Measuring the noise of a power supply with that amplifier
could have side effects. Input impedance is 34 milliOhm.
An adequate coupling cap would need to be >> 50000 uF.
With sth. like that it is easy to zap the FET input via the
transformer. Just imagine what the transformer will do
when the cap is precharged and then the input is shorted.
There is a nutty cartridge out there with a DCR of 0.4Ohms, but it costs more than I would spend on a car! (note I run beaters)
Speaking as one who was for many years an EE in the professional and consumer audio business I can confirm this is indeed true. Audio EEs in general design to the numbers that are spat out of the Audio Precision.
Just repeating Burson's drivel. As if discrete transistors are not made on the same dirty silicon?
Abraxalito,
I find it hard to believe that at some of the companies you work for the EE's would stop at the output of an Audio Precision instrument and didn't also do some serious listening tests. Yes I'm sure there are those who would design to a spec but that is what many companies would consider a product to sell and marketing can take care of the rest, but I don't think the serious players are going to stop at such a simple step. So many new design experiments came out of the companies you worked with, not sure I would love everything they created but they certainly tried to move the bar forward on audio quality and what real measurements were critical and which were not important for quality sound. As you say some engineers design to a spec, like Bose and they are happy with the inferior products that they do design, but I don't think of that company and others like it as truly trying to produce hifi sound quality, they have decided that is just silly and they are making billions of dollars making dreck. low fi audio products for the masses.
I find it hard to believe that at some of the companies you work for the EE's would stop at the output of an Audio Precision instrument and didn't also do some serious listening tests. Yes I'm sure there are those who would design to a spec but that is what many companies would consider a product to sell and marketing can take care of the rest, but I don't think the serious players are going to stop at such a simple step. So many new design experiments came out of the companies you worked with, not sure I would love everything they created but they certainly tried to move the bar forward on audio quality and what real measurements were critical and which were not important for quality sound. As you say some engineers design to a spec, like Bose and they are happy with the inferior products that they do design, but I don't think of that company and others like it as truly trying to produce hifi sound quality, they have decided that is just silly and they are making billions of dollars making dreck. low fi audio products for the masses.
Maybe they should design to the subjective observations of deaf old men instead in order to produce better products?
They have no choice at some level, the customers want both the numbers and the "hearing/feeling".
Some listening was done sure, but only at one company did the engineers go to the trouble of doing fully-fledged listening tests (ABX). Not all aspects of audio electronics were listened to seriously and when the listening showed up some issue to the listener, the EE (me) didn't have a clue about what the physical manifestation of that listening problem was. So to me its reasonable to suppose I'm not atypical in that I was indeed in that case as you put it 'too stupid to know what I was trying to accomplish'.
Indeed so, its just economics. EE's paychecks aren't dependent on getting great reviews in the subjective audiophile press, so there's no particular reason they should care about how things sound.
Indeed, this approach doesn't seem to work in "high end" audio. The issues of the listener must be handled before they occur through effusive marketing materials and attractive industrial design.
Just because of this thread I put a pair LM4562 in my last Mouser order. I gotta' say life would be a lot easier noise testing these when compared to LT1358's. The LM4562 was 5db quieter. The vanishingly small distortion spec is an eye opener! But........
So I put them in my newest rev. of LCRMKIII pcb. Burned it in over night. They were not bad. But they can't capture subtle sonic cues like a faster opamp can. It wasn't like being in the back of the concert hall but it was like having a slight head cold.
a significant amount of musical drama that the LT1358 can translate is just not there with the 20v/us LM4562.
So knowing this, if anyone has any other suggestion of a dual opamp that can beat out my 600v/us LT1358, since you guys believe the high speed slew rate just can't possibly make any difference in the T&M would logic of audio design, let me know.
Jan? Scott? anyone? I'm open.
So I put them in my newest rev. of LCRMKIII pcb. Burned it in over night. They were not bad. But they can't capture subtle sonic cues like a faster opamp can. It wasn't like being in the back of the concert hall but it was like having a slight head cold.
a significant amount of musical drama that the LT1358 can translate is just not there with the 20v/us LM4562.
So knowing this, if anyone has any other suggestion of a dual opamp that can beat out my 600v/us LT1358, since you guys believe the high speed slew rate just can't possibly make any difference in the T&M would logic of audio design, let me know.
Jan? Scott? anyone? I'm open.
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Of course it was the slew rate that did it. Couldn't be anything else. Especially to give you that HF roll off that the back of the hall has...
I very much doubt its due to the slew rate directly, that's just a marker in this case that the part you love hasn't the usual LTP input stage and hence exhibits less sensitivity to out-of-band grunge at its inputs. I'd double check your decoupling - have you observed hygiene in keeping power and signal grounds separated?
A crazy high slew rate does not even necessarily mean an op-amp is "fast". For small signals, the LM4562 could be faster than your LT1358.
Indeed - it doesn't pay to get too hung up on the numbers. But then I'm repeating myself 😀
Seems slew rate has a fair amount of misunderstanding connected with it - its a large signal property and if your opamp is slewing (and its not an I/V converter) then something's wrong somewhere...
Seems slew rate has a fair amount of misunderstanding connected with it - its a large signal property and if your opamp is slewing (and its not an I/V converter) then something's wrong somewhere...
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So - everything i listen to has apparently already been somehow abused by op-amps before i even buy it. Then to confound things it passes through more of the dam things in my source before being amplified by My-Ref chip based mono blocks. I may already be dammed for all eternity!
My only solution to ease this mental anguish is to use my DCB1 (with it's 3 legged purveyors of goodness and purity) to partly offset some of the evil op-amp's influence.
My new mantra = No Harmony Without Harmonics!
Wish i'd never read this thread now, i was happier, life was simpler etc.
My only solution to ease this mental anguish is to use my DCB1 (with it's 3 legged purveyors of goodness and purity) to partly offset some of the evil op-amp's influence.
My new mantra = No Harmony Without Harmonics!
Wish i'd never read this thread now, i was happier, life was simpler etc.
In the case of some 'audiophile' recordings that's quite likely true. I was listening to one of 2L's downloads on my latest modded power DAC and discerned one characteristic sound of opamps there. Whereas on a more mainstream recording (Sony) if they were there they weren't drawing attention to themselves.
I guess we're talking past each other, considering the title of the thread I wanted to point out op-amps don't spoil the soup. Replacing the guts of a highly respected commercial microphone with an op-amp based DIY circuit takes some nerve. Sorry Jan for any distraction, just this came up in this thread.
Bear, on what basis do conjecture that no matter how much care is taken a digital transfer of a master tape will not fool anyone?
EDIT - your words - "Doubtful that anyone would confuse the two".
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