Andre Jute wrote:
wrote:
And what a strange bitch she is!!
And what a foulmouthed little creepy-crawlie you are, Bobby Robbie. And
how dull your mind is.
No feedback!
And an ignorant little twerp besides. Now write on the blackboard one
hundred times: A MOSFET CONNECTED AS A SOURCE FOLLOWER IS THE SS
EQUIVALENT OF A TUBE CONNECTED AS A CATHODE FOLLOWER. A CATHODE
FOLLOWER APPLIES NEGATIVE FEEDBACK. A CATHODE FOLLOWER APPLIES NEGATIVE
FEEDBACK. A CATHODE FOLLOWER APPLIES NEGATIVE FEEDBACK. A CATHODE
FOLLOWER APPLIES NEGATIVE FEEDBACK.
No caps!!
No brains at Bobby Robbie! Capacitors colour the sound.
Just ****ing transformers!!
Mo' iron is betta iron!
What a dumb audiofool bitch!
I really hope you're trying to send us up, Bobby Robbie, because if you
aren't you will spend a lonely lifetime with just your hand for
company.
You're an ingrate, Bobby Robbie, especially after Ms Parker went to the
trouble of showing how you can copy her amp with mains toroidals you
could afford out of the lunch money you take off the smaller kids at
your school in a single day.
Simplicity is true genius. Me, I'm ready to declare Ms Parker a genius.
That gaincard guy must be eating his heart out.
Andre Jute
The only down side of the Parker topology is the input impedance.
She uses an input transformer to get 1Vrms of input transformed to 20Vrms
to apply to the high impedance gates of the mosfet source follower stage.
Thus the IPT has an impedance ratio of 1:400, so if the
R across the secondary is 100k, then this appears as only 250 ohms at the
input.
If you care to examine Ms parker's exact figures, you will see that her amp
is indeeed a low input impedance amp.
Thus the drive impedance from a CD player woulds also need to be very low.
Using a tube preamp or passive switched resistance or 10k pot would be out
of the question.
But a switched transformer attenuator would be OK, since if it was in the
-20dB position for most of the time there is a 10:1 TR reduction ratio, so
a 100:1 ZR,
so that 250 ohms would appear at the tranny attenuator input as 25k, and
able to easily be powered by just about anything.
The trouble with all these trannies trying to keep the bandwdth wide and
tranny
distortion low, somewhat problematical in signal trannies unless ppl
know how to use mixtures of perhaps mu-metal, nickel, and GOSS.
The taste of such materials is a bitter metallic one but to those with
perserverance
and equipped with the idea of reducing active devices to a miniumum,
then the experimental wind and try or suck it and see is a fair way to get
good performance.
Ms Parker has some samples of Sowter wound transformers woth quadrifilar
windings and cores of 50% nickel.
Methinks that in the case of the IPT, why not make it a tapped IPT
that can itself be used as the attenuator device?
Its a lot more work of course, but the cost of a Billington tranny
attenuator
is horrendous, so best thing is to eliminate the need to have such a
device.
PS This thread is already so unpleasant that there is no reason for me
to resist observing that if Stewart Pinkerton had any brains, when he
challenged me to a design contest he would have offered something like
Ms Parker's amp instead of the unbuilt, untested, badly conceived
travesty of an amp he did offer. But then I observe that Ms Parker was
properly educated, and has a good mind with lots of lateral motion, and
we can see she builds what she designs and develops it properly. If we
could persuade such an original thinker to contribute to RAT, our
intercourse would be hugely enriched. (Pun intended, made to show
congenital idiots like Bobby Robbie how one can be an amusing male
chauvinist pig.) But of course she won't come, precisely because of the
nastiness here. RAT is really its own worst enemy.
I doubt we would ever see Sue partake in discussions here or anyplace on
the web.
She wouldn't last an hour without being intellectually raped and bashed by
every mysogenist from miles around.
Patrick Turner.