Audio, hi-fi and car audio - What's your favourite voltage regs?

"Jim Lesurf" wrote in message
...
In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...

I know exactly what this thread was about before your first contribution
to it. It was about the difference between driving the DHT filament with
a voltage source, and a current source, and that's all.

Actually, that is incorrect. It started with a call from Andy to suggest
what PSU designs we favoured for applications like heating in the context
he gave. (cf below)

What you refer to was one of the various topics that subsequently arose.

Yes, you are correct, I had slipped my mind that you had posted on the
original discussion on "favourite voltage regulators".

The issue of how "perfectly" the PSU was floating didn't come into it.

Indeed. Nor have I ever said otherwise. Once again you are jumping to
erronious conclusions.

Am I?,

quote

I think we were talking about the use of resistors *external* to the heater
element, and in which the signal current would not appear if the PSU were
genuinely floating. *Not* the resistance of the valve between its heater
terminals. The point of the resistors being to reduce any effect of the PSU
not being a perfectly floating one.

unquote

I am afraid that your habit of taking things out of context and snipping
away what has been responded to has confused you again if you assumed
otherwise. :-)

See above. I snip because when threads get long (as this one has) if people
don't snip the possibility (nay, probability) is that confusion really will
set in.

I am afraid that your habit of snipping what others have said and then
taking things out of their context is still confusing you. Above you state
various opinions as if they were facts. It may therefore be useful to
copy some of what was actually written to restore some relevant context.
So, according to my records the first posting I made in this thread was
actually as follows:

Yes OK, you really didn't need to post the whole lot just to make that
point. I accept that I was in error in refering to your "first" post.

It was in other postings later one we got to various other topics...

What I wrote was to clarify what Nick had said and give a better
worded explanation for a point he made.

Yet I still cannot see how your post "clarified" one of his.

In view of the fact that you were addressing an entirely different issue
to the one we were discussing, it did not "clarify" anything, rather it
confused the issue.

I appreciate that it has confused you, since that was a different posting
on another issue to the above. As above, your problem here seems to be
that you have conflated and confused various issues and points that have
arisen in this thread. Since you have lost awareness of what I actually
wrote here is the first posting I made on the topic:

] Newsgroups: uk.rec.audio From: Subject:
] What's your favourite voltage regs? Date: Fri, 18 Jan 2008 09:35
]
] In article , Eeyore
] wrote:
]
]
] Nick Gorham wrote:
]
] Ian Iveson wrote:
]
] and the voltage reg will try and regulate that away, with a current
] reg, the signal is common mode, so not affected.
]
] UH ?
]
] Can only speculate at this point as I have never tried using these
] circuits for heaters in audio amps. However...
]
] With 'direct' heating the heater psu is - I presume - connected to the
] same physical place as the cathode signal. Having a 'constant current'
] PSU means the PSU looks like a high impedance connection, so will be
] less likely to have a loading effect on signal drive to the cathode if
] the PSU common mode isolation is poor. i.e. the problem is that the
] cathode signal has to drive any loading it sees due to the PSU, so a
] high impedance might be preferred.
]
] Slainte,
]
] Jim
]

This is the post from you which I erroneously called your "first" post.

And now we come to the crux of the matter.

In this post you refer to "a loading effect on the drive signal to the
cathode if the common-mode isolation of the PSU is poor"

By talking about "the drive to the cathode" you are suggesting that you see
this as a cathode driven amp. With common-cathode audio amps (which is what
we have here) there probably isn't even a signal *at* the cathode, let alone
one *to* the cathode. This is why I regard your post, repeated above, as
being utterly confusing.

Now by "common-mode isolation" I take it you are referring to what we have
above referred to as "perfectly (or otherwise) floating". In other words
this is the impedance *to ground* from the PSU, not the impedance *across*
the PSU. As the cathode is probably at cathode potential as far as signal is
concerned the common-mode isolation of the PSU is a matter of no importance
whatsoever.

Whether the impedance *across* the PSU is high or low will not affect this
common-mode isolation anyway.

And as I pointed out, Nick and I then exchanged emails about this.

Well so you have said. But as I have never seen these emails, nor has Nick
posted anything about them here, as far as I am concerned they do not exist.
You cannot use "secret evidence" to prove your point.

I also made responses to other points you made. Unfortunately, due to the
way you snip and then take things out of context, these then became
conflated in your mind, leading to more confusion on your part.

You made other points agreed. Some of them were interesting and relevant.
Unfortunately you tried to use them to justify what you wrote in the post
quoted above which, as I have already said, did not address the question of
the difference between current and voltage regulated PSUs at all.

I could also note that neither he, nor indeed anyone else, has supported
your own confusions. :-)

I'm not the one claiming that Nick has sent me emails supporting me.

TBH I assume that he and others have had better
things to do, and are content to let me waste my own time. Nick has been
reading this group for long enough to know how patient I can be. ;-
Indeed, Nick and Don have had quite an informative discussion in this
thread.

I agree, I've followed it with interest.

To be honest I think our argument has shown a remarkable amount of patience
on both sides. If you still think that:

quote

] With 'direct' heating the heater psu is - I presume - connected to the
] same physical place as the cathode signal. Having a 'constant current'
] PSU means the PSU looks like a high impedance connection, so will be
] less likely to have a loading effect on signal drive to the cathode if
] the PSU common mode isolation is poor. i.e. the problem is that the
] cathode signal has to drive any loading it sees due to the PSU, so a
] high impedance might be preferred.

unquote

has any relevance to the issue of current vs. voltage regulated filament
PSUs for common-cathode audio amplifiers, or "clarifies" anything that was
said before, or since for that matter, then all I can say is that I cannot
even begin to understand why. As far as I am concerned that post from you
shows that you were seriously confused about the point under discussion.

David.