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Re: Valuable 12AX7 and all this audio foo foo.
Ah yes, audio mumbo-jumbo. Before everyone jumps on my case, I do a fair amount of audio design and I DO know what i am talking about.
Most people forget there is a way to get very close to 'what it's supposed to sound', even without double-blind tests. First of all, one can expect that the artist producing the music has given their blessing to the final product, say a CD, and that is a tacit admission that what is on that CD, assuming it was pressed correctly and has no uncorrectable errors, is IT, the reference material. Next, get a pair of good headphones (it will probably be the last pair you get, anyway) and build a reasonably good amplifier. If you headphones are relatively high impedance dynamic, say 300-600 ohms, you should have no problem getting distortion to extremely low levels, and since it is a well behaved impedance, you will be eliminating 99% of all things that make a particular combo of amplifier and 'speaker' sound different. Then, providing you can separate tonality and spatiality, listen to the material, and you will be pretty darn close to what it's supposed to sound like. Phones have at least an order of magnitude less distortion than any speaker, perhaps excluding directly driven (no transformers!) electrostatics, even at unhealthily high volume. If a recording is 'bad', then that's exactly how it's supposed to sound from a good system - there should be no 'warmth' where it wasn't in the source, and vice versa. I often find that tube afficionados tend to expect warmth from anything. Such people only declare the liking to a particular sort of distorsion, not to high fidelity. Saying that tubes sound better when clipping than transistors is really the same thing - no clipping is supposed to occur in the first place... Speakers are the first point of suspicion. And if you go back into the amplifier, having seen many, even so called 'audiophile' ones, a lot needs to be done on education about proper high current wiring, power supply bypassing and filtering, magnetic shielding, and I won't even start on grounding. Some people need to be told the difference between inductors with a core, and ones wound on 'air', as well as between electrolytic caps and all others. Others need more subtle education, such as learning that relay contacts are not linear resistances (and for a VERY good reason) and that they are prone to microphoic effects. Etc, etc. Saying that cables, tubes, caps, whatever, sound different means nothing without at least theorising why. It was mentioned that the human ear is a curios thing and that it can resolve what measuring equipment cannot. This is nonsense. What measuring equipment? A scope? It operates in the time and amplitude domains and is linear, very different from the ear. There is no ONE parameter that can describe how something will sound, therefore forget about distorsion meters and RLC bridges. There are methods and instruments that can show VERY clearly what the differences between parts are regarding sound, it's just that they are not common, and they are not cheap. A real-time frequency analyzer with spectrogram or waterfall plot capability can tell you a lot of things, but not everyone has one. Someone mentioned that one listens with the brain. This is very important. I have participated in a study that tested 124 individuals for perception of reverbration. It revealed some interesting facts. One is that although the human ear may have a range which falls off severely over 16kHz, the human brain is capable of operating with phase shifts, that translated into a frequency, extend far above this, perhaps as much as an octave or more. It also suggested that the perception of amplitude is more precise than was originally thought of, and in fact, that it can be trained - a number of people in the test group were 'golden ears', (about 30%) their capability of better percieving minute changes in reverbration time tracked to 94%. Bottom line: things are measurable, what needs to be questioned are traditional methods of measurement. Z |
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Re: Valuable 12AX7 and all this audio foo foo.
--- In TekScopes@y..., dhuster@p... wrote:
Ain't no way the human sense of hearing has the bandwidth or thebe showing up in the October 2001 installment of "Q & A"I would respectfully suggest we return to our respective fields of expertise and experience and the central topic of this forum, Tek 'scopes and related items. Enough misinformation has already flowed in other technical forums to to run off members over the whipping of this VERY dead horse therein. I came here to learn what I don't know, and not to be vicariously ridiculed for what I have already learned through my own experience elsewhere. Odd, this is only my second posting and I have yet to get a response to my first on-topic request for information at mssg #278. This is the Tek group, right? Somewhat exasperated; Steve Bringhurst |
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Re: Valuable 12AX7 and all this audio foo foo.
James & Kandy Nunn
"The ear is a funny thing" very true but we do not hear with our ears we hear with our brains and are therefore subject to all the follies of the mind IE we tell ourselves what we want believe and we end up believing it, and I am not talking about Audio.
To me the question has always been that it may sound different but is it necessarily better? Audio is very subjective and having worked in the audio industry in the 60's and 70's (SAE, JBL, Altec) and I can tell you that most of it is hype and the rest is peer pressure. I for one am not a fan of asymmetrical distortion and I find tubes to be "fuzzy" sounding you may call it warm if you wish. That said and done a couple of years ago I off loaded a Mac 275 for $7500 that I had paid $395 for in 1969. . . anit tubes great! Jim |
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Re: Valuable 12AX7 and all this audio foo foo.
OOOhhhh, this has been the cause of some VERY hot debates on the audio newsgroups.
I certainly won't get into it here. I would LOVE to be the participant of a double blind, being the engineer at heart. In my experience, the *biggest* impact on sound is the actual design of the circuit. Second on the list is the quality of the transformers (power, choke, and output - tube amps). Frequency response, phase shift, impulse response, core saturation, etc. all are very important in an audio transformer. After that, WAY down on the list are capacitors, then wire, tube sockets, resistors, etc. I've never been able to really tell a big difference between them. Speaker quality is a huge impact, also. Good speaker drivers have lower distortion in the motor than cheap ones. Most commercial speakers measure really bad w.r.t. distortion. But again, there is stuff going on that instruments can't measure. I can't explain that while my one cheap Sony CD player sounds pretty awful, but measures just fine, a second unit that has been upgraded with better capacitors in the power supply, better op-amps in the output section, and some other minor mods, sounds completely different. Measures the same, but sounds smoother, better pace and timing, just more toe-tappin' musical. Has anyone ever wondered why Tek used Telefunken, Amperex, and Mullard tubes in their scopes and not RCA, GE, Westinghouse, or Sylvania, at least in the small signal positions? I would guess that they knew these were higher quality, more reliable, quieter, more linear, and more consistent. Those same parameters make a difference at 10kHz as they do at 5MHz. Chris TekScopes@... wrote: __________________________________________________________________ Get your own FREE, personal Netscape Webmail account today at |
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Re: Valuable 12AX7 and all this audio foo foo.
Dean, not to get into a big debate here, but there are lots of things going on that test gear cannot measure. I agree with you, as I am an engineer, and I say "speak with data". But, I've listened to solid state amps that measured .001% distortion that drove me from the room and then listened to a single ended tube amp, no feedback, that had 1.5% distortion that had me dancing like a fool.
The ear is a funny thing, and engineering cannot explain it. Measurements of steady state tones tell us one thing, but how an amp reacts in a dynamic time domain is totally different. Amps clip a large percent of the time, and how the amp clips has a lot to do with sound. A graceful clip from a tube amp with no feedback sounds better than the hard clip of a transistor amp with huge amounts of feedback. This is a debate that has been going on in audio for decades. Let's just say that everyone has an opinion, and whatever makes YOU happy is what counts. I agree that audio is ripe with rip offs, but having spent the last 5 years building my own gear, trying wire, resistors, capacitors, tubes, topologies, and measuring it all, I still don't understand it. I can try 3 different .22uF capacitors in a circuit, and they will ALL sound different. It may be subtle, but with good gear with a lot of resolving power, the differences are there. Each one will measure exactly the same on a scope or distortion meter, but sound entirely different. Each cap has differing inductance, geometry of the wind, dielectric materials, and Equivalent Series Resistance, or ESR. Dielectric effects are particulary audible, causing smearing of the signal due to charge/discharge characteristics. You'll never see this on a scope. Now, getting on to magic rocks and other stuff. I do agree that this stuff is of dubious value. Many times a person will insist his $2000 cables sound better as he has to convice himself that he didn't just get ripped off. It's really fun stuff it you look at it at face value. By home brewing and understanding the theory, I can see how much b.s. there is out there. There's also a lot of truth. Tubes DO sound different, as each manufacturer has a slighly different cathode oxide formulation, plate structure, processing procedure, etc. Again, your tube tester may say they are the same, but the signal gets treated slightly different, and it can be heard. For a scope or radio, it probably won't make a diff. Best, Chris TekScopes@... wrote: <Big snip> __________________________________________________________________ Get your own FREE, personal Netscape Webmail account today at |
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Re: Valuable 12AX7 and all this audio foo foo.
Stan or Patricia Griffiths
I am with Dean on this one. There is a special process called "double-blind
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testing" where these sorts of claims can be debunked. If I understand it right, double-blind testing amounts to the listener not knowing what configuration he is listening to and being required to choose between "A" and "B" a LOT of times, enough to get a pretty good statistical picture of whether things like tube brands, oxygen free speaker wire, and precision capacitors REALLY make a difference you can hear. Most audio nuts that I know REFUSE to submit to double-blind tests . . . and I think we ALL know why . . . Stan w7ni@... dhuster@... wrote: Methinks the tops of my boots are needing a few more inches to clear |
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Re: Valuable 12AX7 and all this audio foo foo.
Methinks the tops of my boots are needing a few more inches to clear
the effluent which is building. Ain't no way the human sense of hearing has the bandwidth or the dynamic range that even modest test equipment has. There is not a doubt in my mind that I could write up a page of pure fiction (including some references to Atlantis and perturbences in the orbit of Io) and be able to sell my own homemade capacitors (I think that Saran wrap and aluminum foil will do nicely) and homemade speaker wire (I think that braiding some Solder Wick with spark plug wire may do the trick) and sell these items for fantastic amounts of money to Golden-Eared audio enthusiasts. Easily. It wouldn't be honest, but sometimes when I read all the ads, it appears that this crowd doesn't want honesty. Audio is so darned subjective that no one person can say what's right. More of my opinion (and that's exactly what it is) should be showing up in the October 2001 installment of "Q & A" in "Poptronics". I'll gladly put my 12AX7's on the block. Lessee, here's the ad copy: "Specially burned in for smooth audio quality without the sharp edges one experiences with all new tubes. The lettering on the glass has been removed to improve the transparency of the sound. Tubes with specially-rounded exhaust nipples available upon special order." Dean |
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Re: Valuable 12AX7!
Excuse my ignorance, but what is so special about the 12AX7s compared to
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any of the other twin triodes?. I have been swaping them around for years in various pieces of equipment without much problems. I have several in their original boxes too, how much more valuable that makes them?. Things seem to be getting out of control these days. Joe Orgnero VE7LBI CCA 96-418 -----Original Message-----
From: Michael Dunn <mdunn@...> To: TekScopes@... <TekScopes@...> Date: June 14, 2001 5:39 PM Subject: [TekScopes] Valuable 12AX7! Just a note to those who may have some 12AX7s in their equipment |
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Re: Valuable 12AX7!
In a message dated 06/15/2001 8:43:03 AM Eastern Daylight Time,
europachris@... writes: . 1uF/630V coupling caps in an amp. It is subtle, but there. Ditto fortubes and wire. Speaker cables have a lot more going on than just resistance perI have never read about this in the electronics literature, but look up the phenomenon of "superwaves" in the field of oceanography. In perfectly normal weather, the random energy of the ocean wave trains can suddenly all add up in phase generating a superwave that can engulf ships and islands without warning. In audio, with tens of thousands of waves per second, the same phenomenon can occur. The input transducer (microphone or magnetic pickup) will filter this out initially, but random phase shifts within the electronics can re-phase the waves to produce instantaneous voltage or current amplitudes far above the average at the input. How this sounds depends entirely on how the electronics handles instantaneous overloads. Tube circuits and analog magnetic recorders are much kinder to these transients than are solid state or digital systems. My theory is that a lot of the subjective advantage of tube and analog sound is based on this. Extremely linear phase response throughout the system will prevent audio superwaves from developing within a system, and this would explain the perceived advantages of precision capacitors, coils and conductors. Mike Csontos |
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Re: Valuable 12AX7!
Ahhh, a topic that I'm well versed in. I'm an "audio nut", but am totally not into $100 cable, stones, magic dots, etc. I'm into the DIY tubes and speakers end of it. While there IS a lot of hype, bullsh*t, and stupidity in high end audio, there is also a lot of truth.
Capacitors, wire, resistors, tubes, transformers, ALL of it makes a difference beyond what one can measure with a scope or distortion meter. I am a skeptic, but personally witnessed the differences between half a dozen .1uF/630V coupling caps in an amp. It is subtle, but there. Ditto for tubes and wire. Speaker cables have a lot more going on than just resistance per foot. There are interactions between the wire strands, the insulation, the braid geometry (if any). Inductance and capacitance come into play and how that interacts with the output impedance of the amp. However, I STILL won't pay these ridiculous sums for stuff making seemingly amazing claims. My speaker cable is made from CAT 5 network cable, costing me a total of $40 for the pair. They smoke some $250 cables I had (I didn't pay that for them). Anyway, regarding Telefunken. Telefunken tubes command a high price simply because they were the finest quality tubes produced by anyone, ever. Truly the Mercedes of the tube world. Tele 12AX7's were the quietest, lowest distortion, and longest lasting tube out there (100,000 hours is a typical lifetime). I've got several pairs of smoothplates (borrowed out of my Tek 535A) and some from an old Dynaco amp, and they do indeed sound very nice. I've compared them with current production JJ/Tesla 12AX7's and find them better, but not enough to spend $100 each. I'll use the JJ's at $7 each and be happy. I get the biggest kick out of homebrew audio by building something that uses a forgotten $5 tube (the 1625) that will smoke most commercial gear costing 10x as much. Come see: Chris TekScopes@... wrote: __________________________________________________________________ Get your own FREE, personal Netscape Webmail account today at |
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Re: Valuable 12AX7!
Phil (VA3UX)
The vacuum tube audio guys have gone absolutely "stupid" over this sort of thing. This is the same group that will pay $100 per foot for special oxygen-free speaker cable, $50 for special medical grade 120V wall receptacles, $75 for a bloody "rock" that sits on top of their amplifier to stop electromagnetic radiation from "interfering with the music flow in their cables" (that one is called a Shakti Stone - it should be Shaft-ye Stone). You or I will pay 50 cents or a buck for good quality cap for use in an RF circuit - these guys have been duped into paying 5 and 10 bucks for the same thing because the cap has special musical qualities.
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I agree that you can make some pretty good money from these guys by selling Tek quality tubes (Telefunkens especially, but also Philips and Mullards too). Bear in mind that you'll be competing with this same crowd when you discover that you need a good quality 12AX7 to make something work well, and that you previously sold all yours to them. I'd hang-on to a few. Having said all that - I admit that I sold a pair of used VT-52's (military type 45's) for $300 US - $450 Canadian - to the audio guys on eBay. The VT-52's were in a large box containing 500 used tubes and I paid $15 for the whole box. I'm ashamed - but happy. Phil At 08:35 PM 6/14/2001 -0400, you wrote:
Just a note to those who may have some 12AX7s in their equipment |
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Valuable 12AX7!
Michael Dunn
Just a note to those who may have some 12AX7s in their equipment (e.g., 549 has 2) or junk box:
Check your stuff for Telefunken tubes. There are some strange people out there who pay big bucks for them (on eBay for example). Also, take a look at the tube's plates. If they're smooth (without any corrugations), they're even MORE valuable. I've recently seen (used) smooth ones go for U$25-30 each, and ridged ones for U$15-20 ea! NOS (unused) would presumably fetch even more. Altogether, I've found six smooth ones in my junk and 549! Replaced the 2 in the 549 with some *non*-valuable ax7s I had, and, big surprise, it works just as well ;-) p.s., I just sold mine for U$51, $68, and $123 a pair!!!!! I can only guess that the $123 pair went for so much because of the good condition of the labelling on it! Yet, the other two pairs went in inverse proportion to legend quality. Crazy audio nuts... ----------------------------------------------------------------- Michael Dunn | Surround Sound Decoder & Stereo Enhancer Cantares | Self-Amplified Speakers, Test Equipment 74 George St. | Ambisonic Surround Sound CDs and Recording Waterloo, Ont. | (519) 744-9395 (fax: 744-7129) N2J 1K7 | mdunn@... Canada | ----------------------------------------------------------------- |
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Re: Tektronix 7S14 - URGENT!
Stan or Patricia Griffiths
I hate to disagree, but the Navy Chief had a good point. The military, as
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you know, tends to "go by the book". The book in this case is a Tek manual and it specifies timemark generators. But more important than that, standard timing measurements on scope screens are made from the second graticule line to the ninth graticule line, ignoring the first and last 10% of the sweep. How can you do this if you don't have some reference mark at both of those points? A sinewave with one cycle spread over the entire screen won't do it. You could, I suppose, set your generator's frequency with the counter such that one cycle occupies 8 divisions on the scope screen . . . but even then, there is another problem. Where the sinewave crosses the second and ninth graticule lines, it is traversing the screen at a rather severe angle to those graticule lines. This can lead to errors in viewing this measurement that are well beyond the typical 2 or 3 percent specification of the the scope's timing. This does not mean that WE can't make some very useful timing measurements on scopes with counters and generators . . . we can! Most of us don't have to worry about the stringent rules of a military metrology environment like that Navy Chief certainly did. Extremely fast scope sweep speeds is exactly why Tektronix developed the concept of the "slewed edge" found in the CG551AP and later versions of that scope calibrator. I prepared and presented a stand up presentation on the "Tektronix Slewed Edge" at a metrology conference in LA in about 1979 when I was the Tek TM500 Marketing guru in charge or marketing the CG551AP. The slewed edge is an extremely noval idea on how to calibrate extremely fast sweep speeds, even if you don't have the required bandwidth to view sinewaves at those speeds. Stan w7ni@... dhuster@... wrote: Sometimes, time-mark generators are overrated. The advantage of them |
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Re: Tektronix 7S14 - URGENT!
Sometimes, time-mark generators are overrated. The advantage of them
is that they make vertical marks for easily matching marks to graticule lines. But if you need faster timing checks, you don't need to be slaved to an older time-mark generator that won't give you fast marks. As long as you have a signal generator and a counter (or built-in counter on the generator), you can get accurate timing references. A generator capable of 1 GHZ will give you 1ns/div "marks". And if you have a 100ps/div timebase, that only means that you'll have a "mark" every 10 divisions. You don't HAVE to have marks every division to calibrate, although it is nice to check out linearity, of course. Many of the Hewlett-Packard microwave generators can go higher yet. I had a Navy chief who thought he knew everything tell me once that I couldn't calibrate oscilloscopes if I didn't have a time-mark generator. Pulease! |
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Re: Tektronix 7S14 - URGENT!
Stan or Patricia Griffiths
In most sampling instruments I have encountered, signals start distorting when they
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exceed about 2 volts in amplitude. Damage to the sampling diodes occurs around 5 volts and you never want to apply DC to the input of a sampler. There are a couple of exceptions to this . . . Stan w7ni@... Don Black wrote: Hi, |
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Re: Tektronix 7S14 - URGENT!
Don Black
Hi,
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I haven't had any experience with sampling CROs but believe the plugins can be damaged with input signals greater than 5 to 10 volts (depending on model). Be careful to limit input signals as they're very difficult to obtain parts or service. Perhaps others have some comments on this. Good Luck, Don Black. Stan or Patricia Griffiths wrote: My opinion is that a working and calibrated 7S14 that meets all of its |
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Re: Tektronix 7S14 - URGENT!
Mark Kahrs
And don't forget those batteries in the sampling diode bias.
I personally think that the S14 is a washout. You can only go to 1 GHz with it and with a 79xx you can already get to 500 MHz. So, why go to sampling for the extra 500 Meg? Why not just go for the gusto and get a 7S11/7T11 pair? As I remind everyone, you get what you pay for (and that includes advice) (Most of the time) Mark. |
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Re: Tek 465B: Display Problem (Shrinked to 3 divisions)
Stan or Patricia Griffiths
Hi Shiran,
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No, the trace traveling from right to left is not normal. The first suggestion that I have is for you to take off the cabinet and take a look at the CRT neck pins, about halfway from the front to the rear of the scope. The two coming out of the right side of the CRT shield are supposed to go to the horizontal amplifier. One of them may be disconnected and/or the connectors may be connected to the WRONG pins. It may say right on the CRT shield which color of wire should go to which pin. If those wires seem to be connected properly, then I suspect a problem in the horizontal amplifier, but . . . you always need to start by checking the power supplies first. You will need a service manual to check the power supplies since it will tell you where the test points are and what readings to expect there.. Do you have one? If not, get one . . . then we can go from there. Stan w7ni@... shiran@... wrote: Hi, I am a student and I got my Tek 465B from an eBay auction. I know |
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Tek 465B: Display Problem (Shrinked to 3 divisions)
Hi, I am a student and I got my Tek 465B from an eBay auction. I know
how to use the oscilloscopes, but have no experience in idendifying and fixing problems in oscilloscopes. The problem is that, the trace or a signal width is limited to maximum 3 divisions on the time scale (i.e. when the Horizontal Position knob is fully turned to left). Turning the Horizontal Position knob to right will reduce the width to 1 division on the time scale. I cannot get this to occupy the full with (10 divisions) on the screen. Is there a screwdriver adjustment knob somewhere to fix this or is this an internal problem? (Also I notice the trace travels from right to left, Is this normal?). Apprciate if someone can help me to identify the problem. Thanks - Shiran. |
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Re: Here's a challenge (Type 517 scope)
Phil (VA3UX)
At 08:12 PM 6/11/2001 -0400, you wrote:
Can anyone find the current rating of the 6.3V winding on transformerSorry I can't help you with that, but if you have access to 517 power Sorry John but I don't have access to this thing. It's owned by someone several hundred miles from here. I think he intends to keep it and restore it. But I've asked him to let me know if he changes his mind. Phil -- Thanks, |
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