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Ohms and Amp Buying Guide

There are a lot of terms that can be confusing and overwhelming in the world of bass amplification.  We'll run through some hints and terminology to give you a hand selecting the right rig for you.

Amplifier: Also known as the 'amp' or 'head' - this is what determines your power and tone.  We'll go into some different amp types below and how they can affect your tone.  As for power, that is determined by...

Watts: Simply put: more watts = more volume.  The amount of watts required for your needs may vary between manufacturers, cabinet, your band's stage setup, and whether your amp is Tube or Digital - but for a rough guide: you'll need at least 100 watts if rehearsing with a drummer, if you are doing regular gigs at medium sized venues then you'll need at least 300 watts, and if you are playing outdoor/stadium gigs you will need at least 500 watts to fill the space and compete with other on-stage noise.


 The Ampeg SVT and 810 is the industry standard for festivals and stadium gigs - but probably a little excessive for the Open Studio set...


Cabinet: Also known as the 'cab' or 'box' - this is the enclosure containing the speaker(s) that connect to your amplifier.  They come in a variety of speaker sizes - the most common are 10 inch (usually 2, 4, 6 or 8 in a cabinet), 12 inch (usually 1 or 2 per cab) and 15 inch (usually 1 per cab).  Larger speakers generally tend to be louder, have more low end and a 'slower' response than smaller speakers.  The slower the response time, the more the note 'blooms' out of the speaker(s), however depending on your situation, you may prefer the immediacy of a quicker response time. 

What speaker size and configuration largely comes down to personal preference, trial and error, and brands/models.  For instance, Markbass 2x10" cabinets can give you great results if you are after a lightweight rig for medium sized gigs, however 210s in general can lack a bit of low end.  For larger gigs 2x12" or 4x10" cabinets generally allow you to slam pretty hard - and for stadium or larger/outdoor gigs then you are probably going to be using 610 or 810s.

Moving forward, generally the most important things to determine when purchasing a cabinet are the weight and Ohms of the cabinet (we'll get to ohms in a moment). 

The weight of a cabinet will vary due to the size and amount of speakers, as well as the materials used in the enclosure.  For instance - a Peavey Headliner 410 cabinet is going to weigh almost double that of an Aguilar SL410, even though they have the same speaker configuration, as the Aguilar uses Neodymium magnets in their speakers and lighter materials in the construction of the cabinets, whereas the Peavey uses ceramic magnets in their speakers which are heavier.

Cabinets also give a wattage rating as a guide for how much power they can take before blowing, but this can be misleading as there are more factors than just wattage that determine whether you will blow up your cabinet.

Combo: Quite simply an amp and cabinet in the one.  These are ideal for beginners, rehearsal amps or small gigs.  The advantage is that your entire rig is all bundled up in a convenient package, the downside is that many combos simply aren't up to producing the same amount of volume as larger rigs.  Additionally, you have more options for upgrading and switching if you go for the rig option.


The Fender Rumble 500 combo is a great value for money combo that is light, powerful and versatile.



The ohm rating refers to how much power the cabinet is resisting from the amplifier.  This can be a confusing concept to get your head around, the main thing to remember is that the HIGHER the number of ohms in the cabinet, the LOWER the amount of power you will be getting out of your amp - and if the total ohms go too low, you risk frying your amp

Every amp will give you a MINIMUM ohmage rating - this is usually 4 ohms on most amps (but not always).  Most bass cabinets are rated at either 4 or 8 ohm.

So say your amp is 500 watts with a 4 ohm minimum, this means you can plug either one 4 ohm cabinet, or two 8 ohm cabinets to get the full 500 watts of the amp (250 watts will go into each cabinet).  You can also safely plug one 8 ohm cabinet into the amp, but you will only be getting a maximum of 250-300 watts out of the amp (a bit over half the amp's total wattage). 

If you run the amp at a lower ohmage than it was designed to run at (ie by plugging in too many cabinets) then you risk frying the amp, as more power will be running through the amp than it was designed to handle.

This is important to keep in mind when purchasing a cabinet; if you want the option to add more cabinets later on for larger gigs, best go with an 8 ohm cab.  If you want to keep the gear footprint to a minimum and know that you'll have enough power - the 4 ohm could be a good option. 

Amplifier types:

Amplifiers have two main components: the PREAMP and the POWER AMP (also known as the Power Stage).  There are several different kinds of each that influence the power and tone of your amps...

Preamps basically shape your tone and bring your signal up to an optimal level for gain staging.  Commonly it is responsible for the EQ and GAIN components - but sometimes have additional controls or effects.

Power amps are responsible for (as the name suggests) the amount of power that the amp puts out.  As discussed in the watts section above, more power = more volume!

(Some manufacturers give the option of powered speaker cabinets, so you can use a separate preamp and get the power directly from the speaker.)

Most amps these days are totally digital (or 'Solid State'), however many older amps (and select new ones) use Vacuum Tubes (or 'Valves').  Many people generally find the tone of tube amps superior, and their output is perceived as louder than compared to a digital amp of the same wattage.  Why aren't all amps tube then? Well they are more expensive, very heavy, more fragile, and need servicing every 18-24 months to replace the tubes - which is an expensive exercise in itself.

Unless you are a megastar with a big budget and a road crew, most people will take the hit on the tone for the ease of transport and budgetary savings of a digital amp.  Besides, amp technology has improved markedly in recent years which means that you can get great tone with insane volume sans tubes. 

The Darkglass Microtubes 900 head is a great sounding D-Class amplifier that is lightweight, loud, and loaded with features.  An ideal amp for any situation.


There are also amps known as HYBRID amps which contain tubes for the preamp section, but have a solid state/digital power stage.  This gives you the advantage of some of the tone that tubes offer (including an authentic tube distortion when the gain is pushed hard, ill-advised on a digital preamp!), whilst having the advantages of the lightness of a digital amp.  Preamp tubes generally last a lot longer than power tubes so do not need replacing as often.  

It is important to keep in mind that there are different brands with different models that all offer different things.  Don't assume just because it is tube that it is 'better' than a D-class, or that because it is a MOSFET power stage it is going to necessarily going to be quieter than a tube amp.  Every amp we sell has its place, and if you aren't sure about what to get then we can help you work out a good choice for your needs.

Hopefully this guide helps you understand the different things to keep in mind when buying an amp.  If you think we missed something then feel free to get in touch and we'll help you out.