My Tek 475 is still one of my favourite scopes...
Working on some low noise audio preamp cards many years back, they were misbehaving oddly. We spent ages trying to figure out where the noise was coming from. It got late so we got to the "right, just cut tracks until the noise stops" mentality to try and isolate it. We got down to a single unconnected pin with noise still measurable! Impossible..but... turned out the assembly / defluxing process had left a thin, invisible film of conductive goo on the boards!! A good scrub in strong solvent (that you couldn't use today!) and bingo -- working!
Working on some low noise audio preamp cards many years back, they were misbehaving oddly. We spent ages trying to figure out where the noise was coming from. It got late so we got to the "right, just cut tracks until the noise stops" mentality to try and isolate it. We got down to a single unconnected pin with noise still measurable! Impossible..but... turned out the assembly / defluxing process had left a thin, invisible film of conductive goo on the boards!! A good scrub in strong solvent (that you couldn't use today!) and bingo -- working!
Flux contamination is underrated.
Although I left UCLA in 1985, a tech who was brought in by someone who hated my guts had managed to break portions of it. His motto ought to have been Leave no knob unturned. He loved to use every possible feature (this delayed by that, intensified by another) despite a simple triggered sweep being adequate in almost every case. Things began to fail...
Which isn´t really an answer to my question, but of course it was somehow a strange move from Randi. Although the contention that there should be (and can be) no audible difference between _reasonable_ choosen cables was afair always noted....
Yes, too bad it didn´t go forward. But it is quite funny that in fact Randi weaseled out, but your assertion still is, that otherwise Fremer of course would have .......
But anyway billshurv and SY had "heard different" and of course true believers will never change their mind
But anyway billshurv and SY had "heard different" and of course true believers will never change their mind
Not sure what I have said to mark me as a true believer. Given how downright offensive Fremer was being, I would personally have told him to sod off. This might be why I don't do this sort of thing. Magician vs stand up comic. I mean what could go wrong.
That's because he lived off of Butterfingers and cigs. He also had a hobby of cooking up psychoactives in his back-house lab.
But he was one heck of a circuit designer.
Sounds to me like you have a problem with the TEK power supply. I have a similar problem with a battery powered scope that has an external switching power supply when used with my Stanford Research F1. Worked well on batteries alone, but added garbage when plugged into the AC power supply.
Although imho Randi started the flame a couple of years before, i don´t see really a difference between both actors wrt in this regard.
But anyway, i provided two examples responding to Scott´s remark which illustrate why these meetings between true believers did not work.
And if it is even in the Fremer/Randi event impossible to reach consensus on the "who weaseled out question" (based on the published information including emails, under the assumption that this information was correct) it is imo unlikely to do better in more difficult matters.
Yessir. I like to work with the TEK TDS3052 - but I know it emits loads of common mode noise.
If it is an Infinivision 1000 (or 2000, can't remember) I have the same experience. But not always, seems to come and go. Mine is 4 x 70 MHz, haven't gotten around to hack it to make it 200MHz yet....
Jan
Well what to you think Mr. Fremer's reaction would be to 60 eight legged pieces of dirty silicon added to each channel?
I far prefer the hypothesis that an arbitrary swap of speaker cables should not be expected to alter the sound in any way outside of frequency response variations due to choice of particular amplifier and speaker. Not eliminating well known issues from a test would be dishonest. The Pear cables in question are outliers in terms of L and C and they even show typical simple frequency response differences of almost 3dB in the audio band.
Last edited:
Yes.
No.
1. Get an iso transformer.
or
2. twist amp and scope power cords tightly to the same duplex outlet, and twist the scope probe around the scope PC to the amp PC, twist it around that, then try the measurement again.
If the coupling is the elements of the boxes themselves, this will not work. This will only work if coupling is via the loop;
John
John
> strong solvent (that you couldn't use today!)
I love the smell of a vapor de-greaser in the morning
And then you wake up on the floor of your garage...
Normal people unfamiliar with fashion audio are often surprised by the remarkably poor performance of many ultra-expensive products. They mistakenly assume that an expensive wire will act as a competent wire and don't expect its performance to be orders of magnitude worse than an extension cord from Home Depot.
To be fair they were showing less roll-off from theirs and they showed remarkable restraint in not making outright absurd claims. I don't know what they used to get -3db at 20K from an ordinary speaker I don't remember 6' of even #30 being that bad.
My experience has been that checking even for outright amplifier oscillation is just not done in certain crowds.
Last edited:
John,
They were coming from outlets about 1 m apart (workshop is brand new - fresh wiring etc). Thing is, the Rigol is plugged into the socket right next to the Tek. Amplifier is isolated thru the transformer - assume this is enough?
However, let me try your trick. I'll post some picks up.
Damn. A $600 Rigol is quieter than a $3k TeK machine.
The eye patterns and losses on the ultra premium USB and network cables I have looked at would not meet minimum USB/UL cert requirements and cost around 100X what cables that do meet those requirements cost. But lack the magic appellation. It may be the poor performance electrically that provides the better perceived performance. ?less radiation, perhaps??
What do you expect folks in a nation as small and flat as a postage stamp to do, stare at a picture of the royal family all day ?
Everything preferable to the 7/7 days of Geraldo, Letterman, Leno, and Oprah gossip, even if 90 percent of all news items is online copy&paste material nowadays.
50 bucks on Airforce One renamed D's Duck before NY's eve.
- Status
- Not open for further replies.