Driver to drive?

[Gareth Magennis]

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:6jet7oF30dviU1@mid.individual.net...

"Gareth Magennis"
"Phil Allison"


Not if you clip them like you might a valve amp for example.


** Only fucking half-wits listen to clipped audio from a home hi-fi.


Would a Mosfet amp clip more "nicely" than a BJT amp?


** No.

Any more fuckwit MOSFET myths you want to give an airing here ?

Imbecile.


Er, perhaps.


** Wot a glutton for punishment we have here - folks.


Mosfets don't have the same thermal characteristics as BJT's, which are
more prone to thermal runaway. So perhaps when you are runing Mosfets
hard, there is some kind of compression thing going on which sounds nicer
than a BJT amp exploding after clipping a lot.


** Another 100% fuckwit MOSFET myth.............

Go away - you IDIOT !!!



...... Phil

No, this is good fun, and you might eventually tell me why my supposition is
untrue.



Gareth.

 

[Arny Krueger]

"RichD" <r_delaney2001@yahoo.com> wrote in message
news:b78fc9c2-fe9c-444c-8ac5-606090de2aba@p31g2000prf.googlegroups.com

Who do MOSFET sound better than bipolar, as an audio amp
output driver?

Who do? That's voodoo!

 

[Arny Krueger]

"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in
message news:48D22443.DDA0AA02@hotmail.com

Kevin McMurtrie wrote:

In article <Xns9B1CC001D5128damon161attbicom@127.0.0.1>,
Damon Hill <damon1SIX1@comcast.netnet> wrote:

RichD <r_delaney2001@yahoo.com> wrote in
news:b78fc9c2-fe9c-444c-8ac5-
606090de2aba@p31g2000prf.googlegroups.com:

Who do MOSFET sound better than bipolar, as an audio
amp output driver?

They do? Seems like it's possible to design good
amplifiers either way.

--Damon

Exactly - zero difference in quality capabilities. It's
usually a matter of impedance matching. Silicon
transistors have a fixed loss around 0.5 volts. MOSFETs
have a resistive loss inversely proportional to their
voltage rating. That usually makes MOSFETs less
expensive for low impedances and transistors less
expensive for high impedances.

TOTAL AND COMPLETE GARBAGE.

Agreed. Actually, what Kevin said is the exact reverse of generally accepted
practical knowledge. Bipolar is generally more efficient when the impedances
get really low. MOSFETs were trendy for a while, but most new power amp
designs seem to have bipolar outputs.

 

[Arny Krueger]

<hahn.alan@gmail.com> wrote in message
news:2dea72bd-1108-42d7-b2f3-03e46979c14e@x41g2000hsb.googlegroups.com

On Sep 17, 6:12 pm, RichD <r_delaney2...@yahoo.com> wrote:
Who do MOSFET sound better than bipolar, as an audio amp
output driver?

MOSFETS HAVE WIDER BANDWIDTH ,less phase shift , lower
odd harmonic distortin. on and on.

Not in any relevant way for audio power amps.

 

[Phil Allison]

"Eeysore"

I know of no 'PA' amps currently using mosfets.

** Huh ????

All those hundreds of thousands of MOSFET audio power amps made since the
mid 1980s have not justs disappeared you know - power amps made by H-H &
Harrison Electronics plus C-Audio in the UK , Perreaux and ZPE of NZ,
Australian Monitor and ARX (still in full production) and Jands here in
Aussie - plus many other less well known brands.

The majority are STILL in use, maybe looking just a bit the worse for wear.

Even in the UK - Chevin Research ( based in Yorkshire) A-series amps are
all lateral mosfet designs.

http://www.chevin-research.com/products_a_series.php



...... Phil

 

[Phil Allison]

"Gareth Magennis"

** Bugger off - wanker.

Gareth Magennis wrote:

If a Mosfet amp compresses the bottom end slightly over a BJT,

..... blah, blah , blah .....

 

[Phil Allison]

"Gareth Magennis"

No, this is good fun, and you might eventually tell me why my supposition
is untrue.

** Cos nothing makes it true.


YOU FUCKING Z- GRADE IMBECILE !!!




..... Phil

 

[Arny Krueger]

"Gareth Magennis" <sound.service@btconnect.com> wrote in
message news:AOidnVsvye4VrE_VnZ2dnUVZ8u-dnZ2d@bt.com

Not if you clip them like you might a valve amp for
example.

Straw man. It is entirely practical to build power amps that are never
clipped in actual use. If you don't like how your power amp clips? Get one
with enough output so that it never clips.

Would a Mosfet amp clip more "nicely" than a
BJT amp?

Power amps aren't just devices, they are circuits. Circuit design can
easily trump device characteristics.

In fact the sharpness of the clipping of a power amp relates to things like
how much negative feedback it has, all things considered. If you have a
circuit with lots of negative feedback, it is very likely to clip very
sharply and ideally. If you have a circuit with less negative feedback, the
clipping will be softer, but will occupy a larger proportion of the transfer
characteristic.

I'm thinking driving bass speakers.

If they need lots of power, get a powerful power amp. Forget about what's
inside the box, worry about how the box works.

Is this
what some of these "audiophools" or perhaps PA guys are
getting at by saying they sound better?

This whole "amp sounds better" stuff was fully debunked 30 years ago. Good
power amps sound the same and they sound like a piece of wire with gain.

There are tons of power amps that can't be distinguished from a piece of
wire with gain, while driving well-designed speakers.

There are quite a few amps that meet the same criteria while driving even
the weirdest speaker load.

A really good power amp will destroy a poorly-designed speaker before it
starts sounding bad, and really good power amps aren't all that unique.

 

[Scott Seidman]

wolti_At <wolti@sil.at> wrote in news:b877a9d2-e1fe-4afb-b19e-
bd8c9ff963a6@m44g2000hsc.googlegroups.com:

Hello,

I am currently working on a design where I need to amplify the signal
generated from a glass electrode and a reference electrode. Right now
I have a basic input amplifier with an instrumentation amplifier from
analog devices working. The challenging task on these designs is the
very high output resistance of the glass electrodes (up to 200Meg) and
the noise immunity. The input stage is very simple and all input
traces have a guard ring which is biased to the common mode voltage
(to reduce leakage). The inamp currents are handled by a connection to
the media which the probe is placed in.
Since this is my first design with electrodes I heard a bit around on
the net and some people seem to have a different input stage which is
based on a capacitor and an integrator. I wonder if someone has seen
such other circuits because it would be interesting for me to evaluate
other options.

Thanks for any input,
Christian Walter

With a glass electrode, you have a large surface area of dielectric
between two conductive fluids-- a big capacitor!!


You actually need to use a negative capacitance preamplifier with a glass
microelectrode. I haven't built one, but they're not too difficult.
It's actually an op-amp in a positive feedback mode, with a capacitor in
the loop

--
Scott
Reverse name to reply

 

[GregS]

In article <48D286B7.F1458CB3@hotmail.com>, Eeyore <rabbitsfriendsandrelations@hotmail.com> wrote:

Rich Grise wrote:

RichD wrote:

Who do MOSFET sound better than bipolar, as an audio amp output driver?

Because you believe they will.

Because they CAN. By a country mile. But all people want today is cheap. And
if they want esoteric they want the high distortion of tubes instead of
ultra-low THD of well-engineered mosfet amps.

Graham

Seems like most people like the Hafler amp of old. Is the design still around ?

greg

 

[Jorden Verwer]

Eeyore wrote:

Jorden Verwer wrote:
RichD wrote:
Who do MOSFET sound better than bipolar, as an audio amp output
driver?

The device properties of BJTs are superior to those of MOSFETs in all
respects,

How about SOA for one you UTTER MORON ?
Fine, fine, but that doesn't have any direct influence on what you'll hear,

because it's a boundary condition.

Do you even know what SOA is ?
Like I said, it's a boundary condition. It can influence the performance of

the circuit, but only indirectly, through other design decisions.

except for offset - there MOSFETs have the advantage. Whether you
will actually hear this depends on many more factors.

YET MORE INSANE BOLLOCKS
Now you're being the moron (not that I admit to being a moron before). It

seems that either you don't know what you're talking about, or personal
attacks are a hobby of yours. Because, frankly, everything I said was
true...

Fact - MOSFETs have lower offset than BJTs.
Fact - The fidelity of the sound depends on much more than just device
properties.

 

[Scott Seidman]

wolti_At <wolti@sil.at> wrote in news:d0d44b3f-c410-4dca-b40a-1b7a055c16d4
@f63g2000hsf.googlegroups.com:

I am now checking how this negative
capacitance preamp could improve the design.

http://www.springerlink.com/content/r84r356672837745/

--
Scott
Reverse name to reply

 

[Jorden Verwer]

Eeyore wrote:

Jorden Verwer wrote:
Eeyore wrote:
Jorden Verwer wrote:
RichD wrote:
Who do MOSFET sound better than bipolar, as an audio amp output
driver?

The device properties of BJTs are superior to those of MOSFETs in
all
respects,

How about SOA for one you UTTER MORON ?
Fine, fine, but that doesn't have any direct influence on what you'll
hear,
because it's a boundary condition.

It TOTALLY proves wrong your assertion "The device properties of BJTs are
superior to those of MOSFETs in all respects"
No, it doesn't.

Do you even know what SOA is ?
Like I said, it's a boundary condition. It can influence the performance
of
the circuit, but only indirectly, through other design decisions.

except for offset - there MOSFETs have the advantage. Whether you
will actually hear this depends on many more factors.

YET MORE INSANE BOLLOCKS
Now you're being the moron (not that I admit to being a moron before).
It
seems that either you don't know what you're talking about, or personal
attacks are a hobby of yours. Because, frankly, everything I said was
true...

What the FUCK is this 'offset' you're talking about. Do you mean biasing ?
No, of course not. If I'd meant biasing I would've said biasing. BTW, I

don't see how one component's biasing can be "better" than another one's -
it's simply a design step that's necessary to make it work. I mean, nobody
would say "this amplifier's frequency compensation is so much nicer than
that one's"...

As for offset, here's one explanation (in the context of opamps):
http://en.wikipedia.org/wiki/Operational_amplifier#DC_imperfections

Note that I never claimed that this is relevant in audio applications - but
it's there.

As for your personal attacks towards me, I should mention that I'm under the
impression that your experience with electronics outside audio applications
is fairly limited, given that you've apparently never heard of the term
offset.

 

[Szczepan Białek]

"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote
news:48D26D91.3050802@electrooptical.net...

Transverse waves don't propagate in fluids because there's no elastic
restoring force in that direction, just friction. Thus a transverse
disturbance propagates like heat rather than like a wave, and dissipates
exponentially with distance.

Real waves are always the combination of transverse and longitudinal. The
same is probably in space. It is very important to know if vacuum brakes
comets and spacecrafts. Are such data available?
S*

 

[Jorden Verwer]

Eeyore wrote:

given that you've apparently never heard of the term
offset.

Offset is IRRELEVANT to output devices you complete MORON !
I know that, and I never claimed otherwise. Offset is a form of noise, in a

sense. And like noise, it is caused almost completely by the input
transistors. I'm well aware of all that.

Do do you know what a 'closed loop' means ?
Yes.

 

[Kevin Aylward]

Trevor Wilson wrote:

"RichD" <r_delaney2001@yahoo.com> wrote in message
news:b78fc9c2-fe9c-444c-8ac5-606090de2aba@p31g2000prf.googlegroups.com...
Who do MOSFET sound better than bipolar, as an audio amp output
driver?

**Non-sequitur. If you're saying that MOSFET outputs sound better,
they don't.

As a device, operating at typical bias currents (say) 10-50mA, MOSFETs
exhibit VASTLY more THD than BJTs. Only when bias currents are
elevated (around 0.5A - 1A) do MOSFETs exhibit THD characteristics
which are almost as good as BJTs.

MOSFETs are very tough, have an exceptional ability to deliver high
power, high frequency audio (and RF), but distortion is very high.
They require lots of Global NFB in order to operate linearly.

MOSFETs do not sound better than BJTs. At best, they can sound as
good. All things being equal.

Ahmm.... welll....here we go...

Well, I like mosfet outputs because they are easier to design with, imo.
Bipolars, often need an equivelent of 3 stage darlingtons. This makes it a
tad harder to stabilse the feedback loop because of each stage pole.

Basically, you only need about 6 low current transistors, or so, to achieve
silly distortion and bandwidth figures, with mosfets.

As far as "sounds better", that's all moot. Any competently designed amp
should have thd, imd below audibility.

Anyone that claims that a general purpose PA amp, sounds bad or not good, if
it has thd and imd < 0.005% and slew rates of 100V/us, is pretty much
delusional. Roll on the Ł200 oxygen free mains cable I say....

Kevin Aylward

www.anasoft.co.uk
SuperSpice

 

[Jorden Verwer]

Eeyore wrote:

Jorden Verwer wrote:
Offset is a form of noise, in a sense.

Every one a cracker. Maybe he hasn't heard of DC vs AC analysis ?
Let me put it this way...

Noise-like phenomena, in increasing order of bandwith:
Offset ==> 1/f noise ==> white noise

 

[Jorden Verwer]

Eeyore wrote:

Noise is AC
Offset is DC

End of story.
Not at all. You're oversimplifying. If offset were truly DC, it wouldn't

drift. And it does drift. Likewise, white noise also has an (infinitesimal)
component at DC. It isn't all as black and white as you claim it to be. I
realize this is a very theoretical approach, but I stand by my claim that
offset and noise are conceptually similar.

 

[BobW]

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:qi95d49u6ha3ocin1i5h77ra04vrgi3u5r@4ax.com...

On Thu, 18 Sep 2008 19:55:35 +0100, Eeyore
rabbitsfriendsandrelations@hotmail.com> wrote:



Jorden Verwer wrote:

Eeyore wrote:
Jorden Verwer wrote:
Offset is a form of noise, in a sense.

Every one a cracker. Maybe he hasn't heard of DC vs AC analysis ?
Let me put it this way...

Noise-like phenomena, in increasing order of bandwith:
Offset ==> 1/f noise ==> white noise

Noise is AC
Offset is DC

End of story.

Everything is AC when you get right down to it.

Best regards,
Spehro Pefhany
--

That's right, and similarly, a straight line is really just circle of
infinite radius.

Bob
--
== All google group posts are automatically deleted due to spam ==

 

[BobW]

"Ben Bradley" <ben_nospam_bradley@frontiernet.net> wrote in message
newsn45d4152rl21vf19td1igr4t189lqcpka@4ax.com...

On Thu, 18 Sep 2008 08:44:33 -0700 (PDT), Myauk
aungkokothet@gmail.com> wrote:

I am studying on PIC Reference UPS design manual
http://www.freeweb.hu/t-t/elokep/pic/download/picref01.pdf.

It explained briefly on the sine wave generation scheme. Reading the
program, I understand that it will start putting 0 on the PWM as duty
cycle first. Then next reference value is looked up from the table,
compare with the actual singal read from output via A/D converter from
which a new PWM value will be calculated.

I am looking for a detailed explanation on such kind of singe wave
generation algorithm using a micro controller like PIC.

All I need, I think, is the A/D converter specification, PWM
specification and the instruction of the controller to determine the
values in look up table, calculate the coefficients for compensation,
and some scheme for DC offset correction.

That UPS design does more than what you want to do, and the extras
may be confusing you.

(I always get a headache when looking a PIC-based design anyway)


What else more???

Could anybody please give me some links where I could find such kind
of detailed information??

A little more detail than this with less complex application will be
better.

I only need the sine wave generation part.

The main thing in all that stuff that applies to sine generation is
the lookup table.

You might want to google this:

numerically controlled oscillator


Thanks

Aung Ko Ko Thet

It's too bad this guy uses googlegroups to post rather than a non-spamming
news service. Otherwise, I would gladly share my code on how to make a
PWM-able microcontroller generate sine waves.

Bob
--
== All google group posts are automatically deleted due to spam ==