Fucking Ohms... (HALP)

[UglyCasanova]

Okay, the amp n00b strikes again. So the stack I bought today (Trace Elliot 410+115) came with a pre-amp, but no power amp. So now I'm looking for one that can amplify my signal so that I can make the most of what I've purchased (read: be loud as balls).

For now, just forget about Watts, because my question is regarding Ohms, and specifically Ohms in regards to the pre-amp and the power amp.

The pre-amp is rated at 8 Ohms, and so are the cabinets, as far as I could tell (the stack was put into the new reharsal room which I really don't have access to for another eight days). I know for certain that the 410 was 8 Ohms, but the label on the 115 was totally faded, but for the sake of it, let's assume that they have the same resistance. I also believe they're both 300 Watts, but I'll have to check to be sure.

The rub:

I've been looking at a Trace Elliot PPA600 (2x300W - 8 Ohms). That means everything would be at 8 Ohms (pre-amp+power amp+410+115). Does the pre-amp matter at all in the equation? Will the pre-amp do anything to the Ohms of the power amp? Does the power amp's 8 Ohms mean that each output (A+B) will have 8 Ohms in resistance, or do they split into 4 Ohms each? Would I have one 300W output go into each cab at 8 Ohms or 4?

Man. I'm so sleepy and tired. I can't think for shit. Hope any of this makes sense. I'll try to get access to the rehersal room tomorrow so I can figure out the specs for the pre-amp and the cabs. I'm just in dire need of help from someone who's not a complete idiot like myself.

[lordgalvar]

If the output is 8 ohm it is a power amp. Preamps output at line. It has both

[UglyCasanova]

I'm pretty sure it's just a pre-amp. It's a GP12SMX. It even says "Bass Pre-Amp" on the front of it.

From the manual:

As well as being available in its stand alone rack-mounting format, the GP12SMX Sound Management Series preamp is
included in the following products:-
Amp heads:
AH600SMX, RAH600SMX, AH400SMX, RAH400SMX, AH300SMX, RAH300SMX,

If all is well the front panel will illuminate and assuming that you are correctly connected to power amp and speakers the GP12SMX will be ready to use.

From TalkBass:

The GP12SMX is indeed a bass Preamp [...] unless it has the AH, RAH letters on the model it is not an Amplifier Head.

Also, it was far from loud when I plugged into it... I might have goofed when I read 8 Ohms on the pre-amp though. If I did, I'd still like to know if the power amp at 8 ohms is something I could use with my 8 ohm cabs. I'm guessing I'll need a 4 ohm power amp, but I've already brainfarted so much today...

[lordgalvar]

Yea, just looked it is a preamp. Don't know what that 8ohm out is. Ummm...I don't know. That preamp seemed to confuse people at the talkbass forum I just read.

Any 300w at 8 ohm stereo Poweramp would work fine I think with the line or pre out. Run each 150w channel to eat cab (if they are 300w each)

[UglyCasanova]

But at 8 ohms though? Won't running the 8 Ohm cabs in parallel make them 4 Ohms? Gah. I suck at this.

edited my last post btw. I might have imagined the 8 ohms on the preamp.

[lordgalvar]

It is solid state though...not the tube problems though...unless you get a tube power amp

[lordgalvar]

Alright, I'm on a keyboard so I can type now. If each cab is running 300w at 8ohm you could get a setero power amp that runs 150w-200w per channel at 8ohm. Or one that puts out 200w at 4ohm in one channel and run the cabs in parallel. If you run them in series you would have a 16ohm load an need more power like 400ohm

I tend to like to push the speakers less than they are rated (like if 300w @ 8ohms I only go 150 to 200...I'm sure I could push them harder, but I have always done it that way.)

[UglyCasanova]

I'm so incredibly confused. I thought running two 8 ohm cabs in parallel would make them 4 ohm, thus requiring a 4 ohm power amp. I used to consider myself a fairly intelligent person, but this whole stack ordeal is making me question that.

Maybe some sleep will help...

Edit: posted before I saw your post. I don't know if the PPA600 (which is a stereo power amp) is 8 or 4 ohms per channel. But I'm guessing it'll work either way.

[lordgalvar]

Those PPA600s are expensive.

Something like this would work fine: http://www.sweetwater.com/store/detail/ ... Apj98P8HAQ

[UglyCasanova]

I found one for $220

[ChetMagongalo]

In LG's example you would be plugging each cab into two separate 8 ohm outputs, the two cabs wouldn't be wired together in parallel, they would both be independently receiving an 8 ohm load. However if you got a power amp with a single 4 ohm output, you would have to run the cabs in parallel (one cable connecting the cabs, one cable connecting a cab to the amp) to meet 4 ohms.

hopefully I am right about that, ohms are confusing to me too.

[UglyCasanova]

In LG's example you would be plugging each cab into two separate 8 ohm outputs, the two cabs wouldn't be wired together in parallel, they would both be independently receiving an 8 ohm load.

Now that makes sense!

[ChetMagongalo]

hopefully i'm not misleading you I've found in life a lot of things are unintuitive.

[bigchiefbc]

Yes, if you get a stereo power amp with two 8-ohm outputs, you run each of those to a cab and you're fine. If your power amp only has 1 channel, then you have to run in parallel and it needs to be 4 ohms.

[lordgalvar]

Ha, forgot to mention that part. Thanks! haha.(was watching snowpiercer and kinda half way paying attention to both)

Nice find on the PPA600 (I saw people talking about them going for 400)...

You can find good deals on power amps though if you ever want a back up or kinda setup a guitar rig with it.