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Power amp' help(for Tech21 GED 2112)

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I'm thinking of totally changing my rig & would like a little advice from you guys who know far more about these than my crusty old brain ever will.

I'm wanting a Tech-21 Sansamp GED2112,so will need a power amp suitable the pump this into my Fender Bassman Neo 410 (500w).

The choice seems endless & I have no idea where to start  so I seek advice of greater brains.

I will be doing the internal jumper mod on the GED so give a combined mono output btw.

Thanks in advance.

Edited by artisan

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The GED2112 is a rackmount pre isn't it? I'd look at something like a crown XLS1502. With one cab run it bridged for headroom, but there's the option should you get a second cab to power them separately, which gives control over levels separately. Keep them together in a small rack case. Keep them patched togather and a powerlead like http://www.cablewarehouse.co.uk/display_category.php?search=PW-387%2F2&x=33&y=32 

Paul.

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Right, here we go.  I suppose this will show the pros and cons of this type of set up.

I bought a GED2112 on release last and have run it (amongst other pre-amps) into a Matrix GT1000FX power amp and then onto a choice of enclosures - a Barefaced Big One or (more currently) a pair of Aguilar SL112s.  (The Aguilars just give me the option to run the whole rig in either stereo/ dual-channel mode, mono/parallel or mono/bridged; daisy chaining the cabinets to effectively give me a 4ohm mono 2x12 set up.)

Initially, I did the external jump lead patch thing on the GED (see elsewhere) so the unit would output in mono and also allowing me to just keep it simple by bridging the poweramp for more output power.  The external patch which worked fine aside from the smallish issue that a couple of the knobs on the facia didn't do what they were supposed to, but irrespective, it sounded fine and it was easily reversible should the need require.  About a week ago, I did the internal hack and switched the jumpers, which has been fine; the deep and drive channels combine to output in mono.  I also did the bypass-jumper as well...this allows true bypass of the GED allowing you to use other other pre-stages in line.

By some curious twist of fate, I turned my power amp on this morning and it's playing up.  Damn!  It's been blummin' bomb-proof for five years.  Oh, pink torpedo! :(

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Ultimately, on the poweramp side, just do your diligence and read up as much as you can.  Everyone will have differing opinions.

Personally, I liked the Matrix because, claimed output wattage aside, it was lightweight (9lbs), it fitted into a short Gator rack and looked aesthetically pleasing.  It's been a fantastic piece of kit (until now!), run for thousands of hours, so probably something has just worn out.

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16 minutes ago, NancyJohnson said:

Ultimately, on the poweramp side, just do your diligence and read up as much as you can.  Everyone will have differing opinions.

Personally, I liked the Matrix because, claimed output wattage aside, it was lightweight (9lbs), it fitted into a short Gator rack and looked aesthetically pleasing.  It's been a fantastic piece of kit (until now!), run for thousands of hours, so probably something has just worn out.

Thank you for advice/help & information,I'll have a look at matrix amps as I'd not heard of them before.

Much as I like my current rig(CTM100 & Bassman410) I have arthritis in my knees,severe in my right knee,so a lighter weight rig would be great but I won't compromise on tone.

I always loved Geddy's tone so think this will be a brilliant rig for me,I may look to change my cab for a couple of 112's as well to make carrying so much easier.

 

Edited by artisan

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I don't think you need to worry too much about brand when it comes to a power amp, the whole point of them is to have no tone of their own and just to make things loud and nowadays they all pretty much do that. I'd be looking for things like brand reliability.

You are looking at weight already so you are looking for switched mode power supplies and mostly class D amps. The weight alone will tell you that and you won't hear a difference in practice so that's not an issue.

It makes sense to match your amp to your speakers. If you are going for a couple of 12's, presumably 8ohms ea. then looking for something that gives roughly 300W RMS into 8 ohms makes sense. It'll get everything you can out of your speaker without risk of blowing it. Most of these amps will also give you 500W+ into 4 ohms so you'll have flexibility in how you set up your system if you swap speakers around.

Look for something that will operate in 'bridge' mode. this is a way of operating both amps together in mono so it gives you more power. Look at the minimum impedance (the ohms) the amp will operate at though most bridge mode operations give full power into twice the impedance of the lowest the individual channels work at. So if you take the example above of something that gives 500W per channel into 4 ohms in bridge mode it gives 1000W into 8 ohms and wont work well into 4 ohms in bridge mode. If it operates into 2 ohms then it will be happy into see 4ohms in bridge.

That Crown amp looks good for the money.

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25 minutes ago, Low End Bee said:

I've always just shoved my Tech 21 pre amps into the effects send of a standard head. Is this a bad thing?

Did you mean the effects return? The power section in any good bass amp should work fine.

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47 minutes ago, Tech21NYC said:

Did you mean the effects return? The power section in any good bass amp should work fine.

I wondered this too.

Edited by NancyJohnson

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You are both correct. I meant the return of course. I was having a Chuckle Brothers 'to me -to you' moment.

And it's worked a treat on those share an amp gigs.

 

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Another vote for Crown amps, you can pick up a XLS1500 for £300 on eBay, less if you're luck.

 

Bomb proof, light and powerful. Used to run mine with a BF Big Twin, sounded great.

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Its a misconception that all power amps are the same and uncoloured.

They are mostly different - the higher end power amps are much more full sounding, with more pronounced bass and bottom end.

It debateable what difference it makes for bass guitar, but there is a big difference. There is also a big difference between traditional amps and class D, (the dreaded heft word). BUT class D is more than acceptable - you wouldnt know the difference if you werent A/B ing them.

I currently have a QSC RMX1450 which works really well with bass. (i use a tech 21 VTRM) Flipping heavy though.

I had a Crown 1502 - very light and clear - but if youre going to get one id just consider a couple of things:

1) how many cabs/speakers are you driving? (i used one to power a barefaced sc 1x12 and it was really struggling.

2) if you are bridging you WILL need a different speakon cable to put the amp in bridge mode. It needs setting to bridge, then using a differently wired speakon.

 

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14 hours ago, la bam said:

I had a Crown 1502 - very light and clear - but if youre going to get one id just consider a couple of things:

1) how many cabs/speakers are you driving? (i used one to power a barefaced sc 1x12 and it was really struggling.

2) if you are bridging you WILL need a different speakon cable to put the amp in bridge mode. It needs setting to bridge, then using a differently wired speakon.

 

Presumably you were running the SC on one channel at 300W?  Bridged into 8 ohms those things are allegedly rated at 1050W, which I think (could be wrong) is RMS rather than peak, so should be more than enough for a SC?

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I tried both, that's how I learned about the bridging issue with the xls1502. You need a different cable making up, regardless of whether the amp is put into bridge mode or not. 

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I never got to that. It was going to be £30-£40 for a cable, then the same again for a spare.

When i then rang the local shop for advice to make me one up, they recommended not running any amp bridged.

So i took the amp back for a refund.

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Sounds a bit odd.  As I understand it you just need a 4 pole speakon plug, wired appropriately, instead of a 2 pole one. Should cost about a quid extra.  The amp is designed to be run in bridged mode.

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I couldnt find one to buy locally. Bridging an amp divides opinion. Some say theres no problem at all, some say it halves the life of your amp.

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20 minutes ago, la bam said:

I couldnt find one to buy locally. Bridging an amp divides opinion. Some say theres no problem at all, some say it halves the life of your amp.

It really doesn't, running an underpowered amp into a high ohmage load will kill then output caps faster, and bass amps have to work hard, so they do have a tendency to fail earlier, but there's no issue running an amp bridged.

I made up a Speakon for my Crown XLS to my BF, it was a 4 pole, but it's not the same at either end, one end goes to the amp one to the cab, you have to have it the right way round. Alex at Barefaced pointed me in the right direction.

Edited by WinterMute
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17 minutes ago, la bam said:

I couldnt find one to buy locally. Bridging an amp divides opinion. Some say theres no problem at all, some say it halves the life of your amp.

You've not been getting good advice from your shop. There seems to be something about shop assistants that stops them from being able to say "sorry I don't know"

The only problem with bridge mode is that it doubles the minimum impedance you can use, That's just down to a simple current handling issue. Even then it's hard to think of an amp that won't have adequate protection circuitry built in to prevent long term damage. There's no halving of the life of the amp so long as you don't go below the manufacturers minimum impedance and even then you'd probably only suffer from reduced power availability or a temporary shut down.

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It does divide opinion - although it would seem daft to build in a bridged mode if you couldnt use it.

The QSC RMX1450 is designed to work at 2ohm.

So, if i bridged my 6ohm 900w, 6x10 cab - would that be fine? Specs are:

RMX1450

280 8ohm.

450 4ohm.

700 2ohm.

1400 4ohm bridged.

Would that mean for my 6ohm cab id be getting around 900-1000w when bridged?

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Sorry, didn't mean it didn't divide opinion, it clearly does, I meant there's no detrimental effect to running a stereo amp bridged into a correct load.

You'd have no problem running into your 6x10, it just won't put out the same level as a 4 Ohm loading cab.

 

 

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What you could do, is buy a relatively cheap, Class D amp head with an effects loop, and plug the Ged2112 into the return, bypassing the map's pre-amp.

Or sell your rig & buy something like a Fender Rumble 500 combo (17kg total weight), and plug the SansAmp into the effects loop return on that.

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