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Old 25th January 2012, 03:28 PM   #81
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Quote:
Originally Posted by Russellc View Post
contemplating
Lower rail voltage means lower power, but also means a higher bias current at the same dissipation level.
Then there's the option of playing with the AC bias factor, alter it to 0.25 (down from 0.5) and peak output current will be four times the bias level.

The Aleph 2 is biased at 0.5A per output device, makes 3 Amps total quiescent current.
Read the service manual : Peak output is 10 Amps, makes 200W continuous in 4 Ohm theoretically.
For less easy loudspeakers a better choice.
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Old 25th January 2012, 06:03 PM   #82
AndrewT is offline AndrewT  Scotland
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the set AC current gain factor of the dynamic bias thingus.
For the standard factor of 0.5,
Jacco, could you explain this for me?
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Old 25th January 2012, 06:25 PM   #83
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by KatieandDad View Post
Sorry but you mis-understood my post.

My speakers are INEFFICIENT - they wouldn't suit the F5.

I stated that the F5 is best suited to someone with EFFICIENT speakers.

96dB/W is "Efficient" relatively speaking, be careful how the sensistivity has been measured though. Some manufacturers are blinding us with misleading figures.
Me tinks you mean Less sensitive , very different from efficiency.....
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Old 25th January 2012, 06:33 PM   #84
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Yes the B&Ws needs loads of power,
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Old 25th January 2012, 06:47 PM   #85
a.wayne is offline a.wayne  United States
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Ahhh that they do, most speakers do as a matter of fact, always sounding more "alive" when fed some power...

High sensitivity 2 way speakers sound unbalanced to me, well everyone i have ever heard. To get high sensitivity and a good balance require a large multi driver speaker 3-4 way at the very least.

regards,
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Old 25th January 2012, 06:59 PM   #86
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Quote:
Originally Posted by a.wayne View Post
Ahhh that they do, most speakers do as a matter of fact, always sounding more "alive" when fed some power...

High sensitivity 2 way speakers sound unbalanced to me, well everyone i have ever heard. To get high sensitivity and a good balance require a large multi driver speaker 3-4 way at the very least.

regards,
Wow, tastes do vary...I find the 3 and 4 ways with poorer balance than the 2 ways!

Russellc
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Old 25th January 2012, 07:00 PM   #87
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Quote:
Originally Posted by jacco vermeulen View Post
Lower rail voltage means lower power, but also means a higher bias current at the same dissipation level.
Then there's the option of playing with the AC bias factor, alter it to 0.25 (down from 0.5) and peak output current will be four times the bias level.

The Aleph 2 is biased at 0.5A per output device, makes 3 Amps total quiescent current.
Read the service manual : Peak output is 10 Amps, makes 200W continuous in 4 Ohm theoretically.
For less easy loudspeakers a better choice.
OK, sounds like I have picked the correct amp for my purposes, thanks for the insight.

Russellc
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Old 25th January 2012, 07:16 PM   #88
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Quote:
Originally Posted by AndrewT View Post
explain this
What is there to say ?

The Alephs are not classic single-ended amps with fixed bias, but have a steady-state bias (no signal) plus dynamic bias (with signal at input/output) of the current source.
(as to be expected from the master of sliding bias arrangements in Threshold amps)

My candid camera short version : the connection between output and biasing arrangement fools the bias transistor in believing that the voltage drop across the output source resistor goes down, in effect : more quiescent current (of the current source).
For the long version, read Zen Part II.

Personally, i do not view the Aleph amps as True Class A, but semi Class A.
Similar to Krell's sustained bias plateau, Threshold's sliding stuff.

Without the dynamic bias thingy, it would become a standard SE amp, max output current is quiescent current => AC current gain factor = 1

If the AC gain setting is altered to something near 0, the amp starts to resemble push-pull (high bias Class AB )
See bottom half of the output stage. What happens there when the positive output current goes beyond the static bias current level ?

So :
0 = PP Class AB
1 = SE Class A
Therefore 0.5 = 1/2 Class A (aka semi)


(so, each Aleph amp can be custom tailored to the loudspeaker system in question. Rotten LSP needs bigger supercharger)
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Last edited by jacco vermeulen; 25th January 2012 at 07:26 PM.
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Old 25th January 2012, 07:42 PM   #89
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by Russellc View Post
Wow, tastes do vary...I find the 3 and 4 ways with poorer balance than the 2 ways!

Russellc
I can believe that ... Poorly made/designed speakers, nothing to do with them being multi-way. Done right , no single speaker or 2 way will come close...



Much easier to get a 2 way correct.....................
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Old 25th January 2012, 08:01 PM   #90
ramallo is offline ramallo  Europe
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Quote:
Originally Posted by a.wayne View Post
I can believe that ... Poorly made/designed speakers, nothing to do with them being multi-way. Done right , no single speaker or 2 way will come close...



Much easier to get a 2 way correct.....................

IMMO multiway = multi point sources = multi-problems.

I heard and adjusted (and made) dozens of multiway systems, and my feelings is the best one is the one way (But is very difficult to achive a good performance, my Quad ESL can, but the drawback are a low headroom), the second best is two way, the third best is three way.........

But is my taste
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