and a 2n5133, also the 848 might indicate a bc848 (not sure about the 844 by itself??); the trailing numbers indicate more specific models and manufacturers (mostly irrelevant). If you want to find out more you'd have to search for the datasheets online.

I'll design you a circuit tomorrow (UK time) if you'd like which will give you a simple amplifier. You never stated though what resistors you have though.
Last edited by choonoo.lunn at May 26, 2016,
#9
The 844 is a 2n513 844. The 848 is a 2n43568 848. It made more sense before it got formated. There are a lot of resisters. Im sure if you design a cicuit i could find a resistor to match. Wouldn,t that be easier on us all it would be nice if the power supply was a 9v battery. If you want to wait until ive cataloged the resistors, i can do that. Edit... would you want color codes or resistor values? I just opened a can-o-worms trying to id all these resistors how in the world do you tell which end to start with when color coding? The internet tells me there should be a group of 3 to start with and then a space and one more band to end with. A lot of these resistors are all equally spaced. I hope im not causing you grief here.
Last edited by geo-rage at May 26, 2016,
#10
Ok so assuming that the resistor code starts with the color stripe touching the edge of the cylinder and ends with the stripe not touching the other edge, here goes.100ohm oh all are ending with 10 percent... 1kohm, 2.7kohm 47mohm, 8.2kohm, 220ohm x 2, 10kohm, 470ohm, 150ohm, 150kohm x 2, 160kohm. Also there are some orange drop looking caps 1kv and 1kv 25f and some larger square shaped thingies with 2 leads. 2 reds with black orange stripes and yellow with purple yellow white red and maybe pale yellow. Are these caps? Also there are two very large coke can sized capaciters, dont know what they are. If i have to list ever component in this amp, there are 20 more to go, at least by the end i might know one from the other
Last edited by geo-rage at May 26, 2016,
#11
i think you may be over your head a bit. research theory and circuit design.

the are a lot of good books out there. maybe check a library?
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#12
Had a lot of work to through today so wasn't able to design a circuit yet, thanks for the info on the transistors and resistors, I'll try to design something relatively simple for you, and a 9V battery power supply should be doable.


edit: Your readings for the resistors sound right, some can be difficult to read when they screw up the printing for the lines.
Last edited by choonoo.lunn at May 27, 2016,
#13
That would be awesome. Yeah 9v batteries are not as deadly as mains power though i trasformers are easy to find....well the small stuff. You know i run a lot of stuff on 12v dc solar panels. Thats also an option for a power source. They put out enough to run a good 40 watts.
Im thinking a record player should have a preamp in it that would work for guitar. It might be in the amp part though.
#14
If the record player contains a pre-amp sure, go ahead and use that. There isn't really very much difference between a normal amp and a pre-amp (just when they're used) so you could run a full amp into another (I've done this for a special boost pedal I built).

The design I'm currently working on may have a touch of distortion due to the parts limitations, but if you read up on a circuit design/theory you could learn how to build some really great stuff quite quickly. FYI you say you don't want to buy anything, but you can buy circuit components for pennies online should you wish to do something more adventurous.
#15
Right and i might have to to complete a build but the idea is to make it all out of scrap. I noticed that all my resistors are 10percent and the ones called for on a schematic on the net are all 5percent. What do you think? is the kind of different that makes a thing not work?
Last edited by geo-rage at May 28, 2016,
#16
The 10%/5% is just the tolerance (how much the real value can vary by) 10% is virtually 'nothing' in most circuits. Just to let you know, 2N4356 transistors are MOSFET, they're less useful for normal amplifiers.
#18
Quote by geo-rage
So what are the good kind?


do some reading. you lack the knowledge to complete this project at this point.

not being mean, just honest.
WTLT 2014 GG&A

Quote by andersondb7
alright "king of the guitar forum"


Quote by trashedlostfdup
nope i am "GOD of the guitar forum" i think that fits me better.


Quote by andersondb7
youre just being a jerk man.



****** NEW NEW NEW!
2017-07-07 2017-07-07 Update and a Chat On Noise Constraints *** NEW FRIDAY 7/7
2017-04-13 RUN AWAY from COMPUTERS!!! TCE? RANT ALERT!!!
2017-03-02 - Guitar Philosophy 1001- Be Prepared For the Situation (Thursday 2017-03-02)
2017-02-21 How to Hot-Rod the Hell of your Stratocaster for $50! (Tuesday 2017-2-21)
Resentments and Rambling from a Guitar Junkie
---> http://trashedengineering.blogspot.com/
#20
What I would do, if I were you is buy a ready made amplifier kit. Then you would have a design you could then copy/modify plus the actual experience of building one. Most of them are real cheap and usually the cabinet is optional, so if you already have something you could use as a cabinet so much the better. I have seen these for right around $20 before. At least you would have a proven design that you know works to look at and learn from.
#21
I've been busy recently, but got most of the way through designing a 3 transistor class A-B push-pull amplifier (google it). I've not had time to do analysis yet though so no idea on how well it will function.
#22
I got it working though. Used a rms 1w 9v amp. Sounds good.
Last edited by geo-rage at Jun 8, 2016,
#23
Does it use a mosfet? Thats what they were using on a lot of google returns.
#25
If you draw it i'll try to make it. Im starting on another amp. This time with components. Its not as artistic as making an amp from a telephone but still fun. Hopefully one will sound good. The last one sounded pretty bad to my ears but then i tried out a blackstar micro amp and it sounded similar, so who knows. People like that answering machine in an ammo can sound.
Last edited by geo-rage at Jun 10, 2016,