[Early B.]

I think you can get about 10 or 15 watts of class A out of most big Amps before they switch into A/B in solid state.

Is there a way to determine how many watts an A/B amp is biased in Class A? There are instances where you can't ask the manufacturer.

Also, how do you determine how many watts you normally listen to? Not sure I asked the question correctly.

Finally, if an amp continuously see-saws from Class A to Class A/B and you can't tell when that change occurs, then why does Class A supposedly sound superior?

[Freo-1]

Is there a way to determine how many watts an A/B amp is biased in Class A? There are instances where you can't ask the manufacturer.

Also, how do you determine how many watts you normally listen to? Not sure I asked the question correctly.

Finally, if an amp continuously see-saws from Class A to Class A/B and you can't tell when that change occurs, then why does Class A supposedly sound superior?

 
Because Class A does not have any crossover distortion:  (From an earlier post)
 
 
“ Class A does not have the crossover distortion of AB. Designers use feedback (local or global) to eliminate that form of distortion - but since feedback takes some time in order to come into effect - you get some "open loop" crossover distortion in a transient that a simple measurement won't appear - but may be very apparent in the time domain. The sound will be DE-sweetened vs. a class A. That is a rather large effect. There are other effects surrounding things like device parameters (input capacitances, diode effects, etc. depending upon the device used) that behave much better with class A than AB. Also there are a couple of ways of handling the bias of class A. If the bias is "open loop" then on peaks it can break into AB (though the gain can drop a bit unless you wrap feedback around it and play games with bias level) which can affect the sound.”

[richidoo]

There are other ways to reduce AB crossing distortion besides feedback, and it can be reduced to extremely low levels. The ease is gained without the "warmth" or heat, and without the feeling of suffocation in some high feedback SS AB amps.

The lack of crossing distortion is responsible for the feeling of ease common to class A amps. The midrange fatness and treble glow is due to the relatively higher 2nd and 3rd harmonic distortion in class A amps when bias is just barely enough to keep the load in class A. When bias is high enough to play the music with comfy class A headroom, then harmonic distortion is very low indeed. But class A watts are extremely expensive, so they are usually in short supply compared to AB and D amps. But the harmonic distortion is extremely low in the "first watt." The more power headroom of the class A amp, the lower distortion the first watt will have. Other amp topologies typically have low distortion all the way to clipping. Some class D even reduce harmonic distortion into higher power levels below clipping.

http://www.crownaudio.com/amp_htm/amp_info/how_much_power.htm

Interesting article by Papa Nelson http://www.firstwatt.com/pdf/art_leave_classa.pdf
http://www.firstwatt.com/pdf/art_leave_classa.pdf

[songlove]

Pass labs XA or X series(first 25w class A)

[Cheeseboy]

I have always been impresssed by this unit.  JUNGSON JA88D-09

80 watts 100% Class A integrated with a built in phono section.  Built like a truck and sounds awesome.  Check it out!

http://shop.grantfidelity.com/Jungson-JA88D-09-Integrated-Amplifier-w-Phono.html

The price is right as well.

[*Scotty*]

One of the easiest ways to reduce the audibility of cross-over distortion is to push the point where the signal is handed off from the positive device to the negative device away from where the signal is at its lowest level.
 You are basically masking or drowning out the crossover distortion which has a fixed low level by pushing the crossover point upwards to where the signal level is much louder than the crossover distortion. You have basically improved the signal to crossover distortion ratio.
 This is done by connecting a positive current source to the positive speaker output. You will burn a little more bias current through the positive device but that can be dealt with by up-sizing the heat-sink slightly.
After this has been done you have a Class AB amplifier that has a sweetness to the reproduction of low level signals that characterizes the sound of good Class A amps.
Scotty

[silver_strings]

Those bendinis are intriguing

[JoshK]

I have always been impresssed by this unit.  JUNGSON JA88D-09

80 watts 100% Class A integrated with a built in phono section.  Built like a truck and sounds awesome.  Check it out!

http://shop.grantfidelity.com/Jungson-JA88D-09-Integrated-Amplifier-w-Phono.html

The price is right as well.

Always wanted to hear that guy...intrigues me greatly, but 80wpc 100% Class A claim is horseshit.  Not unless it has heatsinks the size of a fridge.   Otherwise it is active bias sliding class A, which isn't class A per se.

[*Scotty*]

Josh, I think it might be the real deal.

That's a lot of heatsink area, it just might be enough for 80watts of Class A ?
Here is a shot of my 110watt Class AB amp, with obviously much smaller heatsinks.

Scotty

[JoshK]

Closer to believable, but still something fishy in 80wpc.   Thermal heating would imply ~20% maybe 30% efficiency, so let's say 80wpc ~ 320w dissipation /side and that still doesn't look like a space heater.

[srb]

That's a lot of heatsink area, it just might be enough for 80watts of Class A ?

19.5 sq. ft. of cooling area and the fins are pure copper, which has greater thermal conductivity than aluminum (~ 92% versus ~ 49%).
 
Steve

[Rclark]

I have always been impresssed by this unit.  JUNGSON JA88D-09

80 watts 100% Class A integrated with a built in phono section.  Built like a truck and sounds awesome.  Check it out!

http://shop.grantfidelity.com/Jungson-JA88D-09-Integrated-Amplifier-w-Phono.html

The price is right as well.

Will this amp not output into 4ohms? Don't see it listed there.

[Cheeseboy]

Yes into 4 ohms.  I had the very same concerns and called and spoke with Ian at Grant Fidelity.  He still hasn't changed the text on the web site I see.  If I were running some different speakers I would purchase this in a heartbeat.   When my wife finally removes my system from the big room I may have to down size to this. 

[srb]

Will this amp not output into 4ohms? Don't see it listed there.

The JungSon Audio website ("The Spirit of the Gong") says output impedance is 4 - 8 ohm, but don't give the power output.
 
Hi-Fi World May 2006 Review says they measured 112W into 8 ohms and 182W into 4 ohms.
 
Steve

[Cheeseboy]

The reason I was enamoured with this piece was that it had the Phono Pre built in and had been reveiw very well.   I was relegated to a smaller space and that changed when we bought our new home.  Bigger speakers bigger amps.  Just couldn't afford the Claytons. 

[Rclark]

Yes into 4 ohms.  I had the very same concerns and called and spoke with Ian at Grant Fidelity.  He still hasn't changed the text on the web site I see.  If I were running some different speakers I would purchase this in a heartbeat.   When my wife finally removes my system from the big room I may have to down size to this.

Not any time soon, but I might keep an eye out for one of these just to try it and sell it. I want to bounce a few different amp types through my system.