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Old 29th November 2006, 11:52 PM   #11
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by bobsinclar
Oh just forgot,
what could I do to get more power out of it without replacing the supply? I'd like to get 10wattsrms is that possible?actually I didn't choose to clip at about 4 watts it's just the way it ended but i'd prefer 10!
Vince
use inductor instead R or use CCS .........whatever
in both case you need to readjust biasing divider(s)
or just make F2..........if you are lazy
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Old 29th November 2006, 11:57 PM   #12
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"agree with everything ,especially with glorifying Carpenter and me ........"

hehe

you and Carpenter made my amp alive he'll never forget

thanks for the tips, I'll go on working on it following your advises on the global feedback loop...
Best regards!and many thanks Zen , and also JCM and Carpenter,
really nice place here!
Vince
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Old 30th November 2006, 12:02 AM   #13
JCM is offline JCM  United States
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~ I just noticed I totally missed that that was a cascode design. Somehow I looked at that 14 ohm resistor as a filter, not a load resistor, but I see there's no dc cap. there; and that the output is taken from there

The only thing I can think to get more power is to increase the idle current, maybe increase the supply voltage. Might replace the load resistor with a current source - that might be the single biggest improvement. As it is, with the 14 ohm load resistor and an 8 ohm load, the amp is driving a 5 ohm load.
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Old 30th November 2006, 12:06 AM   #14
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So JCM you suggest I just raise idle and replace the 14ohm load resistor with a current source...I'll try that out!
but what do you mean when you say that the amp is driving 5 ohm load?
Vince
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Old 30th November 2006, 12:10 AM   #15
lineup is offline lineup  Sweden
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Quote:
Originally posted by bobsinclar

the amp clips symetrically,
but only when trimming gives me 16v at the 240 drain
when I have 18v at the supply
(I don't know why, but when I put half the supply at his drain clipping isn't symmetric...)

Now the amp sounds wonderful very punchy bass and sweet mids...
.
To have output at half the supply is many times NOT the best solution. Sometimes is, but far from every case.
We have several good examples of this fact.
In Nelson Pass amplifiers and others.


To adjust for symmetrical clipping, if you want high and good QUALITY output
is more important, than then V/2 output.
Especially when we like in this case
deals with a non-symmetrical amplifier topology.

For so called, dual supply and totally symmetrical amplifiers
using NPN + PNP transistors in mirrored configuration,
is another case.
These uses 99.9% of the time output at half the supply.


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Old 30th November 2006, 12:13 AM   #16
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Lineup,
thanks for the confirmation
Vince
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Old 30th November 2006, 03:35 AM   #17
JCM is offline JCM  United States
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The load resistor being 14 ohms, and the load being 8(?) ohms, in parallel, the load is 5 ohms, normally, anyways, I mean for less exotic kind of amps.
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Old 30th November 2006, 04:11 AM   #18
lineup is offline lineup  Sweden
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Quote:
Originally posted by JCM
The load resistor being 14 ohms, and the load being 8(?) ohms, in parallel, the load is 5 ohms, normally, anyways, I mean for less exotic kind of amps.
The theoretical most effective output stage and maybe also best quality higher power output,
is reached when the amplifier load resistor (DRAIN resistor)
is equal to load average impedance (LoudSpeaker).


But lower the resistor from 14 Ohm to 4/6/8 Ohm
in this case will probably increase the total power too much.
A lot of heat to dissipate

But if you have a another good transformer with a bit lower voltage
then it might be worth a new experiment.
Some other component values would need to be adjusted, for sure,
and you may even have to use some other MOSFET.
.... it would be another amplifier .... with another performance ....

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Old 30th November 2006, 07:07 AM   #19
JCM is offline JCM  United States
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Quote:
The theoretical most effective output stage is reached when the amplifier load resistor (DRAIN resistor)
is equal to load average impedance (LoudSpeaker).
True - theoretically.

Quote:
But lowering the resistor... will [result in] ...a lot of heat to dissipate.
One could always take a cue from N.P. and use light bulb filaments for the load resistor. Without turning up the idle current, and maybe supply voltage, a ccs is probably the fastest, maybe only way, to crank up the power output.
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Old 30th November 2006, 09:22 AM   #20
lineup is offline lineup  Sweden
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Quote:
Originally posted by JCM

.... a ccs is probably the fastest, maybe only way,
to crank up the power output.
I agree fully, JCM.
One P-Channel IRFP9240 on top as costant current source.
Not only for cranking power, but for lower circuit distortion at equal power output.


But I don't know ...
... there is something special about the sound of a Power resistor loaded Single end output!
And resistors are more linear than any semiconductor.
Even wire wound power resistors are.

It is much up to what the designer himself fancy to do.


There are always so many choices ... so many ways and combinations.
This is a bit of what makes audio amplifiers so interesting.
There is always a new idea to test ... in theory, simulation
.. and even in plain reality, ........ sometimes.

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