John Curl's Blowtorch preamplifier part II

[SyncTronX]

Hmmm,

What would make a good video drop in replacment for a
TL0072CP ?

I've heard of some folks making a whole board that replaces
the op amp itself.

Wondering how much of an improvement it would make?

Funny thing, on a Joe Cursio tube dac that I have, a buddy of mine was
telling me to upgrade all the audio opamps with video op amps,
that the whole thing would better.

Problem is Joe scratched off all the nomenclature on his op amps
and offers upgrades though his web site.

I'm thinking the upgrades would be less expensive buying through
digikey or mouser, or someone else.

Sync

[dimitri]

Also, the AD844 can be used open loop with excellent audio performance, howzzat for audio nirvana

AD844 output stage is far from excellent, should be replaced by external high current buffer for OL audio nirvana

[scott wurcer]

Originally posted by dimitri


AD844 output stage is far from excellent, should be replaced by external high current buffer for OL audio nirvana

Plain old diamond buffer. Thanks! for the FET's BTW (and socket). It's easier to use than the ones we stock.

[anatech]

Hi Scott,

Plain old diamond buffer.

That may well be, but there is plenty of life left in that design as far as I'm concerned.

Most of mine have been discrete, I haven't tried anything like BUF634 yet. I'm thinking that the parts should track much better in a thermal sense.

-Chris

[john curl]

Apar,,,, the 825 is where I am placing my bet.

[aparatusonitus]

Originally posted by PMA
Yes, almost. But the AD844, e.g., is more than 10x faster, regarding SR, and it counts. OLG is quite same, but the AD844 is CFA, and it must be considered.

Yes Pavel, AD844 is an great opamp (I'm using it as well)...but it has one big flaw...it's out of production, so availability, even for diy purpose, in future is questionable.

Originally posted by dimitri


AD844 output stage is far from excellent, should be replaced by external high current buffer for OL audio nirvana

I'm using AD844 as I/V converter (open loop) + it's buffer...and it does sound pretty good as long as the load is light (TVC S&B TX102 MkIII in my case)

Originally posted by john curl
Apar,,,, the 825 is where I am placing my bet.

Well, I'm placing my bet too on AD825...as error opamp in hybrid super-shunt regulator. One question John...is that Plashe current mirror differential as a load for folded cascade in simplified AD825 schematic?

[infinia]

Why is super high bandwidth , OLG BW and SR more important than low 1/f voltage noise, distortion and DC accuracy?
What is the noise corner freq for a jfet input video amp?

The typical audio source is BW limited anyway so slew rate is not that important> how much gain end-end do we need.... Av=2? Some folks use an attenuator for a preamp.
Compare your video op-amp design to an OP37(OP27, Av<2) for an audio benchmark?

[1audio]

If you go back a few thousand posts you start to get the ideas here. Simply put the traditional measurements don't indicate audio quality which is the reason for this. If they did then we wouldn't be exploring these ideas. If you are happy with traditional solutions its hard to beat a mid '80s Japanese integrated amp. No distortion, perfect RIAA and flawless performance (and to many unpleasant sound).

[Rick Miller]

How about the AD811? I am using it with good results.

[infinia]

Originally posted by 1audio
If you go back a few thousand posts you start to get the ideas here. Simply put the traditional measurements don't indicate audio quality which is the reason for this. If they did then we wouldn't be exploring these ideas. If you are happy with traditional solutions its hard to beat a mid '80s Japanese integrated amp. No distortion, perfect RIAA and flawless performance (and to many unpleasant sound).

haha\ Jap integrated amp
OK I'm all for new stuff, but I still think my Q shouldn't be dismissed by simplification/comparing to mid 80's designs. BTW I think the primary reasons for "unpleasant sounds" are due to those haphazard class AB poweramps and mostly the evil Sanyo solutions.

Are there any technical goals or defined new topology for a preamp?