The new case design for the Boost 'n' Buff v.3 is now in stock. The circuit is finalised and ready to go into production and should hit the street in a month. You can read about the re-design in this previous blog post: http://www.mieffects.com/
Here's a sneak peek at our new Megalith amplifier, the Megalith Gamma.
The picture above is of our final prototype. We've been working on this design on and off for about two years now. There have been a few variations of the design, but in the end we went for a design which exhibited maximum simplicity, but all the tone of its big brother, the Megalith Beta.
The Gamma is an 80W (conservative) 2*6550 based amp, but can also use KT88's KT90's, KT100's, KT120's. The amp can also run El34's, 6CA7's and KT77's but the bias needs to be run a bit cooler, as the plates run at close to 700V. The screens, which are the usual culprit for valve failures, run at a conservative 400V, which hopefully translates into less tube failures. However, I question the ability of current production EL34s, 6CA7s and KT77s to handle these plate voltages (even though they're meant to).
The controls from left to right are clean and overdrive gain, 3 band shared EQ, clean volume, gain volume and contour (yes,... and MI Amp with only 8 knobs!!!). The switches are clean and overdrive bright switches, clean and overdrive EQ shift switches, channel select, overdrive gain mode (low/mid/high), and FX loop on/off. The amplifier will come with a two button foot-switch to switch channels and to switch on/off the FX loop. The two large switches are power and 3 position standby (40W low power, off and 80W high power)
The picture above gives you an insight into the way we prototype. We get a bare chassis made to spec. This allows us to mod and drill of required, but also allows us to test how the mechanical fit will work. We don't use any 3D CAD software, so sometimes we run into issues translating a 2D assembly plan into the real deal.
First thing to note about the Megalith is that it's a high gain amp. By this, we don't just mean one amongst a series of high gain amps, but rather that it has more gain on tap than any amp we know of. To give you an idea, mid-band frequencies can be amplified by up to a factor of 2,000,000 from input jack to the output of the preamp. Then there's the amplification of the power amp! So one of the main challenges of this compact design (the main chassis is only 50cm wide * 17cm deep * 6.5cm high) is stability. Good component layout, use of ground plane, lead dress and wire type are all imperative for stability. However, going too far in the other direction can lead to a rather 'dead' sounding amp, due to too much high frequency coupling to ground. So one of things we aim for is the minimal use of shielded cabling, as this is often one of the main culprits for killing top end.
So where are the transformers? They are located under those huge square metal boxes. One of the things we do which is quite unique is the use of toroidal transformers for both power and output. We design our own transformers (really!). Our design philosophy is to design the transformers to work comfortably under worst-case conditions. For example, our output transformer is designed to work down to 40Hz even if the power amp is pushed into full distortion, putting out close to 200watts, with no hint of core saturation.
So why toroidals? As a general rule, a toroidal will run a lot cooler and radiate much less magnetic field than an equivalent E-core, which is perfect for high power, high gain applications. For output application, they do have limitations to do with DC core saturation, but as long as this is accounted for in power amp design, they're the perfect choice for this kind of design.
They transformers' lower radiation means that the amp will run quieter, and also that you can stand a lot closer to the amplifier without your guitar picking up mains hum from the power transformer, or feedback from the output transformer. To push things even further, we've designed our toroidals with a layer of mu metal on the outside of the windings, which are grounded in order to reduce the radiation further. The final icing on the cake is the square external metal shields, which cover the transformer and shield AGAIN!
With this iteration of the prototype, we were prototyping two new features. The first of these is independent EQ shift buttons for the clean and overdrive channels. This increased the flexibility of the shared EQ on the Gamma. This worked without any hitches.
The next new feature which didn't go as smoothly was our new buffered FX loop design. The previous Gamma has a simple passive loop (foot-switchable). We decided to turn this into an active loop with send and return controls. The idea was to make the loop usable with any effect, guitar or line level, and with any input or output impedance. For this design, we used high voltage solid state transistors running at 250V, so there's no issue whatsoever with headroom! During the design phase, we made sure that the loop had a neutral frequency response using PSPICE modelling of the circuit. This all went to plan.
However, where we came unstuck was the noise of the return circuit. It worked well, but was too noisy. So after a day of brainstorming, we came up with an design with variable negative feedback for the return transistor, which reduced the noise by a factor of 40db, and actually increased the return impedance, to make the loop even more effective.
Anyway, here's a clip of literally the first time we fired up the prototype. Please excuse the iphone audio!
The Megalith Delta high gain distortion pedal design came from years of R&D of our MI Amplification high gain amplifier, the Megalith Beta. It took some time for me to really understand the variables behind great high gain tones. But by designing the amplifier from the ground up, I was able to really grasp how to make a complex, sophisticated high gain sound that kept all the nuances, huge bottom end and the clarity and character of the top end.
The Megalith Delta pedal is a solid state 'model' of the Beta preamp, using JFETs to simulate the gain stages of the preamp valves. The transfer characteristics of FETs are very tube-like, so it seemed that this was a great place to start.
This, of course, is not something revolutionary. A quick peruse of the pedal market and various DIY sites will reveal various FET renditions of valve circuits. However, digging a little deeper shows somewhat limited implementations of these circuits. Often, it's just the exact same circuit as the 'simulated' amp, but with FETs instead of tubes, adjusted source or drain resistances, and 9V operation. Little or no thought it given to the operating points, dynamic range, scaling of clipping thresholds, output impedances, and intrinsic capacitances due to things like the miller effect etc.
As you can see, making a FET stage behave like a particular tube stage is actually a very complex affair. One thing which differentiates our endeavour from others' is the fact that the amplifier in question is our own. I designed every single aspect of the Megalith Beta, and have insights into its working you can't get by simply looking at the schematic. I know what I wanted every tube stage to do, the logic behind each stage design,... even things like the effect of track and cable capacitance. Because of this, I was able to feed all these parameters into the design, and come up with something which is as close as humanly possible to the original.
Now the controls,...
The GAIN control offers a wide sweep in gain, from low-mid gain rock tones, to serious crunch, to every dark shade of brutal imaginable.
The three-band EQ and EQ SHIFT are taken straight from the amp as well. The EQ SHIFT allows three different voicings by shifting the response of the tone stack.
One of the challenges of doing the Megalith in a pedal format was how to integrate the CONTOUR control into the design. The CONTOUR control, which changes the response of the phase inverter, is what really gives the Megalith amp its flexibility. If you want a loose, fatter, vintage high gain sound - turn up the CONTOUR. If you are after a more modern, tighter and cutting high gain tone - turn down the CONTOUR. So in order to mimic this response, I designed a phase-inverter like stage, and integrated the CONTOUR control into it. The combinations of the EQ section will give an impressive number of high gain sounds, just like the Megalith Beta amplifier.
A BOOST mode was added to the pedal as the amplifier really steps up going from "mid" gain mode to "high" gain mode. I thought by adding this as a foot switch, it gives you the option to really step up the crazy. I also figured that mid to high switching was a lot more useful than low to high, as there are already plenty of great options out there for the lower gain sounds. Lets face it, someone interested in the Megalith isn't going to be too stressed about missing the low gain mode!
A big part of the Megalith Beta amplifier's huge gain sound is the 160 Watts of headroom! Of course, this would always be the limitation in trying to emulate a high gain amplifier to stomp box form. But by adding voltage doubling circuitry in the Megalith Delta pedal, it allows the 9V supplied by battery, or DC adaptor, to be increased to 18V within the pedal's circuitry. This has the advantage of producing the crushing low end without mush, much like the 160W output of the Megalith Beta does at the amp level.
Now, the biggest challenge was working out how to fit it all into a case, and keep it stable. For those of you who haven't strapped yourselves in for a Megalith ride,... let me tell you, it's one seriously high gain amp. It's the only amp I'm aware of that doesn't need to be driven with a pedal to get a super-tight saturated gain tone. So packing all that gain into a modest pedal enclosure is not only challenging in terms of layout (there are 110 components in the circuit), but also in terms of stability. After a few failed attempts, I moved to a 4 layer layout, with top and bottom ground planes for shielding. This also necessitated a few circuit tweaks to take into account the extra capacitance to ground.
Finally, I designed an output section which is designed to 'compensate' for the standard guitar amp's clean channel response, so that when you plug the Megalith pedal into a 'reference' clean amp, you get something close to the feel of the Megalith Beta. Having said that, one of the main aspects of the Megalith Beta's 'presence' is the sheer headroom and output power it has. So no, you probably won't unleash carnage and devastation plugging a Megalith Delta into a 5W lunch-box amp. That's just the physics of it,... a reality more inviolable than the existence of fragile harmonics in a crystal lattice.
I feel that, although it may sound cliché, the Megalith Delta high gain pedal is unlike any high gain pedal out there. It came off the back of a complex amplifier design in the Megalith Beta, that already pushes the standard in metal amplifier tones. By emulating the preamp of the Beta, it truly captures the essence of the amp with response and character retained.
Below is a quick demo of the finalised design. It goes quickly from clean, to crunch, to the heaviest of metal tones in under two minutes.
A couple of months ago, we started a Facebook discussion on boost pedals. I was looking at re-designing the Boost 'n' Buff and wanted to make THE booster. We got some great feedback on the matter and it became clear that there were two main uses of boost. Some of you prefer the loud, super-clean, super-simple boost, and others preferred boost with some EQ control to add some sparkle to your tone. So, naturally, I decided to design two Boost 'n' Buffs!
Since discontinuing the first version of our Boost 'n' Buff, we have had a lot of people asking for that simple one-knobber to return - and so it has, in the form of the new Boost 'n' Buff Mini. So the same Class A transistor design was packed into the small, finger-size "1590A" sized enclosure with the same feature set; buffer mode in bypass and +40dB boost when engaged. A flat booster for the lower range of the gain control, and treble booster for the higher range. But one added feature gives the Boost 'n' Buff Mini something extra. A voltage doubling circuit has also been added to provide the boost circuitry with 18V. This means that when 9V DC is added by power jack (the small size doesn't allow for battery), the circuit is supplied, internally, with 18V. This gives more headroom and extra top-end sparkle to your signal - all in a tiny enclosure that could fit on any pedal board.
I then wanted to add an EQ feature to the Boost 'n' Buff so that it could have the flexibility to be integrated into any set-up. However, I also wanted to avoid the large knob count my pedals tend to have. So a neat solution involved adding a three-way mini toggle switch to select between three tone-shaping options, whilst still keeping the same VOLUME and GAIN layout from Boost 'n' Buff v.2.
The EQ options are:
As well as the added EQ feature, I also added a voltage tripling circuit to boost the pedal's operating voltage to ~27V! Unlike the Boost 'n' Buff Mini, v.3 does have room for a 9V battery, and will internally triple the supply voltage of either battery or DC adaptor supply.
Here is a demo we recorded of the prototype Boost 'n' Buff version 3. We tried to show the amount of boost on tap and the different EQ voicings for each of the three modes into the clean and overdrive channel.
All MI Effects overdrive pedals are op-amp based circuits - either using the LM833 or JRC4558 depending on the circuit. It wasn't until my experiments (with relative success) with capturing the tone and response of the Megalith amps in a FET based pedal format, that got me thinking about extending this to other 'amp-like' overdrive sounds.
The initial idea was to try to make an overdrive as smooth as possible, but after tinkering with it a bit, it's morphed into something else altogether. This isn't modelled on anything in particular but we were shooting for a few things:
1) A very natural response, both in terms of tonal balance and overdrive feel.
2) Unlike opamp based pedals, I wanted something that when you roll back on the volume, the sound is virtually clean, but also balanced.
3) Touch response.
4) high gain sounds to have a big footprint, but with a vintage vibe to them,... what I've heard referred to as the 1000lb violin
At its lowest gain, it is a boost/enhancer adding some extra sparkle to your guitar tone. Mid gain mode gives some nice, complex, tube-like overdrive but allows clean-up of your signal via the guitar's volume knob that A/Bs well against your standard clean. Crank the gain and you have a smooth, harmonic-rich, sustaining lead sound from 70's rock to jazz-fusion.
Here is a demo we made with a Les Paul > FET Overdrive > MI Amplification Iron Duke...
This demo with two Strats > FET Overdrive > MI Amplification Iron Duke...
It is always great when a prototype delivers what you want to hear, and this one did. We were undecided on whether this would be a pedal we would put into production, but due to the positive feedback we have received from the demos, we will be continuing with it.
However there are a few tweaks needed before a production-ready pedal can be made:
Keep posted on the blog for the next prototype iteration with the new tweaks, and a new demo.
- Michael I.
This blog series will be an insight into the prototyping and design of new pedals that come out of MI Effects. We wanted to share these processes with you as we find it to be one of the most interesting facets of being a pedal and amplifier company. Most pedal companies keep each pedal design and release a secret, but we thought the process and work that is involved in a new pedal design would be interesting for the gear geeks.
A caveat first: NOT ALL OF THESE DESIGNS WILL MAKE PRODUCTION.
For various reasons, so some of these ideas will be shelved, others will evolve into other projects. So please refrain from questions like "When will this be released?", "Or can I buy the prototype?". As much as we would love to have that information, it really depends on a whole constellation of factors, so any releases will come in good time. Please enjoy the read, and let us know if you would like to see this on your pedal board.
We'd love to hear your feedback along the way, by comments on each post, or via our Facebook page and Twitter. We hope that those interested in design will get some knowledge along the way, and those simply interested in MI Effects will get a sneak peek into what will be released in 2012.
Thanks for your support and see you on the comments page!