> The dual monolithic devices share a common substrate
I thought that was the whole point -- perfect thermal coupling for drift cancellation in a diff pair.
I doubt you can measure the inter-device capacitance through the substrat of 2 devices placed side by side.
Patrick
I thought that was the whole point -- perfect thermal coupling for drift cancellation in a diff pair.
I doubt you can measure the inter-device capacitance through the substrat of 2 devices placed side by side.
Patrick
EUVL said:
Hi Patrick,
You may be right. My only point was that the substrate is in common and it is floating. It might have been nice to have a substrate pin that could be connected to a bias or an ac bypass to eliminate that crosstalk path, but I suspect the two unused pins are NC on the 8-pin DIP version. I also mentioned that because these are fairly large-area devices. I've never tried to measure the drain-to-drain capacitance of one of these, however. I would imagine that these issues are probably fairly unimportant in a typical differential amplifier application, especially when the drains look up into a BJT cascode, as in the circuit I use them in.
Cheers,
Bob
LSK389
Has anybody had any further experience with the Linear Systems LSK389 dual JFET pair to report?
Thanks,
Bob
Has anybody had any further experience with the Linear Systems LSK389 dual JFET pair to report?
Thanks,
Bob
My memory may be off on this, but I seem to recall that the larger Randy Sloane design book also had the bjt/jfet distortion challenge measured, or at least spiced, far in favor of bjts. But like this thread clearly shows, that possible fact doesn't have to result in any material effects at end of the pipe.
That was a little while back, but like seemingly everything he did, was published outside the professional organizations, was not subjected to peer review. Too bad that he apparently chose not to use a weblog variant, such as this forum, to share his ideas and defend them. This thread has been most helpful.
Off topic a little, but John, did you say you had a hand in that towering Grateful Dead setup, the one I remember from the early 1970s? If so, thank you. If not, thank you for mentioning it.
I heard the Dead play through that setup in their 4-hour Oklahoma City show in 1974 (don't recall the date). Clear as a bell. Fabulous quality. I could walk to the back of that big rodeo area and, and just like in the middle, the voices sounded real, like they were singing right to you only yard in front of your face, and not loudly. No drugs involved. The only big show from that time period where afterwards my ears didn't ring. And here I am remembering the great sound almost 35 years later!
john curl said:
Hi John,
I agree. In real circuits and sims, all else remaining equal, the BJT diff pairs tend to deliver lower THD than JFET diff pairs, at least if they are degenerated properly. But I, too, prefer the use of JFETs in the front end, and the distortion of the end circuit as a whole can generally be held just as low with JFETs as with a bipolar input diff pair. Putting it another way, I doubt that the THD of my MOSFET power amplifier would have been any lower if I had used a BJT input diff pair instead of the JFET pair.
Cheers,
Bob
Patch, I did work on the GD "Wall of Sound" system for more than 1 year. I did much of the acoustical testing, electronic xovers, and preamp and microphone electronics. It was really special, BUT you try loading the thing on trucks after the performance when it weighs 15 tons. They got tired of the hassle after a couple of years.
patch said:
And what's really facinating is that 35 years later none of this has trickled down into what's commonly available today. The state of reproduced sound is ridiculous, and I don't take seriously systems that cost more than my house. You can't get an honest critique of them and I don't agree with any approach that doesn't bring the beauty of well recorded music to anybody willing to save their extra money to have it.
All that happens these days is someone steals it with a bunch of disparaging remarks as to the quality of the power coming out of the outlet as the reason for the poor sound. Maybe enough money wasn't alloted for cabling...
I know what's possible and it doesn't take a second mortgage to build it, or a masters degree in RF design.
What's wrong with this picture?
Cheers!
MikeBettinger said:
I just re-read this... What I meant to say, which after a tough day and a few beers didn't quite happen, was: John can be quite proud to have been part of something that had the effect described and it's a shame that your average, hard working, passionate music lover can't walk into a store and buy something that reproduces music with this effect.
I've heard it and have some of the pieces to the puzzle, as do many participants of this forum.
It just irks me when I open a Music Direct Christmas catalog and see them seriously hawking 25K turntables, etc. when I know that the connection can be made for a fraction of that. It really sends a screwed up message about what it takes to enjoy music on a connected level in this interesting time.
I guess I wouldn't mind, if the technology flouted actually made sense and was repeatable. For now what is being offered is overkill and smoke and mirrors.
Thank God for DIY and the ability to take things into our own hands.
Now I'll go have a beer. Mike.
The hiqh quality of large-venue installed sound is just simply out of this world these days.
I have an idea that Bob's and John's names are right up there with those who helped bring great sound into the arena. I'm not kissing boots. I think I'm looking at some foundation work and better. Work that has been used by creative ethical developers, and certainly by legions of faceless pirates.
john curl said:
I know, I don't get out much and have the social skills of a fence post, as well. 😉 I'm working on it.
patch said:
I must be overly picky then, most if not all reproduced music in my personal experience exhibits some fundamental annoying quality that makes me scratch my head and wonder where all of the last 40 or more years of high-end development has gone.
I go to a reasonable number of live events over the course of the year and have experienced good sound but the experiences are not the norm. I go for the music with reasonably good sound being a bonus.
Are there examples of good sounding venues that you'd put on a short list to hear music in?
Regards, Mike.
John Curl, you mentioned Jon Iverson, of ElectroResearch.
I remember reading about his amps in TAS and how they were supposedly designed for the military and then adapted for audio.
Did you hear them and do you know anything about the design and what happened to him?
Thanks SP
I remember reading about his amps in TAS and how they were supposedly designed for the military and then adapted for audio.
Did you hear them and do you know anything about the design and what happened to him?
Thanks SP
Jon Iverson was a genius. He independently designed the complementary differential input stage in the late '60's and MANY other designs. His amp was very good, especially for the time. It used a complementary differential bipolar input stage, and I can't remember if it was balanced out or not.
He was probably kidnapped and killed by professionals. He has not been seen or heard from for about 15 years, and he left his passport at home.
He was probably kidnapped and killed by professionals. He has not been seen or heard from for about 15 years, and he left his passport at home.
Mike,
For sure there exist terrible sounding old and brand-new systems, every one of us could come up with a list a mile long.
For live performances, out in a seat, sitting on a picnic blanket, walking around and talking, I can't tell whether excellent sound is digital or not, line-powered or active. Or often whose horns and drivers are perched around, unless those Community pumpkins.
And, true to this thread, I bet at the front ends of most all - jfets!
The thing that impresses me most is the sound from these massive distributed setups going into stadiums, large halls, mega-malls.
Mike, notably for me, and no doubt arguably:
- Most anything with Disney in its name.
- Pritzker Pavillion in Chicago....wonderful open-air sound.
- AT&T Park in SF (home of the Giants, the most ear-friendly I know of in the MLB....and a great view).
- Arlene Schnitzer Concert Hall in Portland (a shameless plug for a local and smaller and stellar music hall). Most every larger city and university probably has at least one hall this good...or maybe almost as good.
- And in the local-venue vein, some of the best-sounding systems I have heard are in sanctuaries. The smarter congregations whose churches keep getting bigger have poured tons money into their sound and lighting, hired professionals....they know that people want a good show and will come back for more.
For sure there exist terrible sounding old and brand-new systems, every one of us could come up with a list a mile long.
For live performances, out in a seat, sitting on a picnic blanket, walking around and talking, I can't tell whether excellent sound is digital or not, line-powered or active. Or often whose horns and drivers are perched around, unless those Community pumpkins.
And, true to this thread, I bet at the front ends of most all - jfets!
The thing that impresses me most is the sound from these massive distributed setups going into stadiums, large halls, mega-malls.
Mike, notably for me, and no doubt arguably:
- Most anything with Disney in its name.
- Pritzker Pavillion in Chicago....wonderful open-air sound.
- AT&T Park in SF (home of the Giants, the most ear-friendly I know of in the MLB....and a great view).
- Arlene Schnitzer Concert Hall in Portland (a shameless plug for a local and smaller and stellar music hall). Most every larger city and university probably has at least one hall this good...or maybe almost as good.
- And in the local-venue vein, some of the best-sounding systems I have heard are in sanctuaries. The smarter congregations whose churches keep getting bigger have poured tons money into their sound and lighting, hired professionals....they know that people want a good show and will come back for more.
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