[Andre Jute]

Nick Gorham wrote:
Andre Jute wrote:
[snip]

Ok, same thing, repeated this time at 2w output, same conditions as before.

Here is 5v fil

http://www.lurcher.org/~nick/audio/s...0bSpect500.pdf

Here is 4.8v fil

http://www.lurcher.org/~nick/audio/s...0bSpect480.pdf

And to use the 10% reduction mentioned, here is 4.5v

http://www.lurcher.org/~nick/audio/s...0bSpect450.pdf

Sadly, again, there seems to be no magic bullet in reduction of
harmonics higher or not. One interesting thing is the 4.5v fil gave a
small increase in output, but I am not at this moment sure if thats of
any real import.

If you do the same math as I did yesterday, you'll discover that,
assuming your instrument has that fine a resolution, the starved
filaments made the third and higher harmonic worse... Not what we
expected at all.

Anyhow, nothing like the sort of changes Steve reported when not used in
a power stage.

Well, Steve himself warned you, and I tried to.

--
Nick

In your other post you ask what I did to make starved fils work. The
answer is nothing; they either work for you at the margins or they
don't; it may be tube-dependent but I wouldn't know as I work with
only a handful of output tubes. However, I didn't give up on them
altogether for the same reason you state in your earlier post. After
Bill's death I couldn't duplicate his results reliably; we're now
speaking of the time when we used 4.5 or 4.6V fils, roundabout there,
and I couldn't see that the amps were built differently. However I
knew that 300B run longer on starved fils (I had Chinese, very
selected admittedly, that ran 14K hours, and WE from the 90s cooking
strong at over 10K hours), so I chose an arbitrary halfway point for
the fils, where there was still a possible or perhaps likely small
benefit in the harmonics and a certain benefit in longevity. I should
think you're starting to see why I don't prosetylize too hard on this
design feature, why I put it in my circuit and let those who are
interested make up their own minds.

I found this discussion useful for clarifying my mind on the subject,
and you've confirmed that it wasn't just my cackhandedness which
caused me to fail to repeat Bill's results. From my viewpoint that is
a very worthwhile result for the time invested. Of course, if you
don't fail in at least three out of every four attempts to improve
your amp, you can hardly yet describe it as well-developed.

Good luck, Nick.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[Andre Jute]

The braying ass Eeyore wrote:
Andre Jute wrote:

robert casey wrote:

Yech!


Gotta be tough to play in this sandbox....

That's my point. It is a disgrace that RAT is now more of an obstacle
course for real tubies than a facilitating mechanism.

Yet you did nothing to help facilitate west by contributing to the question he
asked.

Graham

Do you lie out of habit, Poopie, or are you senile and your short term
memory gone? We know you know I helped out West because we remember
you crapped on the trail of my post as you crap in every thread I
start or contribute to.

For your information, again, dear Poopie, I reprint what I told West:

*******
west wrote:

I built a typical phono amp with 3 12AX7s, the last tube a cathode follower
(low impedance). It has plenty of gain (70db) and can easily drive any amp
directly. I like using a 100k step resistor volume control instead of a line
amp.
My problem is that when I use any of my tube amps, the sound has limited
bandwidth. A SS amp does not exhibit this problem, if fact the SS sound is
rather impressive to me (for silicone).
With my limited know-how, I'm swagging that an impedance mismatch is the
culprit.
If my contention is correct, is there a simple cure besides using a line
amp? Perhaps some kind of buffer is called for. All comments welcomed and
thank you.

Cordially,
west

[to which I replied]

It's not an impedance problem, West.

You've built a filter consisting of the 100K pot and the following
cable's capacitance.

Reduce the pot to 10k, shorten the cable to no more than a meter (3ft
3in) or preferably 18 inches, and your problem should go away. Or you
can move the pot to before the cathode follower to break the link with
the cable capacitance.

Don't worry about the wretched kibbitzers who will now wield their
little bit of knowledge on you like a club. This is an error that is
often made by professional designers and sometimes even gets into
production.

As a matter of taste rather than electronics, you should also lose the
12AX7, which are suitable only for guitar amps, and build your preamp
with octals, preferably 6SL7 and 6SN7. The CF in particular should be
a 6SN7. If you don't want to reengineer the chassis for the bigger
sockets, at least try the 6CG7.

Another taste tip: A 12AT7 for practical purposes has as much gain as
the 12AX7 and sounds more precise. You can also, if you have the gain
in another stage, engineer in more warmth with the 12AU7.

HTH.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

*********

Remember it now, Poopie? If you still don't, you can look up your
several posts commenting sourly on my post helping out West.

So, Poopie, do you just lie from habit, or are you senile?

Unsigned out of contempt

[Andre Jute]

"flipper" wrote

Well, I did run across a Japanese site where the author built a tube
amp in a toaster oven so maybe I didn't miss much after all

Toaster, eh? Let's see, mount the tubes on the wire rack so they
retract when off and 'pop up' when on. Kewl.

, eh?

Sakuma had a fish restaurant and, according to the legend shared only
with iniatiates, built his first amp in a surplus fish frying pan when
he discovered the joys of sushi, or maybe just a supplier who wouldn't
poison his customers.

You aren't communicating with us by Quijja Board, are you flipper?

Andre Jute
Impedance is futile, you will be simulated into the triode of the
Borg. -- Robert Casey

[Nick Gorham]

Andre Jute wrote:


I found this discussion useful for clarifying my mind on the subject,
and you've confirmed that it wasn't just my cackhandedness which
caused me to fail to repeat Bill's results. From my viewpoint that is
a very worthwhile result for the time invested. Of course, if you
don't fail in at least three out of every four attempts to improve
your amp, you can hardly yet describe it as well-developed.

Good luck, Nick.


Yep, I guess what we can say with some confidance is that there seems to
be little to loose by operating (at least these valves, at this
operating point, etc, etc) with 4.8v fils.

--
Nick

[Sander deWaal]

"Andre Jute" said:


That reminds me. I have a Velleman Digital Preamp that my boy started
work on but lost interest in after fitting a handfull of parts. I put
it aside to complete later but a few years later my eyes and patience
are not up to soldering that many tiny joints. You want it, Sander,
it's yours for the postage.


Well, thanks for the offer, but I'll have to decline.

I don't use preamps, other than RIAA stages.

Ruud Broens perhaps? ;-)

--

- Maggies are an addiction for life. -

[Andre Jute]

Sander deWaal wrote:
"Andre Jute" said:


That reminds me. I have a Velleman Digital Preamp that my boy started
work on but lost interest in after fitting a handfull of parts. I put
it aside to complete later but a few years later my eyes and patience
are not up to soldering that many tiny joints. You want it, Sander,
it's yours for the postage.


Well, thanks for the offer, but I'll have to decline.

I don't use preamps, other than RIAA stages.

Ruud Broens perhaps? ;-)

How about it, Ruud?