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Old 24th January 2012, 04:02 PM   #11
Marra is online now Marra  United Kingdom
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Quote:
Originally Posted by Russellc View Post
As to bad reviews, there is no accounting for tastes, but anyone who isnt liking the sound of their F-5 has either Mis-built it, or is mis-applying it, would be my opinion.

Russellc
I wholeheartedly second that. My F5 drives my Pmc's really well with either a DCB1 or my TVC pre's.
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Old 24th January 2012, 04:07 PM   #12
AndrewT is offline AndrewT  Scotland
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Pd,
the power (P) is defined by the currents (I) and voltages (V) passed to the load (R)
There are three formulae you can use. Pick the one for which you know two values and require the third.

P = V * I = V^2 / R = I^2 * R

If you know the output bias current of a Push Pull amplifier then you also know the peak output current before the amplifier transitions from ClassA to ClassAB.
For your 900mA of bias current, the maximum ClassA output current is 2 * Ib, i.e. max ClassA = 1.8Apk

You need to convert that to effective current (ac or rms). Divide Ipk by sqrt(2) for a sinewave and you get 1.344Aac.

Choose P = I^2 * R since we know I and R.
Maximum ClassA power = 1.344^2 * 8 = 14W of ClassA into 8r0.

Change the bias current of the output stage and you must re-calculate the maximum ClassA output Power.
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Old 24th January 2012, 04:07 PM   #13
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Quote:
Originally Posted by Russellc View Post
As to bad reviews, there is no accounting for tastes, but anyone who isnt liking the sound of their F-5 has either Mis-built it, or is mis-applying it, would be my opinion.

Russellc
I think you read my posting on the F5 build thread.

My speakers are power hungry, as are most of the B&W family.

The guy that built that F5 was after LOUD, and the F5 doesn't really do LOUD, it is better in the FIRST-WATT fraternity providing BRILLIANT musical quality at MODERATE levels.

What he called LOUD was probably deafening. I've measured the power into my speakers at COMFORTABLY LOUD and its only about 6W RMS.
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Old 24th January 2012, 04:29 PM   #14
AndrewT is offline AndrewT  Scotland
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Originally Posted by KatieandDad View Post
I've measured the power into my speakers at COMFORTABLY LOUD and its only about 6W RMS.
And I would use that to estimate my requirement for clip free music reproduction as being a 600W amplifier to play that loud. Yes, +20dB of overhead to allow for transient peaks.
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Old 24th January 2012, 04:42 PM   #15
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Not quite sure how the Aleph4 performs above its 100W Class A rating.

With 48V rails I will bow to your better knowledge.

Ignoring volt drops - a henious crime I hear you call.

96V equates to 67V RMS

With 8 Ohm speakers ~ 600W

Can the Aleph throw these huge peaks ?

To my ears it certainly isn't clipping.


Or have I got it completely wrong with this topology ?

48V gives to 145W.


The rails are SOLID at 48-0-48V with over 1F (yes One Farad) of caps.

Last edited by KatieandDad; 24th January 2012 at 04:44 PM.
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Old 24th January 2012, 04:48 PM   #16
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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.



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Pandu
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Old 24th January 2012, 04:55 PM   #17
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TBPO any DIY project is as simple or difficult as any other.

The Aleph 4 is EASY to build- it works out of the box.

It is HUGE - I agree, but it works comfortably at low volume and has ENORMOUS capabilities.

There is nothing worse than building something only to find that it is lacking.

You might like one of the other Alephs.
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Old 24th January 2012, 04:55 PM   #18
AndrewT is offline AndrewT  Scotland
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Pd,
you have most of the concepts mixed up.

You need to go back a stage and re-learn what you have picked up so far.
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Old 24th January 2012, 05:01 PM   #19
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by KatieandDad View Post
Not quite sure how the Aleph4 performs above its 100W Class A rating.
I am simply drawing attention to the fact that I choose to listen at volumes that give me near to +20dB of overhead for transient peaks.
If I choose to listen at 50mW levels then I know that a 5W amp is much less likely to clip than a 1W amp.
If I turn up the wick and my average level becomes 750mW, then I know that a 75W amplifier will probably reproduce well with little hint of clipping evidence.

If I had to turn up the wick to 6W of average level then I would redesign my music system. I don't have any 600W amplifiers to give me substantially clip free reproduction.
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Old 24th January 2012, 05:05 PM   #20
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Originally Posted by pdhanwada View Post
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

No you are NOT driving each driver at half the power.

Each driver is working within its own frequency band.

Both drivers are being driven fully.

It's over simplistic to say that the BASS is working at 25W throughout its audio range and the TWEETER is working at 25W throughout its range but that is what the set-up is capable of.

In reality the tweeter has less work to do and does get fed with less power .
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