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How do I add a bass pot to a...

HamishR

Well-known member
I had so much success with Chuck's excellent advice on how to add a bass pot to an Expandora and a Rat that now I am curious as to how I might add a bass pot to a Bluesbreaker or Prince of tone and a BB Gun OD. I've always liked the basic tone of a King of Tone pedal but in my rig they are rather bass-lite. Same with the BB Gun - I have built a vero version of it before and it sounded very good except for the extreme lack of low end. I have built an actual 1974 Marshall style amp before and no, it doesn't have a lot of low end either. But with a few simple mods I was able to get a much bigger sound from the amp - now I would like to do the same with the pedal.

Any ideas? I'm about to order a bunch more PCBs...
 

phi1

Well-known member
Study the Timmy bass control, which can be implemented on most op amp / diode clipping dirt pedals.

For plug and play answers, on the BB gun, i would:
-Omit R6 (4k7)
-use a 22uF cap in place of C4
-wire a 5k pot from the junction of R7/C3 to the junction of R6/C4 (you can hook a wire onto the leg of R7, and use the hole of R6 since it’s unused).

You can use sockets to experiment with:
- the new C4. 22u will give full range bass boost with the pot up. Using a smaller value like 10u or 4u7 will still cut some of the lowest frequencies, but boost low mids.
-either R7 and C3 will determine what frequencies are cut when the bass knob is down. If you adjust R7, it will affect the gain.


See if you can come up with something using the same concept for the Bluesbreaker or KoT and report back your idea.
 
Alternatively for a blues breaker with a bass control, check out the Parthenon. It adds a baxandall style bass and treble control after the clipping. If you're wanting to do a simple mod though, the Timmy style bass control is much easier to implement!
 

phi1

Well-known member
Ah great point there’s already a board for that!

I do think there are advantages to having the bass knob be an active control post dirt like that. You can keep the bass cut pre-clipping to reduce the muddiness, while boosting cleaner lows for more oomph.
 

Chuck D. Bones

Well-known member
Or build a Klon, it sneaks the low freq stuff around the distortion stage. If you want the bass clean bleed to be adjustable, then build a Madbean/VFE Merman like I did.
 

Chuck D. Bones

Well-known member
I just finished painting my Merman. As soon as I get it reassembled, I'll post it in the Build Reports. I would like to see PedalPCB offer a version of that in a 125B case. It's a snug fit in a 1590B. With all of the Klon derivatives on this site, that one is conspicuous in it absence.
 

HamishR

Well-known member
I already built a Parthenon and it was underwhelming for me! I guess some pedals just sound "right" as they are, and if you add lows you lose what that pedal had in the first place. That's why I was so delighted when the Expandora and Rat worked so well with the bass pot.

I've a few Klones, some verbatim with the correct diodes etc and some with mods. Meh! I'll look at doing what phi1 suggests. I have copied the Animal's bass pot successfully onto one or two pedals but I can't remember which! I have rather a lot of coloured 1590B boxes around here...
 

PedalPCB

Administrator
Staff member
Thought a little more about what you said, and you're right.... In a time like this everyone can appreciate a little distance, sometimes those germaniums come from some shady sources.

I give you the Isolation Edition. You're going to need a 1590BB.

MerIso.jpg
 

Chuck D. Bones

Well-known member
I have noticed! It's pretty, but it comes at a price. Some of the board traces are longer than they need to be which can cause problems with noise pickup and oscillation. Symmetrical boards tend to be larger, or components crowded together, or both. Compare a Madbean board to a PedalPCB board and you'll see what I mean. Yeah, I'm a bit opinionated when it comes to board layout and for good reason. In my last job, I designed some mixed-signal boards that contained an embedded computer, DSP and precision analog circuitry. We had to go to great pains to get the layout just right. I also designed switching power supplies and switching power amps. With those circuits, 1/2" of trace can mean the difference between working and not working. I am not exaggerating. We had to obsess over the layout and I sometimes drove the board layout guys crazy. In the end, we came up with great products. Many have been working continuously on orbit for over a decade.

Having said all that, I like PedalPCB boards enough to keep coming back and buying more. Robert works his ass off and does a great job. Except for that Merman clone, it's an abomination. 😜
 

PedalPCB

Administrator
Staff member
The symmetrical layouts are the product of genuine OCD.... Not just "I like things a certain way", but the real deal.

There is generally a little more thought put into the designs than just making them pretty, but that is certainly a priority after the initial layout is done.
I'm fully aware that do sometimes break the rules though, there's no denying that.

I'm familiar with "proper" layout techniques, but thankfully we don't have to worry too much about high-speed traces, differential pairs, trace length matching, etc etc.

I must say though, I feel like the majority of my layouts (with a few exceptions) are actually less crowded than the other guys... Not that it means anything aside from making my eyes feel better.

You know you like that Sea Monk layout, cmon dude, those germanium diodes are temperature sensitive. I'm placing them as far away from the rest of the active circuitry for a reason. Sure, it means a 125B effect now has to go in a 1590DD enclosure, but that's the price you pay for tone. :ROFLMAO: :ROFLMAO: :ROFLMAO:
 

Chuck D. Bones

Well-known member
If you could just put another 0.050" between film and ceramic caps and another 0.100" between any electrolytic caps over 10uF, I'd be able to install some of the fatter silver-mica, film and aluminum caps I have in my stash. I can make 'em fit now, but it's not pretty. Some of my boards look like Fred Sanford's backyard.
 

PedalPCB

Administrator
Staff member
When you say between film and ceramic caps, you mean when they're bumped up against each other?

Some of the older layouts were really bad about spacing around electrolytics and I'm trying to improve that on new layouts and redesigns.

Several of the older layouts are in dire need of a redesign.... One or two of them make me cry when I see them. :censored:


I should add, in regards to what I said above.... some of the "layout liberties" will have to change a bit when we move forward into ARM processors and beyond... That's a whole different ballgame.
 
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