Frequently Asked Questions:

“What does “bias” knob do? What is Bias?”

The bias control is used to adjust the voltage level of at least one of the transistors in the pedal. This allows you to keep the sound consistent in pedals with temperature sensitive germanium transistors and also alter the sound and performance to taste. The bias control adjusts the transistor voltage levels, their operating point(s), and sonic characteristics.

There are different strokes for different folks. Some players like to leave a fuzz on almost all the time and use their guitar’s volume control to add dynamics to their sound. They will typically set the bias control high, say 3 o’clock, for more clean headroom.

Another player told me he loves his MKII with the “level” and “attack” all the way up, but with the bias set low. This allows him to get a very saturated fuzzy lead tone that sustains well and still has all the articulation and harmonics he likes, but is somewhat gated and better behaved during sparse passages where he likes it to be dead quiet and not feed back on stop/start passages.

Some players swear by the original circuit, loaded with original transistors, battery power only, unaltered in any way. The nice thing about our bias control is that even if fitted to an original circuit that never had one, you can still produce the exact same circuit simply by leaving it at ~3 o’clock. Ditto for the tone switch, input trim, and DC jack. They allow you to keep the circuit original as well as expand the pedal's capabilities.

The effect of bias adjustment is a bit different for each fuzz and there are different levels of clean up from one fuzz to the next. A two transistor fuzz like the Italian (vox tone bender) or a fuzz face is typically going to clean up more than a higher gain 3+ transistor fuzz. As a general rule, moving the control clockwise increases bias voltage, producing a more open, less gated fuzz, with lots of volume and clean head room. Turning the bias control counter clockwise lowers the voltage giving a gated saturated fuzz tone. You can use our bias control to make slight adjustments to improve headroom and compensate for temperature changes in germanium fuzzes. You can also use it just to get different sounds and performance characteristics. Even in fuzz pedals with silicon transistors where temperature really isn’t an issue, we like to have the bias control to get spitting saturated gated sounds at very low settings, or more clean headroom and articulation at higher settings.

Bias is kind of like the idle of your grandpa’s 1966 carbureted Dodge Dart. If everything’s tuned up and working properly, you probably don’t think about it, you just turn it on and go. A 1966 germanium Fuzz Face is the same way. If it’s working properly and you’re in a climate controlled room, you hit the button and play. Even if something’s slightly off, like an imbalance in the carburetor’s air and fuel mixture, or the bias of one transistor transistor stage; it may still run/work, but not have good performance. Sometimes you may not notice anything until it’s very cold. It may not want to start at all, or it will run terrible. If it’s hot, it may overheat.


“I'm looking into an Mk I fuzz and reading about your Mk I mini ... What is the difference between the OC75/AC128 and the all OC75 configuration please? Don't know much about the Mk I, what are the tonal differences and which is more "correct"?”

Both transistor sets are very close to the original OC75 + 2G381 sound. There are sonic differences, but they are subtle in the mkI mini's. They both share a Mullard OC75 as the first transistor.  The first position is responsible for setting the general input tone characteristics, so they are fairly similar in terms of the input signal getting amplified.  In a MKI circuit, the tonal subtleties of the Q2 and Q3 get lost more so than some other fuzz circuits, so the differences are minor.

The all Mullard OC75 (3X) MKI is generally "gnarlier" sounding.  It has a little less bottom and a bit more upper mids hump, grainier break up (in a good way), and the 3X OC75 generally have more sonic artifacts, most noticeably on the note decay. This is a hair closer, or more "correct" in terms of the original 1965 Mullard OC75 + Texas Instruments 2G381 MKI sound.

The OC75 + AC128 set is better behaved. It has a bit more full freq. bottom end, a bit smoother break up, and typically doesn't have as many sonic artifacts as the all OC75 set. Some players actually prefer this transistor set because it retains the characteristic Mullard OC75 tone, but tames the MKI's unpredictability a bit and makes it more "controllable".


"I am interested in your MKII mini. While I understand tone is quite subjective, which transistor set do you prefer in this circuit? Or what are the subtle differences between them? Does your stock (unspecified) transistor set get very close to the sound of the "fancy" NOS transistors?"

Most original produciton 1960's MKII Tone Benders came loaded with Mullard OC75's.  They sound great, with a nice velcro grit to them.  There were some oddball 60's MKII's with Mullard OC81D, and they are typically smoother with more mids focus and slightly less gain than the OC75's. Those are considered the Holy Grail transistors by some, probably not just because they sound good; they're also just impossible to find these days.

We offer the Mullard OC75's for those that want the security of knowing they can get the classic original 60's MKII sound, but as the above suggests, there isn't a specific transistor set that is necessarily "best" in this circuit. We also offer other NOS Mullard devices like the OC81Z, which are close to the OC81D sound, but closer in gain to the OC75. 

Then there are the "standard" germanium transistor sets that are selected purely by measured specification requirements and by ear.  We use transistors that give sound and performance close to the original Mullard OC75 or OC81D. With these sets the part#, year or country of manufacture, etc... are not important. We only care about how they sound and perform in the MKII circuit.  We can offer these for a less $$$ because they are not as scarce as the original Mullard transistors.

If you just want a great sounding MKII, the "standard" germanium transistor sets are carefully selected to be close in spec. and tone to the originals. Due to the careful selection, the actual tonal differences between the sets are very subtle. If you want to spend less and just have a great sounding MKII fuzz, get the standard germanium transistors.

We also install an internal trim pot that allows you to adjust the input level to tailor the sound to your needs. It also allows the MKII to work well with varying input signal levels and it does not affect the sound at all when bypassed (full clockwise). This "input trim" control is kind of like turning the volume on your guitar down a hair, but doesn't thin out the sound. Great for keeping hot pickups from f%$king up your fuzz tone by driving your MKII's input stage too hard. 

Sonic Boom FAQ’s

"Where, in the circuit, is the effects loop wired? Between repeater AND distortion/booster ? What was it intended for ?"

Yes, the effects loop is between the distortion/booster sections and the repeater section.  Specifically, the "FX send" is "AFTER" both the booster AND the distortion and the "FX return" is BEFORE the repeater.  So, the idea is that you can use whatever other effects you want with the Sonic Boom and still keep the booster and fuzz sections at the beginning of your chain where they sound best, and keep the repeater at the end where it sounds best. The “Distortion” is actually a classic fuzz circuit closely related to the Fuzz Face. Like many classic fuzz pedals, the input of the circuit is designed so it interacts directly with your guitar’s pickups and volume control, essentially making your guitar’s volume knob another control over the fuzz. If you place any buffered pedals before the fuzz, it will not sound good and you will not get the same control.

“What do the little trimmers inside of the pedal do?”

The trimmers inside are used to tune parts of the circuits.  Specifically, in the early models with germanium transistor option, one is for the bias of the fuzz based on your particular transistors, and one is for the range of the repeater oscillator. They come adjusted for optimum performance from us and should never need adjustment.

“Do you make an expression pedal for the Sonic Boom repeater speed? If not, what kind of expression/volume pedal, do you recommend for use with the Sonic Boom?”

We do not make an expression pedal for the Sonic Boom repeat rate at this time. For now, based on several customer recommendations and our own trial, we  recommend using the Yamaha FC7 Expression pedal.  Any expression pedal with a pot value of ~100K will do, but a reverse log taper 100K spreads the taper best. Most people seem to like the FC7 for its price and convenience. The FC7 expression pedal also allows you to cut out the repeat effect while still retaining the volume boost of the repeater section, basically acting as another gain stage or booster by just rocking it back all the way.

"I read somewhere, hand made (Sonic Boom) pedals will be stopped ? Is it right ? What kind of pedals do you plan to release in the future ?"

That's not exactly correct.  All of our pedals are hand made in Los Angeles, CA. In addition to doing high quality exact reproduction PCB's for vintage pedal clones, repairs and reproductions of vox onboard effects, and so on; we're starting to build some pedals like the Sonic Boom with printed circuit boards. PCB construction allows us to squeeze the size down a bit for a smaller, more ergonomic pedal board friendly enclosure. 

"What is the difference between PCB and P2P?" "Which is more reliable?" "Is one easier to work on or sound better?"

PCB vs P2P (point to point) differences are the physical size and look of the pedal. "Point-to-Point" is not inherently "better" than PCB construction in the Sonic Boom. Both pedals have the same circuit, build quality, and sound. If anything the PCB is a bit more "hi-fi" to my ear; which makes sense simply due to being physically smaller with shorter signal paths.

When you consider overall layout and general design of a finished product a PCB is often the best choice in all respects. Given a good design, constructed in the hands of an experienced builder; point to point vs pcb, or turret, or eyelet board, etc... does not matter.  I've seen plenty of point to point builds where design is poor and/or overall build is just poor and it's still an all "point to point" build. This is scary to see in amps when components assembled point to point vibrate so much they've come loose and/or shorted out against each other or chassis under high voltage! 

On the other side on the coin, a friend just brought me a "boutique" multi effects pedal with a modern plated through hole printed circuit board that was "assembled" in the Netherlands. It wasn't working because two of the parts were NOT SOLDERED to the PCB in any way and the input jack was shorting to a switch because the enclosure was not drilled so the parts were spaced properly to avoid this. Just not designed or built well at all; and that was all pcb construction. Long story short: PCB vs P2P (point to point) does not matter in terms of the build quality, reliability, or sound of the Sonic Boom; just your preference in the physical package.

“I like the sound of the palm wah in my Vox guitars.  Do you make this as a pedal?”

No. Most people seem to like to use this or that wah of their own preference and placement in the signal chain, we do not currently make the wah, but opted to let people use their own and place it anywhere they want with the optional FX loop. We prototyped a version of this Vox palm wah circuit in a more user friendly traditional foot controlled wah rocker enclosure, but have not as yet released it as a regular product.  It is scheduled for release in 2017.

More Sonic Boom Frequently Asked Quesitons:

What should I use to power my Sonic Boom?  The Sonic Boom can be powered with one 9 volt battery or a 5.5x2.1mm barrel connector - center negative –positive ring.  Just make sure you actually read or properly research the specifications of your power supply adapter to confirm it meets those specs.  If you’re not sure and can’t determine which power supply you’ve got, just use a battery until you know.  Any 2.1mm negative center “Boss” style barrel adapter putting out between 9-10 volts @ ~100 to 200 mA of current is OK.

"Can I 'daisy chain' my Sonic Boom with other pedals?" 

 Yes. This pedal is normal 9v negative ground, like most modern production stompboxes, so YES you can daisy-chain it with other 9v negative ground pedals.  You can not daisy chain the sonic boom with positive ground pedals or vice versa unless you’re using one of the ISOLATED multi-power supply units such as Voodoo Labs Pedal Power or Decibel Eleven Hot Stone Deluxe power supply. Those types should work fine, just make sure you are using the 9 volt/100-200mA, NOT 12 or 18 volts.

"I tried powering my Sonic Boom (or any pedal with a DC jack) with an (XXX) adapter and now the 9v jack doesn’t work, even with the power adapter you recommend.  It still works fine with a battery."

  Most “Boss” style barrel adapters have a 5.5mm outer ring and a 2.1mm center pin.  However, some have a 2.0, 2.1, 2.5mm etc…  There are also some oddball adapters that look like they will fit but actually have slightly larger or smaller contacts.  This difference is usually fractions of a millimeter and too small to recognize by eye.  So, if you’ve tried an adapter that is not actually the correct size for your Sonic Boom, and then tried one that is correct, but found that your pedals will still not power up through its power jack, this may be due to the jack contacts being stretched out by inserting a plug of the wrong physical size.  In that case just let us know and we will send you a repair authorization to replace your jack. 

"A unicorn came and told me that I could get to the top of a magical psychedelic candy mountain of tone by simply fiddling with the two trimmers inside my Sonic Boom pedal.  Now my pedal doesn’t work right. What should I do??"  

Stop dipping your crack in formaldehyde.  Seriously…should you “accidentally” adjust these or find the repeater and/or fuzz do not sound “right” anymore like they used to, you can send it back to us to re-set it for you, or if you have a voltmeter and some patience we can tell you how to adjust the bias to the fuzz and adjust the repeat range by ear.


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