Designing an amp...

[TKoP]

I was going to post this in the Monolith thread, but seemed a little off topic, but I've got the barebones understanding on what it takes to design a speaker now. What are the issues involved with designing an amp? And what would be the issues with a tube vs. SS. I've seen some kits available and wondered if any might worth the $$.

 

[MakeMineVinyl]

Amplifier design is a huge topic which would take pages (or a book) to adequately cover. I would recommend a Google search for that one.

Generally a kit from a reputable manufacturer will be fine, but really the golden age of good amplifier kits from the likes of Heathkit, Eico or Fisher are long gone. Offhand I couldn't name a current amplifier kit manufacturer, but then I haven't looked for one recently either. You probably won't save much money building a modern kit; its more about the fun of building than saving money.

Unless you have very efficient speakers (over 90dB), you probably don't want a tube amplifier. Efficient speakers act as a magnifying lens for very low level abnormalities in an amplifier like crossover distortion and high order distortion in general. Tube amplifiers have much less (or no) crossover distortion and their distortion components are generally lower orders (2nd, 3rd, 4th, 5th in descending order). Single ended triode amplifiers generally have a strong 2nd harmonic (which is benign since it is a musically related octave), a much lower 3rd, and no crossover distortion since there is only one output tube. Also, single ended triode amplifiers refuse to go into hard clipping. The problem is that they only have about 7 watts of power. Push pull tube amplifiers generally top out in the <75 watt range unless you pay very big bucks.

Solid state amplifiers of course are way less expensive and can easily have hundreds of watts. The problem is that they have no soul, but that's just my opinion!

 

[TKoP]

I kind of thought that would be the case -- and I was thinking more along the lines of a headphone amp vs. a speaker amp. There are dozens of DIY headphone amps out there in ALL kinds of flavors. Was just curious if any non-pro might be able to design a "good" amp. I'd want to do it for the "fun" aspect, but i wouldn't want to do it if it weren't going to be at least "good".

 

[MakeMineVinyl]

I kind of thought that would be the case -- and I was thinking more along the lines of a headphone amp vs. a speaker amp. There are dozens of DIY headphone amps out there in ALL kinds of flavors. Was just curious if any non-pro might be able to design a "good" amp. I'd want to do it for the "fun" aspect, but i wouldn't want to do it if it weren't going to be at least "good".

I wouldn't even consider attempting to design an amplifier from scratch with no specific training as you would have to tackle such fundamental design decisions as 'what transistors do I want to use and in what topology' among other things, and then do all the design math. This is especially true with a tube amp in which there are voltages which can kill you, along with the need to spec an output transformer.

Building a headphone amplifier kit can be just as rewarding, and you know the design already "works", while all the parts are supplied. If you want to get adventurous, you might attempt a build of an amp from a raw schematic designed by someone else (who presumably knew what they were doing....), and maybe modifying it where you feel confident to do so. Parts for something like this can be purchased from Digikey.com, although you would still be on your own for a chassis.

If you do decide to build a tube amp, be very careful about contacting circuits with high voltages. Doing so can cause extreme pain. Don't ask me how I know this....