Author Topic: Building amps (Read 2347 times)

maverickf1jockey · « **on:** August 20, 2007, 07:22:14 PM »

Have you ever built your own valve amp?
If so could you give, in layman's terms, pointers on what works and what achieves certain tones.
I am also interested in how the THD Hotplate works; is it a transformer or something more complex?
Ideally I wouldn't want to build an amp higher than 50W(RMS)

Oli · « **Reply #1 on:** August 20, 2007, 07:57:51 PM »

I'm going to be a stick-in-the-mud and say that from the questions you ask, that you shouldn't build an amplifier (sorry!).

The number one reason is: Safety.

With tube amplifiers, you will be working with voltages and currents so plentiful that they could kill you many times over. If you are not sure what kind of circuit will create what kind of sound, then (for your safety) you aren't ready to be building amplifiers of that calibre. It is much more complicated that you might think, and if you're thinking that you can build an amplifier for cheaper than say, Marshall, you can't.... believe me, i've considered it myself!

If you'd like to explore the world of creating your own stuff, i'd highly recommend building a couple of pedals- not quite as glamorous as amplifiers, but certainly cheaper and most importantly- safer :)

Not the answer you'd have liked, but you don't want to have a +500v potential across your vital organs!

As for the THD hotplate, it's more complex than a transformer. It's a 'reactive resistance' to emulate the characteristics of a working speaker. Again, i wouldn't advise trying to build one, because you've got to make sure that you can disappate 48W of heat correctly, otherwise you'll kill your amp! The added danger with it is that when you go to test it 'for real' if you forget something, it'll be goodnight Mr.Amp too, but with a THD or equivalent, you won't have that problem.

maverickf1jockey · « **Reply #2 on:** August 20, 2007, 08:14:37 PM »

The reason I asked what circuits achieved what was because I wanted to know. From what I can interpret from your post the fact I don't know prevents me from learning from experience as the vast multitude of pedals are transistor technology - a slightly different discipline.
My motivation was to create an amp to a reasonable quality at a lower price than the retail price of many boutique manufacturers.
Also if I were to do this I would obviously do my utmost to preserve my life and so would follow advised safety precautions. I don't see what experience has to do with things if I am following guidelines set by people more experienced than myself.
I am not after a particularly revolutionary amp design I want to know the pros and cons of each one to create something which fits my purposes as best possible.

HTH AMPS · « **Reply #3 on:** August 20, 2007, 08:27:36 PM »

I'd agree with Oli - learn to read schematics and build some fuzz pedals. This will give you a very good grounding without the danger of the 450v you'll get in a typical amp.

You could try getting a schematic for your own amp and try to trace the conections inside - thats what I did when I dipped my toe into working on valve amps.

:twisted:

maverickf1jockey · « **Reply #4 on:** August 20, 2007, 08:32:43 PM »

It's a nice concept but there is no way I'm going to risk trashing my amp trying to get at the amp chassis (my amp is a combo and has a very awkward cabinet design (tilts back for better projection)).

WezV · « **Reply #5 on:** August 20, 2007, 08:41:42 PM »

i built an amp from a kit with detailed instructions and it worked well, but it didnt teach me how amps worked and how to achieve sounds

if you want to build an amp then start by researching the kits that are available and how many of them will come with detailed insttructions on how to build one. a lot of the kits on the market are 'parts only' without instructions

If you want to actually design an amp you have a lot to learn first, a kit is just an introduction to the practical side of actually putting one together. best go somehwere like the ax84 forum and start reading

http://www.ax84.com/

LazyNinja · « **Reply #6 on:** August 20, 2007, 09:33:00 PM »

I think it's best to start by modding amps before you try building a whole amp. Stomp boxes sound like a good place to start as well.

Oli · « **Reply #7 on:** August 20, 2007, 09:42:04 PM »

Quote from: maverickf1jockey

The reason I asked what circuits achieved what was because I wanted to know. From what I can interpret from your post the fact I don't know prevents me from learning from experience as the vast multitude of pedals are transistor technology - a slightly different discipline.
My motivation was to create an amp to a reasonable quality at a lower price than the retail price of many boutique manufacturers.
Also if I were to do this I would obviously do my utmost to preserve my life and so would follow advised safety precautions. I don't see what experience has to do with things if I am following guidelines set by people more experienced than myself.
I am not after a particularly revolutionary amp design I want to know the pros and cons of each one to create something which fits my purposes as best possible.

Look at schematics, study, compare! Look at the difference between the preamp stage of different amps, Marshall, Mesa, etc. See what differences and similarities there are.

If you are trying to build an amp to boutique specs, then you won't do it at a lower price than say Matamp (for example). Their Little Rock amp (priced at £300 approx i think), is only available at this price because there is no customisation and therefore they can aquire components with a bulk discount.

What you seem to be after is what Wes said, building a kit, then perhaps you can modify it.

Tube technology and transistor technology do have their differences, but the circuit principles behind them both are the same. I would suggest you have a look at RC networks to get an idea as to how tone is shaped.

opprobrium_9 · « **Reply #8 on:** August 21, 2007, 05:14:03 AM »

i second Oli's lucid observation about novice building, however, if you are still interested in the layman's terms, go here (mind you, this stuff is really basic):

http://electronics.howstuffworks.com/amplifier.htm

JamesHealey · « **Reply #9 on:** August 21, 2007, 08:22:36 AM »

learn how amps work, read the tube amp book by aspen pitman, check out the ax84.com forums, also www.thegearpage.net 's technical forum has some great advisors.. I'd firstly learn a few basics.

eg, how to drain capacitors, how to bias an amp using the 1ohm resistor to ground method.

and then start modding the shite out of an already built amplifier something like a JCM800 which has a million schematics out there.

HTH AMPS · « **Reply #10 on:** August 21, 2007, 11:35:36 AM »

If you want cheap (but good) amps to learn on, you should look at old Selmer T&B , Carlsbro or Simms Watts amps. All point-to-point wired and easy to trace the circuit.

:twisted: