John Curl's Blowtorch preamplifier part II

[john curl]

Actually, we can do better, especially at both low and at extended frequencies above 20KHz (for superior transient response). I hope to show interested people, how. We did this about 1/3 century ago.

 

[elektroj]

8. Tape noise. Yes, noise

Did I miss anything?

Oh yes, I did! Noise reduction systems!

Wanna count how many tantalum capacitors are in direct signal path on Dolby Cat.22 cards (Dolby A)?

Voice from the back: " Dolby A is cr*p, we've switched to Dolby SR long time ago".

OK, so be it. I once counted ICs on Cat.280 Dolby SR card. Most were duals - 5532's and TL072's. Amplifiers in total = 72 ! Yes, seventy two. Some of them are in detector's chains, but not seventy.

 

[1audio]

What would a diehard audiophile say seeing those curves?

Response Curves of Analog Recorders

Why would you use 30 IPS?

Getting flat response is quite difficult with tape. And it needs lots of continuous maintenance. Perfect audiophile obsession.

 

[elektroj]

Getting flat response is quite difficult with tape. And it needs lots of continuous maintenance. Perfect audiophile obsession.

Audiophiles usually don't have any test equipment and don't do measurements.

They just swap components.

 

[Pano]

Speak for yourself. I'm an audiophile and do a great deal of measuring. So did the audiophiles who taught me. You can't paint us all with the same brush.

 

[a.wayne]

+10

There's a naturalness to voices , instruments and recorded space with analog R/R that is very Much absent with digital, it's at the frequency extremes where it falters to digital ...

I have no use for Dolby .....

 

[elektroj]

Relax, Pano, I was just kidding.

 

[a.wayne]

Actually, we can do better, especially at both low and at extended frequencies above 20KHz (for superior transient response). I hope to show interested people, how. We did this about 1/3 century ago.

All ears .....

 

[john curl]

I can get very good response to 10Hz with 30 ips. I will show HOW, sooner or later, IF I get the chance.

 

[Pano]

Relax, Pano, I was just kidding.

No worries, it's just that everyone loves to take a poke at audiophiles for some reason. We aren't all Audiophools, by any stretch.

 

[Pano]

Did I miss anything?

Yep, that despite your scary laundry list of tape faults (all true!) it still sounds damn good when done right. How can that be?

That said, I've heard 24/96 recordings made by SY with Scott's mics and preamps that are just as lovely and "warm" sounding as any tape, without all the tape problems. So it can't be that hard to do digital right.

 

[john curl]

first: Ampex, second Supermaster (Mobile Fidelity custom electronics)

 

[john curl]

A direct digital master, without any serious manipulation, would probably sound very good to 'wonderful', so SY should copy his tapes (perfect coping capability, I am told) and give or sell them to demos at major audio shows. Why not?

 

[a.wayne]

Err, wasn't Sy involved recently , custom cables and all ..

 

[john curl]

Maybe he could start a new business, and supply quality demos. It would be a service to the audiophile community, but he has to do more than one or two customers to make a difference.

 

[john curl]

Original Rec-Repro response then low freq correction, final result

 

[john curl]

graphs

 

[bcarso]

simulation

Sorry George it's known as full court press time, you sent your designs to fab and surprise, surprise they work. It's 24/7 work right now, not audio but good stuff. I think others have capture the gist, there is a transition from lumped to continuous models that requires judgement based on several factors. Importantly the skin effect is fractional f in nature and does not plug into a normal simulation environment.

Just noticed this: Electromagnetic modeling of three dimensional integrated circuits

Brad

 

[SY]

So it can't be that hard to do digital right.

It's not. Use good mikes, a decent ADC, and make use of the wide dynamic range to prevent ever hitting the red line. Like I've said, I spent years using some pretty good analog tape equipment, and I'd never go back.

 

[elektroj]

Original Rec-Repro response then low freq correction, final result

Clever trick, John. Final results are indeed impressive.
That EQ looks more than just twin-T to me and probably requires another gain stage, no?