Heavy Metal

A heavy favorite for heavy metal

The Heavy Metal distortion rack effect module compares to the Boss MT-2 Metal Zone. Since its introduction in 1991, it has become the second-best-selling Boss pedal of all time, and one of the overall best-selling pedals ever, with well over 1 million sold. Due to its popularity, the design remains unchanged since its debut. However, it is also one of the most-modded pedals, hinting that maybe it is close, but not quite, what metal players really want.

Description

The Boss MT-2 Metal Zone pedal was introduced in 1991, as metal music was booming. It has become the second most popular Boss pedal of all, despite others being in production for decades longer. Over 1 million of them have been sold, making it one of the more popular pedals ever. In spite of that, the MT-2 is a loved by some, hated by many, and a big "meh" to others.

The circuit itself is technically large and complex, particularly for a distortion. The Boss engineers put in a lot of work trying to get super high gain, with manageable noise, no muddy/flubby bass, and enough punch to cut through any mix, all tailored for emerging metal artists that were beginning to dominate popular music in the late 80's and early 90's.

But the engineering complexity spilled into the controls. Many found the Level, High, Low, Middle, Mid Freq, and Dist made it difficult to dial in their tone. Plus, there is still some noise, mids that need managing, and a lot of shrill high end. The magic wasn't really there for many players and they moved on. Those that took some time to figure it out were hooked.

Many thought the tone was almost what they wanted. With a pedal that was relatively cheap, mass sales, and lots of unimpressed buyers, a vibrant mods market quickly emerged. The details of the mods were often murky. It was difficult to know what to ask for. From a technical perspective, with such a complex circuit, there are many, many points where small changes could be made. While there didn't seem to be any single thing that appealed to everyone, there were small groups of mods that together found very happy customers.

The pedal is still made as it was originally. It still sells well, perhaps in part because of the healthy market for mods to change it up. Regardless of whether you prefer the original circuit, or one of the mods packages, or just a few specific mods you know about, most can now get the metal tones they want from an MT-2.

The GC Heavy Metal is our version of the Boss MT-2. We offer most of the mods that are available, including custom combinations of mods.

The standard controls of Level, Distortion, Hi, Mid, and Lo perform their obvious functions. The Mid Freq control adjusts the range of frequencies controlled by the Mid control. On its own, it sounds like a fixed wah. One of these days maybe we'll offer an option to attach an expression pedal to that one...

Since the mods are so important to the success of this circuit, let's cover some of them at a high level to prepare for the discussion of all the options below. It is a bit messy and confusing. The mods weren't really designed. They were "discovered" in bits, then combined and changed up. While some of the mods have names, it isn't always clear what might actually be meant to be included. The mods overlap in the parts they impact, as well as the functions they perform, but some are compatible and can be combined. There is no way to avoid some of the mess, but we have spent considerable time sorting through the various mods so that we can offer great-sounding versions of the circuit that should meet expectations of those seeking out those mods.

First, we support the original circuit without mods. Well, sort of. There are no special parts in the entire Boss design. It isn't the parts that make the circuit, it is the design. Some of the parts that are used score higher for low cost than for quality. Many introduce noise, which is very bad in a ridiculously high gain circuit like this one. While we have the original circuit as our base configuration, it already starts with quieter, better parts. These changes do not impact the tone of the circuit, just the noise level. Some of the popular mods replace many components in the stock pedal. Many of those are just quieter versions of those components. The Keeley mod is like that. Some of the Keeley mod changes are just swaps for quieter parts, a good idea no matter what else you might do. As a result, our "Keeley Mod" option includes less part swaps than you may expect because several of those changes are already part of our base circuit.

Those part swaps that don't change the tone, just the noise, are the first types of mods we support. You get them for free without asking in our base configuration.

There are some other part swaps that also lower the noise but do impact the tone. In this circuit, a lot of the noise lives in the highs. If you trim the highs down a bit, you can remove loads of noise. But you lose a little bit of the highs and presence when you do it. Most mods have a side effect, and that's the side effect of this second type of noise reduction mods.

Another popular type of mod is gain reduction. This circuit seriously has far more gain inside it than is necessary to hit even the most high-gain metal tones. Trimming it back doesn't even sound like gain loss. It comes out as more clarity, less mush. You might hear some of the fuzz getting tamed down to high-gain, which you may or may not prefer.

Bass players know that low bass gets muddy with lots of gain and distortion. Trimming a bit of the very lowest bass that is difficult to hear can tighten up the remaining bass and get rid of the mud. But you lose some low bass.

The circuit can be harsh. There are a couple of mods to make it a bit smoother. These usually add some low mids/upper bass (or rather don't cut it), or trim some highs.

The midrange often needs some attention. There are some popular mods for that. In fact, the most popular mods are largely focused on better handling of the mids. It changes the character of the tone considerably. For better or worse, your call.

Finally, there are mods for the clipping. The circuit uses a simple pair of silicon diodes to do some hard clipping. Normally, in a distortion circuit diode clipping is a really big part of how the distortion is generated. In this circuit it is still important, but not to the same extent due to the massive gain clipping in other components. You can still get substantial changes in tone, volume, clarity, and feel by changing the clipping. This is often included in some murky way in many of the mod packages available. We split it out separately so you can specify it clearly and get what you need.

So that's what the Heavy Metal is all about - the wide range of tones available from the MT-2 in its many modded versions. It's easy to get option-happy, but we recommend you keep focused so that you don't end up with so many knobs and switches that you'll never find that magic combination of settings you liked yesterday.

We provide some recommendations about the options as well as a few option groups that others have found to be just what they wanted.

Of course, YMMV! The MT-2 pedals are pretty cheap, so you should be able to beg, borrow, or steal (just kidding!!) one or two, probably even with some mods, to try out before you make your option choices.

Since we're talking about a large number of possible mods and a really huge number of combinations, all of which are variations on a "metal tone" theme, it is difficult to try out or even describe all the possibilities. It's definitely worth thinking about what you've heard and liked or what you don't like about the MT-2 before jumping into the options.

Here are some of our opinions on the available mods. Bear in mind that we're not really metal players here, so we may be a bit off the mark. We actually think the base pedal (with our base updates mentioned above) sounds pretty good, but some of the mods are definitely nice.

To us, the popular mod packages, including the Keeley mods, Diezel, and Bogner mods are far more similar than they are different, and not wildly different from the standard configuration. Perhaps that is because we include some of the basic changes to lower noise and use better components in our base configuration. However, all those mod packages also include changes to clipping configurations and those can be very noticeable. We offer those clipping options both separately and with the mod packages. We don't really think of them as just part of a mod package. If you get those mods with those clipping changes, they are quite different from the base circuit, and somewhat different from each other. Clipping aside, our Keeley mod package is very similar to our base circuit tone. The Diezel and Bogner mods give similar results, although the Bogner mods probably provide a bit more highs and volume, although both change up the mids.

For clipping, you can spec out any of a wide variety of configurations we can support. The base circuit has a symmetric pair of silicon diodes. The mod packages recommend various combinations of silicon and red LED clipping diodes. Most of those configurations have similar results. The distortion is cut back and the sound is more open and crunchy. The complexity and levels of gain in this circuit tend to cover up small differences in tweaks. This is true with the clipping configs. It is difficult to hear the differences between many of the clipping options, although easy to hear the difference between them and the standard clipping. If you want to keep all the gain, then you'll probably want to have the original clipping config available. It you want to cut it back a bit and open up the sound, try one of the LED configs, maybe the symmetric pair of LEDs. Those two choices give tone options that are easy to hear and build around.

The Less Gain Mod #2 has a big impact. It takes you out of really high gain down to super crunch, with considerably less noise. it's almost like having Crunch and Gain channels on an amp. (And no, we don't offer "Less Gain Mod #1". We had one, but when we tried it, we decided it wasn't so great and don't offer it presently.)

When we first started thinking about the Noise Gate option, we didn't like the idea and didn't really have high hopes for it. It isn't really a proper noise gate, and it has no controls for threshold or anything else. It is just a pair of hard clipping diodes to ground. When your signal gets down to the forward voltage of the diodes, the entire signal is suddenly sent to ground so that no sound comes out the circuit at all. Germanium diodes are often used for this mod because they run at a lower forward voltage, letting your signal fade down quite a bit before chopping it off, which obviously kills sustain. But we didn't like them and they didn't really work that well. But as we experimented, we got the sense that maybe this mod had some merit. Eventually we found a fairly uncommon vintage silicon diode that worked really well. In our testing, we were able to get more sustain (hold notes longer) than is probably ever needed before the noise fades to a barely audible sizzle before complete silence. Those diodes work really quick on palm mutes, too. While you still get all the noise while you're playing, that noise is mostly covered up. The Noise Gate option ends up working far better than we expected. Of course, if you are playing high-gain metal, you probably already have something in your rig to manage the noise, so this may not be necessary. But if all you're using is an MT-2 and you have too much noise, this is most definitely something worth considering.

There is more info about all the mods below to help guide your decisions. Keep in mind that the standard MT-2 controls of Level, Distortion, Hi, Mid, Lo, and Mid Freq gives you 6 controls to start with, which can be quite a bit to sort through to find that tone you're looking for. Adding more controls and options will make for a wide module, easily getting up to 3". The more options and controls, the harder it is to find what you're looking for. Consider carefully what you want changed from the base MT-2 sound and focus on that. In our opinion, it is also OK to just pick one of the mod packages (if you are interested in them to begin with) and have those changes built-in as opposed to switchable. The differences aren't that much to switch between. The clipping options are on separate switches from the base mods, so you might prefer an unswitched base package along with an unswitched clipping option to save a couple of switches and some $$$.

Configurations

Heavy Metal - compares to Boss MT-2 Metal Zone, with and without popular mod packages

Options

Many of the popular mods specify the exact part that is changed in the circuit, along with what the new value should be. For example, "change C34 to 47n". In this case, C34 refers to capacitor 34 on the Boss MT-2 board. Our parts have different numbers, but we still use the Boss part numbers in the mod descriptions to prevent confusion. We'll change our part that corresponds to the Boss part number. If you look at your GT board, you won't be able to find the Boss part numbers.

Yes, most of these mods are free or nearly free when you order them upfront!

For popular mod packages that include clipping changes, you specify your clipping options separately. And remember you get some of the noise changes as part of the base config.

Some of these mods can be combined, as we have done in a couple of our mod groups. You can see if they conflict by looking at the specific parts impacted, and what they do. In particular, if you have some switched mods that you want to switch together on a single switch, you may be able to avoid adding some switches and extra cost. Let us know.

In clipping options, "LED" refers to red LED

There are many other possible mods. If we don't list what you want, just ask for it. If it doesn't use any of the specific parts noted in our mods below, we can probably do it but it won't likely be switchable.

Some overall comments about the available mods… Remember, the popular mods are mods for a pedal. It is difficult and impractical to do very much inside the tight confines and crowded boards of a pedal. Most of the mods are designed to change how the mids are handled, reduce the high gain noise, and reduce the gain. There are multiple ways to accomplish all those goals, and pedal tweakers have found multiple ways to do it. The mod packages, such as Keeley, Diezel, and Bogner have results that are more similar than they are different. If it was easier to make some other changes inside a pedal, perhaps all of those mod packages would have chosen other ways to accomplish their goals. We recommend thinking about what you dislike or want improved about the original circuit before choosing mods.

Since we are building from scratch and don't have pedal constraints, it is easy for us to use quiet components, for example better capacitors and op amps. We do that by default. While some mods claim swapping components will greatly reduce the noise, that alone won't have much impact. It helps and doesn't cost anything, so we do it. Most of the noise is due to the high gain of the circuit.

If you want to address the high gain noise, you'll need to do more than just swap to better components. But do you need to? Chances are good that if you play a high gain pedal, you have a high gain rig and you play high gain music. You probably already have noise gate or noise reduction gear in your chain. So maybe noise in this circuit doesn't matter that much.

However, if you do care about the noise in this circuit, consider the Noise Cut capacitors option. You'll trim off some highs and presence, but not enough to get rid of all the noise. It's a trade-off. The Noise Gate is a different trade-off. You might lose a touch of sustain, but it definitely cuts the noise between notes. Or consider the Lower Gain option. That is a bigger trade-off. It takes you almost out of the High Gain tone down to a super crunchy, less distorted tone - nice but pretty different.

Diezel Midrange Mod - Changes up your control over the mids. Lose a bit of Lo control.

Remove C25

Change C34 to 47n

Remove C35

Recommend single or switched clipping configs of:

LED, LED

LED, 1N4007

open, 1N4007

silicon, silicon (stock circuit config)

This mod may include a switch for clipping, depending on your clipping choice

Switched Diezel Mod - Same as the Diezel Midrange Mod but you can switch between the mod and stock circuit

Parts switched: C25, C34, C35

Recommend single or switched clipping configs of:

LED, LED

LED, 1N4007

open, 1N4007

silicon, silicon (stock circuit config)

There is one switch for the mod, maybe a second switch depending on your clipping choice

Bogner (aka Boogie) Mod - Similar in results to the Diezel Midrange Mod, also with some impact to Lo control

Change C34 to 47n

Remove C35

Change C36 to 100n (Same as Mids Sweep Mod below)

Recommend single or switched clipping configs of:

LED, LED

LED, 1N4007

open, 1N4007

silicon, silicon (stock circuit config)

This mod may include a switch for clipping, depending on your clipping choice

Switched Bogner (aka Boogie) Mod - Same as Bogner Mod, but you can switch between the mod and the stock circuit

Parts switched: C34, C35, C36

Recommend single or switched clipping configs of:

LED, LED

LED, 1N4007

open, 1N4007

silicon, silicon (stock circuit config)

There is one switch for the mod, maybe a second switch depending on your clipping choice

K Mod - Our version of the Keeley mod. Smoother, less noise, less harsh, better clarity. Note that most of the Keeley changes are already incorporated in our base configuration, so the difference between our base config and Keeley mod isn't as big as you might expect (except for the different clipping options).

Change C9 to 100n

Change C17 to 1u

Add clipping capacitor (not in original MT-2 circuit)

Includes the K Mod Clipping Switch Mod (below).

One switch, for clipping

Switched K Mod - Same as the K Mod, but you can switch between the mod and the stock circuit

Parts switched: C9, C17, clipping cap

Includes the K Mod Clipping Switch Mod (below).

Total of two switches

Switched Diezel and Bogner Mods - Get the Diezel and Bogner mods on a switch so you can switch between them, but not the stock circuit. To us, the difference isn't that big, but if you have a different experience, this gives you both of them.

Some components are switched, but some changes in common between these two mods are made permanent in the circuit.

Recommend single or switched clipping configs of:

LED, LED

LED, 1N4007

open, 1N4007

silicon, silicon (stock circuit config)

There is one switch for the mod, maybe a second switch depending on your clipping choice

Smooth Input - By default, the bass is reduced quite a bit at the input so that the high gain doesn't turn it to mud. This mod allows more bass to come in. Probably OK most of the time, but could lead to some flubby distortion. There is so much other stuff going on in the circuit that this is difficult to hear the impact most of the time.

Change C42 to 100n

Switched Smooth Input - Same as Smooth Input, but can switch between mod and stock value. Probably not worth adding a switch since the difference is subtle much of the time.

Parts switched: C42

Clipping Cap - This mod adds a small cap along with the clipping diodes to trim a little noise and harsh treble. Part of the Keeley mod. On its own has little audible impact, but similar to the Noise Cut option below.
Switched Clipping Cap - Same as the Clipping Cap mod, but on a switch. Not really worth switching on its own, but maybe as a part of a custom switched mod.
Tighter Bass - Allow some trimming of the very low bass to improve the clarity and tightness of the remaining bass. Reduces flubbiness a bit. Does help with clarity if you don't mind trimming the low end a bit.
Switched Tighter Bass - Adds a switch to turn Tighter Bass mod on and off
Less Gain #2 - Usually part of other mods packages, available for you to select separately if you know your mods packages. Helps reduce gain. This is a substantial change in gain and the overall character of the tone. Takes you out of the High Gain metal zone and puts you into Super Crunch or Lighter Distortion mode. Sort of like an amp Crunch channel vs High Gain channel.

Change R41 to 15K

Switched Less Gain #2 - Put the Less Gain #2 mod on a switch to turn on/off. Nice option to give you something like a Crunch Channel option to go with the normal High Gain channel sound you get from the stock circuit
Quiet Op Amps - There are 4 opamps in the circuit. The original circuit uses M5218 op amps in an older inline package. These are NOT special in any way. Their specs are nearly the same as other op amps that have better clarity and less noise, both important factors for this circuit. Instead of supporting ho-hum op amps in an uncommon package, our base configuration switches to a much more common DIP-8 package, which opens up a huge number of op amp change possibilities. By default, we use the standard 4558 op amps, with specs like the M5218 to keep close to the stock sound.

You can get pretty carried away with choices here and spend quite a bit on high end op amps. We recommend focusing on Boss IC3 and IC4 for upgrades. You won't get as much bang for the buck swapping IC1 and IC2. Some op amps are free upgrades, like our usual favorite TL072. You could put four of them in for no charge and reduce noise, add some tubeyness, and take off a little warmth found in the 4558. So that is our recommendation. If you want to spend some money, try OPA2134 or NE5532 or other high end op amps for Boss IC3 and IC4. The difference in any of these op amps in a high distortion circuit is small. You may or may not hear it. The noise level difference is very small with the high gain. Little of the noise is due to the op amps themselves.

This is not switchable

Noise Cut - There are several places in the circuit where capacitors are used to cut back very high treble content, where the noise lives. Many think the stock circuit still has too much noise and harsh treble. If you want to tame it, we can make some modest changes to those caps to do a little more filtering of the noise and top end. You may lose a little presence and highs, if you can hear it with all the noise around it to start with. You might want to consider adding the non-switched Clipping Cap option, which does the same thing, just in another spot in the circuit.

Change C10 to 100pF

Change C18 to 100pF

Change C22 to 120pF

Change C26 to 220pF

Change C28 to 120pF

Change C32 to 220pF

This is not switchable

Mids Sweep - Usually part of other mods packages, available for you to select separately if you know your mods packages. Changes the range of the Mid Freq control.

Change R36 to 100n (or maybe 68n if you prefer that version of the mod)

Switched Mids Sweep - Mids Sweep mod with an on/off switch
Noise Gate - This adds a pair of uncommon diodes in the signal path. When the signal drops down to the cutoff voltage for the diodes, the diodes stop transmitting and the sound is muted. Some find this useful to kill noise when not playing. When you start playing, the signal level goes back up and your sound goes through. This is a crude way of doing this because it is not adjustable. The diodes we use will allow your notes to sustain longer than you probably need them to. As they fade out, there will be a subtle fizzle just before the silence begins. And we do get silence, even with quick palm mutes. Of course, your mileage may vary a bit depending on your chain, your pickups, etc. You may still hear some noise or your sustain may be cut back a bit. However, for its crudeness, it works surprisingly well. Of course, if you are running a high gain, high distortion rig, you probably already have a solution for high gain noise and this option may not get you anything you don't already have. But if this is the only/last noisy effect in your chain, it may be just the ticket.
Switched Noise Gate - Puts the Noise Gate option on a switch
K Mod Clipping Switch - Gives you 3 clipping configurations on a switch. These are the switched options you get with the Keeley mod.

Configs:

open, silicon (asymmetric)

silicon, silicon (symmetric, stock config)

silicon, silicon/LED (asymmetric)

3-Way Clipping Switch - Gives you 3 clipping configurations on a switch. Each config has two "sides". Each side can have up to 2 diodes (silicon, germanium, or LED) and/or 2 MOSFET transistors configured as MOSFET diodes. For this circuit, we recommend no more than 2 diodes of any type on any side, but read up on your clipping configs and choose whatever you like! Most diode selections won't cost extra unless you get into germaniums, rare vintage diodes (don't waste your money!), or something exotic. The extra cost is for adding the switching, extra board, etc.

The clipping diodes in the original circuit are long out of production, difficult and expensive to find unless you are Boss. But they are NOT important to the tone, other than the fact they are silicon. We use 1N4148 silicon in our base configuration. It is not an audible difference.

Some configs that work well in this circuit include:

silicon, silicon (stock circuit config)

LED, LED

LED, 1N4007

open, 1N4007

open, 1N4148 or other silicon

silicon, silicon/LED (ala Keeley mod)

This mod lets you pick any 3 configurations to switch among with your 3 switch settings, including other configs not listed.

2-Way Clipping Switch - Same as 3-Way Clipping Switch, except you choose only two configurations for the two switch positions
Custom Clipping - If you just want to change the clipping config of the base configuration without adding a switch (ie - always use the same clipping config), choose this option. Select whatever config you want. Note that if you select a simple config of no more than 2 silicon, or LED diodes per side, then there is no cost. More complicated configs add a board and some more work and parts.
5150 Mod - Some think this group of mods sounds similar to a 5150 amp. Similar to Griffin Death Metal Mod.

Change IC3 to OPA2134

Change IC4 to NE5532

Change C17 to 1u (part of K Mod)

Remove C25 (part of Diezel mod)

Remove C35 (part of Diezel and Bogner mods)

Mids Sweep Mod using 68n instead of 100n cap

Noise Gate Mod

Smooth Input Mod

Less Gain Mod #2

Change R14 to 46K

Noise Cut Mod

LED, LED clipping configuration

This mod cannot be switched, although some individual pieces could be switched

Diezel Mod 2 - Start with the Diezel Mod and add a few tweaks

Diezel Mod

Less Gain #2 mod with 10K resistor

Smooth Input Mod

Mids Sweep Mod

LED, LED clipping configuration

This mod cannot be switched, although some individual pieces could be switched

Diezel Mod 3 - Another tweaked Diezel mod package

Diezel Mod

Less Gain Mod #2 with 22K resistor

LED, 1N4007 clipping configuration

This mod cannot be switched, although some individual pieces could be switched

JCM800 Mod - Some think this group of mods sounds similar to a cranked Marshall JCM800

Diezel Mod

Less Gain #2 with 22K resistor

open, 1N4007 clipping configuration

This mod cannot be switched, although some individual pieces could be switched

Mixed Mod - Some Diezel, some K Mod, some tweaks

Remove C25 (Diezel Mod)

Remove C35 (Diezel Mod)

Change C9 to 100n (K Mod)

Change C17 to 470n (tweaked K Mod)

Mids Sweep Mod

Smooth Input Mod

This mod cannot be switched, although some individual pieces could be switched

Components - All the component swaps that seem worthwhile are already part of our base configuration or part of the mods above. If there is something else you would like, just let us know.
Other Voltages - We haven't had time to try this yet, but we could if you are interested. This would definitely change the level of distortion and gain, but perhaps too much. If you want to tame the circuit that much, maybe this isn't the circuit you really want.

Front Panel

On/Off indicator LED
Level
Distortion
Hi
Mid
Lo
Mids Freq
(optional) numerous switched options are available

Rear Panel

Audio In
Audio Out
On/Off Footswitch
On/Off Override
DC Power
DC Power LED

Module Width

2" standard
3" with options
wing configurations not currently available

Power Consumption (aprox)

20 -35mA depending on options

Base Configurations

Part #	Description	List Price
MOD-HEAVYMETAL	Heavy Metal module	$240

Options

Part #	Description	List Price
MOPT-HM-DIEZEL	Diezel Mod	$0
MOPT-HM-DIEZELSW	Switched Diezel Mod	$19
MOPT-HM-BOGNER	Bogner Mod	$0
MOPT-HM-BOGNERSW	Switched Bogner Mod	$19
MOPT-HM-KMOD	K Mod	$0
MOPT-HM-KMODSW	Switched K Mod	$19
MOPT-HM-DBSW	Switched Diezel and Bogner Mods	$19
MOPT-HM-SMOOTH	Smooth Input Mod	$0
MOPT-HM-SMOOTHSW	Switched Smooth Input Mod	$19
MOPT-HM-CLIPCAP	Clipping Cap	$0
MOPT-HM-CLIPCAPSW	Switched Clipping Cap	$19
MOPT-HM-BASS	Tighter Bass	$0
MOPT-HM-BASSSW	Switched Tighter Bass	$19
MOPT-HM-LGAIN2	Less Gain #2	$0
MOPT-HM-LGAIN2SW	Switched Less Gain #2	$19
MOPT-HM-OPAMP	Quiet Op Amps	$0 - TBD
MOPT-HM-NOISE	Noise Cut	$0
MOPT-HM-SWEEP	Mids Sweep	$0
MOPT-HM-SWEEPSW	Switched Mids Sweep	$19
MOPT-HM-GATE	Noise Gate	$5
MOPT-HM-GATESW	Switched Noise Gate	$25
MOPT-HM-KCLIP	K Mod Clipping Switch	$35
MOPT-HM-3WAY	3-Way Clipping Switch	$35-TBD
MOPT-HM-2WAY	2-Way Clipping Switch	$35-TBD
MOPT-HM-CUSTCL	Custom Clipping	$0-TBD
MOPT-HM-5150	5150 Mod	$15-TBD
MOPT-HM-DZL2	Diezel Mod 2	$0-TBD
MOPT-HM-DZL3	Diezel Mod 3	$0-TBD
MOPT-HM-JCM	JCM800 Mod	$0-TBD
MOPT-HM-MIX	Mixed Mod	$0-TBD
MOPT-HM-COMP	Change Components	$0-TBD
MOPT-HM-VOLTS	Change Voltage	$0