Under construction 
This amp must of occured to Mr. Pass while developing and fine
tuning the J-Low speakers. Since the F1 seems to play well with
high pass filters and full range cone speakers, that need the
filtering to be able to boost output. At least that's the idea i got
reading the website. Although i seem to remember Mr. Pass
mentioning that 10 watts might not be enough power. Maybe a
power current source amp doesn't have the same limitations as
normal amps. (i think i may be in over my head here!)
How would this amp sound with my Straight 8's? ...maybe better
if i had an external crossover?
m.
tuning the J-Low speakers. Since the F1 seems to play well with
high pass filters and full range cone speakers, that need the
filtering to be able to boost output. At least that's the idea i got
reading the website. Although i seem to remember Mr. Pass
mentioning that 10 watts might not be enough power. Maybe a
power current source amp doesn't have the same limitations as
normal amps. (i think i may be in over my head here!)
How would this amp sound with my Straight 8's? ...maybe better
if i had an external crossover?
m.
Interestingly, he mentions Lowther and Fostex drivers, but not the Jordon drivers in the J-Low. The Jordons are not particularly efficient, so you are probably right. However I do remember Nelson mentioning using a Zen enlightened amp or whatever the one with lightbulbs is-and that was about 10 watts also. I'll bet that it works fine with the J-low in normal listening.
He also mentioned I think that this current (haha) amp is going to be quite expensive. Does it make sense that it might have the monster choke that the recent Zen amps have?
He also mentioned I think that this current (haha) amp is going to be quite expensive. Does it make sense that it might have the monster choke that the recent Zen amps have?
Nelson Pass said:
Not bad. Not quite as elegant as the originals (Be Yamamura's Dionisio 27s), but not bad.
An externally hosted image should be here but it was not working when we last tested it.
se
I have just read what the F1 is stuff like. How do the speakers /normally they are voltage driven electro-acoustic transducers, and their characteristics are valid only for voltage drive/ enjoy current drive? This should result in poor damping and much worse frequency characteristics compared to voltage drive.
PMA said:
See:
It is well suited to sensitive full-range drivers such as Lowther or Fostex, and allows easy use of parallel loading networks to tailor the driver response.
I think "allows" is a bit of a misnomer. Unless you want a big hump in your bass response (as you increase source impedance, your response starts to resemble the driver's impedance curve), seems to me the loading networks would be pretty much a necessity.
Either that or you'd have to increase the mechanical losses in the driver.
se
PMA said:
Sure, you can do that. But given that one of the main appeals of full range drivers such as the Lowthers and Fostexes is that they can be used without any intervening electronics between the amplifier output and the driver, I'm not sure that many will consider that an "advantage."
"Gee, I didn't have to have all that stuff in there before."
How do you figure the small output power? Don't forget that there's an impedance peak at the driver's resonant frequency.
Let's say our current source amplifier is outputting about 350 milliamps RMS. Into 8 ohms, that's about 1 watt. But at the speaker's resonant frequency, the impedance will be significantly higher than 8 ohms. 100 ohms is not unheard of. So using a speaker with an impedance of 100 ohms at resonance as an example, shoving 350 milliamps into that comes to 35 watts.
Not yet.
se
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