Repeated the wet sock scan and its not consistent. Hard to tell if anything works this way then. I was afraid of that. Very high Q resonances require an extremely slow frequency scan to avoid phase shift problems.
I noticed another interesting effect last night. If I put the speaker near the computer CRT monitor and scan, some frequencies make intensity waves travel across the screen (horizontal bar-like, but clearly sinusoidal modulation, with vertical motion).
I noticed another interesting effect last night. If I put the speaker near the computer CRT monitor and scan, some frequencies make intensity waves travel across the screen (horizontal bar-like, but clearly sinusoidal modulation, with vertical motion).
Attachments
With such high Q tube resonances, it will be very tough to isolate the tube from picking up acoustics. A very tiny acoustic pickup of the right freq. and for a few seconds will bring up the full amplitude resonance. It will take extreme measures to avoid any feedback. I don't think a heavy chassis will help this problem at all, it probably enhances it. You're really going to need exotic things like lead and aerogel and deadened shielding boxes to fix this.
smoking-amp said:
Don,
I will not tell anything else on the subject because such ideas are not mine and there are patents and copyright on it. I am just a simple user.
This has been investigated for nearly 30 years now and it has resulted in a really new science of musical sounds. Something totally radical and not imaginable until you experience it.
At this point I really feel to mention the genius together with the foundations of his new science and some of his creations (some of them are commercial products since many years):
http://moss.sitonline.it/
http://moss.sitonline.it/1/prodotti_164051.html
I heard that the site will have soon an English version.
I can only tell for sure that once you have the fortune to listen to the full MOSS system you will never go back.
45
P.S.
MOSS = MOde Shape System
MOSS 
Well, we probably can shield out the broadband acoustic pickup stuff (microphone effect), but the high Q resonances look nearly hopeless:
System suspended on air bearings with battery power, with modulated laser beam signal input and output thru vacuum chamber windows.
Neg. feedback comes to mind as the only practical fix for them.
Don
Oh,... for measuring the resonances (and attempted attenuation schemes), we just need to set the oscillator on a known resonance, and measure the steady response.
Well, we probably can shield out the broadband acoustic pickup stuff (microphone effect), but the high Q resonances look nearly hopeless:
System suspended on air bearings with battery power, with modulated laser beam signal input and output thru vacuum chamber windows.
Neg. feedback comes to mind as the only practical fix for them.
Don
Oh,... for measuring the resonances (and attempted attenuation schemes), we just need to set the oscillator on a known resonance, and measure the steady response.
leadbelly said:
Hmmm what about the guys like me who admit to the psychoacoustic pleasure of tube glow
There is plenty more for your brain in that system.
There is no room for aesthetic without functionality there.
If I get the consent from the author I will load some pics, though the live emotion is just shocking, both for eyes and above all for the ears. Guaranteed.
45
"This is the right way to do the job."
Nice. Suspended by some elastic or a spring? How well does it work?
"If I had to hide it inside a box I'd just use sand! "
Does kinda look like one of George's (Tubelab's) procedures for tubes that didn't make the grade at 3X rated dissipation. A tube "hanging".
Maybe could put the tube in a bottle of clear silicone oil instead of lead, then suspend the bottle.
Nice. Suspended by some elastic or a spring? How well does it work?
"If I had to hide it inside a box I'd just use sand! "
Does kinda look like one of George's (Tubelab's) procedures for tubes that didn't make the grade at 3X rated dissipation. A tube "hanging".
Maybe could put the tube in a bottle of clear silicone oil instead of lead, then suspend the bottle.
Not sure I quite understand the focus on damping at this stage of the game. The whole point of the thread originator was that there is something about DHT's that results in more richness and depth to the output, that gives a perception of more realistic timbre (at least for some listeners). The hypothesis was raised that internal mechanical resonances in the tube might be responsible for this effect.
If the point is to demonstrate that the resonant behavior that Don shows, is due to mechanical feedback, then comparing the same tube, with and without excitation is an obvious thing to try. But wouldn't it be simpler just to remove the tube under test from the sound field? Put the speakers in another room, outside, whatever. A wet sock around a high voltage tube? Yikes! We get nervous about schematics on here without mains isolation.
Carry on,
Sheldon
If the point is to demonstrate that the resonant behavior that Don shows, is due to mechanical feedback, then comparing the same tube, with and without excitation is an obvious thing to try. But wouldn't it be simpler just to remove the tube under test from the sound field? Put the speakers in another room, outside, whatever. A wet sock around a high voltage tube? Yikes! We get nervous about schematics on here without mains isolation.
Carry on,
Sheldon
"A wet sock around a high voltage tube? Yikes! We get nervous about schematics on here without mains isolation."
Yeah, that was a little overboard I guess, don't try that one at home folks. (didn't work anyway) It was actually a damp sock, not a dripping wet one, rolled up around the tube with a foam layer over it to handle it. All in the interest of science.
"wouldn't it be simpler just to remove the tube under test from the sound field? "
Yes, all one needs is to use some headphones to listen, with the speaker on or off to check for feedback effects etc. When I get my Hammond 124B xfmr, or if Andy can try it out. He's the one who best knows the DHT effects.
Yeah, that was a little overboard I guess, don't try that one at home folks. (didn't work anyway) It was actually a damp sock, not a dripping wet one, rolled up around the tube with a foam layer over it to handle it. All in the interest of science.
"wouldn't it be simpler just to remove the tube under test from the sound field? "
Yes, all one needs is to use some headphones to listen, with the speaker on or off to check for feedback effects etc. When I get my Hammond 124B xfmr, or if Andy can try it out. He's the one who best knows the DHT effects.
Sheldon said:
I start from the end: the hypothesis is wrong. Demonstrated and always repeatable (as is for any true scientific claim).
Without excitation of its mechanical resonances the DHT sounds simply better.
The experiment has been done not only for a DHT (or other tubes) but for any component of the audio system.
Damping (in its literal meaning) is not the right thing to do.
An elastically suspended object at subsonic frequency works by means of
inertia reaction for our purposes.
Basically the (big) difference is: damping the resonances means that you are attenuating a negative effect that is already masking and irreversibly degrading your sound, while inertia reaction simply does not make it happen, not only as consequence of speakers acoustic feedback but anything of the outer world that can excite your components!
45
45 said:
The hypothesis is that mechanical motion inside the tube (probably filament) is what is causing the effect Andy reports. Your evidence that it is incorrect?
45 said:
To everyone? And your evidence for this is?
45 said:
In the necessarily subjective context of what one finds enjoyable, "negative effect" is simply a value judgement, unless one can show that virtually all listeners make the same negative judgemet. Given that in the typical system (and I add the qualifier, typical, only in the consideration of scientific uncertainty), one cannot duplicate the performance experience (as in, indistinguishably from live), then "irreversibly degrading your sound", does not have the same meaning as "inaccurately reproducing the input signal". Your "degradation" might be someone else's enhancement.
There can certainly be correct and incorrect ways to assign cause and effect for audibly distinctive system differences. The same cannot be said for how one chooses to experience recorded music.
Sheldon
Sheldon said:
Yes and now everyone has a true method to verify it. Also it is accessible to everyone because you don't need a mortgage!
What would be an evidence?
A picture of a flat frequency response attached here?
Well....it could be anything!!!
Sheldon said:
I just wrote my opinion on the sound (which is not only mine however, but in this contest it is). Sorry if I didn't specify.....
Then we are only speaking of objective and measurable stuff and here I see you have nothing to tell!
45
45 said:
Let's review:
1. Andy started the thread with the subjective opinion that DHT preamplifiers make music, particularly stringed instruments, sound more real to him.
2. Two basic possibilities ensue: The DHT more accurately preserves detail in the music, or the DHT adds something that makes the music sound different (better or worse, each gets to decide).
3. The first case seems to better explain the observation for reasons previously explained.
4. A possible explanation for a music compatible addition, is a subtle contribution from vibrating elements within the DHT - energized (most likely) by feedback from the sound field.
5. Don's measurements confirm that DHT's can be quite microphonic (which we already knew). But they also start to characterize the resonance of individual triodes, some of which is low Q, but some is high Q.
6. As relates to the the starting point of the thread, the next most obvious (to me, others my have different priorities, and as Don is actually generating the data, his matter most) questions are:
a. How the measured characteristics correlate with sonic impressions, and is there a pattern/amplitude which corresponds to Andy's observations, i.e., is there a subjective effect that could be described by some as increasing the impression of realistic instrument timbre for stringed instruments?
b. Is this effect dependent on feedback from the speaker output?
Objective measurements link cause and effect. Choice of effects is subjective.
Sheldon
Sheldon,
you are missing a fundamental point.
Indepentently of listening impressions: if you want to get objective and repeatable results about DHT resonances affecting the signal, you need a reference controlled condition: absence of resonances excitation.
Otherwise your conclusions can be just random because subject to systematic errors.
Can you put yourself in that condition?
If not, you cannot sort out this point:
If not, how can you state that? :
If not, you will be not able to respond to your questions.
45
you are missing a fundamental point.
Indepentently of listening impressions: if you want to get objective and repeatable results about DHT resonances affecting the signal, you need a reference controlled condition: absence of resonances excitation.
Otherwise your conclusions can be just random because subject to systematic errors.
Can you put yourself in that condition?
If not, you cannot sort out this point:
Sheldon said:
If not, how can you state that? :
Sheldon said:
If not, you will be not able to respond to your questions.
45
45 said:
???
http://www.diyaudio.com/forums/showthread.php?postid=1745347#post1745347
And
http://www.diyaudio.com/forums/showthread.php?postid=1758353#post1758353
I perfectly understand the need for a negative control and have so stated - twice. My point is that, rather than pursue a research project on isolating the tube via various mechanical means (damp socks, sorbothane, elaborate lead/coil assemblies, etc., why not simply remove it from the sound field. But hey, Don is providing the data, for which I am grateful - his call.
Sheldon
Sheldon said:
Removing the valve from direct sound field (i.e. putting the valve and speakers in two separate rooms) is no guarantee for insulation. Also, for the listening session, if you put them too far cables are a big issue.
The walls, especially, and the ground (low) pass a lot of vibrations anyway and their absorption can be quite variable. So you are not in a controlled (unambiguous) condition. The best absorption materials, for the audio range, I know have poor very absportion below 500Hz.
With all respect for Don, I cannot see a systematic method and unambiguous results which can guarantee true absence of DHT resonances excitation in the audio range (see post 161). The dynamic range in his measurements looks quite limited, there is a lot of background.
45
Instead what I was telling before has been exhaustively experimented by MOSS.
You can repeat it if you want. I gave all the necessary information.
Or you can give it for granted, measure it later and just listen to the results, not only insulating the valve but also the other components of the amp. Transformers first (that are even simpler to insulate because are already heavy).
45
You can repeat it if you want. I gave all the necessary information.
Or you can give it for granted, measure it later and just listen to the results, not only insulating the valve but also the other components of the amp. Transformers first (that are even simpler to insulate because are already heavy).
45
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