Hay, I consider building an SS amp which has the randall rg-80 red channel and a Fet twin as clean. I haven't chose a power amp yet.
1. Can I use any power amp after any preamp or do somethings have to match?
2. From reading Temmu's book I got that a transistor power amps are better then a chipamp but are harder to built. Is the hard work worth it?
3. This question is not really connected but I still ask her: I have a problem with debugging stompboxes. I can't understand how to do it can anyone point to a simple guide?
1) Basically "all power amps are the same", may vary somewhat in sensitivity.
2) Discretes by definition can be more varied, but unless you need something very specific, chipamps are great.
3) That question is very general, there's not a single answer, but basically you should first check that it passes signal , even if "unprocessed" and then analyze what it "should" do to it and why it's not doing so.
No reason not to use a chipamp other than discrete transistor amps look cooler. Chipamps are compact, function extremely well when built properly and sound almost identical to their discrete counterparts. Keep it simple, use an IC (chipamp).
Okay thanks. And do I have yo use a chipamp circuit that were designed for guitar amplification or just any project will do?
Basically all published chipamps are Hi Fi types, fine for guitar because you will basically create your own sound on the preamp and then faithfully re-amplify it.
Most "chip amps" are basically just opamp style circuits with the difference that they can handle more power than an ordinary low current, low voltage opamp. So, a chip amp - like generic opamp - is a rather simple "function block" that lends itself to many applications. The circuitry you wrap around them defines how "HiFi" the resulting amplifier be. Many of Peavey's Transtube / Vypyr amps, Vox Valvetronix amps and even Pritchard amps are based on a simple chip amp but all the extra circuitry makes them very different from generic HiFi designs.
It's really not an issue of what's best and what's worse. Chip amps are an excellent solution for a great deal of applications and especially shine out with their simplicity, which still lends into offering complex features like protection circuits and reliable thermal tracking in a single, very compact package. But they have some inherent problems too:
- You can't really access their internal architecture. The design is what it is and there is virtually no way to tweak it.
- They tend to be limited to moderately low power applications. eg. You will have hard time finding, say, 150W - 1500W chip amps. You can naturally bridge and/or parallel connect several chip amps but in many cases this is not the most optimal or even easiest solution to implement. If you need higher power you likely need to use discrete circuits.
- Chips may become obsolete. Once it's out the market, the only way to fix an amp with that chip is a total rebuild, something often not possible or worth the effort. In discrete solutions obsolete components more likely have a similar substitute and no total rebuilding is required.
- Chips may have inherent design flaws that are impossible to fix. See point one. The TDA729x series is a notorious example: a very fragile chip that easily fails in many circuits. Hardly anything can be done to prevent it since it's totally impossible to modify the chip's internal architecture to fix the problem.
Okay, and which chipamp is usually recommended to use for getting about 50-100WATT?
LM3886 or LM3876 seem to be a common solution to 40 - 70W range
TDA7293 or TDA7294 seem to be a common solution to 70W - 90W range
But there's plenty more of them too. Try Google.
In range > 100W the best choice on my opinion is LME49830+power mosfets.
http://www.national.com/ds/LM/LME49830.pdf
http://www.national.com/an/AN/AN-1850.pdf
http://www.national.com/an/AN/AN-1849.pdf
LM3886 is a tried and true chip faithfully putting out better than 50w on 4 and 8 ohm. They're cheap to boot which is also nice.