If you want more power look at the F5-Turbo.
Increasing MOS-FETs on their own will not increase power output.
In order to increase power you do need more output devices but that enables you to increase the power supply rails without stressing the MOS-FETs. Drive circuitry changes might also be necessary.
If you want more power - look at the Aleph 4, it is 100W/Channel in Class A.
Increasing MOS-FETs on their own will not increase power output.
In order to increase power you do need more output devices but that enables you to increase the power supply rails without stressing the MOS-FETs. Drive circuitry changes might also be necessary.
If you want more power - look at the Aleph 4, it is 100W/Channel in Class A.
I'm not familiar with that notation.
However, most of the lesser Pass amps will run in Class A to a certain point and then continue on in Class A/B.
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Yes, the F-5 is a First Watt family member, and while it is a little more powerful than most of its family members, it is still a nitch type amp. You either need fairly efficient speakers, or a pre amp with plenty of gain and fairly efficient speakers, or use it in a near field situation where not much gain is required.
When used with in its capability, it is a stupedous amp. Sometimes its odd what it does and does not drive well. I have a small set of 2 ways, which can really soak up the power. Other than a nearfield situation or one where one has a pre with gain and doesnt need a lot of volume, they are not an ideal match. I have another set of 2 ways, which are not so power hungry and about 91 db efficient which it drives like crazy. Also, my large Econo Waves with 15 inch JBL 2235H and B&C DE 250 compression driver and it will drive them extremely well, VERY powerful.
For your speaks, sounds like The aleph is the way to go....of course the F-5 Turbo will likely change all that.
Russellc
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This next explanation is simplistic - it contains errors but will serve to illustrate what I am trying to say.
Lets take a Class AB amplifier.
Some novice thinks it might be possible to convert it to Class A.
It has supply rails of V volts and a bias of I amps.
During operation the ouput transistors nominally carry I bias + 0.5 x I out(rms)
This will generate a small amount of heat ~ I x V which has to be lost by the small heatsink.
Are you familiar with SOAR (Safe Operating Area) ?
A transistor may be rated at 150W , 100V and 15A. However, not all at the same time and only with the transistor kept impossibly cool.
Generally it might take 50V at 1A and then it might take a bit of thermal abuse.
OK, back to our Class AB amplifier.
If we increase the bias we will indeed increase the point at which it stops running at Class A, however, the transistors will now be carrying more current and will be generating more heat.
SOLUTION - bigger heatsinks - keep the things cool.
PROBLEM - are we approaching the SOAR envelope.
SOLUTION - double up on the output transistors so they are carrying less current each.
Eventually we can get to the point where the amp is running in Class A.
OK - you night need to tweek the drive circuitry.
However, once we are in Class A and the outut is swinging from +Vcc to -Vcc. There is nothingthat we can do in order to increase power other than increase the rail voltage.
Whoops - SOAR comes into play again.
More voltage - more power through each transistor, more heat.
This is ONLY a generalisation - DO NOT use this as a lesson to go playing with your Class AB amps.
In the Aleph 4 we have 6 Mos-Fets, each biassed at 400mA, and running with PSU rails of 48V.
They get damn hot even with HUGE heatsinks.
Lets take a Class AB amplifier.
Some novice thinks it might be possible to convert it to Class A.
It has supply rails of V volts and a bias of I amps.
During operation the ouput transistors nominally carry I bias + 0.5 x I out(rms)
This will generate a small amount of heat ~ I x V which has to be lost by the small heatsink.
Are you familiar with SOAR (Safe Operating Area) ?
A transistor may be rated at 150W , 100V and 15A. However, not all at the same time and only with the transistor kept impossibly cool.
Generally it might take 50V at 1A and then it might take a bit of thermal abuse.
OK, back to our Class AB amplifier.
If we increase the bias we will indeed increase the point at which it stops running at Class A, however, the transistors will now be carrying more current and will be generating more heat.
SOLUTION - bigger heatsinks - keep the things cool.
PROBLEM - are we approaching the SOAR envelope.
SOLUTION - double up on the output transistors so they are carrying less current each.
Eventually we can get to the point where the amp is running in Class A.
OK - you night need to tweek the drive circuitry.
However, once we are in Class A and the outut is swinging from +Vcc to -Vcc. There is nothingthat we can do in order to increase power other than increase the rail voltage.
Whoops - SOAR comes into play again.
More voltage - more power through each transistor, more heat.
This is ONLY a generalisation - DO NOT use this as a lesson to go playing with your Class AB amps.
In the Aleph 4 we have 6 Mos-Fets, each biassed at 400mA, and running with PSU rails of 48V.
They get damn hot even with HUGE heatsinks.
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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.
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.
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.
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.
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.
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.
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.
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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.
Thanks
Pandu
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
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.
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.
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.
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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