[Eeyore]

Ian Iveson wrote:

Eeyore wrote:

I haven't suggested that West uses a 10k pot. The cathode
follower would prefer the 100k.

On the basis of what principle do you say that ?

It's a 12AX7. Look up the curves and draw yourself a 10k loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

A Cathode follower doesn't have a 10k load you nitwit ! The cathode R is likely
to be a kilohm or two.


You would have to make a guess at West's operating point, since he
appears to be keeping it a secret.

Perhaps he'd like to tell us ?


You might consider, having drawn your line, whether a 12AX7 is
appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the more the gain,
and the less the current, the clumsier it becomes.

CFs have a gain of ~ one. Have you totally lost the plot man ?

Graham

[Ian Iveson]

Arny Krueger wrote

It's a 12AX7. Look up the curves and draw yourself a
10k loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

You would have to make a guess at West's operating point,
since he appears to be keeping it a secret.

You might consider, having drawn your line, whether a
12AX7 is appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the
more the gain, and the less the current, the clumsier it
becomes.

When does a CF have any gain at all?

Gain in the forward loop, Arny. It's a feedback circuit, as you know.

A CF built on a 12AX7 is a bit of a straw man. Why use a hi-mu
triode for a stage that *always* has less than unity gain?

Quite. Although there may be some circuits where it could be useful.

Looking at good quality circuits of sucessful commercial designs, a
12AU7 seems to be more to the point.

Possibly OK driving a 10k load and, given a typical operating point,
OK for a longish cable too.

cheers, Ian

[Ian Iveson]

Eeyore wrote

I haven't suggested that West uses a 10k pot. The cathode
follower would prefer the 100k.

On the basis of what principle do you say that ?

It's a 12AX7. Look up the curves and draw yourself a 10k
loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

A Cathode follower doesn't have a 10k load you nitwit ! The cathode
R is likely
to be a kilohm or two.


You would have to make a guess at West's operating point, since he
appears to be keeping it a secret.

Perhaps he'd like to tell us ?


You might consider, having drawn your line, whether a 12AX7 is
appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the more the
gain,
and the less the current, the clumsier it becomes.

CFs have a gain of ~ one. Have you totally lost the plot man ?

I'll stop teaching you if you get fractious.

Read my reply to Arnie wrt gain.

Nothing else deserves comment.

Ian

[Eeyore]

Ian Iveson wrote:

Eeyore wrote

I haven't suggested that West uses a 10k pot. The cathode
follower would prefer the 100k.

On the basis of what principle do you say that ?

It's a 12AX7. Look up the curves and draw yourself a 10k
loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

A Cathode follower doesn't have a 10k load you nitwit ! The cathode
R is likely to be a kilohm or two.

You would have to make a guess at West's operating point, since he
appears to be keeping it a secret.

Perhaps he'd like to tell us ?

You might consider, having drawn your line, whether a 12AX7 is
appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the more the
gain, and the less the current, the clumsier it becomes.

CFs have a gain of ~ one. Have you totally lost the plot man ?

I'll stop teaching you if you get fractious.

LMFAO !


Read my reply to Arnie wrt gain.

Nothing else deserves comment.

Lord Above !!

Do explain how you make a cathode follower with a gain greater than one. You're
simply obfuscating because you were talking nonsense and you got caught out.

Graham

[Eeyore]

Ian Iveson wrote:

Arny Krueger wrote

Looking at good quality circuits of sucessful commercial designs, a
12AU7 seems to be more to the point.

Possibly OK driving a 10k load

Just "possibly OK" ???

Do you know the first thing about valves ?

Graham

[Ian Iveson]

Eeyore tiresomely persisted

Ian Iveson wrote:

Eeyore wrote

I haven't suggested that West uses a 10k pot. The cathode
follower would prefer the 100k.

On the basis of what principle do you say that ?

It's a 12AX7. Look up the curves and draw yourself a 10k
loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

A Cathode follower doesn't have a 10k load you nitwit ! The
cathode
R is likely to be a kilohm or two.

You would have to make a guess at West's operating point, since
he
appears to be keeping it a secret.

Perhaps he'd like to tell us ?

You might consider, having drawn your line, whether a 12AX7 is
appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the more the
gain, and the less the current, the clumsier it becomes.

CFs have a gain of ~ one. Have you totally lost the plot man ?

I'll stop teaching you if you get fractious.

LMFAO !


Read my reply to Arnie wrt gain.

Nothing else deserves comment.

Lord Above !!

Do explain how you make a cathode follower with a gain greater than
one. You're
simply obfuscating because you were talking nonsense and you got
caught out.

I haven't said a CF has a gain of any particular value at all. You
just made a false assumption that I judged you might get right (fat
chance) and now you demonstrate you can't read. If you think a
feedback circuit is obfuscation, you are dafter than I thought. That's
quite daft.

I gather you still haven't tried a 10k loadline on the 12AX7's
characteristic curves. Try the 12AU7 too, while you're at it.

Your dependence on received wisdom hasn't done you many favours in the
past, Graham, especially as it appears to be non-transferable in the
absence of fundamental understanding. No point in me encouraging it.

Ian

[Eeyore]

Ian Iveson wrote:

I haven't said a CF has a gain of any particular value at all.

I suppose the task mentally defeated you ?


I gather you still haven't tried a 10k loadline on the 12AX7's
characteristic curves. Try the 12AU7 too, while you're at it.

Do please explain how drawing a load line would provide any useful information
wrt a cathode follower.

How about addressing the issue instead of responding with obfuscation this time
?

Graham

[Eeyore]

Ian Iveson wrote:

Your dependence on received wisdom hasn't done you many favours in the
past,

Good Lord you're stupid !

Graham

[Ian Iveson]

Eeyore nagged

I haven't said a CF has a gain of any particular value at all.

I suppose the task mentally defeated you ?

I leave that kind of stuff for Patrick.

I gather you still haven't tried a 10k loadline on the 12AX7's
characteristic curves. Try the 12AU7 too, while you're at it.

Do please explain how drawing a load line would provide any useful
information
wrt a cathode follower.

How about addressing the issue instead of responding with
obfuscation this time
?

For who? West is too stupid, and you are too rude, to learn.

I don't know which part of "characteristic curves" you don't
understand.

Perhaps you might explain why you think they don't apply to a CF?

Or why, if you drive a 10k load with a typical AX7 CF, a 10k loadline
drawn through the DC operating point would not be appropriate? As you
say, there is likely to be 100k at the cathode, which is hardly
significant in parallel with the 10k for the purpose of an AC
loadline.

But you still haven't tried, have you? It would be worth your while to
grasp the point if you wish to try your hand at designing something
with valves in it.

Ian

[Eeyore]

Ian Iveson wrote:

Eeyore nagged

I haven't said a CF has a gain of any particular value at all.

I suppose the task mentally defeated you ?

I leave that kind of stuff for Patrick.

Exactly, it's over your head.


I gather you still haven't tried a 10k loadline on the 12AX7's
characteristic curves. Try the 12AU7 too, while you're at it.

Do please explain how drawing a load line would provide any useful
information wrt a cathode follower.

How about addressing the issue instead of responding with
obfuscation this time ?

For who? West is too stupid, and you are too rude, to learn.

I don't need to learn anything from you. I started learning valves about 38 yrs
ago. Besides, you just said you leave the hard stuff for Patrick to do.


I don't know which part of "characteristic curves" you don't
understand.

I don't know what part of them you imagine is relevant to cathode followers.


Perhaps you might explain why you think they don't apply to a CF?

Or why, if you drive a 10k load with a typical AX7 CF, a 10k loadline
drawn through the DC operating point would not be appropriate? As you
say, there is likely to be 100k at the cathode,

Where did I say that ?


which is hardly significant in parallel with the 10k for the purpose of an AC
loadline.

But you still haven't tried, have you? It would be worth your while to
grasp the point if you wish to try your hand at designing something
with valves in it.

LOL ! Incidentally a 12AT7 used as a cathode follower has an output impedance of
~ 250 ohms.

Graham

[Chris Hornbeck]

On Mon, 09 Apr 2007 20:07:55 +0100, Eeyore
wrote:

Ian Iveson wrote:

I don't know which part of "characteristic curves" you don't
understand.

I don't know what part of them you imagine is relevant to cathode followers.

All of them. That's the point.

All good fortune,

Chris Hornbeck
"Oh, life is a glorious cycle of song,
A medley of extemporanea;
And love is a thing that can never go wrong;
and I am Marie of Roumania."
- Dorothy Parker

[Patrick Turner]

Sander deWaal wrote:

Patrick Turner said:

So a 100k pot would offer no audible losses over a 10k pot.

Indeed.

The 10k pot would load a previous CF with too low a load if tubed.
Just because we have a triode set up as a CF which gives low Rout 1k,
it doesn't mean we are permitted to use loads lower that the common
cathode gain stage.

That's why I suggested to put the pot (switched attenuator) in front
of the CF, wit a selector switch if one so desires.

My initial post seems to have been lost in the battle of wits that
followed.
I don't have the stamina to write hundreds of lines of text about
something that can be done with in a single paragraph..........


Well we have this guy with his phono amp with CF output,
and probably incorporating a an RIAA FB loop,
and with only a gain pot between it at the outside world.

Then I challenge his reasoning and cheekily ask him and the group about
20 questions
after being told not to do so, and to pass over certain posts.
I mean well, but find this atmosphere dull, and suffocating.


I probably have failed miserably to get people
to think so they could solve all their own problems.

Many don't wanna think, they just wanna sit around lazily
and never ask questions of themselves, just ask the group, "save me,
alas I miss bandwidth.."

I think we have to be responsible for the bandwidth we create.

But yeah, you'r right, a CCF after the gain pots is always the more
better way to do it
because the Rout always remains low, and the HF losses are not going to
occur
becayse the Cin to a CF is less than 20pF.
This means another damn tube set up after the gain pot.


Patrick Turner.


--

- Maggies are an addiction for life. -

[Mark Aitchison]

Eeyore wrote:

Mark Aitchison wrote:

100k step resistors not the same as 100k potentiometer

Would you care to explain your philosphy behind that statement ?

Graham

100 k step resistors means step resistors of 100k each, so total
resistance = N times 100k; 100k potentiometer means 100k from end to
end. The important question was whether the potentiometer is 100k
end-to-end, and my initial reading of the posting was that the step
resistors are 100k each (which makes a v-e-r-y high value
potentiometer!)... everyone else worked out it was short-hand for a 100k
potentiometer, which makes more sense. If this is a stepped volume
control, with 100k between steps, the h-f has to be really bad, so bad
as to be obviously wrong.

[Patrick Turner]

Arny Krueger wrote:

"Ian Iveson" wrote in
message k
Eeyore wrote:

I haven't suggested that West uses a 10k pot. The
cathode follower
would prefer the 100k.

On the basis of what principle do you say that ?

It's a 12AX7. Look up the curves and draw yourself a
10k loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

You would have to make a guess at West's operating point,
since he appears to be keeping it a secret.

You might consider, having drawn your line, whether a
12AX7 is appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the
more the gain, and the less the current, the clumsier it
becomes.

When does a CF have any gain at all?

A CF built on a 12AX7 is a bit of a straw man. Why use a hi-mu triode for a
stage that *always* has less than unity gain?

Looking at good quality circuits of sucessful commercial designs, a 12AU7
seems to be more to the point.

Typical THD from a 12AU7 or 12AX7 in common cathode at 1Vrms output is
less than 0.1%
with loads of greater than 3Ra.

When the load is put in the cathode circuit, the same open loop gain
exists
as exists for the common cathode connection.
Closed loop gain is always less than unity for cathy folls.

But the gain reduction due to the series voltage NFB is a much higher
factor in 12AX7
than in 12AU7, and so if there was 0.1% open loop, closed loop gives
0.1% / 70 if open loop gain was 70.
So expect 0.00143% THD with 12AX7 CF.

But you still only get a 0.0005Arms current swing if the AX7 idel
current is 0.7 mA.

Using a 12AU7, if idle current is 4 mA, a 2.8mArms I swing is possible.
open loop gain is reduced by a factor of 1/15, so THD = 0.0066% at a
volt,
and obviously quite low enough, hence although the 12AU7 isn't as linear
as the 12AX7,
it has more oomph!

One will find that the 12AU7 with a 4mA CCS cathode load will provide
a wider bandwidth and capacitance loading won't cause such appalling
distortions at
the lower frequency that you get with 12AX7 as the CF tries to act as an
AC peak detector
as F rises.

Patrick Turner.

[Patrick Turner]

Eeyore wrote:

Ian Iveson wrote:

Eeyore wrote:

I haven't suggested that West uses a 10k pot. The cathode
follower would prefer the 100k.

On the basis of what principle do you say that ?

It's a 12AX7. Look up the curves and draw yourself a 10k loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

A Cathode follower doesn't have a 10k load you nitwit ! The cathode R is likely
to be a kilohm or two.

You would have to make a guess at West's operating point, since he
appears to be keeping it a secret.

Perhaps he'd like to tell us ?

You might consider, having drawn your line, whether a 12AX7 is
appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the more the gain,
and the less the current, the clumsier it becomes.

CFs have a gain of ~ one. Have you totally lost the plot man ?

Graham

Catholic Followers do have gain.

Its called open loop gain, and is Vk / ( Vg - Vk ), right?
And this gain, A, = µ x RL / ( RL + Ra )

But followers are examples of high amounts of local series voltage NFB
loops.

So they have close loop gain and this = Vg / Vk, which is always less
than 1.0000, OK?

And you can have a 10k load for a CF, and the guy you said was a nitwit,
isn't.

Please adhere to conventional and well known and defined generic
engineering language at all times,
so we know what you are talking about.

Patrick Turner.

[Eeyore]

Mark Aitchison wrote:

Eeyore wrote:

Mark Aitchison wrote:

100k step resistors not the same as 100k potentiometer

Would you care to explain your philosphy behind that statement ?

100 k step resistors means step resistors of 100k each, so total
resistance = N times 100k; 100k potentiometer means 100k from end to
end.

I could barely believe anyone could have done that ! OTOH it would explain the
observed HF roll-off without even the need to include a longish cable in the
explanation.


The important question was whether the potentiometer is 100k
end-to-end, and my initial reading of the posting was that the step
resistors are 100k each (which makes a v-e-r-y high value
potentiometer!)... everyone else worked out it was short-hand for a 100k
potentiometer, which makes more sense. If this is a stepped volume
control, with 100k between steps, the h-f has to be really bad, so bad
as to be obviously wrong.

One wonders !

Graham

[Eeyore]

Patrick Turner wrote:

Eeyore wrote:
Ian Iveson wrote:
Eeyore wrote:

I haven't suggested that West uses a 10k pot. The cathode
follower would prefer the 100k.

On the basis of what principle do you say that ?

It's a 12AX7. Look up the curves and draw yourself a 10k loadline.

What good would that be for a cathode follower ?

The characteristic curves don't care about circumstance.

A Cathode follower doesn't have a 10k load you nitwit ! The cathode R is likely
to be a kilohm or two.

You would have to make a guess at West's operating point, since he
appears to be keeping it a secret.

Perhaps he'd like to tell us ?

You might consider, having drawn your line, whether a 12AX7 is
appropriate for driving a long cable in any case.

My opinion is that a CF is a clumsy instrument, and the more the gain,
and the less the current, the clumsier it becomes.

CFs have a gain of ~ one. Have you totally lost the plot man ?


Catholic Followers do have gain.

Its called open loop gain, and is Vk / ( Vg - Vk ), right?
And this gain, A, = µ x RL / ( RL + Ra )

But followers are examples of high amounts of local series voltage NFB
loops.

That's one way of looking at it. A perverse one IMHO. I simply prefer to see it as
another kind of application of amplifying devices. I can assure you no solid state
designer considers emitter followers in that light yet functionally they are doing
the same thing.


So they have close loop gain and this = Vg / Vk, which is always less
than 1.0000, OK?

Yup. That was exactly my point in fact. It will always be in the range typically say
0.9 0.99.


And you can have a 10k load for a CF, and the guy you said was a nitwit,
isn't.

I never said you can't have a 10k load. I disputed the need to 'draw a loadline' on
the published curves with a 10k load.


Please adhere to conventional and well known and defined generic
engineering language at all times, so we know what you are talking about.

Do please explain where to draw this load line and its relevance to a CF.

Graham

[Peter Wieck]

Patrick:

Something to keep in mind, a bit of poetry from Schiller:

Against stupidity, the gods themselves labor in vain.

In a slightly lighter vein, from Dorothy Parker:

You can lead a horticulture, but you can't make her think.

What makes *you* think that you can do any better than these two
against invincible ignorance?

Peter Wieck
Wyncote, PA

[Patrick Turner]

Peter Wieck wrote:

Patrick:

Something to keep in mind, a bit of poetry from Schiller:

Against stupidity, the gods themselves labor in vain.

In a slightly lighter vein, from Dorothy Parker:

You can lead a horticulture, but you can't make her think.

What makes *you* think that you can do any better than these two
against invincible ignorance?

Nothing makes **ME** think I can do any better than the persuasive
Dorothy Parker types of this world, or any gods in another world.

I know I cannot really have any great effect here on this planet, I am
but
one very insignificant male gender person of an unromantic character
and
undesirable age and un-photogenic appearance who farnarkles around
with tubes in audio amp circuits, guided by a tiny amount of applied
intelligence.

I have zero claims to fame, and have gotten use to the fact I will never
be famous, never be rich,
so I may as well try to teach my craft if I cannot sell it much or
obtain breathtaking reviews in Stereophile, for which I would have to
pay an obscenely large amount of money.

I still get a nice sense of satisfaction when someone plays some music
through my gear
and they look at me and say things like, "why did I waste all that money
on that
other crap?"

I sometimes feel like the circus performer still doing the trapeze at
age 60....

But at least if I fall, its only off the chair to the ground, not from
50 feet up.

I do hope its not an unwanted sustained shock from 500 volts that sends
me to the floor.

One can only hope, try to be good....

People should not take my apparent terseness as a sign I am fed up with
ppl, I ain't, and I still enjoy talking about the audio manufacturing
experience.

It seems only natural to me to try to encourage the best efforts from
everyone
I meet, so they benefit the most.

Is hard to treasure quality based on cost cutting and absent minded
design,
and I urge tinkerers to consider the long term effects of what they are
doing.

I once was extending the house of a university arts professor in 1982.
He'd had me build a couple of beautiful rooms, then he engaged a pool
builder to build a
nice 12 metre swimming pool in the large yard beside his tennis court.
He had the most stunningly attractive daughter, age 17, and when the
pool
was filled, she liked to soak up sun quite topless which slightly swayed
my gaze
and delayed completion of the work I did on the house nearby.
Her father came to me one day to ask where he should place a pool fence
and what height it should be.
He said he'd like to use a brush fence, which would be a screen for
privacy.
So I said let's take a walk around the outside of your property, and
look back
at it from the point of view of understanding the mind of a passing
person looking in, as we might look back upon ourselves, and so that we
may better undertsand the situation,
and ourselves.
The guy got the drift of what I was saying.
Very soon, an optimal solution about where the fencing was to be placed,
and a fencing contractor was hired, and Bridgette could bask in all her
glory
without passerbuyers peering in.
I had to feel sorry for the fencing guy, a young fellow I knew well.
Bridgette "hung out" while he tried to work, and I comiserated,
but mentioned casually that if he laid a finger on the girl he'd be in
deep dodo.
And so would I have been, had I tried anything.

So there are times in life when we must be wise, step outside of
ourselves,
and look at ourselves from afar, and ask, who is that man?
Then we must let the thoughts about ourselves flow.

And there are times we must step firmly on our tongue,
and sit heavily on our hands, lest a cock drag us to regret.

I recall that after I completed work for that family, and moved on,
I used to occasionally meet Bridgette in the disco bars around town, and
we
often had a chat, and a dance, a drink, but she was a rich man's young
daughter,
and I was the slightly old swarthy hired help from across town, and
simply
not amoung the right class of person for her to **** with.

I've never cared that I have spent most of my life working in dirty
gear,
and being lower caste. I feel no shame.

But at least i knew where to put a fence up,
and how to speak to his highness about it, without mentioning his
princess for a moment,
and without either of us being embarrased, and without the slightest
hint of a fee,
because for a lot of the time I just enjoy talking to people.

Patrick Turner.











Peter Wieck
Wyncote, PA

[Mark Aitchison]

Patrick Turner wrote:

Catholic Followers do have gain.

I have some Pope valves... does that count?

[Patrick Turner]

Mark Aitchison wrote:

Patrick Turner wrote:

Catholic Followers do have gain.

I have some Pope valves... does that count?

Only if you go to church on a Monday and take Annode along,
for special prayers for the low Catholic Impudances.

Patrick Turner.

[Iain Churches]

"Mark Aitchison" wrote in message
...
Patrick Turner wrote:

Catholic Followers do have gain.

I have some Pope valves... does that count?

Sorry no. They should be Chinese valves -
cathay followers:-)