Re: 845 first impressions, 22dec07.



Ian Iveson wrote:

Patrick Turner wrote:

I finally got one of the two monoblocs operational tonight
with a pair of Chinese 845 connected in parallel for SE
operation.

There you are, taking advantage of all those poor underpayed
and incompetent natives again...

Indeed. I agree I am a user, grimy greasy grister and exploiter.

But the Chinese ARE FREE to charge more for their tubes....

I have KR Audio 845 ready here but first I will make sure
its works
OK with the "expendable" Chinese tubes.

Poor buggers died at their machines...for what? You could
put a positive spin on it, and say something like
"absolutely the best valves ever for breadboarding".

I agree entirely. But anyone I ask has not the slightest valid plausible
reason as to why Our Universe exists.
people might as well die. I sure will eventually.

I am asked, "How are yer Patrick?"
I answer, "I dunno."
"Huh", they go...
"Well," I mention, "if you know why you are, you might know how you
are."

So then they ask "Howya ya goin?"

And I answer,
"By car, and often slightly further by bicycle."

They go "Huh", and so it goes.

My local butcher used to engage me thus every time I bought meat at his
fine little shop.

I think he eventually learnt to question the obvious.

Poor *** went broke, gave up, then got a divorce from his missus...

I hope I didn't cause that.





The results gave 53 watts at 2% thd into 6 ohms, slightly
more than I
had calculated for and with Ea = 1,025Vdc, Ek = 148Vdc, Rk
= 2k2,
and Ia thus 67mAdc.

Congratulations.1kV!

You're still alive, I notice.

Perhaps you could post the telephone number of your local
A&E. Should you fall uncharacteristically silent, we can
call for an ambulance.

yeah, the 1kV is always nervous nellie time for me.

I've trained myself with several shocks over the years to be wary,
but the way I have set up the rails means I have +750V and -500V and its
unlikely
I would get a boot off the 1,250V total supply voltage.



Rk for each 845 is a bunch of series parallel R on
heatsinks totalling
90 watt rating but only make 10 watts, so the underchassis
heatsink can
be touched

[etc, etc.]

Fer ***'s sake...a circuit diagram and a piccy would have
saved a million words.

Not this time. Not until I have finalised the details this week,
and then when I am 100% happy, I might post something to accompany
information already at my website about 845 amps.

Anyway, considering the amp is a commercial product, I find
it genuinely difficult to know what to say.

No matter what you consider, you always find it difficult to say
anything.
Feel free to be silent, nobody will object...

Another failure,
of course, would be grounds for derision, but success is
supposed to be normal, isn't it? Do I congratulate Scania
for making lorries?

Just as well as folks at Scania are making trucks to bring you your food
rather than have trucks made by yourself.....
You might starve if they were yours...

OTOH, it can't be denied that it's a serious accomplishment.
Perhaps, if I were a miner, I would congratulate Liebherr
for making the T282B.

Go right ahead...

And I congratulated Hockney for painting The Splash.

I liked the girl with nice boobs in the Movie 'Splash' much better....

I congratulated her on her breasts.

So, OK, well done.

A couple of questions, if I may.

Have you measured distortion at full power at the lower
frequency extreme you mention? Or perhaps the lowest
frequency at which THD remains below, say 2%, at full power?
I'm interested because, despite having 2 output valves in
parallel, you still have quite a high winding ratio.

Unlike so many makers who try to cheat the laws of physics
and conform to the lowest common denominator,
I always prefer to have high voltage swing, low current swing
with triodes wherever i use them.

The load of about 6k for TWO parallel tubes with Ea = 1,050 approx is a
very nice
load for 845, its about 5 x Ra, and thus Rout is nice and low,
THD is also low, and efficiency quite high for class A triodes.

With Ea slightly higher at about 1,070V I got 59watts from PdaQ = 150W,
with some grid current. Thye onset of grid I
with 3 x EL84 triode drivers cap coupled is a gentle compression of the
wave
rather than hard clip, so the actual average power level
can be higher if we allow the extra THD/IMD on peaks of transients.

I only want about 45 watts at clip...

If it
is intended to be a general purpose amp, and therefore able
to drive insensitive and low-impedance speakers, I wonder
how solid the bass will be. I'm not questioning your
transformers, as you've probably done them well...it's an
architecture point I'm pondering.

I also wonder.

But everyone who has purchased amps from me knows they give excellent
bass AND treble, which is simply the result of a wide BW OPT, and
tube line up, with well applied NFB so that there is almost as much NFB
applied
at 20Hz and 20kHz as there is at 1kHz.

I like to shape the open loop gain structure so gain is stepped below
20Hz and above 20kHz.
The last thing you want is high amounts of NFB applied at 7Hz and 70kHz.

But you do NOT want any early drive stage to saturate up to full PO
within the 20kHz to 20kHz range.

This is a big ask with an SE amp because the OPT must have
high Lp and low Cshunt, yet because of the air gapping the Lp
will always give much lower Lp than a PP amp with similar core size.

But one can cheat just a little with a 50 watt ceiling, knowing
that average levels will be the same as with a 12 watt amp.
Therefore the Lp of the OPT can have equal inductive reactance
to RL at 25Hz instead of say 20Hz with the lower power amp.

The 50W ceiling merely gives much better transients and lower THD/IMD
for average speakers of say 88dB/W/M efficiency.

I have not finalised the air gap yet and have not yet plotted the
inductance and core saturation frequency/voltage graphs.
But at present the Lp = 40H approx, medium PO.






More than that, I have been thinking about "legitimate
presentation", which is my current interpretation of "high
fidelity". My idea is that there have been a succession of
epochs, and a variety on niches, through the history of
domestic audio equipment. Within each there has been an
established social network of aficionados, who have adopted
particular styles of equipment. It is these social movements
that I contend lend the equipment "legitimacy". Only the
mainstream in each epoch, however, is "authentic". I am
trying to construct a distinction here to subsume the
"reproduction"/"how I like it" dichotomy, replacing it with
a resolvable "authentic"/"legitimate" axis, ahem.

For a flavour of what I mean, consider that in the time of
Mozart, orchestral instruments were different from their
modern forms. It is consequently rare now for authentic
Mozart music to be played, if at all. However, Mozart played
on modern instruments is clearly considered to be
legitimate, not just because that is how Mozart sounds to
everybody now, but because his music evolved along with
positive developments in instrument technology: progress was
made with his music in mind. Further, if there were a
minority branch of development, where a different movement
of devotees had arrived at another way of optimising the
instruments for playing Mozart, then that could be
legitimate too.

Similarly, each epoch in the history of the development of
domestic audio has seen a dominant topology that I would say
is able to play the music recorded at the time
authentically. Within each epoch, particular niches, when
supported by a movement of devotees, establish other
legitimate presentations.

Now, it is clear to me that a SET, together with sensitive
and well-behaved speakers, can provide an authentic
presentation of vinyl, and a legitimate presentation of
modern sources and media. They were mainstream, and since
then they have been a continuing widely-supported niche.

The question this has been leading up to is this:

Is your amp a waste of 845s?

No.

The amp gives what is regarded as hifi in terms of well known
technical measurements, good SNR, low enough THD/IMD,
wide enough BW, and low enough Rout, and high enough power
ceiling for its intended use.

My experience has been that real triodes or pentodes and beam tubes
connected as triodes
make superlative audio amplifiers.
Many listeners tell me triodes give a warm detailed and and more
emotionally moving experience
of music than that produced with solid state highy negative feedback
designs.

And this experience is not confined to triodes, and extends to
beam tetrode and pentodes when used with suitable loops
of medium amounts of NFB.




All those parallel valves, for example, might disqualify it
from legitimacy.

Its a common criticism that parallel tubes do not sound as "pure" as
a single triode.

But once paralleled, 2, 3, 4 or more paralleled tube merely
become ONE SINGLE TUBE because all the anodes are tied together,
and its impossible that separate signals from each tube can somehow
ever be applied to the anode OPT winding simultaneously and "mixed".
The signal at the OPT primary is the same at each parallel tube anode.
And so differences between tubes matter no more than differences
between sections of cathode, grid and anode were one to cut up a large
single tube
into sections and connect in parallel.

If someone listens to it driving typical
modern speakers, the best they can get is "this is how I
like it". That can't be what music is about. It can't be
enough to make it *right*.

Well it is in fact what the experience of recorded music IS ABOUT, imho.

Its entirely vanity if I sell people what they don't like.



Unless loads of people listen and a movement gathers. That
is only likely, IMO, if you have a *musical* mission. You
need to create a new niche with a critical mass of devotees.

So, what's the mission? What's the Turner Sound?

I find it difficult to describe what you want because all the words one
might
use have already been repeated endlessly by so many others about
their attempts to enliven speakers and transport people away
to where they wish to escape to from their daily struggle to exist.

There are fine makers of cellos, pianos, and guitars.
I hope I am amoung the finer makers of amplifiers.



Ian

PS...Mozart may have been too late...

No, he was too early.

Imagine if he was around today wil all the aids available for great
sound!

A friend of mine in Sydney, David Skinner, a fine musician and composer
of
music for documentaries and movies showed me his pint sized studio last
night.
His system is all SS, and quite good in fact, and he has that natural
talent to grasp the feeling of the visuals and provide sympathetic and
empathetic sound to accompany
the story, scenes, emotions.
He uses samplers, a keyboard, and a guitar, and so would Motzart if he
were around.
Bach also was a little wasted on his century, and could have been around
about now,
and his genious with intertwined tunes for each instrument could have
been more breathtaking than they are already.
Maybe he'd have been less religious though, and had less time to spend
making 21 children that
he in fact sired. A man of God, and of the ***, to be sure now.

My friend and I jammed a bit awhile with other friends at this party,
another priceless memory
was created....


Oh, and:

http://www.liebherr.com/me/en/products_mc.asp?menuID=106220!1944-0

As we type, hundreds of trucks of such ginormous size are carting
mountainfulls
of minerals from Australia's vast mines to waiting trains and then onto
ships to China
for conversion into Chinese export goods and Chinese way of life
improvements.

Hence our so called surge of prosperity with rising interest rates
and meanwhile the US has this terrible loans crisis, and hopelessly over
expensive
foreign policy, and falling interest rates.

Luckily, a tiny fraction of the national prosperity is trickling in my
direction.

But my 91 yr old mum might need a wheelchair soon, and her house is full
of staircases,
and although business isn't bad, life still is full of problems....

Patrick Turner.
.

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