Which basic amps can drive 1 ohm loads ?

Im sure you do have plenty of real world experience, but so do I, with ALOT of different gear in countless configurations(yes I used to be a dealer for alot of high end gear in Ma. and RI.).And I probably have just as much if not more real world experience with what an Aragon amplifier is capable of. No Im not a dealer anymore, nor have I been for the last 3-4 years(got out of the business at just the right time before the tradgedy in NYC)but I do have solid experience with Aragon's running Apogee speakers with ease, as back in 97-98' I sold a few pairs of the older Palladium's to folks with low impedance Apogee speakers. To this day I know that at least 1 of my old customers is still running the combo and enjoying it as much today as he did when he first purchased them 6 years back.

What Im adamant about is a statement that these amps cant run low impedances reliably for extneded periods at high output volumes when I know for a fact this is the farthest thing from the truth.

Here's something else to think about folks. That is, the lower the impedance, the less time that the amp stays in Class A and the sooner it switches over to Class B. The more switching of operating Class that takes place, the "grungier" and less consistent the amp will sound ( in most cases ).

With that in mind, a "typical" amp that is of a "rich AB" design is typically 6 - 10 wpc at 8 ohms in Class A and then switches over to Class B at power levels above that point. If one has a 4 ohm load, the same amp will only run in Class A up to about 3 - 5 wpc. At 2 ohms, you get 1.5 - 2.5 wpc in Class A and at 1 ohm, you end up with .75 - 1.25 wpc in Class A. As such, one would have to have an amp that is VERY richly biased if you wanted to stay in Class A mode for the majority of listening on a very low impedance, low sensitivity speaker. In order to do this, you need an amp that has GOBS of heatsinking and current capacity to say the least. Otherwise the amp will both starve itself and cook itself to death at the same time.

With that in mind, a rather unique approach regarding bias levels were chosen when John Curl designed the Parasound JC-1's. The JC-1's are switchable between "rich biasing" and "very rich biasing" for these purposes. In the lower bias mode, it runs in Class A up to 10 wpc and then switches over to Class B mode. In the high bias mode, it runs in Class A up to about 25 - 30 wpc* and then switches over to Class B above that point. Using this approach, one can let the amps idle in "low bias" mode when not in use, which will keep them as warm or warmer than most other amps, and then switch over into high bias mode when listening. This approach allows one to have the benefits of "ultra high bias" in terms of sonics yet retain the benefits of "medium to high bias" by cutting down on power consumption and heat build-up. I'm not suggesting that this amp is the right amp for Apogee's or any other specific speaker, but that it is a very unique and "user friendly" approach to designing real world products.

Doing the math with the JC-1 as a reference and starting off with the conservative rating of 25 wpc of Class A operation available at 8 ohms, this would give us something like 12.5 wpc @ 4 ohms, 6.25 wpc @ 2 ohms and slightly over 3 wpc @ 1 ohm. All of these figures are based on the amp operating in Class A and then switching to Class B operation above that point. Given that most listening occurs with less than a watt or two being used ( except for rock music ), the JC's should retain their sonic characteristics relatively consistently for most uses with just about any load. This is due to the consistent electrical characteristics that the amp would display while remaining in Class A operation and the lack of switching distortion that all amplifiers will demonstrate when pushed harder.** Sean
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* Stereophile measured 27 watts in Class A on their review samples.

** This is all based on theory and not first hand familiarity with this amp. I chose it as i was familiar with the electrical characteristics of the amp as advertised and as measured by Stereophile. Other amps, like the Bear Labs Symphony, Pass Labs X series, larger Krell's, etc..., may perform quite similarly due to the very high levels of bias applied to the output stage.

Sean, that was a relief. I knew I was familiar with your name. The JC-1 is a great amp, so I heard.

Having the X600, I don't have to do math (luckily). I just follow the needle.

At <1 ohm, I need to go to live levels to swing the needle into AB. AND at that point, if it weren't for the needle, I wouldn't have ever noticed.

There is a fellow in our Apogee group who has the most advance listening rooms I have seen. There are Apogee Full Ranges forward, Apogee Duetta Signatures righ and left, with Divas in the rear.

This fellow employs a lot of Aragon's as great workhorses. They do the Duetta Signatures, and are on the bass panels for the Divas, and Full Ranges.

He also says Aragons are great amps for starting points. All these are 4 ohm speakers.

For Scintilla, one fellow tried an Aragon 4004 MK11 that overheated.

I use the McIntosh MC-2100 to drive my Apogee Duetta
Signatures. Transformer coupling eliminates most amp
matching problems. They sound super with the McIntosh
"transformer" outputs.

http://www.apogeespeakers.totalserve.co.uk/scintilla.htm

Though the thread is a bit old, this is geared towards Muralman.

Aragon Paaladium true specs(not their conservatively posted specs):

8 ohms: 150 watts in class A operation, 500 watts in Class AB(listed: 125 watts CLass A, 400 watts Class AB)
4 ohms:80 watts Class A operation, 850 watts in class AB(no rating given for class A, 600 watts given RMS for class AB)
2 ohms:45 watts Class A,1400 watts Class AB(listed rating for 1000 watts RMS)
1 ohm: 25 watts Class A, >1500 watts Class AB(no listed rating. But Palladiums are recommended to be on seperate 20amp circuits if driving loads 2ohms or lower regardless)
.5ohms:15 watts Class A, >1500 watts class AB(no listed rating)

Though Ive heard a few folks state that the amp doesnt fully "double down" its output rating as the impedance drops, Id like to point out that NO AMP can double down its true output, no matter what the mfg. claims. Alot of amps state that they can to some extent, but in reality its not physically possible.

Each Palladium is a true differential balanced monoblock. Each block features a 2000kVA Toroidal with 140,000uf capacitance, 24 output devices that are rated for a total of 2400 watts per side maximum.Heatsink mass is also very similiar to the x600's btw muralman, and is LESS than 10% in total mass surprisingly which is in line with all the other specs on the amp in reality. The 8008BB is basically half the ratings listed above, the 4004mkII is also very similiar with less output. All 3 can drive Scintillas with ease. And I know of a handfull of folks driving Apogee 1 ohm speakers with Aragon products(Along with some older Krell models too)as stated earlier.