kimothebeatmaker
Well-known member
- Joined
- Jul 20, 2018
- Messages
- 62
That's not what I see. RV12 does that, but RV11/C79 is a crude treble leak.RV11/C79 - adds saturation by adjusting the drain current on the input FET amplifier altering the even harmonic levels of the signal being passed
RV11 is what I said it is. RV12 isn't on the schematic I posted.That's not what I see. RV12 does that, but RV11/C79 is a crude treble leak.
It's a pre-existing circuit, I was thinking of taking out the caps 47uF, and putting the transformer in its place.If your objective is to add "mojo" then you hardly need a fancy op amp. But it will need more drive than an MC33079 because the distortion of a transformer ("mojo?") is proportional to the voltage across it. So driving it differentially like in that circuit is good. Are you committed to a quad op amp? Is this from a board that's already built or are you going to build this? If you are still designing, then maybe just design for NE5532. Otherwise, you'll have to find a quad with some kick. What is the transformer? If the transformer has a split secondary to configure for a 2:1 step down (or has a 2:1 arrangement such as by reversing it), do that so that you have to put more voltage across the primary to get the same level out. Then add 2x gain in the output stage by making R44 10K to make up for the step down. Again this is to maximize "mojo". But bear in mind that you're not going to really hear any difference unless the transformer is relatively small and you really torture it. Unless maybe you're one of those folks that can hear that sort of thing anyway.
It's RV10 that does the bias trick. RV11 is some kind of tone control.RV11 is what I said it is. RV12 isn't on the schematic I posted.
Rv10 is the pot resistor next to the jfet to bias the dual n channel jfet. Rv11 is the jfet saturation control like I said. I’m looking at the board right now. The BV10K is a potentiometer. One with an actual knob. Rv10 is a resistor with a turn screw pot on it to bias the jfet. Has nothing to do with saturation or tone control.It's RV10 that does the bias trick. RV11 is some kind of tone control.
Agreed.Rv10 is the pot resistor next to the jfet to bias the dual n channel jfet.
It's a weird treble bleed, that indeed creates distortion because it overlaods the voltage-follower.Rv11 is the jfet saturation control like I said.
Did I say different? Oh yes, it bias the FET, which has undeniable effect on saturation and harmonic structure. And I never said it was a tone control.Rv10 is a resistor with a turn screw pot on it to bias the jfet. Has nothing to do with saturation or tone control.
Rv11 is a knob on the front that adjust the drain current on the jfet. Rv10 is a voltage bias for the dual channel jfet. One is calibrated to spec on the inside of the box for the unit to work as intended and left alone, the other is a feature on the outside of the box that is adjustable without opening up the box. You said that is not what Rv11 does, as Rv12 does it. I stated there is no Rv12 in the diagram. You said Rv10 does it. I said no, Rv10 biases the jfet. Nothing to do with saturation. Again Rv11 is the pot that controls the drain current on the jfet. Not Rv12, or Rv10. But we're getting off topic.Agreed.
It's a weird treble bleed, that indeed creates distortion because it overlaods the voltage-follower.
Did I say different? Oh yes, it bias the FET, which has undeniable effect on saturation and harmonic structure. And I never said it was a tone control.
Do you agree with the fact there is no DC current into RV11, because there is capacitor C79 in series? As a result it has no effect on the FET bias.Rv11 is a knob on the front that adjust the drain current on the jfet.
Agreed. It could be argued that it sets the FET's current, though.Rv10 is a voltage bias for the dual channel jfet.
One is calibrated to spec on the inside of the box for the unit to work as intended and left alone, the other is a feature on the outside of the box that is adjustable without opening up the box.
I still claim that RV11 is a treble bleed, and I said in my first post that it's a crude source of distortion. And RV12, as a bias control, also changes the operating point of the FET, which in turn changes the distortion profile.You said that is not what Rv11 does, as Rv12 does it.
Correct, I had misread that for RV10.I stated there is no Rv12 in the diagram.
You said Rv10 does it. I said no, Rv10 biases the jfet. Nothing to do with saturation.
No. You can say that as much as you wish, but it's simply not true.Again Rv11 is the pot that controls the drain current on the jfet.
That wouldn't be conclusive, because no one has the OP's ears and auditory preferences.Why not pick a trafo, clip it in circuit, record some tracks showing an A/B comparison (a "mojo test") then post samples? That would be about a couple hours effort or so to get to the bottom line and seems vastly shorter than the time already spent pulling weeds.
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