[Andre Jute]

Reminded of my roots by Al Marcy (tubegarden) in his recent posts, I
reprint an exchange with someone who built a $400 tube kit and wanted
to improve it:

*******
From: Will )
Subject: what should I do now?
View this article onlyNewsgroups: rec.audio.tubes
Date: 2003-10-20 21:07:19 PST

Ok,

I built a kit (bottlehead) and I love it and Im going to build another
but
not until later (xmas gift, win lotto, etc).

I still feel like I want to know more about what I am building than
connecting terminal 14 to terminal 2. What is a good book to read or
project
to build (cheap) to help me understand audio equip better. Ive taken
multiple electricity classes @ a tech college + factory training level
(Im
a BMW Tech) so I have a good understanding of the majority of most of
the
tube project schematics Ive seen (and general electricity) with the
exception of the actual tube portion itself.

thx,

-will
********

And my reply:


Will

I built a SEX kit from Dan Schmalle (Bottlehead) for a review in Glass
Audio about six years ago.

You dont say which kit you built. But it is worth considering that Dan
originally designed his amps to be of use to those experimenting with
tubes who dont have facilities or want to spend the time making
metalwork (normally the most time consuming part of building an amp
unless youre really tooled up and experienced). The name of his first
amp, Single Ended eXperimenters Amplifier, tells you the purpose.
Unfortunately most people who built it wanted to preserve it lovingly.
General purpose idiots on RAT (there are always a few here) abused me
for putting mine in a large and sturdy but ungainly box with plenty of
space for additional and large components. As Dan intended when he
designed it, I made some pleasing experiments on it, and used it for a
while to break in Lowther drivers, before passing it on to someone
else. Dan soon developed that super little amp into several others. It
may be that your present Electronic Tonalities amp is suitable for
experimenting on.

My GA article demonstrates a few things one can do with even a
well-designed amp to study various changes.

A few important parameters that are not obvious even to someone
knowledgeable about electronics, to be gained by working with actual
amps and your ears as measuring instruments in addition to whatever
else you have (I started with only an old AVO analogue meter), include

adding chokes to the power supply

making the power supply choke input rather than cap input

making the rectifying caps bigger or smaller

replacing electrolytic caps with film (polyprop)

replacing silicon rectifiers with faster ones, and then with a tube
rectifier.

All of these affect the quality of the sound, and its presentation
quite fundamentally. It teaches a basic principle of amp design
unfortunately rarely discussed in the irrelevant welter of discussion
of date codes on Mullard tubes, that the power supply is the most
important part of the transfer function of the complete amp.

Moving on to more sound-shaping, in the signal section, you can also
try:

rewiring for a higher output impedance if the transformers allow it

making a makeshift reflected primary impedance change by mismatching
speakers to output taps

fitting better quality transformers

changing the quality of coupling caps (they should of course all be
film)

changing the value of coupling caps after a study of the Miller Effect


changing caps in the cathode circuit

All of this teaches and demonstrates circuit theory, including
subtleties about the actual load on signal tubes as distinct from the
apparent one.

A very fine tube study tool often overlooked is the computer already on
your desk, on which

with in any drawing program you can put up transfer curves (plate
current vs late voltage vs negative grid bias with the signal level
superimposed along the slope of the output transformers primary
impedance, from which you can calculate output power and the frequency
distribution of distortion

with a spreadsheet (Excel is common and good), which you either build
yourself from the formulae in the RDH (see below) or find from Jim de
Korts DIY site, or that of the excellent John Brocic (Al, whats the URL
of his site?), or that of the superb Steve Bench, study changes in all
other parameters

as an example, you can determine the minimum of negative feedback with
which your amp will be stable (see RDH below), and then by soldering
alteration determine if lowering the NFB sounds better

All of this is very useful for understanding complicated interrelations
which could be expensive or impossible to study on real amps without a
whole plethora of measuring equipment.

At this point you can move on to swapping tubes:

fit a beefier driver to deliver more current to the grid of the power
tube requires fundamental redesign, of which you should by now be
capable

change input and driver topologies first to SRPP and then to anything
that takes your fancy

try input and interstage transformers from surplus or cheap
(Southwestern???) sources

try inductive constant current loads either by wideband chokes or by
faking it with silicon (see Steve Benchs site or old copies of
Bottleheads Valve magazine)

swap tubes because some types are fundamentally more precise or sweeter
than others (6SN7, 417A)

discover that 12AX7 belong in invisible current pre-amps and 6DJ8 is
for poseurs with cloth ears

swap tubes of the same type for better brands if you want to be a
fashion victim

All of this teaches that within very wide margins the quality of an amp
depends less on the tube types or brands it is built with than the
thought with which it is designed, and the determination with which it
is developed.

Finally, you can make truly fundamental changes, which may require more
sensitive speakers because they trade off power for better quality
sound:

change a Class A/B output amp to operate in Class A1

change pentodes to operate as pseudo triodes

fit real triode output tubes (may require an airgapped output
transformer see also Bottleheads sit for shunt power feed alternative,
which he calls parafeed)

You can also develop your amp to a lesser extent, once you have
everything else as you want it, by replacing ancillary components:

a good pot for a cheap one or even a stepped attenuator

good quality connectors and switches

ceramic sockets with connectors plated silver or gold

This is mickey mouse stuff. There is even pickier stuff. I use Cardas
wire, for instance, because I can afford it and find George Cardass
golden section ideas aesthetically pleasing, but in general, if the
wire will carry the current and is rated for the voltage at 70 degrees
or over, you wont hear any difference. If the amp is wired already with
a reliable brand of UL1017 (someone straighten me out if that isnt the
600V 70 degree spec), you wont hear any advantage for rewiring with
something more expensive. All copper wire starts out oxygen free all
wire starts absorbing oxygen the minute it is cut. There are some minor
exceptions that dont affect consumer audiophiles: On very long runs of
speaker cable there is an audible distinction between using Cardass 5TC
and the normal audiophile figure of eight crap sold for more per foot
by others. The biggest difference you can make with wire is by simply
shortening your connection leads.

By the time you worked through all this, if your ears are good and you
are not impressionable (i.e. not a fashion victim or too impressed by
your own cleverness) you will understand the first thing about amps,
which is that a well amp is in balance with itself, its sources and its
speakers, and of course with you. There is no single parameter of
goodness, and there is no better judge of quality hi-fi engineering
than your own ears. It is unfortunate that this is an expensive and
time-consuming journey, but arrival is very rewarding indeed. I wish
you luck.

The book you should have above all others and study religiously (Im not
jokingI have a copy in each of the lavatories in my house I use, and
several others in at my design desk and worktable and so on) is F
Langford-Smith biblical opus, the Radio Designers Handbook, published
in facsimile of the last tube era edition by Butterworth Heinemann,
shorthanded on newsgroups as the RDH. Earlier it was called the
Radiotron Designers Handbook, but secondhand copies are as pricey as a
new one. Next to your soldering iron, the RDH is the best investment in
your tube education you will ever make.

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

[[email protected]]

Andre Jute exuded:
Reminded of my roots by Al Marcy (tubegarden) in his recent posts,

and a bunch of blather followed.

It has been promulgating bad information and poor design since long
before 2003, and seems to have learned nothing since then in any case.

So, why would it bother to repeat the same blather over and over...
Oops... that is its style in search of one who might know no better and
mistake it for something with knowledge.

Peter Wieck
Wyncote, PA

[[email protected]]

Hi RATs!

Each of us may judge any design by our own experimentation with what we
have in front of us.

We do not have to listen to rude little snots telling us it is all too
intellectual for mere mortals. Some pigs indeed think they are more
equal than others, on or off Animal Farm.

If you wonder about how something might sound, try it yourself.

The nuisance critics just like to see their excrement in type. That's
cool. Me, too. But, I listen for myself, as others seem to me to get a
few of the finer points out of sequence.

That is, by my local, personal standards. I am not proposing that any
human is more than a bag of bigoted bull****. I am simply suggesting if
you try something and listen, you will not have to care what rude
people post on the Internet. You will only learn what pleases you. You
may freely share your results. They may freely attempt to bash in your
head. **** them **** you **** me **** it

Each of us is allowed to misunderstand those true facts in our own way


Actually, it is a bit worse than that, each of us is condemned to
misunderstand anything we are not willing to discuss.

We may even misunderstand after long discussion. Nothing is ever
perfect. Well, except some RAT's personal designs Or their
"professional" designs

Life ain't great, but, we each get to pick which part we think is
worst, and best, if anything.

As I learned by boring tedium and long fear in that TV mini-series in
Viet Nam - the only important question anyone ever has to answer is: If
you're up to your neck in sewage and someone throws some **** at you,
do you duck?

Personally, I just eat as much **** as I am in the mood for, then vomit
it back at the *******s. It ain't like real fun, but, it is pretty much
what passes for life on this freaking asteroid.

So, listen and enjoy, and post what ever the hell you want. Nobody
really cares, it is just fun. Well, sometimes.


Happy Ears!
Al





wrote:
Andre Jute exuded:
Reminded of my roots by Al Marcy (tubegarden) in his recent posts,

and a bunch of blather followed.

It has been promulgating bad information and poor design since long
before 2003, and seems to have learned nothing since then in any case.

So, why would it bother to repeat the same blather over and over...
Oops... that is its style in search of one who might know no better and
mistake it for something with knowledge.

Peter Wieck
Wyncote, PA

[Lord Valve]

Do you have anything germane to the thread, or are you just interested
in proving to all herein assembled that your attitude is very close to
that of a snotty little girl?

LV




wrote:

Andre Jute exuded:
Reminded of my roots by Al Marcy (tubegarden) in his recent posts,

and a bunch of blather followed.

It has been promulgating bad information and poor design since long
before 2003, and seems to have learned nothing since then in any case.

So, why would it bother to repeat the same blather over and over...
Oops... that is its style in search of one who might know no better and
mistake it for something with knowledge.

Peter Wieck
Wyncote, PA

[[email protected]]

wrote:
Hi RATs!

And so forth.

Al:

Relax. Jute is the functional equivalent of the resident mole in
"Whack-a-Mole", only the mechanical example is more intelligent, or
certainly imparts better information. Apart from that, you are correct
in that it really is only your taste and preferences that matter at the
end... beware of others defining them for you.

You seem to like Full Frequency Single Drivers... I do not. However, I
will state for the record that I once heard John Coltrane playing a
solo Sax passage on such.... brought tears to my eyes. So, I can
understand their momentary appeal. I would criticize the speakers for
their faults, but not the person who prefers them. And I see nothing
personal in those criticisms of my choices... they are only mine, after
all.

This is not rocket-science, nor is it even particularly exotic... the
processes and materials have been around largely unchanged and largely
unimproved since the 1920s, with the exception of better materials and
parts. As such, it is within the grasp of bumbling amateurs (assuming
they live through a couple of exciting B+ experiences and learn
therefrom), through past-master engineers.

Peter Wieck
Wyncote, PA

[[email protected]]

Lord Valve wrote:
Do you have anything germane to the thread, or are you just interested
in proving to all herein assembled that your attitude is very close to
that of a snotty little girl?


In point of fact, given the OP, what I wrote is germane. Oh, you mean
of the drivel that it exuded? Point is there that the subject (thread)
is, like the proverbial horse, thoroughly dead. Only the likes of the
OP would attempt to beat further activity out of it.

Peter Wieck
Wyncote, PA