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I wanted to make (another) pedal for a good friend who is a great drummer and ok bass player. I was thinking about doing a TSU with a switchable cap for switching between bass and guitar. Is the 51p (C3) the one I need to increase? I was thinking of making it switchable between a 51p and say a 220n? If this is not the right cap to monkey with please let me know. I was also going to add an always on buff and blend because, well why not? Maybe a stage 3 as well. Anyways, any insight is appreciated. I have a cold sixer ready to go and will be firing up the iron soon. Let me know what you think, thanks.
EDIT: Looks like C4 is the one to monkey with. Interestingly it appears the landgraff adds the 220N, while stock 808 is 47n. Since it will be for bass, could I go to 560n, or even 1u for full bass response? Aside from the typical ‘socket and see” responses, does anyone have any practical experience as to what might work best?
Look for the coupling capacitors. See image below.
C1, C2, C7 and C8.
Since C2 and C7 at 1uF will let more Bass frequency through than you would ever insert with any guitar or Bass those are fine. C1 at 22nF is what limits just the guitar frequencies to come through.
C8 at 100n will let most Bass frequencies through but I would still suggest making that value 220n or go higher if you plan on making some Doom Metal or Movie Soundtracks.
220nF is going to allow plenty of Bass signal through but it will not hurt to go 470nF, 680nF or 1uF especially if it is Keyboards or a really detuned Bass or Baritone guitar.
You could make C8 220n (or higher) and then put a 22n on one side of a DPDT switch and then put either a 220n, 470n or 680n on the other side and connect that to C1 and make it switchable from stock (22n) to whatever value you like. So even though C8 will be a 220n now when you flip C1 to “stock” it will all be the same six and one half dozen only allowing frequencies for 22n flow through the circuit.
I believe that you may be able to change C4 and R7 to affect the tonal characteristics of the pedal if you look at the part of the schematics of the two circuits that are similar. I modded a version of a Boss OD-1 circuit to add more low frequencies by changing the values.
The situation is complicated by the fact that the R5 and C3 interact–together, they form an RC filter that defines the frequency at which the bass signal through the gain/clipping stage will begin to be rolled off. However, R5 determines the maximum gain factor for the pedal, with smaller values resulting in an inversely proportional higher available gain. For example, going from the stock 4K7 resistor to a 3K3 will raise the gain factor by about 40% (4.7/3.3). The stock 4K7/0.047uf combination of the Boss pedal yields a bass rolloff frequency of 720Hz, which is the typical Tube Screamer rolloff point. Going to 3K3 and 0.33uf will drop this value substantially to about 146Hz, letting a lot more bass through the gain stage. However, going this low may result in a boomy/muddy sound, particularly with humbucker guitars.
You may want to install SIL sockets in the R4 and C7 solder pads on the board, so that different values can be tried without need for desoldering and resoldering. Once you find alternative values you like for R4 and C7, you can put the stock and new value resistors and caps on DPDT switches to select the different values.
You can use the formula calculators at http://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php for determining rolloff frequencies.
Say if you want to keep the gain the same, you can use the stock resistor value of 1K, but maybe change the cap to 470nF giving a rolloff frequency of 339Hz. A 680nF cap would drop the rolloff frequency to 234Hz and a 1uF cap to 159Hz. You can use the R value to increase the gain if so desired.
For my OD pedal, I used the stock 4.7K resistor switchable to a 3.3K resistor to increase gain, but that resulted in a rolloff frequency of 1027 Hz with the stock cap of 47nF. The switchable cap values were 47nF (stock value), 68nF and 100nF. With the 3.3K resistor engaged, the 68nF cap produced a rolloff frequency of 709 Hz (close to the default standard for the pedal), and the 100nF cap produced a rolloff frequency of 482 Hz.
or do not install any parts between pads A and B. Then put a Tone TwEQ in there.
or use a Buff N Blend and blend the amount of bottom end you need.
Thanks guys, I have the TS, stage 3, and BNB populated. Should I run the Stage3 and TS in series in the loop?
The Tube Screaming Ultra does not invert the phase so you do not want to place Stage 3 in series inside the loop.
If you still want a Stage 3 Boost in the combo design then place it in series outside the loop like any other combo circuit design. If it were me I would include the Stage 3 in series after the Tube Screaming or any other additional circuit to be used as a Tube Screaming Enhancer.
Thanks for always being so helpful Barry. So should i just wire the whole thing like I would any other multiple? From S3–>BNB–>TS? I guess I thought the effect had to be in the loop for the blend to work. I was hoping to blend clean into the TS. Also, please note I want to leave the BNB always on and not have a FS for it. Should I jumper the 1-2 and 7-8 connections to make it in always on mode? Also, if my whole idea sucks, I haven’t wired anything, and I can just make a standard double with the S3 and TS, although I am running out of friends to give those to.
The Tube Screaming Ultra is in the loop of the BnB.
The Stage 3 is not in the loop or it would invert the signal. You only need the Stage 3 if the other circuit in the BnB loop is inverting in order to make it non-inverting.
So for me it would be Input: -> TUS w/ BnB -> Stage 3 -> Output
Barry, one more thing. Do I need to jumper the footswitch connections to make the BNB always on? 1-2 and 7-8?
Since you have a Stage 3 as well I doubt there is a need for an additional always on Buffer or is there?
Gotcha, ok. I will wire it up this weekend and report back
So after much thought, I made it simpler. To give him the ability to add bass I did a Tube Screaming preamp with a BuffNBlend. Sounds awesome. We are going to rehearse tonight, will let y’all (yeah, I’m from Texas) how it sounds on bass. I will use the TS Ultra and Stage3 I already populated for a double build. Thanks for all your help
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