#1
I want to build an amp that will sound awesome and distort nicely for metal/rock. Maybe with all the rain I have a good chance at finishing it before my guitar build :O

I looked up the parts, and not too expensive, though I dont know where to buy valve amp transformers in the UK.

Ive been looking up schematics, and they look easy enough to build, Ive worked on HV/mains stuff before.

I dont know what makes a good sounding amp, so are these any good?
http://russ.valve.amps.20m.com/2valve.htm
http://g.landry.myweb.absamail.co.za/uTube2.htm

Id want it to be ~10w power, but still good for practising


Im using an irongear steamhammer pup, if that helps.


Thanks
#2
Either may sound nice, but neither will do metal. Also, neither is close to 10w. The volume difference won't be that much, but your headroom will go out the window.

Check out the Hi - Octane amp here. It may be more along the lines of what you are looking for.

http://ax84.com/classicprojects.html

edited.
Last edited by end_citizen at Sep 16, 2009,
#3
When you say the parts arent expensive Im guessing you havent priced the iron to go in it yet. The PT and OT are whats gonna set you back. Last P/P 10w power amp I built the OT and PT were 70% of the cost in parts.
#5
thanks, I really know nothing about amp design or valves

looks like your right about transformers :/ do they exist in the UK?


If I built a 10w amp, would it still sound good turned down to 1w or is that something that needs to be designed in?

thanks,
#6
http://www.freewebs.com/valvewizard/

Check this site out. The links will have sites to buy parts from in the UK/Europe. It is filled all kinds theory and such.

As for your question: You don't turn it down to 1w. You just turn it down. It will sound different at different volume settings. For metal, you typically don't want much power-tube saturation. For bluesy/classic rock stuff, you'll want that saturation that comes from cranking it up.

^Those are generalities, and are subjective to the individual's desired tone.
#7
thanks thats good.

I noticed some places sell 1:1 isolation transformers for valve use. 240 * 1.4 gives about 300v dc rectified.


so 1) 300v is enough?

2) is there any safe method of skipping the transformer, i.e:
IEC > 0.5A fuse > bridge rectifier > smoothing caps etc..

Im asking this mostly because I dont understand why the transformer is needed if the voltage is right, and to save £30 also would have less sag. Im guessing that removing it would also reduce noise in the amp.

I already have a suitable transfomer to run a heaters from.


thanks
#8
Quote by Kramdra


so 1) 300v is enough?

2) is there any safe method of skipping the transformer, i.e:
IEC > 0.5A fuse > bridge rectifier > smoothing caps etc..


thanks



1) That's about right. It depends on the tubes you plan on running. 300v would run about any tubes, it just may not have enough headroom to have a decent clean sound.

2) I'm not sure about this, so I'll let someone more knowledgeable answer here.
#9
You could skip it, but your only going to be able to get 120 or 240V depending on where you are living, and there are going to be other limitations that will occur. I would not advise it all. You would still need a transformer for the heaters though.

Edit: 300 volts is also pretty low for some tubes.
Last edited by XgamerGt04 at Sep 17, 2009,
#10
You need that transformer. Without it you are running a big risk with your personal safety.


If you want to be "el cheap" here's an idea...
There are lots of xformers out there with dual 12V secondaries and 240V primaries.

Wire the one 12V side to 12 AC, this will be your input voltage, the 12V AC supply to your xformer is your "mains". The 240V connects to the other 240V. Now you are left with a unused 12V tap.

The 12V tap can be used for the heaters (the dual triodes at least.). The 240V that goes into the 240V can be tapped off for your B+. This gives you a B+ of approx 340V DC.

This will give you isolation and a heater voltage.
Btw 340V DC is a great voltage for EL84s, perfect imo. Maybe a neat SE ended design? 5W...
#11
Check out the kit build tutorial in my sig, I walk through the construction of an AX84.com SEL (Single Ended Lead) amp. It's the preamp from the hi octane previously mentioned but with iron for a bigger power amp. It comes stock with a KT88, which is good for 20 watts in single ended mode. You can however use pretty much any type of power tube you want (except the EL84 and 7591 to name a couple of production tubes). I'd recommend trying out a JJ 6V6, JJ and/or Tung Sol 6L6, and JJ KT77s myself. That will put you in the 6-14 watt range.

Get the pre punched chassis and the variable bias option...the "trying out different tubes" thing is a no-go without the variable bias. And the chassis...lets just say unless you have metal working tools, it sucks.
Quote by kcdakrt
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#12
kurtlives91 do you mean using two transformers 240-12 with the second wired in reverse? this would be very cheap.
If I used 240-15 -> 12-240 it would give a slightly higher output too. I would guess most transformers are safe past 300/400v RMS

DLrocket thanks ive been reading your build. The SEL looks good, Im reading the stuff on Ax84 too.

I have metal working tools, almost unlimited supply of alu and steel sheet
Last edited by Kramdra at Sep 17, 2009,
#13
Quote by Kramdra

I have metal working tools, almost unlimited supply of alu and steel sheet



Awesome!
Quote by kcdakrt
DLrocket89 makes my ug experience better!


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Kit Amp Building Tutorial