LostInMyMindPalace
New member
Simple question that is well beyond my expertise. Does anyone know what exactly is happening when you switch between the gain structures? Are different items being added to the circuit etc?
How does the fender bassbreaker gain structure knob actually work?
- Thread starter LostInMyMindPalace
- Start date
FuseG4
Our Neighbor Totoro
Re: How does the fender bassbreaker gain structure knob actually work?
I can't find a schematic so it's all conjecture.
I'm guessing they accomplish it they way a lot of pseudo-channel-switching is done. The cathode resistor on the section of the tube controls the bias of the tube and a smaller resistor is generally more gain given the same plate load resistor. I'm guessing they are changing the bias on the gain stage using the knob to switch cathode resistors. Cathode resistors also have bypass capacitors to increase gain and shape the response, those are usually switched at the same time.
This is how they do the "more drive" or "boost mode" on a lot of amps including hot rod deluxe, they have two sets of cathode resistor/bypass caps switched with relays so it pops less, it's probably something they just decided to put on a knob this time.
I can't find a schematic so it's all conjecture.
I'm guessing they accomplish it they way a lot of pseudo-channel-switching is done. The cathode resistor on the section of the tube controls the bias of the tube and a smaller resistor is generally more gain given the same plate load resistor. I'm guessing they are changing the bias on the gain stage using the knob to switch cathode resistors. Cathode resistors also have bypass capacitors to increase gain and shape the response, those are usually switched at the same time.
This is how they do the "more drive" or "boost mode" on a lot of amps including hot rod deluxe, they have two sets of cathode resistor/bypass caps switched with relays so it pops less, it's probably something they just decided to put on a knob this time.
LostInMyMindPalace
New member
Re: How does the fender bassbreaker gain structure knob actually work?
Seems to me its affecting the tone contols aswell. In Low gain its very bassy, whereas in mid it is more balanced and high seems to sound thinner to my ears. Is it adding more 'presence' for lack of a better word aswell as gain?
Seems to me its affecting the tone contols aswell. In Low gain its very bassy, whereas in mid it is more balanced and high seems to sound thinner to my ears. Is it adding more 'presence' for lack of a better word aswell as gain?
Rex_Rocker
Well-known member
Re: How does the fender bassbreaker gain structure knob actually work?
I'm no expert, but I think it's common practice in amp design to cut more bass pre-gain stage the more distortion you add to keep things from getting flubby. So my guess is that's probably what's happening.
I'm no expert, but I think it's common practice in amp design to cut more bass pre-gain stage the more distortion you add to keep things from getting flubby. So my guess is that's probably what's happening.
LostInMyMindPalace
New member
Re: How does the fender bassbreaker gain structure knob actually work?
In this video at the 3 minute mark https://www.youtube.com/watch?v=snWPT-o_Zyk&t=1s Phil says it might be stacking the pregain tubes? Is that possibly the answer?
In this video at the 3 minute mark https://www.youtube.com/watch?v=snWPT-o_Zyk&t=1s Phil says it might be stacking the pregain tubes? Is that possibly the answer?
FuseG4
Our Neighbor Totoro
Re: How does the fender bassbreaker gain structure knob actually work?
I dunno if he's got any idea. I can't find anything for or against it but it's not an amp with a lot of tubes to begin with. It's possible a tube section gets switched in and out.
And the thing about it being dark in low gain, could be the switch is switching additional stuff in and out in the tone stack but since there's no schematic,
Without looking in the amp its all conjecture I think
I dunno if he's got any idea. I can't find anything for or against it but it's not an amp with a lot of tubes to begin with. It's possible a tube section gets switched in and out.
And the thing about it being dark in low gain, could be the switch is switching additional stuff in and out in the tone stack but since there's no schematic,
Without looking in the amp its all conjecture I think
Jacew
New member
Re: How does the fender bassbreaker gain structure knob actually work?
That sounds like it moves the overall distortion. Adjusting singal levels so that other end you have one stage distorting and two on the other end. Or more?
Same difference you get with upping the gain vs. lowering it and adding boost.
That sounds like it moves the overall distortion. Adjusting singal levels so that other end you have one stage distorting and two on the other end. Or more?
Same difference you get with upping the gain vs. lowering it and adding boost.
FuseG4
Our Neighbor Totoro
Re: How does the fender bassbreaker gain structure knob actually work?
It's possibly a combination of cathode resistor and bypass cap values combined with switching a tube section in and out. Either way both methods would involve a lead from the switch to a tube. The resistor and bypass cap are also connected to one of the pins.
Doing it this way would somewhat change the gain levels and harmonic response of the amp which is what leads me to believe this is how they did it.
Also leads me to believe they could have just as easily put functions on normal push push switches and made them footswitchable but...
the dsp/cpu is certainly for reverb and for the cab sim on the xlr out.
It's possibly a combination of cathode resistor and bypass cap values combined with switching a tube section in and out. Either way both methods would involve a lead from the switch to a tube. The resistor and bypass cap are also connected to one of the pins.
Doing it this way would somewhat change the gain levels and harmonic response of the amp which is what leads me to believe this is how they did it.
Also leads me to believe they could have just as easily put functions on normal push push switches and made them footswitchable but...
the dsp/cpu is certainly for reverb and for the cab sim on the xlr out.
Similar threads
