i might build a class a amp

[cream123]

should i build from scratch or build a kit

with all the stuff i want i might need to build from scratch!

hi, as you can tell i'm new to making amps, as in i've never made one before. does anyone know of any SIMPLE kits to make a class a, 30 watt, with 1 speaker output amp head with 2 12ax7s and 2 el34s somewhere along the lines of an orange brit amp i.e. anywhere from creamy distortion to a nice crunch to a nice grit and a good clean. i know it's a lot to ask and i know i won't get it all. maybe i should just build from scratch

edit: and maybe tube reverb
and possibly a dist and a clean channel with eq



I KNOW THIS IS WAY TO VAGUE TO ANSWER COMPLETELY!! PLEASE BEAR WITH ME AND TELL ME WHAT I NEED TO KNOW
NOT ALL OF THE THINGS MENTIONED IN THE EDIT ARE NEEDED!

 

[JumpMarine]

Re: i might build a class a amp

IMHO, you will be much better off building from a well documented kit like Mission Amp's 5E3 Tweed Deluxe. Fairly priced, great quality componants and even better customer service and instructions.
Check out these sites for TONS of info:

www.missionamps.com
www.18watt.com
www.tedweber.com
www.ax84.com
www.trinityamps.com
www.firebottle.com

 

[flank]

Re: i might build a class a amp

you need to do alot of research man. seems like youre in way over your head at this point

 

[firebirdVII]

Re: i might build a class a amp

should i build from scratch or build a kit

with all the stuff i want i might need to build from scratch!

hi, as you can tell i'm new to making amps, as in i've never made one before. does anyone know of any SIMPLE kits to make a class a, 30 watt, with 1 speaker output amp head with 2 12ax7s and 2 el34s somewhere along the lines of an orange brit amp i.e. anywhere from creamy distortion to a nice crunch to a nice grit and a good clean. i know it's a lot to ask and i know i won't get it all. maybe i should just build from scratch

edit: and maybe tube reverb
and possibly a dist and a clean channel with eq



I KNOW THIS IS WAY TO VAGUE TO ANSWER COMPLETELY!! PLEASE BEAR WITH ME AND TELL ME WHAT I NEED TO KNOW
NOT ALL OF THE THINGS MENTIONED IN THE EDIT ARE NEEDED!

I think that that would be a class AB amp.

 

[cream123]

Re: i might build a class a amp

yeah i'm going to do A LOT of research!

 

[missionamps]

Re: i might build a class a amp

There is much debate over this subject and statements but one of the things you have to keep in mind with Class A amps is that in order to keep the PA (power amp) section running in Class A, you must also limit the amount of drive to the PA.
This is a simple matter of tweaking the preamp section so that it can not develop enough signal swing to drive the PA out of Class A.
With respect to your preamp section, (including a phase inverter if you chose to run Class A push pull), you'll need to set it up so that it can never swing a negative going signal so far down that it can cut one tube off for any part of it's full 360 degree swing... if it does, that is the defintion of class B.
Since there would be two tubes in push pull it is called... Class Ab.
Absolutely nothing wrong with that either, it just isn't really a true Class A amp anymore.

The ability of the Class Ab amp to allow one tube to be cut off for a little bit of the cycle also means you can drive both tube higher for more ultimate output compared to a Class A amp. Yes a tiny tiny bit of more distortion but it is really minimal if set up right with good transformers and proper tube balance.
Why does the Class Ab amp make a little more power?
Because the cutoff tube has a chance to momentarily cool and rest.
Wattage and current ratings of power tubes are DC ratings, not the actual AC (audio in this case) output!
This is a very common misconception and notion.
You can, in fact, build a Class Ab amp with proper forced air cooling where it can easily make 160% of it's DC rating in output power.
That means two EL34s, (rated at only at 25 watts each), actually can run almost 80 watts output.
More so if you want to set up a Class B amp... but more difficult because of the cut off and subsequent distortion.

In truth, 25 to 30 watts Class A with two EL34s is probably at or maybe just above their max clean output power limit in most homebrew amps.

For you though, I would recommend a cathode biased Class Ab amp.
Build it using larger power and output transformers with the power tubes idling higher in DC current so it sounds similar to a true Class A amp.
A pair of EL34s with in cathode bias with about 420vdc on the plates would be fairly easy and it can be done with a 150ma PT, 3k4 to 4K OT, solid state rectifier , a pair of 12AX7s and very little negative feedback from the OT.
What to build?
A simple but modified, cathode biased, single channel black face Deluxe with EL34s, Vol, Treble, Middle and Bass comes to mind.