New Esoteric Integrated Amps F-03A/F-05!!!

[audio bill]

Originally Posted by jdandy

myjazz123.......Into a 4 ohm load, such as the Guarneri Evolution the Esoteric F-03A can output 60 watts of Class A power per channel. Although the Evo's sensitivity of 86dB/1w/1m is not as efficient as any number of other speakers, 60 watts is still enough power to drive those speakers to a respectable volume with sufficient reserve power to ensure accurate dynamics. 15 watts output is enough power to have the Evo's singing at approximately 98dB measured at one meter. Sitting approximately 3 meters away from the speakers will typically reduce your volume about 6dB. This means that a comfortable 90 to 91dB volume level can be achieved with the Esoteric F-03A loafing along at 15 watts average output with momentary peaks reaching near 60 watts. So as long as you are not trying to achieve rock hall volume in a large room a 60 w/p/c amplifier will work perfectly well with the SF Guarneri Evolution.

My preference for the Esoteric F-03A is based on it being a Class A amplifier and I like the shutter that hides the secondary controls. I have never owned a Class A amplifier, that is if you don't count a couple headphone amplifiers. The new Esoteric F-03A intrigues me for those reasons.

Dan - Just to clarify one point if I may regarding Class A power amp operation. While a solid state Class A power amp like the one in the F-03A integrated will indeed double its output power into a 4 ohm load compared to the 8 ohm rating, it does not maintain Class A operation at the higher power levels. It all comes down to limitations of current available from the power supply and the amount of power the heat sinking can effectively dissipate. As such into impedances lower than 8 ohms it can provide the rated power cleanly but that output will only be Class A for a portion of its maximum rated power. I'm certain that it will sound superb regardless!

[jdandy]

Originally Posted by Weirdcuba

Dan, is Hermine coming over the top of you? Hope everyone is ok. (Exceedingly off topic).

Jim.......Hurricane Hermine is close. This is a screen shot from 9:30 PM. It looks like the eye of the hurricane will make landfall between Crawfordville and Perry in the next hour or two. The marker is where I live. Fortunately the wind speed is holding at 80 mph which isn't all that serious. I am getting 15 mph wind with 25 to 30 mph gusts and pouring rain when the red and yellow bands pass. If the eye stays on its present course it looks like we might dodge the bullet.

[Weirdcuba]

Horses must be freaked out. Mine go nuts in a big storm. Be safe.

Sent from my iPad using A.Aficionado

[jdandy]

Originally Posted by Weirdcuba

Horses must be freaked out. Mine go nuts in a big storm. Be safe.

Sent from my iPad using A.Aficionado

Jim.......Gus is locked in his stall, not out in the weather. I can watch him in the stall on a monitor in the house via a high-power WiFi camera installed under the eave of the roof on the feed room. I just checked, he's doing fine.

Wind is beginning to pick up speed and some of the down pours are torrential but it appears the eye is going to miss us.

Back to the original topic, the new Esoteric integrated amplifiers.

[Weirdcuba]

Be safe. Luckily, our place in Boca seems to have been spared (this time). Look forward to hearing yours and Gus's report in the morning.

Sent from my iPad using A.Aficionado

[2fastdriving]

Originally Posted by audio bill

Dan - Just to clarify one point if I may regarding Class A power amp operation. While a solid state Class A power amp like the one in the F-03A integrated will indeed double its output power into a 4 ohm load compared to the 8 ohm rating, it does not maintain Class A operation at the higher power levels. It all comes down to limitations of current available from the power supply and the amount of power the heat sinking can effectively dissipate. As such into impedances lower than 8 ohms it can provide the rated power cleanly but that output will only be Class A for a portion of its maximum rated power. I'm certain that it will sound superb regardless!

I have some doubts about this. Can you provide some supporting information? What you are describing is a class A/B amp, I think.

[audio bill]

Marc - I expected that this would be questioned and have been searching for supporting info as you requested. Unfortunately so far I haven't found it, but I know that I've read this several times including once within the last month or so. I will continue my search and when I find it I'll post it here. You are correct that when the Class A output stage goes beyond its limit it switches to Class A/B operation, and that's exactly what happens with Class A amps when operated into lower impedances. Many Class A/B amps operate in Class A for their first few watts and then switch to A/B.

[audio bill]

Still unable to locate the detailed technical explanation that I saw. In my research I noticed that even the Accuphase "Pure Class A" power amps like their A-47 only state Pure Class A operation into 8 ohms. Because of its robust power supply, output stage and overall build quality it does continue to double its output power into lower impedances even going down to 1 ohm (very impressive!) but it doesn't state that it maintains Class A operation into those lower impedances. I believe it would be impossible to do so unless the output stage and heat sinking were sufficient to support 360 watts per channel into 1 ohm which would require a significantly larger and even more massive amplifier.

[audio bill]

Hopefully this isn't considered OT; I think it's alright since it's directly related to the new Esoteric F-03a amp being a Class A design. After extensive searching I was able to find one of the sources which documented the technical explanation regarding power output of Class A amps into impedances lower than 8 ohms. Since it was posted on another forum I know I can't link to it, but I'll copy the basic explanation here for reference.

This applies to solid state push-pull output stages like used in the Esoteric Class A designs as well as those by Accuphase and many others. Single ended output stages are inherently Class A by their nature since only a single device carries the signal. Transformer coupling of an output stage as used by some amps maintains a basically constant output power across varying loads without an increasing power into lower impedances.

As power = resistance x current x current , and maximum class A current is determined by the bias current, the class A power is proportional to the resistance. To make it clear a 100W class A amplifier has 50W class A at 4 ohm and 25W class A at 2ohm. This happens for true class A. Some designers have sliding bias schemes to increase bias depending on signal prediction, but IMHO they are creating new problems and can not be considered class A anymore. Bridged amplifiers increase voltage swing capability, but not bias current. Class A power for a bridged amp is the same as that of a single unit even though its maximum output power is much higher.

The class A power specification is mainly established by the amplifier bias current . It is specified as the maximum power delivered by the amplifier to a 8 ohm resistor without switching off any of the active elements. The theoretical class A efficiency rating is calculated for an amplifier having a power supply with the minimum power supply voltage needed to deliver that power, ignoring any losses. Most of the time the amplifiers have much higher voltage in the power supply than this value, and can be operated at higher output power outside class A.

Hope this helps to clear things up a bit (and not add more confusion!)

[TOGA]

It has to be this one. !

http://www.esoteric.jp/about/whatsne...andioso_f1.pdf


Toga