Anyone with experience building valve amps?

[petemoore]

I'm sure someone out the will have 120/4V transformer.
  I didn't catch 4v for what...if DC, it's not 'too hard' to cobble that using a regulator, you have to watch how much current per regulator and all...

[sean k]

On the nite glow the guy uses a 230/6.3V power transformer for his output transformer. That means the turns ratio is about 30/1 which adds up to 7.6k/8ohms but to be able to do that in the States or Canada, or anywhere else with 120 VAC in the wall you'll need a 120/4 transformer... or a 120/3 with a few windings unwound.

[g.]

beware... some radio power transformer were autotransformer and are not safe.
just check if the widings are isolated...

you can use output transformer from small SE (el84), the  6BM8 pentode section is a kind of 6BQ5 (small el84).

[Brymus]

Thats the first thing you need to do is figure out what trannies you have what the windings are.
Then decide if you wann use those tubes or if you can use your trannies with something else.
A single ended amp with two tubes is quite simple.
The Hammond 125 ESE is a good OT or the 125E has alot more windings and ways you can use it.Push Pull even single ended.
If you are just gonna scrap everything but the chassis why not sell it and use a new blank chassis?
Lots of options.
Try SEWatt.com http://www.sewatt.com/forum  for schematics of simple amps using tubes and all the info you need to build one.
You have to register but its one of the best amp sites IMO
18 watt.com http://www.18watt.com/  and the amp garage http://ampgarage.com/forum/ are two other excellent sites but geared to more complex push pull designs by Marshall (18wattcom) and Ken Fisher and Dumble (theampgarage)
You can build a modded Valve Jr - Champ type amp fairly cheap try AES for trannies and tubes http://www.tubesandmore.com/

[davent]

Last year i built a little SE amp based on the Fender 5f2a to use as a tube/pedal auditioner. Two knobs, volume/tone, two tubes and stays fairly clean depending on how hot the guitar pickups are. The schematic i followed was at Steve's diy guitar pages but that site seems to be missing. I put in parallel preamp sockets so can audition 12a_7 family of tubes, 6s_7 tubes or 6eu7's. Actually did a lot of mods but the stripped back basic circuit is a nice simple good sounding building block or jumping in point. Here's the basic 5f2a, ditch the tube rectifier and replace it with solid state to simplify and lower costs further. http://www.freeinfosociety.com/electronics/schemview.php?id=802

Another well documented build is the P1 and P1x at ax84. Good forum there as well.
http://ax84.com/p1.html
http://ax84.com/static/p1/AX84_P1_080708.pdf
http://www.ax84.com/bbs/index.php

One that got a lot of attention at Sewatt is the Jones Octal One which i think is based on a Fender 5c1. Uses a 6sj7 for the preamp and your choice of octal power tube.  http://www.freewebs.com/jonesamps/JonesOctalOne.pdf  Is suppose to remain fairly clean and work well with pedals. Sewatt has a forum for the Octal One, may have to register to see it?

http://www.sewatt.com/octal-one

Other Jones schematics. http://www.freewebs.com/jonesamps/jonesampsschematics.htm

dave

[StarGeezers]

  We've built 2 Octal Ones , which we gig with (miked)... Really a Great sounding amp!!! For more gain we replaced the 6SJ7 with a 6u8A and have some Killer Tones... Built 2 of those also ... Pretty easy  The discussion is at www.Sewatt.com   Octal One / replacing the 6SJ7    Great little Amps ... and cheap to make too...

[doitle]

Cheap you say? That's music to my ears. I am really interested i attempting to build something and modify it and learn from it but I dont have much money to spend on the hobby. I'm a college student and have a minimum wage job to pay for food and rent.

[StarGeezers]

I'm Retired... sorta' in the same boat ...hahaha

[GREEN FUZ]

The problem with these " can anyone suggest/recommend" threads is you`re left reeling with so many choices/decisions. Several interesting options here.

[StarGeezers]

 Sorta' like women ... Pick one , then deal with it ...    hahahaha

[GREEN FUZ]

Story of my life .

[brett]

Hi
Single ended (or Class A amps) are very inefficient.  A small push-pull amp will usually be a better option.   The Firefly is cool (12AU7 output valve), but is low power (1W).  A good way to get into valve amps might be to start with a second hand Epi Junior (Class A EL84 amp) and modify it by adding stuff like a tone control, power soak, better filtering and output transformer.  Once familiar with valve amps, you might as well build something classy, like the 18W lite (see www.18watt.com).  Kits are available.  The results are a serious good vintage amp (of 10 to 20W output).
just my 2c..

[petemoore]

   Yupp...I've built some nice amps !
  Still I'm always looking for those nice big [free] transformers.
  I remember seeing stuff like that in dumpsters...aughhh.
  Time to check C-list 'free' again ! There was a free organ but it was a long ways away, I don't know if it'd fit in a Camry.

[GREEN FUZ]

Hi
Single ended (or Class A amps) are very inefficient. 

I`ve heard/read this before. In what respect? Current consumption? Overheating? How does this inefficiency effect the sound? Am I starting to sound like Walters?

Once familiar with valve amps, you might as well build something classy, like the 18W lite (see www.18watt.com).  Kits are available.  The results are a serious good vintage amp (of 10 to 20W output).
just my 2c..

Sounds great and hopefully something I can work up to.

[Boogdish]

Class A consumes more current while idling and has a smaller current swing from peak to peak of the output signal.  In addition to this, the output transformers for single ended amps are almost always bigger, heavier and more expensive than a push-pull transformer of the same power handling.  I've recently come to realize I'm bad at describing sounds, but to my ear the distortion of single ended Class A amps is harsher than push-pull.  For clean stuff, single ended class A sounds really good.


All of that aside, I think a champ or a tweed princenton is a great first build.  There's a lot less than can go wrong in one of those and it can really boost your confidence.  Put it in a chassis with plenty of room and you can expand on it as you learn more about amps and want to try new things.

[Derringer]

as I said before ... and I'll elaborate a little too
keep this ASAP ..... A(S)impleAP
gut what you have there and get some parts that you know will work


don't worry about Class A being less efficient than class AB ... more inefficient how? Less Tones per standard based Mojo? What? Don't worry about it ... doesn't factor in here.

I'd recommend that you go Class A, relatively simple to build, sounds unique. Get transformers that you KNOW will work ... don't be basing a project like this on a lord knows how old and operational tranny when you can just get a known working one designed for the specs you'll need to run 1 power valve and one Pre-amp valve,

I'd completely recommend trying to build a AX84 P1 into that enclosure. You'll want to build bigger and better afterwards which is what this is all about anyway ... right?


Enjoy!

[g.]

I'd recommend that you go Class A, relatively simple to build, sounds unique.

+1
SE are nice

[Derringer]

I retract my suggestion of the P1 ... I just realized the size of your chassis. The Xformers for the P1 probably won't fit there very nicely.

You'll need to find a project with a small enough topology.

[brett]

Class A (single ended) amps are great.  But you can't use a power transformer for the OT.  Nor anything that you can easily build yourself.  It has to be gapped.  I have built several OTs, and I'm familiar with the maths, so it wouldn't bother me, but generally you'd have to be very keen or mad (or both  ).  SE OTs are rather expensive, even for low power ratings (and here in Oz we pay about 2 x the US price!!).

[GREEN FUZ]

Class A (single ended) amps are great.  But you can't use a power transformer for the OT.

This guy managed to do it but I must admit a lot of this stuff is over my head so I couldn`t say whether or not it was accomplished with ease.

http://enginerdamps.blogspot.com/2009/02/gibson-les-paul-junior.html

...SE OTs are rather expensive, even for low power ratings (and here in Oz we pay about 2 x the US price!!).

Yes, I`ve been finding that out. This isn`t going to be an overnight project for me but I`m narrowing down my choices to either a Champ/Angela or one of the Octal variations. Or...