The MOD Squad

Note that I shorten pin 3, then mount pin 3 to the board via the 0.015uF cap. All of my shileded cables are grounded to pin 4. Next time I'll leave pin 4 un-trimmed to make this easier on the underside of the board.
1755660601614.png
 
That looks like a nice and easy mod, I thought you would like the switching with the DPDT on-on-on switch since it just makes more sense. (Thanks Passinwind for that idea)
Did you work out the capacitance with C2 in series with the voicing caps ? I think that C2 will affect the value of the wet HPF caps just a tiny bit but the higher C2 is the less effect it will have.
I wonder if you can easily bend leg 3 of the BTDR2 module straight out instead of cutting it short, I will have to wait a while before I make another one since I bought one of every other board Nathan has for my round 2 builds. He was out of stock of the Bathtub PCB's when I bought the others.
 
Tassieviking said:
Did you work out the capacitance with C2 in series with the voicing caps ? I think that C2 will affect the value of the wet HPF caps just a tiny bit but the higher C2 is the less effect it will have.
Click to expand...
Good question, I’ll check my notes. My current build has a 1uF in place.
 
So, in terms of simply bending the pin, that would work well. However, I needed to cut Pin 3 because I had already installed the module for my previous design.
I checked how the capacitance of C2 would impact the Fc values. Because the Fc of C2 is so low compared the the voicing switch Fc's. It makes very little difference.
I did notice that I didn't change the Fc when I shift C2 down to 0.47uF. At this value, the Fc is between 50 - 40Hz at -3dB/octave depending on where the mix pot is set.
I think I'd go back to a C2 at 1uF which gives me a Fc ~20Hz.
0.68uF would get an Fc ~30Hz.
 
Tassieviking said:
This might be one mod on the BassDude that not many have thought of, change a few values on some components and add a second Bright cap on top of R12 and you have a Marshall JTM45 preamp, of course the JTM45 has 2 channels, one with and one without Bright caps so place both caps on a switch if you do this mod.

What do we need to do?
We could place a 68k resistor between the input jack and the PCB but I would not do that, the only real difference is that V2A does not have a cathode capacitor C9 and we need to add the 500pF Bright capacitor on top of R12.
R16-1k6, R17-820R, C8-100uF (120uF), C9-Leave Out, R12-Add a 500pF capacitor over the top, Tone Stack-please yourself with this one.

The more serious modder would also change the tone stack to a classic Marshall tone stack, we would just mount the pots in the box and then wire the resistor and the 3 capacitors to the pots themself and then run 3 wires to the PCB at the right places. ( C7 / C10 junction and R15 / Master junction and also a ground wire )

If you build a JTM45 BassDude then it might make sense to try some 12AY7 tubes in the real BassDude so they sound different, you might just need one 12AY7 and one 12AX7 in the BassDude but you just have to experiment with different tubes.
Click to expand...
Ooooooooo, I like the idea of turning the Bassdude into a JTM45!
 
I haven't tried it yet myself but when I do it will be on a new PCB, I just wanted to point out the possibilities that exists with the PCB.
If you do build one please post some pics of your build and let us know what you think.
Cheers
Mick
 
Here is a sample of my updated MOD for the Bathtup Reverb.
Note that the Dry path stays clean:
[This is my original case, not my updated graphic]
 
I like to read Rob Robinettes amp pages and I thought I might make myself a small 1-2watt Soldano SLO preamp and a separate poweramp and stick them in pedals, after I drew up the preamp schematic in KiCad I thought it looked very familiar and guess what ? It is nearly an exact copy of the Mesa Boogie Dual Rectifier preamp circuit, maybe more familiar to me as the C2CE Wrecking Ball pedal as I recently built one.
There are differences in component values and there is 1 resistor more in the Soldano SLO circuit, not too hard to change on a build.

On Rob Robinettes web page he describes some good mods to the Soldano SLO that would work fine with the Wrecking Ball pedal, I especially like the cold clipper resistor mod he describes, a switch to change from Soldano - Marshall - Grid Clip distortion. I think I have to try this mod on my next build for sure, and the whole page is good reading as well.
Heck, I might even build myself a Soldano SLO using the Wrecking Ball PCB, it is very easy to do, the only hitch would be getting an extra resistor between Valve 3 terminal 3 and the PCB. I guess I would most likely remove the pin that goes between the tube PCB and the main PCB for pin 3 and somehow jam a resistor in there.

Have a look at Robs pages and you will see what I mean, especially the cold clipper mod with 3 resistors and a switch.
https://robrobinette.com/How_the_Saldano_SLO-100_Works.htm#Cold_Clipper

Soldano

How the Soldano SLO-100 & 50W Functions
robrobinette.com

Soldano

How the Soldano SLO-100 & 50W Functions
robrobinette.com

Cheers
Mick
 
SamuelG said:
Here is a sample of my updated MOD for the Bathtup Reverb.
Note that the Dry path stays clean:
[This is my original case, not my updated graphic]
Click to expand...
Hi @SamuelG. I replicated you Bathtub Reverb mod, and it’s amazing! Thanks for sharing and documenting it. I also used the shielded cable where you did, but I wonder how much noise would be introduced if I hadn’t used shielded cable. Did you try it at first without shielded cable and experience unwanted noise or were you just being cautious?
 
ThatDude said:
Hi @SamuelG. I replicated you Bathtub Reverb mod, and it’s amazing! Thanks for sharing and documenting it. I also used the shielded cable where you did, but I wonder how much noise would be introduced if I hadn’t used shielded cable. Did you try it at first without shielded cable and experience unwanted noise or were you just being cautious?
Click to expand...
Hi,
Glad it worked for you!
I use shielded simply for caution sake :)
 
SamuelG said:
Here is a sample of my updated MOD for the Bathtup Reverb.
Note that the Dry path stays clean:
[This is my original case, not my updated graphic]
Click to expand...
I like that little tune in the clip, did you download it or make it ?
If you downloaded it do you remember where and what it is called ?
That beat has really grown on me to the point where I might have to get a looper just to test pedals with, my arthritic fingers have not improved my atrocious playing one tiny little bit. I don't think I will get a looper as good as yours but then I never torture people by playing where anyone can hear me. Well, my better half gets to hear it sometimes but then there was that "for better or for worse" agreement.
 
SamuelG said:
I did notice that I didn't change the Fc when I shift C2 down to 0.47uF. At this value, the Fc is between 50 - 40Hz at -3dB/octave depending on where the mix pot is set.
I think I'd go back to a C2 at 1uF which gives me a Fc ~20Hz.
0.68uF would get an Fc ~30Hz.
Click to expand...
Hey @SamuelG , could you clarify this a little, please? Do you mean the dry signal, or the wet? What do you mean with "I didn't change the Fc when I shift C2 down to 0.47uF"? I wanted to follow your instructions above, where the 0,47uF for C2 should give a Fc of 21.9Hz, but now I am confused a little ... Thanks a lot!
 
Hey Winterbloom,
From the original design, I change the high voltage C2 to 0.47uF. In my first effort I used a 1uF cap because that is what I had on hand. But a high voltage 1uF cap is large! So, if you use a 0.47uF HV cap, you will not have any audible HPF from the C2 coupling cap. After C2, there is a dry path (tube only) and a wet path (through the reverb module). So, for size sake, I’d recommend you instal a HV 0.47uF cap on the underside of the PCB.
Per “I didn’t change the Fc when I shift C2 down to 0.47uF” I was referring to lowering the overall C2 capacitance from my original 1uF cap to a smaller 0.47uF cap. This reduction in C2 capacitance does not impact the Dry signal and it does not impact the HPF settings of the switched caps (this is because of how capacitance adds up in series circuits).
Hope this helps.
 
SamuelG said:
Hey Winterbloom,
From the original design, I change the high voltage C2 to 0.47uF. In my first effort I used a 1uF cap because that is what I had on hand. But a high voltage 1uF cap is large! So, if you use a 0.47uF HV cap, you will not have any audible HPF from the C2 coupling cap. After C2, there is a dry path (tube only) and a wet path (through the reverb module). So, for size sake, I’d recommend you instal a HV 0.47uF cap on the underside of the PCB.
Per “I didn’t change the Fc when I shift C2 down to 0.47uF” I was referring to lowering the overall C2 capacitance from my original 1uF cap to a smaller 0.47uF cap. This reduction in C2 capacitance does not impact the Dry signal and it does not impact the HPF settings of the switched caps (this is because of how capacitance adds up in series circuits).
Hope this helps.
Click to expand...
Thanks a lot! But why did you say, you want to go back to 1uF? If I understood you right, then the 470nF C2 will cut the dry signal at 40-50 Hz (which would be to high for me). I am afraid I will cut my dry signal to much with the 470nF. A 40 Hz Low Cut for Bass Guitar is audible and will cause phase issues. So I want to have Fc at a smaller frequency. If I got you right, the 1uF value is best for this. I ordered some 1uF 400V film caps from Siemens/Epcos, which have 23 x 11 x 8,5 mm. So I hope they will fit under the PCB.
 
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