Matrix GT800fx v GT1000fx - review + vids

[billmeedog]

Power-Amp NOOB questions!!!

Its not a headroom thing making the difference as I only pushed the 800 to a max of 60w - thats what my cab takes. That means the 800 had around 200w of clean headroom while the 1000 has 280w.

Hi Paul,

GAS-ing for a GT1000FX! Thanks for this demo...

Could you pleas explain your assertion that your "cab only takes 60W?" I'm not sure I get that (assuming your referring to your Zilla 2x12 - perhaps you were not?)

Also, could you explain briefly how it works that the power-amp's total-output can be greater than the total-wattage rating of a user's speaker-cabs? I'm still a little confused about that, and sorry for coming across as a noob with that question (...I have a feeling I'm about to get schooled about how power-amp volume knobs aren't really volume knobs but input-attenuators, or something like that - LOL!) I'm planning to load-up a couple of old ADA 2x12-cabs with some sweet EV12M's, (then each ADA 2x12 will handle 400-watts...I think?) but right now they each have two (2) 50-watt Celestions in them (thus 100W @8-ohms total for each ADA 2x12) Could I gain-stage such an under-rated cab setup in such a way so as to NOT blow the speakers? Again, sorry for the "noobishness."

Thank you for any such info you can offer!

Bill

 

[Trazan]

Could I gain-stage such an under-rated cab setup in such a way so as to NOT blow the speakers? Again, sorry for the "noobishness."

Yep.

You need to know at what input level the amp will deliver its rated max output. E.g. the Matrix will deliver this at 0 dBu.

The AxeFx II will output 20 dBu when the output light clips.

If you then decrease level internally in the Axe by -20 dB from where a patch clips, the Matrix will deliver its max when both the Axe's and Matrix's analog outputs are maxed. From there, each -3 dB down in the Axe will result in half the wattage from the Matrix.

If you want to calculate the exact amount of dB's down to achieve a desired output:

10*log(desired wattage/current wattage) E.g. 10*log(100/280) = - 4.5 dB


Soooo....if an amp will deliver 280 watt when receiving 0 dBu, and you want it to put out max 100 watt....you need to lower the Axe a total of - 24.5 dB from where it clips. (A good way to go about this is to max the Global Gain for your desired output when adjusting your loudest patch to reach clip point, then lower that Global Gain by the amount needed.)

And make sure boost/pad for the output is set to 0dB!

Hopefully I'm making some sense...

 

[billmeedog]

Yep.

You need to know at what input level the amp will deliver its rated max output. E.g. the Matrix will deliver this at 0 dBu.

The AxeFx II will output 20 dBu when the output light clips.

If you then decrease level internally in the Axe by -20 dB from where a patch clips, the Matrix will deliver its max when both the Axe's and Matrix's analog outputs are maxed. From there, each -3 dB down in the Axe will result in half the wattage from the Matrix.

If you want to calculate the exact amount of dB's down to achieve a desired output:

10*log(desired wattage/current wattage) E.g. 10*log(100/280) = - 4.5 dB


Soooo....if an amp will deliver 280 watt when receiving 0 dBu, and you want it to put out max 100 watt....you need to lower the Axe a total of - 24.5 dB from where it clips. (A good way to go about this is to max the Global Gain for your desired output when adjusting your loudest patch to reach clip point, then lower that Global Gain by the amount needed.)

And make sure boost/pad for the output is set to 0dB!

Hopefully I'm making some sense...

Hi Trazan,

I REALLY appreciate that informative explanation. Thank you so much! I'll have to give this some thought, and of course if I end up with a new amp (such as a Matrix GT1000FX) I will do the necessary preset & global gain-staging.

Thanks again...and yes you "made sense!"

Bill

 

[paulmapp8306]

Tarzan pretty much nailed it. Basically - the OP of the amp is dependant on the input signal level - not necessarily where the amps output knob is set.

i set things up in a slightly different way, but to the same ends. I pushed the AFX and Matrix output knobs up full, with no cab connected (which is perfectly same on a SS amp). I then raise/lower the global output gain until the MATRIX Signal light starts to flicker. That happens when the Matrix output is at -9db. In my case (an 8 Ohm Cab) that is around 40-45 Watts (every 3db down halves the power). Taht gives me a rough output - and the global gain slider can then be raised/lowered by the required dbs to match the cabs power handling (in my case, I raise it a couple of dbs as my cab is 60w but if you had a 120w cab you could raise 4db - if you have a 240w cab you can raise 6-7db etc).

and to answer your first question, yes its my Zilla cab. Its 2x12 loaded with a V30 (60w) and a G12H aniv (30w) speakers. Placed in parallel, the power is shared between the speakers which means the cabs max power handling is TWICE the lowest rated speaker - in my case the G12h - and gives a 60w power handling. Im thinking of changing the G12H to a CL80 which is rated at 80w. That would then make the V30 the lowest rated speaker - and change my cabs max power handling to 120w.

Again - hope all that made sense.

 

[Humidfume]

Thank you so much for these videos! I actually prefer the 800's mid, when it comes to working in a mix live etc I'm not sure that the extra low and highs of the 1000 (with the negative, albeit tiny reduction in the mid thickness) would be as beneficial as the mid thickness you gain from the 800. Just personal taste though, I'm a very mid style player (Lamb of God etc).

I highly doubt that it would make much of a difference, but since we're comparing the subtleties I thought I'd chime in on why I'd choose the 800.

Cheers!

*EDIT**

Actually.. after comparing a few videos I think the 1000 is growing on me.

*EDIT*

Nah, definitely the 800. Breaks up sooner, sounds thicker.

I'm done with this or I'll go crazy!