Aleph X - mosfet temperature

[moamps]

Originally posted by yoke
So, I can take new mesurment with real load ( loadspeakers ) or I can place some resistors ? I have 8 x 75 Ohm 5W...in paralel 8x75 would give 9.37Ohm ... would that do ?

That may do. I'd suggest you measure the frequency response of your amp at the output voltage of about 5V.

Regards,
Milan

[yoke]

thanks will do :-)

[lineup]

Originally posted by yoke
lineup, thanks for replay...I tought to ask about the amp before I turn all room up side down :-)

Looks like your amp have like -1dB at 40-50 hertz
Quite normal, to me

Remember that for a loudspeaker that we buy
and is told to have frequency response 40-20.000
this value means -6dB data, mostly
and -6dB at 40 hertz, IS NOT A SMALL speaker
it is most often a floor stander with height 1 meter (3.3ft)

small speakers, monitor style, may even have -6dB at 70-80 hertz, at best!
and -12 to-15dB at around 40-50 point


Compare this to your amp with -1dB at 40 hertz

============================================

Many stepped volume attenuator controls ha got -3dB steps
because -2dB -3dB is around where we can hear any clear difference

My guess is your loudspeakers are way above -2dB -3dB value
while your amplifier obviously,
as your simple CD-tone Resistor load test shows this,
is good and normal in frequency response

it is such data we may get and expect
from a Nelson Pass construction
he doesn't make too bad amplifiers, you know

============================================


One thing that, in my opinion, is vital for low frequency play,
good bass in power amps
is POWER SUPPLY
and the single most important component in a power supply is TRANSFORMER

SMALL transformers will sag, drop in voltage a power delivery
at a bit higher power output
and especially at lower frequencies, say below 100-120 hertz
and certainly around and below 50-60 hertz

number 2 in important component in POWER SUPPLY
is Big Filter CAP = Electrolytic
the size and location of these

so especially if your transformer is not biggest type
you may be able to compensate this a little bit with having MORE CAPACITANCE

Nelson Pass has told us, that he has found
some rather big CAP or CAPs rather CLOSE to output power transistors,
is what he prefer.
That is at the PCB where power MOSFET are attached

But to ensure a lot of power available
at frequencies of 30-200 hertz
we should:

1. make sure our transformer is 3-4 times more VA rated than output power
2. see to we have enough much energy stored in supply caps
to deliver currents to MOSFET output

==============================================


The above was a bit about amplifier and BASS.
But as I told you,
your amplifier does NOT show anything bad, not normal, at those BASS tones.


so, as I have told before, You should make sure:

Point 1. speakers have good response of BASS reproduction level

Point 2. seems okay, as you used CD-player tones for your amp test
and so the whole line level chain in your audio system (anything before power amp input)
was tested along with your amplifier


Regards
lineup

[Nelson Pass]

-1 dB at 40 Hz is not good enough IMHO. I suggest you try
to get a couple more octaves out of your bottom end, probably by
quadrupling the value of coupling capacitors.

[yoke]

thanks everyone for replay...unfortunate vikend is over...so I have to get back to ''normal'' life :-)))))...my girlfriend doesn't like all that wires on the floor :-) can't see reason why :-) so I will have to wait for another vikend...


in mean time, could some tell me what are the coupling caps in this amplifier

thanks

[vuki]

Originally posted by Nelson Pass
-1 dB at 40 Hz is not good enough IMHO. I suggest you try
to get a couple more octaves out of your bottom end, probably by
quadrupling the value of coupling capacitors.

I guess yoke measured it via his TVC, so this is where that -1dB came from and I doubt he can do much about it even with larger coupling cap.

Yoke: coupling cap would be that 4u7 at your TVC.

[yoke]

I just look at the part list for AlephX and it only mention C12/13 as decoupling cap ( 47uF ), is that it?
...it's paralleled with power supply capacitors..
or does it mean that I need more capacitors in power supply ?

For now the power supply is not finished, I have 3x12000uF per rail...will have 3x22000uF ( 6x22000 per channel )

[yoke]

Thanks Vuki

and yes, I mesure trough TVC

[yoke]

just quick report...
I remove 4.7uF from input of TVC and the bass is back
right now the aleph30 is playing
Thanks everyone for the answers and help...especially to the ''one and only''

back on slamming