ad_smith

hi, i am looking to make an amp head for a 16 ohms speaker in an amp cab i made. i dont know anything about electronics but when i get decent plans i can easily follow them and put it together (its something i was born with i think :P ) (plus i have a freind doing electronics at university whos coming back soon and im gonna get him to give me some pointers)

i am looking to make a valve amp with basically just a volume switch, treble and bass. i would also like maybe a tremolo but that might asking a bit much.

anyways, ive had a good search around the internet and found hundreds of plans but there all to complicated for me. what i was looking for was a plan that has the curcuitry set out as if it were just a drawing of what the inside looked like in real life with just some markings on it like, what the valves are and where they connect to, things like that. i have attached a rubbish picture i drew to give an example of what i mean.

this may be asking a lot but if anyone can help i will appreciate it alot

thanks
adam[/img]

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Johnson777717

I'm not too sure that you're going to find a layout diagram for an amp. That doesn't mean they aren't out there, it just means that I haven't seen too many.

The great thing about schematics, is the opportunity to layout the components yourself, keeping with the schematic. This allows you to provide your own customization. Most circuits are pretty flexible as to how you layout the design. Of course, kind of like a race, you're trying to find the shortest distance between two points to reduce resistance, signal distortion, space etc. After you're done, you can truthfully say that you did some design work on the circuit!

Are you familiar with the schematic symbols, and what they represent? The basic symbols are pretty easy to pick up. You can find a pretty simple and downloadable reference here:

http://www.aaroncake.net/electronics/schem.htm

Most of the schematics that I layout take a few revisions. I can compare it to a school report, where you start off with a rough draft, then make improvements, then review, then improve, then review, then improve, on and on until you can't find anything to improve. Then you can build it.

Johnson777717

Also, if you find a schematic that you like. I'm sure you can post it here, and someone may be kind enough to do some layout design with you. Hint Hint. :wink:

mozikluv

i believe what he really wants is a parts layout diagram with a corresponding foil track layout. you will usually find this kind of set-up in the manufacturers datasheets of Sanyo, Tripath and several others. :lol: this is a kind of set up where you don't have to fully understand what you are doing, just follow the parts placement and voila its done. :cry:

__________________
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ad_smith

i am looking to make a jcm 800 head amp. in the schematics ther is a switch for 4 ohms, 8ohms and 16 ohms, so this should work with my speaker cab.

ive looked closely at the schematic and i've got to grips with some of it like the power socket, ground wires, resistors, diodes but thats about as far as i got.

im really looking for info on how to set it out and what wires connect to what bits of each component

i have 2 diagrams of the jcm 800 (its the complete thing i think but in 2 pdf's)

http://www1.korksoft.com/~schem/mars...s/2204_pre.pdf

and

http://www1.korksoft.com/~schem/mars...s/2204_pwr.pdf

i need to be able to build this without using a pcb coz i havent got the resources to make any.

i am in england and our power rating is different to yours so that needs to be taken into consideration.

if any could shed any light on the matter i would appreciate it very much

cheers
adam

Nigel Goodwin

Valve equipment was made for years before PCB's were used, it's quite easy to do. First you need a metal chassis, either aluminium or steel (aluminium is easier to work). You mount the heavy components (like the transformers and choke) on the top of the chassis in suitable positions, and cut holes in the chassis for the valve holders - special punches used to be available for this. You can then simply wire all the components underneath the chassis from pin to pin on the valveholder sockets. Where there's not enough valveholder pins you simply bolt pieces of tag strip in place to hold the component connections. An alternative method of construction (slightly later) used tag boards, rather than tag strips, with the components mounted across the tag boards with wires to the valveholders.

It would perhaps be a good idea to plan it out on paper, before you start cutting holes.

Your biggest problem is likely to be be the transformers and choke, these will be VERY expensive - probably more than you could buy an amplifier for!.

As for being in England (if you filled your location in, we would all know already! - amazing how many people don't though) it's not a problem at all, the only difference is the mains transformer primary - and most of these types of transformers are dual primary anyway.

ad_smith

if i could make it for around £200 that would be about my limit. if not then i could look for something more basic, just something with a volume, treble, mid and bass control, input jack then output jack to connect to my cab.

how much am i looking at (in £'s) for all the bits for this?

Nigel Goodwin

The circuit you posted the link to was pretty basic already, a standard 50W valve amplifier. The expensive bits (as I mentioned) are the transformers and choke - you need to find a source and price for those before you do anything else - I would think you're probably looking at £100 upwards or so. There are various valve parts listed here http://tubeampdoctor.chw-computer.ne...hp?language=en, which may give you some idea of the prices of parts.

Next most expensive parts are the valves themselves, again price them up beforehand - particularly the EL34's.

All the other bits are going to be fairly cheap, as I said, the transformers are the killer!.

BTW, if you want to see a homemade guitar amp, have a look at http://www.duncanamps.com/dds2250v/dds2250v.html - the pictures of the underneath show the point to point wiring I mentioned, although he has used some PCB's as well (probably for the semiconductor parts he used).

ad_smith

what bits from the jcm 800 can i buy from that site, and what are the names of the valves and any of the other bits i can get from there?

Nigel Goodwin

I think you can probably get the valves from there, I only posted that link as representative of the sort of prices things are. Presumably, if are wanting to build an amplifier that sounds like the JCM800, you will need the correct transformers for it - the output transformer in particular makes a big difference to the sound of a valve amplifier.

BTW, I never asked - I'm presuming you are wanting it for lead guitar?.

ad_smith

yeah i play lead guitar. i really want an amp that gives me a really clean sound and then i can put my effects pedals down and get my different sounds from that.
i just join a band that play all this new punk and new metall guff, but i would like an amp head that would be well suited to playing dave matthews, radiohead, jeff bucley and the like.

do you know what the name of the valves i need for a jcm 800 are and what transformers i will need?

Nigel Goodwin

The output valves are two EL34's, the phase-splitter is an ECC83, and the preamp uses two more ECC83's.

A quick web search found this site http://www.shinrock.com/Audio-Transf...ransforma.html which lists the transformers at 90 Euros each.

aevans17

If I were you I would leave the amp building up to the pros. For the amount of money you will spend on building your head you could easily buy a good used 50W head, or a brand new AMP.

Here is a 50W Marshall halfstack for $300 on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll...category=38075

Here is a 100W Marshall Head for $60 also on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll...category=38075

Besides AMPs are hard to build, and that's not even talking about an amp that sounds good. If you already have a cabinet that you built great. I play guitar too and I know that there's a thousand people out there that will tell you their amp is the best, and 1000 more who will tell you 1000 reasons why those thousand are wrong. But here is my 2 cents about guitar amps. TUBES are the BEST!!!! Solid state sucks!!!!! If you can afford $350 dollars then buy a fender blues jr, or the simpler fender pro for like $250. If you want to play metal and need the overdrive buy an effects pedal and put it in front of one of the amps I mentioned above. If you can afford more then buy a tube marshall head and then whatever cab you think is best. My fender blues jr. is only 15W amp and it easily competes with my friends 60W Crate.

Here is a fender pro jr combo from musicansfriend for $279 and I'm sure you could find one used for less.
http://www.musiciansfriend.com/srs7/...se_pid/480861/