My First Big Amp

[citizen_insane]

After having enjoyed building the CMoy and SOHA amplifiers, I'm now getting the itch to try something with a little more power. Specifically, a tube preamp/poweramp setup to drive my Infinity Primus 250 speakers (recomended 10-150watts, although I think I'd go for 2x100W, I don't need to bump hard or anything). Now I know they arn't super high end and that any old consumer amp will do fine, but I'd like the experience of building my own amp and it'd leave options open for building some high end speakers in the future. Now the problem, I'm a student and I don't have a lot of money. Are there any good, reasonably cheap, designs that people here would suggest? I'm a little overwhelmed by the number of designs discussed here and since I don't know much about amplifier design, there isn't really any way for me to determine what's good and what isn't.

[SY]

To do a high power tube amp with any chance of success will take some significant money (good output transformers are expensive and the inevitable smoking of some power supply components will also dent the bank account) and two or three intermediate-level tube projects under your belt.

Preamps are a different issue. Lots of good designs out there, but to narrow the choices, start with defining your requirements (how many inputs, what level, how much gain...).

[SHiFTY]

A good place to start is around 25-40 Watts. This will put you in the territory of something like a Stereo 70 Dynaco. You won't need 100W as "tube watts are bigger"!

For those speakers, you want push-pull, Pentode/Ultralinear, using EL34/KT88/6550/6L6GC tubes.

I would recommend restoring a vintage amp, or building a kit of some kind, scratch building is pretty hard to get right first time.

Make sure you read the safety thread.

[Original Burnedfingers]

A good place to start is around 25-40 Watts. This will put you in the territory of something like a Stereo 70 Dynaco. You won't need 100W as "tube watts are bigger"!

I find in my playing with SS amplifiers verses tube amplifiers is that a 60 watt tube amp seems to keep up nicely with a 200 watt SS amplifier.

Just my .02

[citizen_insane]

Originally posted by SHiFTY
A good place to start is around 25-40 Watts. This will put you in the territory of something like a Stereo 70 Dynaco. You won't need 100W as "tube watts are bigger"!

For those speakers, you want push-pull, Pentode/Ultralinear, using EL34/KT88/6550/6L6GC tubes.

I would recommend restoring a vintage amp, or building a kit of some kind, scratch building is pretty hard to get right first time.

Make sure you read the safety thread.

I will def read the safety thread before the build to remind myself what not to do

I don't really have any problem working from schematics, and unless a high level of amplifier knowledge is required just to make it work, I feel I'd be perfectly comfortable jumping straight into a completely DIY project. Are there any schematics for the amps you suggested that are quite good you'd recomend?

Thanks!

[citizen_insane]

OOps, almost forgot you SY! (Mods - I tried to edit my previous post, but couldn't figure out how, sorry for the posts right in a row)

In regards to inputs, I'd like to have 3 inputs, 1 for my computer, 1 for random Aux (mp3 player, cd player, etc) and 1 phono. I assume I'll probably have to build a phono preamp in order to get any worthwhile sound out of my record player.

[SY]

OK, then if you plan to have your power amps require 1-1.5V for full power (a bit more sensitive than average), you can just use a unity gain linestage. There are a lot of good designs for those running around the web and in standard texts. It will also be the least critical bit, so a good place to start.

I'd build the phono stage as a separate bit, and do it after you have the line stage up and running. A good quiet phono stage is one of the most difficult things to design and build properly, so it's best to go through higher level grief as a learning experience before tackling that one.