Schertler consoles / mechanics / discrete dc coupled electronics without nfb?

[Michael Tibes]

This guy has built a modular mixer with an unusual mechanical concept and also unusual electronics:

https://www.schertler.com/en_IT/arthur

https://www.youtube.com/watch?v=qL22CXt78fw
https://www.youtube.com/watch?v=FGx50LwjOWs (german)

On the one hand side the mechanics might be an inspiration to DIYers, on the other hand he says he was using discrete class A electronics without coupling caps (DC coupled) - and without negative feedback. Are there any schematics around of something similar? I have never seen anything like that, but I'd be surprised if he was the first to develop such a circuit. His modules even seem to be very fair priced at first glance. I really wonder how he achieves a mic preamp with a wide gain range without changing nfb? Probably not just fixed gain stages with potentiometers in between? 

Michael

 

[boji]

A electronics without coupling caps (DC coupled) - and without negative feedback

Yeah I thought NFB was the cat's pajamas. Douglas Self told me so.

 

[TwentyTrees]

I remember Sound On Sound did a piece on this a little while back:

https://www.soundonsound.com/reviews/schertler-arthur-modular-mixer

It seems an elegant approach to the trend towards smaller project recording setups and away from the giant desks of yore, and I love the fact that the modularity extends to the mechanics as well as the electronics. Flexible, customisable and potentially great for maintenance too (unless that modularity introduces any significant new failure points, of course). The SoS article does raise a few question marks, though, mainly around ergonomics and teething troubles.

 

[[silent:arts]]

An older discussion:
https://groupdiy.com/index.php?topic=63751.msg807044;topicseen#msg807044

 

[abbey road d enfer]

Hugh Robjohns summarizes that very well:
"in my experience most ‘zero NFB’ designs, including this one, turn out to be what I’d consider ’minimal NFB’ designs. But semantics aside, Schertler’s design intention is clear, and the absence of significant amounts of negative feedback is evident in both the mixer’s sound and technical specifications."
"any potential reduction in capacitor dielectric distortion is overwhelmed by the relatively high THD"
BTW Studer did that in the 70's with their A720 amplifier. Almost no global NFB, replaced by a lot of nested NFB.

 

[gyraf]

Oh, it's so good, I think like you.

Spambot suspect: Please verify/prove to us that you are entirely human, or you risk getting eliminated..!

Jakob E.

 

[Tubetec]

I have a schertler Unico in for repair ,
Impressive unit I have to say ,very nicey concieved and built ,belton spring with interesting balanced drive and recover stages ,
Two very thick layers of steel bettween the transformer and the spring tin make it  absolutely hum free even at extreme settings.

The customer had a short term over heat of the treble amp by the looks ,its 35 watt and the bass is 150watt, the TDA7394 is perfect ,I just think on that particular night he may have driven the amp more than usual I redid the heatsink paste ,but I cant find any other issues .

I like the idea with the Shertler console where the designer has intentionally designed in the overload characteristics to be gracefull ,it harks back to the earliest tube preamps of say the BBC where a soft over load was designed in for the purposes of signal compression/limiting before the transmitters . Your always going to get unwanted transients in music ,the way these are handled is important , high feedback op amp strategies tend to overload very abruptly  and even if its a sibilence or vocal pop that lasts milli seconds the subjective anoyance can be bad. The more gracefull overload of simpler tube apparatus allows colour to be dialed in over a wide range from unoticable to fuzzed out ,its a very effective way to deal with problematic program material that has microtransients well above nominal level ,vocals ,smaller stringed instruments like mandolins ,Violin or fiddle come to mind ,tin whistle is another instrument where nasty intermodulation distortion can occur on the peaks ,its naturally produced by the instrument and the player , program chain gain/overload and miking technique can make the difference between a good or bad day in studio for the humble penny whistle player and everybody elses ears who's listens to it for that matter.Ribbon mics are another great way to tame unwanted upper harmonics too of course .