100W Ultimate Fidelity Amplifier

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#11,381
xrk971 said:
Glad you got it sorted out and it’s not blowing up now. It was too high of a bias current then.



Power assuming a sine wave signal is P=V^2/R where V is volts rms and R is ohms.

Vrms is Vpp/2.83 (assuming sinusoidal signal). A MOSFET push pull amp loses about 4v off each rail. So that’s 8v from Vpp. +/-63v rails is 126Vpp, minus 8v loss is 118v. 118v/2.83 is 41.7vrms. 41.7v ^2 /8ohms = 1738v^2/8ohms is 217w - assuming clipping doesn’t occur earlier - which you need an OScope to confirm.

Max is 217w - you can do better in some amps that use bootstrapping. It allows swings in Vpp greater than actual rails.

Hope that helps.
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This helps immensely - thanks for taking the time to show me the calculation(s) and advising the actual rationale behind it.
 
#11,388
AX14 bias

rehman said:
power up the board and connect voltmeter across (parallel) 5W resistor. set the selector to 200mv range and measure the reading. turn the bias pot until you get 15mv reading with no signal input.
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Thanks, that was quicker than I anticipated, can you tell me how many turns the inductor needs and the diameter as well, is there any particular value for the resistor on which the inductor is supposed to be wound on to ?
 
#11,390
anoopkrajan said:
Thanks, that was quicker than I anticipated, can you tell me how many turns the inductor needs and the diameter as well, is there any particular value for the resistor on which the inductor is supposed to be wound on to ?
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I don't see an inductor on the AX14 schematic - are you just asking to put it off-board? I typically use 1.0uF (which is 6-8 turns of 1.0mm wire around a AA battery or pen), and a 10ohm 2-3 watt resistor should suffice.
 
#11,391
Here you are.
 

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#11,395
rehman said:
hello every one. i build A40 last week, sounded damn good but the whole project will go way too expensive so i have decided to build A33. i want to feed a33 through p30 preamp. is that suitable ?
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The P30 can feed any stereo amp so yes it will feed the A33.

May I ask, what you mean about the A40 being too expensive? You can use the same PSU with the A40 that you will use for the A33. Even the same heatsink. Since you already have the A40 built, I don't see how building the A33 will save money.

Thanks, Terry
 
#11,396
still4given said:
The P30 can feed any stereo amp so yes it will feed the A33.

May I ask, what you mean about the A40 being too expensive? You can use the same PSU with the A40 that you will use for the A33. Even the same heatsink. Since you already have the A40 built, I don't see how building the A33 will save money.

Thanks, Terry
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actually transformer is the most expensive part of project. as i will need two transformers one for each module. one transformer costs about 2000PKR so two will cost 4000 one output transistor cost 120 four more transistors 480 more. one pair of 10000uf 100v cap costs 350. for A40 i will need more caps. the A40 that i build was not belonged me.

iam decided to make A33 first then upgrade to A40. A33 can give me 180W per channel easily with one transformer. making a 40 and not getting the power how much A40 can give?
also iam decided to make pre amplifier with input source selector with digital switching.

my be iam wrong at some point
 
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