Well it is stormy threatening kind of day here, so I guess Scott and I can agree on something!
I take it the AD797 failure rate is in ppm's and I just got lucky with my one bad one?
Maybe I should help EM a bit: the universe is actually about 13 BILLION (13.000.000.000) years old. So EM's device would, in this analogy, reach only about 1/3rd of the universe
jan didden
Maybe I should help EM a bit: the universe is actually about 13 BILLION (13.000.000.000) years old. So EM's device would, in this analogy, reach only about 1/3rd of the universe
jan didden
Jan,
Thanks, so in reality it only reaches 1/3 of 1% of the Universe, sorry for calculatorslip.
This must be real disappointment to all of those who actually want a machine to measure things that are not there.
Vac
Scott,
I am serious about statistical information, three of the four in the front end matched closely enough in noise it seemed selection was not required. The fourth started off noisy so I opened it's output resistor. Eventually it over heated and became a more classic failure. I do not expect anyone makes perfect parts.
Yes it may be I mishandled that one, but all the others were fine and in circuit it was paralleled with the rest. How it was handled before it got to me is part of the process that we have little control over.
The only indication of initial problems was a bit more noise. I really don't know what modern IC failure rates are as they are so low it is extremely rare for me to get a part that actually fails!
No slights intended. I assure you when I wish to be nasty, it will be clear!
ES
Scott,
I am serious about statistical information, three of the four in the front end matched closely enough in noise it seemed selection was not required. The fourth started off noisy so I opened it's output resistor. Eventually it over heated and became a more classic failure. I do not expect anyone makes perfect parts.
Yes it may be I mishandled that one, but all the others were fine and in circuit it was paralleled with the rest. How it was handled before it got to me is part of the process that we have little control over.
The only indication of initial problems was a bit more noise. I really don't know what modern IC failure rates are as they are so low it is extremely rare for me to get a part that actually fails!
No slights intended. I assure you when I wish to be nasty, it will be clear!
ES
No offence taken, I told John questions about costs, yields, problems that folks are working on, etc. are off limits.
After a period of not finding anything important enough to talk about, I have come to realize that the concept of 'tone controls' has not been much discussed. Therefore, I would like to discuss WHY Mark Levinson, so long ago, decided to remove tone controls from the Levinson JC-2, and why we have kept up the tradition with the JC-80, the Parasound JC-2, and the CTC Blowtorch.
Now, a little history of tone controls:
Around 1950, an article appeared in WW describing a very elegant tone control circuit, by a circuit designer, P. J. Baxandall. This circuit made very good 'curves' BUT it was difficult to implement, so it was not used by most tube preamps of the day, including Marantz and Dyna, who used alternate approaches to put tone controls into their preamps. I lived with the Dyna Pas3(x) preamp for about 10 years. However, I found that I rarely, if ever, used the tone controls. Mark Levenson had the same experience.
Therefore, he thought that we should drop the tone controls in order to put the 'money' into the parts, instead. This simplified the preamp, considerably, and we went on to get worldwide success with the product. (more later)
Now, a little history of tone controls:
Around 1950, an article appeared in WW describing a very elegant tone control circuit, by a circuit designer, P. J. Baxandall. This circuit made very good 'curves' BUT it was difficult to implement, so it was not used by most tube preamps of the day, including Marantz and Dyna, who used alternate approaches to put tone controls into their preamps. I lived with the Dyna Pas3(x) preamp for about 10 years. However, I found that I rarely, if ever, used the tone controls. Mark Levenson had the same experience.
Therefore, he thought that we should drop the tone controls in order to put the 'money' into the parts, instead. This simplified the preamp, considerably, and we went on to get worldwide success with the product. (more later)
Hi John,
I made many Baxandall tone controls in the day, and I thought it was basically the standard, majority approach. What was difficult about it?
By difficult, are you just referring to the fact that it needed one additional triode stage? If so, that would be better described as a cost issue.
I'm OK with no tone controls, by the way. I'm tempted to wonder if the equipment of the day, tube amps and speakers, made tone controls a bit more needed. I also remember loudspeakers with what were effectively tone controls on them.
Cheers,
Bob
> Meten is weten, als je weet wat je meet...
But that's the problem, Jan.
Is one ever certain what one measures ?
Patrick
No, not absolutely certain. But, with experience, and with repeatability, and measuring the same things in different ways, comes increased confidence that the results are correct.
It's all we have anyway.
jan didden
Mark Levinson changed his mind later. I have a Cello Palette and it is superb to master records. Without it Michael Fremer would not have given me praise for "The best reissue of Santana, Abraxas". The tapes i got where horrible in many ways but i got it fixed well. I used it in my system too but to change the settings with each recording reduces the convenience factor to zero. There is an "On" and "Bypass" switch on the Palette and keeping the knobs in the zero position changes the sound surprisingly little but with the filter banks in the chain ( in the zero position ) there is some wide band noise audible.
Ultimately i took it out. Still i think the world needs an high end equalizer.
Ultimately i took it out. Still i think the world needs an high end equalizer.
All older Tannoy pro stuff had tone controls on them, still running K3838. Good idea by itself, but all the models I had showed that switches and vibration rich environments do not mix, at least not with the switches Tannoy was using.
@joachim, fully agree. Why not have one that only treats the part of the spectrum where room treatment often gets progressively difficult and where most of the difficulties tend to occur, lets say <300 Hz, and gets out of the way above that.
@the remark that preamps used to have tone controls but no longer (source amnesia but remembered) I guess this might also have to do with higher linearity in recording industry today. The average studiospeaker has much straighter FR now than 30 years ago, just like most of the other stuff they use, so a more standardized global benchmark has surfaced. Another reason might be the demise of vinyl. Lived in the US and Japan in the eighties and early nineties, as well as in good old Europe. Incredible differences between pressings on the three continents. You just needed tone controls. Source material now just needs less user compensation.
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The problem with variable equalization is making it ultra high fidelity, yet cost effective. It should be a reminder that the Cello Audio Palette cost about $6500 when it was made, and it is IC based. You can buy a lot with that sort of 'extra money'. For example, my Watt 1's only cost about $5000/pr new. I have never felt that adding a 'tone control' to them, would improve listening quality. However, I have found that adding a 'sock' in front of the tweeter, can make it more listenable with average material.
Separate EQ of the room (which I agree should be dealt with using multiple subs and room treatments and speaker placement) from Tone Controls to deal with problems with recordings.
IMO the world needs a good tone control. Virtually any recording in your collection will sound different on your system that the system used to mix the recording. Different Electronics, Different Speakers, Different cables (if you will) and Different room acoustics.
So just the freq response between what you hear on you system and what existed when the recording was made is enormous. And it is very likely different for every single recording in your music library. People go to extraordinary lengths to design and build neutral/good sounding equipment yet the equipment can't do anything to resolve the first order errors introduced in the differences between what was heard in the control room and what you hear in your listening room.
More tomorrow it is late on the East Coast.
IMO the world needs a good tone control. Virtually any recording in your collection will sound different on your system that the system used to mix the recording. Different Electronics, Different Speakers, Different cables (if you will) and Different room acoustics.
So just the freq response between what you hear on you system and what existed when the recording was made is enormous. And it is very likely different for every single recording in your music library. People go to extraordinary lengths to design and build neutral/good sounding equipment yet the equipment can't do anything to resolve the first order errors introduced in the differences between what was heard in the control room and what you hear in your listening room.
More tomorrow it is late on the East Coast.
The Dayton Wright SG equalizer was based on a single ended class A discreet current sourced differential pair for each channel which fed LC filter circuits tuned to each of 8 bands for program correction follwed by a discrete class A buffer. The inductors were individually tuned for each frequency band. They demonstrated it at trade shows using a square wave with 1 channel in full boost and feed the ouput into the other channel at full cut and the square wave was reassembled - something a typical ic based equalizer couldn't do - not because of the use of ic's, but the filter matching between channels was not as good as the individually tuned filters Dayton Wright took the time to test and trim and the 1.5 hz to 700 khz amplifier bandwidth used. The high frquency filter in the MK 2 version had discreet class A Bessel filters and the low frequency filter was a Butterworth class A if they were used. I am recapping and updating one with metal foil resistors and Blackgates at the moment being carefull to maintain the original filter tuning.
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