I am thinking of a servo output tube buffer driving an output transformer, I think eliminating the large valued coupling capacitor should prove to be a sonic improvement. Anybody tried it and can confirm my speculation?
Analag
Analag
Tube And Servo
- Thread starter analag
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CJ
Well-known member
Hmmmm, which tube? What about DC? mAYBE AN TUBE OP-AMP CONFIG.
eVER DO ANY WORK WITH A TUBE TEK TUBE OPAMP LIKE THEY USE ON THERE EQ'S?
CAPS off. sorry Kurt!
eVER DO ANY WORK WITH A TUBE TEK TUBE OPAMP LIKE THEY USE ON THERE EQ'S?
CAPS off. sorry Kurt!
Samuel Groner
Well-known member
Why the servo around the output stage only and not around the hole thing?
Samuel
Samuel
[quote author="Samuel Groner"]Why the servo around the output stage only and not around the hole thing?
Samuel[/quote]
The input stage is AC coupled to the output follower so attempts to control DC would meet no success.
When adding servos to opamps we have no access to internal nodes so we put the servo around the entire subcircuit. However, you can apply the servo at any point in a DC coupled circuit as long as you don't bias components out of working range. Audiophiles do it all the time.
Typically, the input makes sense on amplifiers so the correction applied can be fairly small.
I have never done servos for tube circuits, but my experience with servos on solid state circuits have lead me straight back to capacitors. It was never because of inferior measurements, but due to feedback from listeners. I couldn't argue with that.
Wouldn't this buffer above have a pretty low headroom at the output? Perhaps good for headsets?
Samuel[/quote]
The input stage is AC coupled to the output follower so attempts to control DC would meet no success.
When adding servos to opamps we have no access to internal nodes so we put the servo around the entire subcircuit. However, you can apply the servo at any point in a DC coupled circuit as long as you don't bias components out of working range. Audiophiles do it all the time.
Typically, the input makes sense on amplifiers so the correction applied can be fairly small.
I have never done servos for tube circuits, but my experience with servos on solid state circuits have lead me straight back to capacitors. It was never because of inferior measurements, but due to feedback from listeners. I couldn't argue with that.
Wouldn't this buffer above have a pretty low headroom at the output? Perhaps good for headsets?
Samuel Groner
Well-known member
Sure, I would DC couple this, of course.
Samuel
The schematic that I posted has pretty good head room but not enough for my liking. The one I have for my personal use is way more dynamic in terms of headroom and linearity, since it's intended purpose is a line amp gain has been set to 5. I'm swinging something like 30V up and down.
Analag
Analag
