John Curl's Blowtorch preamplifier part II - Page 2480 - diyAudio
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Old 22nd July 2012, 10:20 PM   #24791
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I find than many of us are on the same track. Phono is a hassle, BUT it can really show off a well designed audio system with a few really well done and preserved, demo discs.
I have a whole box full of vinyl records that I would not play for any rational reason, they sound just that bad, and they probably sounded that bad when they were new.
Yet, WHEN things are right, we can get to the TRUE ESSENCE of the music with a certain selection of vinyl discs, coupled with the best playback equipment.
Think of it like a sports car that is used for a variety of uses. It can be fairly noisy, and you can feel virtually every bump in the road. It won't haul a trailer very well. It might be OK for a commute, but maybe not over a longer distance, like a vacation, and certainly not with more than 2 people. Critics can argue that anyone who owns a sports car is either a snob or a fool, YET take this sports car on a twisty back road, and WOW! That is if your tires are up to shape, etc.
The parallel here is a phono playback system. IF the vinyl is first class, (kind of like a twisty back road), and your tires are first class (like a very high quality phono cartridge), and you are reasonably in tune (audio playback system reasonably adjusted), then you can get WOW as well from your phono playback system.
Not very practical though, and usually we have to rely on other modes of either automobile or music storage.
You might think of digital as like the electric car. Quiet, hi tech, efficient. Yet, compared to a quality gas automobile engine, it might be lacking in 'performance' for the most part. Digital does get better and better, but I still cannot live with it as a hi fi source, exclusively. I hope for better in future.
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Old 22nd July 2012, 11:47 PM   #24792
RNMarsh is offline RNMarsh  United States
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Originally Posted by DF96 View Post
Yeh, us techies are boring like that - we assume that people say what they mean and mean what they say. So every time you say something, I should assume that you really mean something different? That would certainly fit with what you have said so far, and the 'evidence' with which you back it up. Trouble is, it makes meaningful discussion quite impossible. At least it will save me some time, as I won't have to point out the errors or shortcomings in what you say; instead I will just assume that you don't mean it anyway.
Great.. that way you wont have to think too hard.

Or. perhaps I am writting in short hand to you..... This stuff has been gone over a lot in the past. Some get it, like JC, and some dont. Sorry it isnt complete enough for you here. But I am not going over the long version here with you. Lets talk about John's blowtourch. We're on page what now? Thx - RNM
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Old 23rd July 2012, 12:05 AM   #24793
RNMarsh is offline RNMarsh  United States
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I find than many of us are on the same track. Phono is a hassle, BUT it can really show off a well designed audio system with a few really well done and preserved, demo discs.!
I like and have heard a lot of great LP's on my system. And, I had many classical performances on rare albums from Europe et al. The best i heard to date wasnt with a CD player.... it was via demian martins liitle guy, the PK100 into a BenchMark DAC1 from high resolution downloads in FLAC or WAVE files. It is a quantum leap (dont go taking me literally!) over CD. Instruments sound most real in my house for the first time.

[JC, come over and try the twisty roads of hwy 49 with me in my modified ZR1 or modified CTS-V! I like high-performance in everything.... women, cars, art, video, audio. Why settle for less? ] -RNM

Last edited by RNMarsh; 23rd July 2012 at 12:08 AM. Reason: its all in the details --
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Old 23rd July 2012, 02:19 AM   #24794
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Well Richard, I am glad to know that you have found something significantly better than normal CD. I have an Oppo Blue Ray player being modified (about 6 mo late) that I hope to get better SACD and DVD. I also have a new computer with 24/192 capability, but I have not learned to use it yet.
I have heard a lot of hi end digital at CES over the years, but nothing knocks my socks off, so far.
Unfortunately, I can't feel comfortable driving on freeways, anymore. I have basically, just one good eye, and IT needs new lenses. I just drive my 944 around town.

Last edited by john curl; 23rd July 2012 at 02:31 AM.
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Old 23rd July 2012, 03:06 AM   #24795
RNMarsh is offline RNMarsh  United States
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Default maybe I should pick u up?

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Originally Posted by john curl View Post
Well Richard, I am glad to know that you have found something significantly better than normal CD. I have an Oppo Blue Ray player being modified (about 6 mo late) that I hope to get better SACD and DVD. I also have a new computer with 24/192 capability, but I have not learned to use it yet.
I have heard a lot of hi end digital at CES over the years, but nothing knocks my socks off, so far.
Unfortunately, I can't feel comfortable driving on freeways, anymore. I have basically, just one good eye, and IT needs new lenses. I just drive my 944 around town.
Maybe I can come get you sometime when we are both available to visit. drop me an email and give me your phone number. If my own eye sight keeps getting worse, I'll have to start selling cars.... these two are scary quick and not for traffic driving anymore in close quarters. Anyway, since I left living in the Bay area about 15 years ago, we have a lot of catching up to do. CUL(ater). "Dick" Marsh
BTW - the best all analog I ever heard was at Dave Wilson's home with your electronics and custom (by you) tape deck playing Dave's masters. The CD player I use now uses a computer disk drive instead of the usual consumer cd player drive and best IC's and still seems like a stop-gap solution... though very much more conveient to use and operate and no wearing et al. But DSP and digital is really getting good now and so - being an early adopter type - am looking into its performance now. The OPPO is super great base to start with. Should give you a lot of enjoyment.... I got excellent 3D setup which is great HD res and picture is better than at an iMAX. Long live analog!

Last edited by RNMarsh; 23rd July 2012 at 03:30 AM.
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Old 23rd July 2012, 03:13 AM   #24796
gpapag is offline gpapag  Greece
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Originally Posted by scott wurcer View Post
George, It is almost impossible to believe a TO-39 transistor being microphonic enough to be audible in an ordinary sound field. You get a 3D stress tensor applied to the die from the can, die attach, and die system this gives rise to a 3D strain field that causes parameter and operating point changes. Put real numbers on these and you are way down in the noise. More likely the "engineer's fickle finger" removes parasitic oscillation especially in a metal can, the damping of the finger is certainly negligible.
Scott
The direction of energy flow you are describing, is not the one I meant to convey (no parameters and operating point changes as well). See my initial post:

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Even transistors can sing horribly when stressed/overdriven. Why? (*)
And the harmonic content of the distorted output changes when the “ singer” is damped with a finger touch (this simply means that the mechanical motion in turn distorts the electric signal, i.e. microphony).
(Says the metal can to the die: … You Don't Move Me - Ana Popovic on Don Odells Legends.mov - YouTube )

I will try to explain in a more boring way :
Strong electrical signal –“working” signal of the transistor-induces (assuming piezoelectricity) alternating mechanical stress within the die.
The die is strained accordingly.
This tinny strained mass transmits vibrations to the part of the metal can to which it is attached to (high mechanical impedance, efficient transmission).
Vibrations are transmitted to the rest of the metal can surfaces (some reflections occur as well).
The whole can is now quite a large vibrating surface to efficiently emit acoustic energy in the air.

In turn now (the microphony part), these vibrations of the can are transferred back to the die as mechanical stress. The die is strained and (assuming piezoelectricity again) generates electrical signal - analogous to the vibrations it receives from the can - at the electrodes of the transistor. This delayed and distorted “microphonic” signal, is mixed with (injected into) the “ working “ electrical signal of the transistor electrodes.

You may be correct about the “fickle finger” removing (shunting to ground?) parasitic oscillation.
I am been kept away from my bench. I can not replicate the test now. Besides, I don’t remember which finger I used then.

The anecdotal (porn) story I am referring to, goes something like this:
The amp bare PCB is on the bench ~ 30 - 40cm from my ears. I drive the circuit with sinusoidal signal and intentionally increase the drive, watching on the scope the power rails and the output of the amp feeding a dummy load.
A thin metalic sound comes from the PCB while the amp is overdriven, again and again. I locate the sound source ( two driver transistors in that initial case) .
While overdriving the amp and watching the distorted output, I place my finger over one or the other of the noisy transistors and the distorted amp output signal on the screen becomes a bit less ugly.

I have noticed emitted sounds from transistors on other amplifiers too that I have overdriven.

George
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Old 23rd July 2012, 03:27 AM   #24797
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You're probably thinking John Pfeiffer.
I know about Jack Pfeiffer, one degree of separation in fact. Maybe it was pre-Red Seal.
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Old 23rd July 2012, 05:25 AM   #24798
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Have you been to Marco Polo's final destination city - the end of the Silk Road --- XIAN? Its fantastic!
No not yet, someone else was asking me the same question only yesterday. Its on my mental list of places to visit for sure - I hear the dumplings are excellent.
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Old 23rd July 2012, 05:44 AM   #24799
jcx is offline jcx  United States
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I have read of thermal expansion coefficient mismatch causing "oil-canning" motion in T0-3 cans

but these thermal expnasion based motions are not technically piezoelectric and not "reciprocal" http://books.google.com/books?id=1x_...sducer&f=false

doped Si in chips is also not piezoelectric - it can be piezoresistive, the resulting Vos modulation by package strain is discussed in Av 4000x strain gage amplification

Last edited by jcx; 23rd July 2012 at 06:04 AM.
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Old 23rd July 2012, 06:08 AM   #24800
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Originally Posted by bcarso View Post
Concur! Although I did hear a tuning fork crystal break in overdrive once.

And I was looking at the bottom of a TO-5 2N5416 (if memory serves) as it blew up, and the flash was visible through the blue Kovar-sealing borosilicate glass around the base and emitter leads Still no sound though.
I heard sound when hats were popping off the base. Before that they were flat, after that they were round.
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