The funny thing (to me) about the old Klipschorns is that they're about the most realistic sounding speakers around - if listened to from the next room.
My take-away from that common observation is that their significant flaws are washed away and their virtues (low FM distortion especially) remain.
It's important to use very low powered amplifiers with such sensitive speakers, partly for clean performance at normal listening levels, and partly so that dirty listening levels (as bcarso puts it: when entertaining guests) happen at a safe volume!
Much thanks, as always,
Chris
I used and tuned 45dcoe webers on a custom car I was developing. The info about the weber design is published in book(s) but not the details you need for your car. The placement and size of the multiple holes on the side of the jet determines when the richening comes in (load-wise). You can actually tune for power or economy over a broad rpm/load range with the webers. A good source of info on them can be found at Ferrari..... thier dealers have the all the weber jets/parts for tuning.
THx-RNMarsh
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You got it !!
Easy and Not Critical.... and less fudging with comp after the pcb/build layout is factored in. My question about SR is answered now -- it does seem to have audible affects and faster being better. Maybe a new rule needs to be made about what the min SR should be for amps. The .5-1v/usec is too low. And, how high before there are no more audible improvements?
THx-RNMarsh
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Do we have any idea of the thresholds for distortion and IM ?
Is-it Slew rate, or its consequences in distortions in global feedback based sytems (servo)?
I ask this question, because, if I noticed some improvements with very high speed OPAs comparing to relatively slow ones like TL072, I never noticed the same with no global feedback ones. Dadod could tell us about its experiences on it.
Or, is-it a difference in phase at the bandwidth limit ?
Usually, due to their higher open loop bandwitch (once compensated for closed loop stability) the CFAs can maintain a constant feedback ratio higher in frequency. (Both not enough with our actual tranies speeds).
Or is-it the expansive behavior of CFAs, promoting transients ?
OS, while you are on this, it should be interesting to play with your best VFA, reducing for a test, the impedance of the feedback path in order to increase the bandwidth and see if any improvement.
If you can still see the ears, and the tits on the udder, it's not inflated enough.So does over inflating make the cow more spherical and thus easier to model ?
What might qualify as a high slew rate servo op-amp these days:
ADA 4627-1
Low offset voltage: 200 μV maximum
Offset drift: 1 μV/°C typical
Very low input bias current: 5 pA maximum Extended temperature range: −40°C to +125°C ±5 V to ±15 V dual supply
ADA4627-1 GBW: 19 MHz
Voltage noise: 6.1 nV/√Hz at 1 kHz
ADA4627-1 slew rate: 82 V/μs
High gain: 120 dB typical
High CMRR: 116 dB typical
High PSRR: 112 dB typical
ADA 4627-1
Low offset voltage: 200 μV maximum
Offset drift: 1 μV/°C typical
Very low input bias current: 5 pA maximum Extended temperature range: −40°C to +125°C ±5 V to ±15 V dual supply
ADA4627-1 GBW: 19 MHz
Voltage noise: 6.1 nV/√Hz at 1 kHz
ADA4627-1 slew rate: 82 V/μs
High gain: 120 dB typical
High CMRR: 116 dB typical
High PSRR: 112 dB typical
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If you mean did I used the feedback theory and math? I studied it at University a long time ago but never used it in my professional work. Now in time of free simulators if I know main principles and rules I can come to optimal compensation in not so many steps. What's wrong in that? Is it good enough explanation? And I showed many different simulation result, output at full power, clipping, just take a look in the amp thread. I did extensive simulation and finally when I built it it worked whit no need for any changes, specially non in the compensation.
If you know how to read Bode plot it's quite simple.
By the way I like my VFA amps (my first VFA was the one from RCA booklet could be fifty years ago) and started with CFA not long ago and I was hooked.
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It may be some or all of those things at work contributing to a more accurate sound reproduction.
Need super low THD amps that SR can be varied. How do you make such without 'significant' change or increase in distortion -- and compare. OS's VFA and CFA have CFA 4X higher SR than VFA.... will that VFA sound same as CFA if its SR was increased to the same approx SR of CFA? If it does or does not sound same.... then we go from there. Start comparing VFA and CFA with one parameter changed and compare.
But over several decades, the CFA topology and high SR along with vanishingly low distortion all seems to dominate over PSRR and other parameters et al. Maybe we are getting closer to knowing why. When I developed the first DC-coupled compl-push-pull CFA amp topology I did a lot of listening and testing..... we didnt have good PC and CAD et al... so for me it was intellectual power and prototyping and tests and measurement and listening. The hard way. The only way. So, I have been Very interested in what hi perf CAD can do and show. I'm impressed at the results so far.
JC.... you have your work cut out for you now. Get hold of one of these guys and CAD masters and give another run at a new Blow Torch kind of product..... As fine art and applied art.
THx-RNMarsh
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Look here Jacco others, every now and then some of us need to go down a side alley for a quick knife fight. We'll join the main fray again after we've finished business.
Say, what's this thread about again?
Add a turbo and that buick will get out of it's own way. By the way land rover used that 231 for a lot of years did they not . Youtube shows an old rover with that engine pulling a new one out if the mud so the replacement was how good ?
It was used for a long time. It was the defacto performance engine for a lot of years. TVR griffith 500 had a 5 litre version. It was still rubbish! But it was all we really had.
A lot more to it than just the jets, and that is the bit they don't explain well. I had to trawl high and low for our of print books until it clicked. Plus a lot of help. Let's just say US hot rodders understand webers a lot better than UK ones! I ended up getting a set of letter drills and making my own jets. Very few understand that, up to around 3000RPM you are running on the idle jets and progression drillings and just richen the mains until with a smokey fart it pulls
I do not put down the <cfa principe as such, but I think CFA has become a sort of a monstrosity - we now have thusands i foipks callain their amp ounds better because of their use of the CFA princple. That I do find it hard to believe on ts own. It implies that all you have to to do is go the CFA way and all your problems are solved. To be honest, my experience gith CFA amps is very limited, just 3 or 4 DIY projects from the web, and none of them but one sounded "right" to me, except that one being Andrew's Ovaion amp. There was nothing "wrong" with it, and it demonstrated an awesome presence which was almost physical.
I think that the recent attention paid to the CFA principle, and certainly the advertising of it, by companies such as Maranrntz has served to praise the CFA priniciple to a status level it was never intended to have.
Regarding Dick's question on amp speed, I agree 0.5/peak V is a bit weak. Personally I feel much better if that reads as 1.5 V/uS per peak Volt, or three time as much. There is something seductive about speed of response.
I think that the recent attention paid to the CFA principle, and certainly the advertising of it, by companies such as Maranrntz has served to praise the CFA priniciple to a status level it was never intended to have.
Regarding Dick's question on amp speed, I agree 0.5/peak V is a bit weak. Personally I feel much better if that reads as 1.5 V/uS per peak Volt, or three time as much. There is something seductive about speed of response.
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A lot more to it than just the jets, and that is the bit they don't explain well. I had to trawl high and low for our of print books until it clicked. Plus a lot of help. Let's just say US hot rodders understand webers a lot better than UK ones! I ended up getting a set of letter drills and making my own jets. Very few understand that, up to around 3000RPM you are running on the idle jets and progression drillings and just richen the mains until with a smokey fart it pulls
Briefly, there were also the emulsion tubes and ventury resizing and all sorts of variables..... the Ferrari dealer in Sacramento had so many weber parts i could tune the carb to the cam etc for smooth power from idle to max rpm. but they do not handle high air flow volume... so you need several of them on a larger engine (like 2.5 ltr or more). I eventually went to a custom manifold for a Holley 4bbl carb feeding a turbo... same there... mix and matching of parts to size the turbo to the motor then added a 3 stage fuel fuel enrichment injectors turned on by adjustable manifold pressure switches. After all that got tuned to perfection, I added 150HP shot of Nitrous Oxide and alcohol/water injection. I monitors the exhaust temp with thermal couples. The 2.5 ltr Nissan motor (heavily modified inside and all drive train, axles etc) ran 27 psi manifold gauge pressure plus 150HP shot of nitrous. That is about 500HP from a 2.5ltr 6 cylinder motor back in the day when you run things like that creation on the street. The ignition system was a whole another project to keep pressures from killing the spark. The competition clutch assemble would melt under full power....... I had to give up at that point because I couldnt find a clutch assembly for that engine which could hold the power... which was immediate and without lag.
Yes, I know about webers and tuning them. I dont go into anything part way including audio without trying to find the limitations and reducing them.
THx-RNMarsh
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Don't you think it is exactly the contrary ? So few % CFA amps in the market ?
There is nothing to "believe". And the sonic difference of the same AMP with two input stages (VFA/CFA) with the same gain will not be so obvious. You may even prefer the VFA at first sight. Like you could prefer a photography with slightly enhanced sharpness and color. But there is something common to all the CFA amps that i had and that made me chose them even when i did not knew what they were. better details separation, more fluid trebles, less fatigue on the long time (And in recording studios, you spend long hours each day). Not day and night, as I said, it is very subtle.
Notice OS and Dadod explored the CFA topology very recently. One for power amps, one for preamp. They are both spare of comments about their listening feelings, but it seems they both liked-it. Dadod designed a preamp whitch can be switched between CFA and no feedback loop. OS severall amps with both technologies and same OPS/VAS.
While I tend to prefer CFAs, I used, of course a lot of VFA, both for power amps and pre-amp. So I have nothing against any of those. But I cannot understand that some, who never tried-it, please notice this, are so crossed against CFA like if it was some kind of heresy against some mysterious religion.
OS had made a fantastic work, proposing a set of amps with the same OPS and VAS. In the both topologies. They are quite complex, using the best practices and components, all as low distortion and high bandwidth we can dream of. I believe he was a VFA guy (means not with a long experience in CFAs). When he says, at the end, he tend to slightly prefer, between all of them, a CFA one, some, in this forum said he optimized the CFA while its VFA was under designed. Note that it is exactly the contrary: it interested-me to see OS designing CFAs with VFAs practices and reflexes (adding stages to reduce distortions, while CFA guys tend to reduce the poles and fight for speed) and to see its results. (Amazing ;-).
On my side, when I published a comparative study between the two topologies, in order to allow people to better understand both of them, I was accused of all the sins. (always by the same people)
Oh Lord. What the hell ? Why such a bias ?
It's like the front and rear traction for cars. Both can be correct, both can perform, but it is a different feeling: just chose your poison, and, as you did, dvv, let the others chose their own.
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Not a good analogy. If you want all out performance rwd has major advantages. for a passenger car FWD is lighter, more fuel efficient and gives more cabin and boot space. And no room for 4WD in your analogy.
FWIW I don't think there is a witch hunt. I see a couple of 'night and day wife in the kitchen heard it' evangelists on the CFA front and some head scratching from others trying to understand why slew rates that would allow you to jam the entire AM radio band would make an audible difference. Add the bravado of hiding behind a keyboard and small skirmishes appear. With the best designs there really should be no way you can tell them apart when connected to the 3 most flawed parts of the chain (speakers, ears and brain).
billshurv, did-you realize what you wrote ?
All this junk (electronic) is made for the pleasure of our "ears and brain".
Did-you play records for the pleasure of your measurement instruments ?
Christophe, I am NOT knocking any one principle over the other As I clearly said, my experience with CFA topology i very limited, and truth be told, over the years I met many an VFA amp which left me sone cold. In the coure of my oen development of my take on the VFA theme, I have come to learn how to mak the amp's opem loop bandwidth hit 150 kHz and remain stable, using very common off-the-shelf devices at very popular prices (e.g. 2SA1381, 2C3503). If I was willing to complicate matters a bit more, I expect I could do even better, I don't because I see no need for yet more, the achivable actual slew rate is way above 100 V/uS by then. Since I'm not planning on selling them, I have no futher need for a better spec sheet. My concern lies with a small global nfb factor, since I am concinced that amps using less lobal NFB tend to sound better than those using more of it, in any technology.
While I am not inclined to experiment with CFA just now, due to time contraints, a time will come when I will pay some attention to them. When it does, I will quizz you on your experiences, I hate wasting time on rediscovering hot water.
While I am not inclined to experiment with CFA just now, due to time contraints, a time will come when I will pay some attention to them. When it does, I will quizz you on your experiences, I hate wasting time on rediscovering hot water.
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