John Curl's Blowtorch preamplifier part II

[john curl]

Keep on target. You amateurs cannot afford REAL discrete devices at this point. Let others make second tier designs somewhere else on this website. Let us approach our objective, and we all might learn something. Why? Because we will be matching apples to apples, not apples to oranges, or its equivalent.
For the record, I already KNOW how to make extremely high performance discrete designs, and have been doing so for more than 40 years. It is the rest of you, who wander in the dark, so to speak, and are equally quick to jump to a partially discrete design without learning about topology differences with IC designs.

[john curl]

Joachim, a friend of mine just dumped a bunch of 78's. What a loss. You know, from hi end experience, why we waste our time with phono. It is just like why people waste time and money eating at a great restaurant, or enjoy a wine better than 2 buck Chuck. It gives a sense that there is more than just McDonalds out there, although that might well do much of the time.

[2quad]

Ooops, sorry John. I have some LT1028s ant LT1115s in my drawer. Should I blow the dust of them now? I know that the almighty Doug Self don't like them. But they have really low noise. And to me - just sitting in my drawer for years and years - are really cheap

The strange problem in not-so-hi-gain amps combined with really low noise is the current demand to drive the low impedance feedback. If asked 25+ years ago, I would have added a LT1010ct inside the FB loop to drive the feedback.

[Joachim Gerhard]

So what is the goal ? Less then 1nV/qHz with only one Opamp is hard. Paralleling 4 whould bring the noise down by 6dB and the quadruple could drive nearly 100mA.

[simon7000]

Originally Posted by john curl

Joachim, a friend of mine just dumped a bunch of 78's. What a loss. You know, from hi end experience, why we waste our time with phono. It is just like why people waste time and money eating at a great restaurant, or enjoy a wine better than 2 buck Chuck. It gives a sense that there is more than just McDonalds out there, although that might well do much of the time.

John

Twice now I know where Thunderbird fortified wine was presented to wine tastings, both times there were tasters who pick it as a good wine!

As to old 78's there were many performances recorded that are not available elsewhere, the emotion of the music is there no mater how poor the reproduction.

Does anyone have any idea how many new recordings come out each year? How many of those will you want to listen to years later?

I know John you still groove to the "Purple People Eater!"

ES

[Joachim Gerhard]

Here in Germany we have no shortage of new Vinyl comming out. Many of those are from a digital master of cause but our artists here find it kind of prestigious to bring out a piece of PVC in a paper jacket. Some times a CD is packed in for free.

[john curl]

2 quad, this is NOT about you! It is about engineering design. OF COURSE, you should put anything that you have in you junk box in your own circuit, IF you chose to make one, but it is not good engineering to chose these devices, TODAY, for modern audio reproduction when cheaper and faster IC op amps are available from the same manufacturers or someone down the road. I would save these devices for test equipment, that is where I use them, today, and have for the last 15 years.

[2quad]

So do we have a ranking of low en/in devices suitable for audio? Low Ib is also important. Other parameters?

[2quad]

Leaving the ultra-minimalistic for a short while, why don't real phono amps have balanced inputs? The cartridge itself is inherently balanced, ground is just a shield from the amp to reduce hum.

Several manufacturers offer good instrumentation amps intended for microphone preamps. TI, AD, Thats etc. These may be used as a really good phono front end.

To bad that the consumer audio industry never understood the real meaning of "balanced"

[Joachim Gerhard]

Thats what i do with my 3 Opamp INAs. I tryed integated INAs and i could never get a certain sharpness in the sound away. Also the internal resistors are quite high so you have to make compromises between gain and noise. An INA made of 3 separate Opamp allows to avoid that compromise.