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Old 24th January 2012, 05:39 PM   #31
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The Aleph 4 runs at Class A up to 100W

If you do a bit of homework you will see that, in order to achieve concert performance, you would need impossibly high power outputs.

For true Opera Nirvana you might need over 10kW if not more.

The Aleph 4 probably runs into Class AB at over 100W but boy, that's better than 25W

The Aleph 4, in my opinion is Musical Nirvana. Beats the ML and Krell 250 - but that's my choice.

Last edited by KatieandDad; 24th January 2012 at 05:43 PM.
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Old 24th January 2012, 05:42 PM   #32
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Originally Posted by KatieandDad View Post
The Aleph 4 runs at Class A up to 100W

If you do a bit of homework you will see that, in order to achieve concert performance, you would need impossibly high power outputs.

For true Opera Nirvana you might need over 10kW if not more.
Thanks for your help. Will do the home work on aleph 4 in next few days/weeks then would make a decision

Thanks
pandu
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Old 24th January 2012, 05:49 PM   #33
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TBPO the only real cost differences between building the smaller Pass amps is the number of MOS-FETs, the amount of heatsinking and the Power Supply.

Matching MOS-FETs isn't beyond the DIYer. I bought 50 to get the 24 that I needed.

The transformers and the big PSU caps are comparable in cost between the various amps.

If you hunt E-Bay you can get the heatsinks cheap. I paid £40 for the whole lot for mine.
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Old 24th January 2012, 05:53 PM   #34
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Here's a full build from start to finsh.

There are many more.

Aleph 4 Strickly DIY Project Build
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Old 24th January 2012, 05:54 PM   #35
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Originally Posted by pdhanwada View Post
It is 25 watts max per channel into 8 ohms. Does it mean that x watts in A and 25-x in B mode. What is the x when bias is set at 900mA.

What happens when we double the mosfets as recommended in the second design.

Let me know.

Thanks
Pandu
I think the original question was not quite answered.

When the bias is reduced, the heat is reduced at quiescent.

When you double the output mosfets the quiescent current is increased, so that the amp can remain in Class A for lower Z loads. The output power remains the same.
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Old 24th January 2012, 05:59 PM   #36
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??

If you double the output MOS-FETs the quiescent current is reduced through ech output device but still remains through the pair.

Each MOS-FET is now dissipating less.

YES, the amp is now capable of driving a lower impedance load - up to a limit.
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Old 24th January 2012, 06:21 PM   #37
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No, if the bias point (voltage) per mosfet is the SAME, then the quiescent current through the pair is DOUBLED.

You have TWICE the dissipation, not half.
One does not (in the F5) use a pair of mosfets per rail and then decrease the standing current usually. Kinda defeats the point.

The limit of the Low Z load is according to doubling the current. Assuming you want to remain in class A, etc...

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Old 24th January 2012, 06:31 PM   #38
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I'll bow to your better judgement, But the Aleph 4 is capabable of 100W/Ch Class A against the F5 with 25W/ Ch
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Old 24th January 2012, 06:41 PM   #39
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Ok, why?

What is the rail voltage on the Aleph 4?
What is the rail voltage on the F5?

How many devices in the output of the Aleph 4?
Running at what current PER device?
Total current per rail?

This will explain why one is 100watts and the other is 25watts...

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Old 24th January 2012, 06:56 PM   #40
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Originally Posted by pdhanwada View Post
Aleph 4 is not for me for now. It is too huge. My DIY capabilities are at a minimum. And also with respect to my room and speakers

The following specifications were pulled from B&K ref30 preamp.

Output Impedance: 221 Ohms
Input Impedance: 50 k Ohms
Signal to Noise Ratio: 98 dB CCIR 2 k Weighted
Maximum Output Level: 3 V rms
Input Sensitivity: 2 V in, 1.5 V reference out
Noise Test Reference Level: 46 mV

Does F5 suite above specifications

My speakers are Paradigm signature S4. It is 3 way bigger bookshelf.
Do you think 25W is enough to drive speakers whose efficiency is 90db and nominal impedence is 8 ohms. My paradigms are bi ampable. Is it better to use two channels to drive single speaker Meaning two stereo amps driving two speakers. Then I would be powering each speaker with 50 W capability instead of 25 W.



Thanks
Pandu
Regarding the B&K Ref 30, I believe the 3V max output is a B&K OM typo, and it is actually 9Vrms max (AD712 running on +/-15V rails), just like all the other B&K preamps of this vintage that I've seen...
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