QSC RMX2450a Two Channel Power Amplifier: question

[gwangi]

So I have a question, it's been about 25 years roughly since I've used a rack mount bass pre & power amp and Micah over at ARKHAM Audio is going to be producing some Arkham Zephyr prea amps at the beginning of the new year and I wanted to get a good separate rack mountable power amp and I was curious what the experts here on TalkBass thoughts were regarding the OSC RMX2450a for a perfect match for the Arkham Preamp:

RMX 2450a

The RMX2450a amplifier from QSC features a compact chassis, XLR and 1/4” balanced inputs, Speakon® and binding post outposts for convenient connectivity

www.qscaudio.com

I'll be using 2 Bag End S15-N cabinets

 

[ihixulu]

The RMX line sounds great but is heavy by today’s standards. If you don’t mind the weight, they are great reliable amps.

At the end of the day, there are many ‘perfect’ matches. It comes down to how much power you want to push and whether the amp has the necessary electrical sensitivity to work well with your pre. (the RMX will work with the Zephyr fine).

FWIW, I use my Zephyr with a Crown XLS2 1002, bridged for 1000w into 4 ohms and it’s very light. It also has a good adjustable HPF built in, very handy.

 

[agedhorse]

The 2450 is way too much power for your cabinets bridged. Run in dual mono mode, if your cabinets are 8 ohms, that’s 500 watts to each cabinet which is fine if you are careful and have reasonable expectations. If your cabinets are 4 ohms though, that would be too much power.

That’s a very heavy amp though. Have you considered a light weight bass amp with a power amp input feature on it? Either an effects return jack or an aux input?

 

[gwangi]

The 2450 is way too much power for your cabinets bridged. Run in dual mono mode, if your cabinets are 8 ohms, that’s 500 watts to each cabinet which is fine if you are careful and have reasonable expectations. If your cabinets are 4 ohms though, that would be too much power.

That’s a very heavy amp though. Have you considered a light weight bass amp with a power amp input feature on it? Either an effects return jack or an aux input?

Each cabinet is 8 ohms, I wouldn't run it in bridged mode, thank you so much for your input, you are highly respected here on TalkBass.

 

[walterw]

ugh, that thing would be an absolute brick to move around, it's almost 50lbs!

if you do go with an old-school rack power amp, i'd suggest looking around for something lightweight. there should be a ton of them out there for sale used and cheap now that all the soundguys have moved on to powered cabinets

i myself use a sansamp into a QSC PLX 3002, it's way lighter than even the smaller RMX boat anchors. one side of it gives me 900w into my two 8Ω single 15 cabs, way more than enough. even that is heavier than the modern class D stuff but it's not so bad

 

[agedhorse]

ugh, that thing would be an absolute brick to move around, it's almost 50lbs!

if you do go with an old-school rack power amp, i'd suggest looking around for something lightweight. there should be a ton of them out there for sale used and cheap now that all the soundguys have moved on to powered cabinets

i myself use a sansamp into a QSC PLX 3002, it's way lighter than even the smaller RMX boat anchors. one side of it gives me 900w into my two 8Ω single 15 cabs, way more than enough. even that is heavier than the modern class D stuff but it's not so bad

The original PLX series is pretty bulletproof IME. I still have a dozen or so of this series of amps in my pro audio inventory, though most are now available for sale as that part of the business is being wound down.

 

[Mike Caldwell]

Each cabinet is 8 ohms, I wouldn't run it in bridged mode, thank you so much for your input, you are highly respected here on TalkBass.

The RMX and PLX amps have a parallel input mode, basically a built in Y cable, plug into ch.1 input and it will feed both channels.
Also apply the clip limiter and the high pass filter option, the high pass has two settings, 30hz and 50hz, try the 50.

The mentioned Crown XLS 02 series amps work fine and have the built in Y function, two input levels settings and multiple choices for high pass filtering. Those are also much lighter weight.........says the guy who still uses Crown MA3600 power amps, the bulk of the rest of my amps are all the latest QSC PLX series or the PL2 series.

 

[CryingBass]

The original PLX series is pretty bulletproof IME. I still have a dozen or so of this series of amps in my pro audio inventory, though most are now available for sale as that part of the business is being wound down.

That's a tell. Being an old guy, I was very glad to see that industry in the hay-days.

What's next: Neural implants via RF-99? Per-audience-member mixes?

Pass

 

[walterw]

Per-audience-member mixes?

there are already "silent disco" setups where they pass out wireless headphones to everybody, maybe have a subwoofer just for the tactile thump, and there they are, to an outside observer you have a dance floor full of people moving around to mostly silence

 

[Zooberwerx]

RMX series? I have a handful of the 1450's & 2450's but an earlier platform. I wish I didn't. They're great for a permanent install like a club or rehearsal space. Come to think of it, I have extras we salvaged from a now-defunct cinema.

Riis

 

[GreyBeard]

I use a mesa preamp/di into the fx_return of whatever amp I'm playing through. Like age horse wrote. The RMX2450 is a real lead sled that makes my back hurt just to think about it. If you are set on using a head/cab setup, look at the Quilter bass block as your head. 800 watts at 4 ohms and light as a feather. It has a preamp you can bypass through the return

 

[Mike Caldwell]

For anyone following along around the time the first PLX series came out the QSC RMX series was reintroduced as budget series amp based on what was their top of line EX and MX series.

The original Powerlight came out and introduced the world to light'ish weight high power amplifiers.
I rode the Carver PM and PT amplifier train for a while. The PT's were really light weight for a 650 watt per channel amp at that time.

Actually I still have a Carver PM600 sitting on the floor right now running my computer speakers.

 

[walterw]

RMX series? I have a handful of the 1450's & 2450's but an earlier platform. I wish I didn't.

they'll keep your house from blowing away in a tornado so there's that

 

[CryingBass]

there are already "silent disco" setups where they pass out wireless headphones to everybody, maybe have a subwoofer just for the tactile thump, and there they are, to an outside observer you have a dance floor full of people moving around to mostly silence

 

[dannylectro]

Ya know, I recently bought a new QSC power amp for some passive PA speakers I occasionally use and just for laughs, I plugged my Mesa Subway Pre/DI into it and fed my Subway stack of 115 & 210… and it sounded incredibly good. But not enough good to replace my 8lb TT800…

 

[byacey]

That's a tell. Being an old guy, I was very glad to see that industry in the hay-days.

What's next: Neural implants via RF-99? Per-audience-member mixes?

Pass

Suddenly I feel very old. The PLX and RMX were cutting edge back when racks were typically loaded up with 1500 and 1500A's.

 

[agedhorse]

Suddenly I feel very old. The PLX and RMX were cutting edge back when racks were typically loaded up with 1500 and 1500A's.

I remember when the PLX was released... I reduced all of my amp rack weights by ~70%