The clean and dirty channels each have different tonestacks. The clean is very close to the Fender AB763 design in most Blackface Fenders. The mid cap value is lower (0.022 instead of 0.047) but other than that it appears to be the same design. I’m exactly sure what that does to the tone but if you plug those values into the Duncan Amps Tonestack Calculator you will get a frequency response chart.
Not sure about the dirty channel though.
Just found this on Rob Robinette’s site
“The Super Reverb, Concert and 68 Custom Deluxe Reverb use .022uF mid caps where all other AB763's use .047uF.”
That page also hs a frequency graph comparison. It appears to shift the mid frequency centre upwards from around 500hz to 800hz and scoops the mids out by about 2 - 3db less than the other blackface models.
I am no expert on any of this stuff. Just have a curious nature and am trying to get to grips with a basic level of understanding. The Rob Robinette site is fascinating for geeks 😁
Display MoreJust found this on Rob Robinette’s site
“The Super Reverb, Concert and 68 Custom Deluxe Reverb use .022uF mid caps where all other AB763's use .047uF.”
That page also hs a frequency graph comparison. It appears to shift the mid frequency centre upwards from around 500hz to 800hz and scoops the mids out by about 2 - 3db less than the other blackface models.
I am no expert on any of this stuff. Just have a curious nature and am trying to get to grips with a basic level of understanding. The Rob Robinette site is fascinating for geeks 😁
The pot value matters just as much. On the typical Fender/Boogie BMT tonestack the mid pot has a low value (10kOhm from memory) compared to the other two. The cutoff freq for an RC filter is 1/2piRC so the cutoff freq is inversely proportional to both the cap value (in Farads) and the R value in Ohms.
Well I guess we will have to wait till the Kemper Stack upgrade where we can type in the the value of the pots and caps, that would be cool 
The pot value matters just as much. On the typical Fender/Boogie BMT tonestack the mid pot has a low value (10kOhm from memory) compared to the other two. The cutoff freq for an RC filter is 1/2piRC so the cutoff freq is inversely proportional to both the cap value (in Farads) and the R value in Ohms.
Thanks.
It looks like that crate and the Blackface Fenders (including 0.22 mod in the Super Reverb) also share the same 250k pot values for bass and treble. I think all the two knob channels have a fixed 6.8k fixed resistor for mids while the three knob channels have a 10k linear pot for mids which means that at 68% of its travel it is acting like the fixed resistor in the 2 knob channels.
Thanks.
It looks like that crate and the Blackface Fenders (including 0.22 mod in the Super Reverb) also share the same 250k pot values for bass and treble. I think all the two knob channels have a fixed 6.8k fixed resistor for mids while the three knob channels have a 10k linear pot for mids which means that at 68% of its travel it is acting like the fixed resistor in the 2 knob channels.
OK - so does a B/T two knob tone network have a third cap in the network for the mids?
OK - so does a B/T two knob tone network have a third cap in the network for the mids?
Yes its either .47 or .22 depending on which version (almost all .47) but with a fixed 6.8k resistor rather than pot. The web page I linked to shows the full schematic and talks it through in a way that an idiot like me can almost understand 🤣
Yes its either .47 or .22 depending on which version (almost all .47) but with a fixed 6.8k resistor rather than pot. The web page I linked to shows the full schematic and talks it through in a way that an idiot like me can almost understand 🤣
Thanks for that page - lots of good stuff. Three band tone stack circuit for the Showman is included further down. The mid pot is 10kOhm and the bottom of that pot runs to ground. Interesting to see how that network is set up - the signal forward from the tone stack to the volume control and on is fed from the wipe of the treble pot. The bottom of that pot gets some portion of the signals from the bass and mid caps and the top of that pot gets the signal from the treble cap. I recall that if you turn all the tone pots to zero on amps like this the amp is silent - all the signal is wasted to ground no matter what the volume settings.
Well I guess we will have to wait till the Kemper Stack upgrade where we can type in the the value of the pots and caps, that would be cool
So, what I understand is that liquid profiling is very limited in its application.
Because only very well-known and widespread sound stages are offered, which limits the whole thing very much.
The basic idea of the Kemper profiling was to profile "your" amplifier individually.
So I'm just as limited when using a liquid profile as when using a normal modeller?
Namely exactly on the models the manufacturer offers.
I tried the different tone stacks from Fender and my Crate VC-3112 in
https://www.circuitlab.com/editor/#?id=7r7n9d
rdmyers's Profile - CircuitLab
The differences are remarkable.
