Well, in "Picking capacitors" slew reate may have been mentioned ( don't care to check it, 3 metres away in the library ) - but VERY briefly. Since it was also a thinly disguised advertisement for what later became known as Wonder Cap, there was no warning saying film caps can have VERY large differences in slew rate. From just a few (single digit ) volts per microsecond to aprox 600 ( at least back at the article publishing, but is not much different today ).
What's clear about this is that you don't understand what slew rate is, and why a capacitor of any reasonable quality cannot limit it. But go ahead, cite a reference about a coupling cap limiting slew rate. I will not be holding my breath.
I cannot have a technical discussion with you when you refuse to be specific. You've been asked for specifics, that means capacitance value, dielectric type, voltage rating, DA, DF, ESR, the whole lot. Nothing! There's no point in continuing this.
Regarding differences made in production; IF that first amp heard at friend's contained "vintage, definitely in limited supply, not to be available again- ever" caps of superiour quality, and the one bought later with whatever best available from the current production, but inferiour to vintage caps - you WOULD mind. That's why manufacturers avoid such situations at all costs - and build with whatever is currentlyproduced and likely to remain available in at least few years ahead. That means an old(er) design may well be, ultimately, superiour sounding for this very reason.
You have not stated clearly why vintage caps are better, only that you don't like the new ones. And, I expressly stated that "sounding better" doesn't count!
With the miniaturization and advent of SMT /SMD, unfortunately MOST of the best capacitors once used in trough hole variety have been dropped. Simply because they can not withstand the temperatures of the SMD/SMT soldering process - further made worse with the introduction of the lead-free solder ( which requires yet even higher temperature ). Only the most THERMICALLY robust varieties of film capacitors remain available in SMD form - and those are NOT the equal in quality of say polystyrene as dialectric material. And, yes, capacitors DO have different sound quality - even IF the electrical measurements, down to the last DA and whatever electrical parameter ( triboelectrics, anyone ? NO mention in "Picking Capacitors" , THE fatal flaw of teflon caps ... ) are identical.
That's your opinion, and we all get that. But you have not supplied any proof at all!
When you say "capacitors DO have different sound quality - even IF the electrical measurements...are identical." what you're saying is that even if there is no difference in the resulting wave form parameters, time, energy, frequency (spectrum), there is an audible difference. And that the cause of that difference cannot be measured either! That's where we part ways. That's impossible, and I challenge you to prove it against all electrical and scientific data in opposition.
Now try to figure this one out ...
I do know how a DC servo works. And did post its use at the input as the ultimate no-no.
No, you don't, because a DC servo isn't applied to the input!
Sooo - if your preamp input is directly coupled to a phono cartridge AND there is a catastrophic failure of preamp ( one of the rails blown, latching to whatever remains, blown input semiconductor, etc, etc ) - would you still insist on direct coupling ( best for sonics, no doubt about that ) - or would you insure yourself from blowing up an expensive cart by using ( best quality you can get ) cap ?
No, you have no idea how a DC servo works or you wouldn't be making the above statement. It's absolutely NOT a risk to the input device!
No, that scenario is not stupid. Because it does SOUND better than having to insert another gain stage between the preamp input and - call it that way - driver of the "power amp". And yes, although not +-50 V rails preamp, it was close : +- 45V rails. But, I agree it is not the normal way of doing things and incompatible with most other equipment.
You are , of course, free to think this way. But I ( or anybody else ) can not convince to the contrary anybody - online. Only on the real demo floor, with real equipment of high enough quality.
But your opinions defy science and electronics in specific. You've fallen back to the old audiophile crutch once again: "You have to hear it on equipment of high enough quality". Anyone who disagrees doesn't have equipment of high enough quality. Do you not see how ridiculous that makes you look?
Yes - because a SINGLE "20-20K" minded component in the entire audio chain, from the microphone to the whatever used as the end transducer back to sound, is enough to throw the spanner into soundstage works. Now - go to any studio - and count 'em ...
You can claim "soundstage" all you like, but it remains undefined, and not clear. We simply cannot use that term in a real scientific discussion because it has no definition.
No, I do not want the whole chain to play up to 100MHz - because I am realist. It is unlikely to happen - ever, but certainly not in my lifetime. However, ANY stage that can be made large bandwidth will contribute to more accurate recording and reproduction. And I have NEVER said that < 20 Hz and > 20 kHz is more important than 20 - 20K, or even more important 100 to 10K band. Only if this core band is OK, would I try to stretch to either of the extremes. As the easiest way to start doing it is in amplifiers, I started with them.
Once again, we're into the absurd. So we have a chain limited to 20-20kHz. And now you claim that one device that is say 10-100kHz improves everything? What's it improving if there's nothing there in the first place? Take this example: a full bandwidth audio system (any definition, even yours) has a 3kHz low pass filter inserted in it, which is clearly audible to everyone. Now, you insert, anywhere, an amplifier with flat response to 100kHz, or heck, 1mHz. With your warped logic, that causes an audible improvement. How? Does it somehow undo the 3kHz LPF? This is simply idiotic.
There are microphones made specially for music that go to 100 kHz.
And they are impractical for most applications. It doesn't matter, nobody's using them. You've again focussed on the rare example, citing it as typical. It's not.
As I type this, I am lidstening to...
Nobody cares what you're listening to. Know why? Because you don't share it! It is, therefore, a lie and a myth.
However, I did not know clarinet has so much output above 20 K - at very least to 40 kHz, during the solo clarinet passage. One learns every day...
And the beat box used by the percussionist goes to 50 kHz on this recording - some at least 5 metres from the mike; clarinet between 2-3 metres, depending on player's position on the stage.
Again, if you're going to talk about energy without talking about it's intensity and level, you're not working with reality. The statements above are meaningless.
I agree there is no such thing as zero tolerance parts -
But that's exactly what you called them! It can't be both!
but the best approximation, as most probably used for the AGI, is some Hewlet Packard RLC meter. OK, " measured to be exactly 123456 ohms, with the tolerance from the absolute correct value as specified by XY measurning instrument" - would that satisfy you ?
No! That's not how things are designed, especially if put into production.
And, yes, the values of resistors in RIAA circuit are printed down to the last ohm - like 23732 ohms and NOT 24 K 1% ( or any other value/tolerance) . Caps are not - because, for those less familiar with film caps, even picking them up with anything more than feather touch can change their value - let alone re-printing them. For this reason, no desoldering and measuring the super precise ( aka close to zero tolerance ) parts from AGI 511 ( or anything else built with even approaching this quality of parts ) is NOT recommended.
Wrong! I've measured literally thousands of capacitors, all types and values. Not one has ever changed value by being picked up! Not one, unless it was defective.
No, I did NOT confuse kHz with MHz - correct as written. However, you are right, AGI 511 overall HF limit is set by its line stage, which is approx 100 kHz.
Then you were dead wrong by stating there were no RF signals below 90mHz. There are many, and some of the strongest you'll ever encounter. I cited exapmles.
You are correct in stating that whatever has been used in a studio has been way off the accuracy of the RIAA precision of AGI. Then again, it is not AGI's fault to try to strive for the precision - and studio folks being satisfied with sloppiness.
The attempt at that kind of precision is pointless when the rest of the system is at +/- 1dB or worse. Actually, far worse. There's simply no point at all.
I do not know which schematics of 511 you did find online. It is NOT a single op-amp - in addition, there are ( bipolar?- would have to check it ) transistors used as feed-forward - that's where 100 MHz+ capability of the circuit is coming from, not from the slow IC op-amp.
Here are the 511 schematics on line. You'll need a free account to download it. If you have other information POST IT!
I agree installation and grounding are paramount in any phono ptreamp. But none I am aware of can reject this much RF garbage as 511. Enough is to see the open box - plenty images online.
I've seen the pictures, it's nothing compared to the construction of audio equipment designed for use in the kind of RF fields encountered at broadcast facilities.
I disagree - there still is nothing comparable up to today.
I cited two examples of equipment from that era, direct competitors, that had comparable performance. The only difference is, they succeeded in the marketplace, and the 511 did not.
The only gripe I have with 511 is the use of that ribbon cable for all the connections - because that adds approx 80 pF of capacitance per each input, unfortunataly sometimes this is too much for some of the best MM phono cartridges - after the cabling from TT to preamp has already contributed at least 100 pF - if not more.
You're obsessing about preamp capacitive load when you should be concerned with the composite frequency response of the cartridge, tone arm, interconnecting cable, and preamp. Nothing will ever come close to your claimed RIAA accuracy of the 511, and it won't be a problem with C loading.