• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

'Splain this to me pleeze....

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#61
Just talking basic Physics, those fins have only a "decorative" application; tubes are NOT cooled by conduction and in any case they are not thermally coupled to them, but a couple centimeters away, so .....

Tube elements are inside the best insulator possible: a Thermos flask: "floating" in vacuum inside a thin wall glass capsule.

Only cooling possible is by radiation.

If any, those fins can keep case walls cool, but not tube elements.

Also agree preamp maker either got that case cheap or chose it for good looks, nothing beyond.
 
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#62
Grafting a valve follower onto an opamp stage can only degrade its performance. The opamp stage's output impedance is fractions of an Ohm in the audio range; it needs no external follower (with output impedance in the kiloOhm range) to operate. Combined with a very low B+ voltage and poor loadlines these kinds of things are more closely related to guitar effects pedals, except that they can't be turned off. Just say no.

All good fortune,
Chris
 
#64
JMFahey said:
Just talking basic Physics, those fins have only a "decorative" application; tubes are NOT cooled by conduction and in any case they are not thermally coupled to them, but a couple centimeters away, so .....

Tube elements are inside the best insulator possible: a Thermos flask: "floating" in vacuum inside a thin wall glass capsule.

Only cooling possible is by radiation.

If any, those fins can keep case walls cool, but not tube elements.

Also agree preamp maker either got that case cheap or chose it for good looks, nothing beyond.
Click to expand...
Thanks for the information
 
#66

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#67
academia50 said:
Perhaps Kevin Deal can convince you that it is possible.

Do me a favor, can you translate it for me, I don't speak English fluently...thanks

https://www.primaluna-usa.com/primaluna-evo-100-tube-dac
Click to expand...

Guy built a tube oscillator and filters the sinewave into a square wave and brags how good it looks. Not sure how much I believe this as you can see part of the crystal oscillator right in his photo. No way could you build an analog style RC oscillator with enough precision to do anything serious. Like the cathode follower connected to an opamp all it does it make things worse by increasing output impedance. I guess the limited bandwidth of the tube would improve your jitter 🤣
 
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#69
Do me a favor, can you translate it for me, I don't speak English fluently...thanks

https://www.primaluna-usa.com/primaluna-evo-100-tube-dac
Click to expand...
Oh, what a bunch of nonsense, lies, cheap marketing, unbearable.
Should have expected it when I read "Prima Luna" on the page title, KINGS of Snake Oil and Hyperbole.

A few pearls:

* They claim THIS:

Point To Point Wiring​

You spend a lot of money on interconnects. So why have the signal go right from the RCA jacks or speaker terminals into circuit boards with copper traces so thin you can hardly see them? What’s high-end about that?

PrimaLuna employs Point to Point Wiring on all products. The entire signal path, including resistors and capacitors, is painstakingly hand wired with heavy-gauge cable by craftsman.
Click to expand...
then show THIS:
EVO+100+DAC.jpg

WTF? 😱

They claim THIS:
First a note on the tube itself: The tube is a very rugged, long-life Russian military Triode specifically designed for oscillation purposes... which is its function here. It is running very conservatively so life expectancy is roughly 5 to 10 years of operating time. The small glass envelope guarantees very low microphonics.
Click to expand...
Then show:
image-asset.jpeg

Subminiature tubes are famous for being microphonic.
Some of them are so microphonic that they can actually self-sustain (enter an electromechanical oscillation) if you thump them with your finger.
Click to expand...
Guitar DIYers have unsuccessfully tried to use them in pedals or in DIY preamps, famous Seymour Duncan had to recall his preamps using them, go figure.
Tons of complaints around, as well as hardly working "solutions"
Such as wrapping them in heavy gauge copper wire:
33_super_tube_damper-1170x632_c.jpg

or
Mounting the pre-amp or line amp stage circuits on a separate chassis or circuit board that has shock mounts (like springy rubber grommets) might help some
Click to expand...
For a full thread on them: https://www.diyaudio.com/community/threads/microphonic-sub-miniature-tubes.131069/

And so on and on and on, but the Nobel Prize goes to:
Many DACs weigh in at ten pounds or less. The EVO 100 Tube DAC weighs nearly 29 pounds!
Click to expand...
Definitely a sign of quality, but then:
I wonder WHY they used bent sheet metal for the chassis, they should have used 1/2" thick cast iron for it, for a 100 pound DAC, how´s that?
 
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#72
Boydk

" You really shine with your lack of knowledge."


Boydk said:
Take a look at the picture. And notice the 2 QUAD 16pins OPAMP´s.
Project just flat out lies about it.

View attachment 1070148

You really shine with your lack of knowledge. Don´t believe everything you read from manufacurers 😉
Click to expand...
They are not OPAMP, they are analog switches DG412DY


I would have to report you for violating the rules of the forum, here we talk about technical issues, and you are offending me by qualifying me with the sentence above.
It seems that you like to make a fool of yourself by stating things that you ignore.
Now yes, enough for me.
And it would be nice if some moderator puts the padlock on this thread, it has long since deviated from the topic of the OP
 
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