Question on Amp Technology

[eulogious]

Hello All,

So I was surfing around the net looking at different amp companies because I was bored. I was browsing around JL's site, and came across this tid bit of info:

Until now, the accepted approach for building high-fidelity Class A/B amplifiers has been to utilize "Complementary" output stages, which use different types of transistors to "push" the speaker and "pull' the speaker. The problem with this approach is that true "mirror-image" transistors are impossible to create, leading to asymmetrical clipping behavior. The negative side of the waveform runs out of voltage (clips) before the positive side does.



Another approach is to use the same type of transistor for both push and pull but without buffering from the load impedance. This solves the problem of asymmetrical clipping, but leads to significant increases in distortion as load impedance drops, making this design less desirable (in our opinion) than the "complementary" approach.

JL Audio amplifiers solve the entire issue once and for all with a revolutionary Class A/B circuit that employs identical N-Channel MOSFET transistors for push and pull with true buffering from the load impedance. This is accomplished via a patented circuit that reverses the operation of one of the transistors in each pair to achieve absolute power symmetry and extremely low distortion over a wide range of load impedances.

I then went over the the new Phoenix Gold website (which is really cool if you haven't checked it out. I like it) and was looking at the new TI amps and came across this:

Key Features

Overbuilt Dual Unregulated Power Supplies
Handwound Power Supply Transformers
Ultra Fast and Nasty Power Supply FET's
Isolated Pre-amp Section
Aluminum shaft potentionmeters
Panel Mounted RCA's
1/0 to 4 gauge Power Terminals
Clip Indicators
Extruded Aluminum heatsink with Evenflow technology
Heatsink features 10g per mm of mass
Integrated cooling via endcap vents
Each amp is shipped in its own soft felt protective cover
Audio Precision Quality Control Verification

So this made me think, WTF, I have never heard of this "problem" mentioned by Jl before, what gives? It also raised a few questions.

So to start... This is not a bash on any brand, and I am not trying to single out any brand, I just have a few questions on the components that are used in these amps and the technologies that go along with them. I do not want to start a brand war and get flamed. That is not my intent. The brands used are only for example purposes.

Now that my disclaimer is done my questions

1. Is what JL saying hold any weight? Or does it really just not matter, and it's all a marketing ploy? I am looking for actual facts to back up the answers on this one, and/or reasons why it doesn't matter, and/or even real world experiences between the different technologies, just not opinions please

2. What are the "Ultra Fast and Nasty Power Supply FET's" mentioned on Phoenix Gold site? And can I upgrade to these badass mofo's since I am taking off my FETs today? If I can upgrade I will just throw these bad boys on there.

So not knowing all that much about car amp technology, I am just curious about how the amps really work, and the components that make them work, and that's what spurred my interest in finding out more. I know that there sare some smart people that have talked with/are engineers that have worked with these amps on this board, so having any insight to what makes amp ticks would be great! Thanks!

[Eric D]

As far as the point JL is making, yes it is a valid point, but what they are talking about is something you likely will not hear.

It is similar to thinking that 8ga speaker wire will sound better than 10ga. 10ga speaker wire is so huge, going any larger is just a waste you can't hear the difference.

The counter point to this is that some of the best amplifiers in the world use complementary NPN, PNP output pairs. If JL thinks that this point makes them better than a $25,000 Krell amplifier for example, than they can go ahead and think that.

In the case of the PG point, I am guessing what they are getting at is that a lot of modern FETs can spank those from just a few years ago. So, they are using more cutting edge devices then cheaper "jelly bean" parts off the shelf.

[eulogious]

This is the info I was looking for! Thanks!

I figured that it probably made a "difference", but one that really didn't matter. I have been doing car audio stuff for a while now, and I never heard about this so called problem, which really made me think. That and after opening up my amp while trying to figure out while it's blown, I would like to know more about the technology inside the amp, so I have some understand of what it all does. Up to this point, it was all just "magic"

Is there a special place to order these newer, better fets? I found a stock replacement for my tantrum fets on digikey, but I would really like to order better ones and throw them into my tantrum. Might not make a difference, but at least I will know that the best that I can get are installed in my equipment!

Really glad I found the phorum, it's really filled in alot of the blanks that where in my head about how the amp actually works!

Anyone else have anything else to offer?

[Eric D]

For the most part putting the same FETs in as original is the best way to go. If you replace the FETs with better ones, the driving circuit for them may need to be tweaked. If you don't get it right the amp may overheat, draw too much idle current, or even fail.

Most of the amp technology we use today is 50 years old or so. Companies are always digging up so called "problems", for which they magically come up with solutions. I guess the bottom line is an audio company will only be as successful as its marketing department can make it.

[eulogious]

That's good advice. I was leaning towards doing that anyways. I figured if it was that easy to just "upgrade" then every one would be doing it. I knew that the circuitry had something to do with the equation. Thanks again for the tips!