Lightest Poweramp?

[::::BASSIST::::]

What's wrong with the Focus SA? It seems like the dream amp. If you want a rack rig, just strap the SA down to the bottom of the rack box.

I love my Focus SA and have no plans (at this time) to sell it. As I said in the initial post I was just curious to see what else is availabe that is rackmountable and light yet still powerful.

Also, the Focus and 1u pre I am getting wont both fit in my 2 space rack bag. I think I can make them fit in an unorthodox way, but it would take some ingenuity.

 

[Passinwind]

I continue to be amused how many people seem to think the PLX4 thangs are somehow better than the PLX2 and the poor ol' guy is on the ropes bleeding ; } - from what I've looked at they are the same in almost all respects save for config of channels and ohms loads and I think I recall Bob saying this as well.

I could hang on to the comparator for a few more days and test the old series vs the PLX2, but I trust Bob's word anyway. I assume you're actually meaning the original PLX series, eg 1602, 2402, 3402, et al? I've owned three of those, plus the Focus Series II, a couple of Crown K2s, lots of old school Crowns, and the latest-greatest 7 pound Class D switcher which I posted the picture of earlier in this thread. They all have worked fine for me as long as I was realistic in my expectations.

To be perfectly clear, I feel that any of these topologies are essentially interchangeable sonically if they're implemented properly. Bob's message (correct me if I'm wrong Bob) seems to be to buy on features such as warranty, physical form factor, matchup to specific speaker loads, etc. The 1804 and the SpeakerPower SP1-1000 happen to be what I think makes sense for my current playing situation, but I wouldn't begin to presume to tell anyone what might work best for them beyond comparing the various feature sets.

Actually the PLX2 are pretty shallow to my way of thinking. Fits in standard sized rack with lots of room in back. I'd never buy a shallow rack, no room to put cables and straps and my bass stand and...

Only the two -04 variants of the PLX2 are shallower and (8 pounds) lighter than the old series. They tend to balance a bit awkwardly IMO in a lightly loaded deeper rack -- if that matters to you. I wanted something that stacks neatly with my DIY "head", and does good power into stereo 8 ohm loads, but if I wanted bridged operation or the other extra features of the -02 variants, I'd be perfectly happy with either the now discontinued older series, or the newer PLX2s. They both sound fine for my purposes. The watts/dollar ratio of the 1804 as I use it was pretty attractive to me as well, but again, you need an application that necessitates dual mono or stereo operation to take full advantage of that.

 

[Ostinato]

Good info...the 02s have the filters too...that would work really nicely with Acme cabs...

 

[bongomania]

So, just to stir the pot a little:
(A) Lots of threads here have included lots of anecdotal claims that the AI or QSC lightweight amps lacked "oomph" compared to the CA-9.
(B) I gather from recent discussion that the only scientific explanation for this is poor gain matching between pre and power amps.

Do I understand that correctly, or are there other common factors that would explain the "mass hallucination" of difference in the sound or feel between amps? I'm genuinely curious to learn more. If gain matching is it, then what are some examples of typical specs we should look for, i.e. what is a "good" match of preamp output voltage to power amp input sensitivity? Is there a good ratio or other rule of thumb?

Edit: to keep this on topic, maybe it could be framed as "what are the ideal preamp output voltages (or other user-identifiable qualities) to get maximum punch from an AI or similar ultralight amp?"

 

[Ostinato]

So, just to stir the pot a little:
(A) Lots of threads here have included lots of anecdotal claims that the AI or QSC lightweight amps lacked "oomph" compared to the CA-9.
(B) I gather from recent discussion that the only scientific explanation for this is poor gain matching between pre and power amps.

Do I understand that correctly, or are there other common factors that would explain the "mass hallucination" of difference in the sound or feel between amps? I'm genuinely curious to learn more. If gain matching is it, then what are some examples of typical specs we should look for, i.e. what is a "good" match of preamp output voltage to power amp input sensitivity? Is there a good ratio or other rule of thumb?

Edit: to keep this on topic, maybe it could be framed as "what are the ideal preamp output voltages (or other user-identifiable qualities) to get maximum punch from an AI or similar ultralight amp?"

*Puts down beer*...I'd like to know this as well. Anyone? *grabs popcorn*

 

[Passinwind]

*Puts down beer*...I'd like to know this as well. Anyone? *grabs popcorn*

Well, the modest tests I outlined earlier in this thread are just the beginning as far as I'm concerned. I've been building my own preamps for years, and I definitely have some theories on impedance and gain staging issues, but I'm not gonna spill just yet!

 

[Chef]

OK, I'm interested...is this stuff gonna go in this thread, another thread, or stay top secret?....

Well, the modest tests I outlined earlier in this thread are just the beginning as far as I'm concerned. I've been building my own preamps for years, and I definitely have some theories on impedance and gain staging issues, but I'm not gonna spill just yet!

 

[jock]

Something like this? I just bought one of these second hand, not had a chance to try it out yet though.
pic for size comparison:

Please let us know how this amp works out for you. I´m really interested as I want to make my DIY cab a powered one.

 

[Bob Lee (QSC)]

(B) I gather from recent discussion that the only scientific explanation for this is poor gain matching between pre and power amps.

It's not about "poor gain matching" between preamp and power amps. It's just gain differences between one amp and another, but the gain controls on the front allow easy adjustment; that's what they're there for. For more oomph, turn up the gain, and/or put a hotter signal into the amp. The power amp is a gain stage, not an EQ or tone stage. Think of it that way, and you'll have an easier time dialing in the sound you want regardless of what brand or model of power amp you use.

 

[Passinwind]

OK, I'm interested...is this stuff gonna go in this thread, another thread, or stay top secret?....

Alan,

I'd love to make it all sort of an open source thing. Even if I eventually produce something to sell I'd rather do things that way. I'll start a new thread as soon as I have anything worthwhile to say--I promise! For now I'll just mention that in some cases using a good quality mixing board to drive your power amp seems to make more difference than maybe it ought to. Or from another perspective: perhaps not all bass preamps are equal in their abilities to drive commercial power amps? Take all this as a WAG (wild-assed guess) for the moment though.

 

[greenboy]

A lot of bass guitar preamps are not so hot at it, for sure. In defense of their designers, a lot of them weren't originally designed to work with true SR amplifiers, and for that matter, the diverse array of input levels that basses nowdays are capable of.

 

[MakiSupaStar]

Great thread boys. Running an old Carver 2.0i (I don't think they even make it anymore) pushing 1000W mono @ 4 OHMs. I really like it, but it's frickin' heavy. Subscribed...

 

[::::BASSIST::::]

An easy cheap way to boost the signal of any pre is to use an ART Tube MP mic pre in the chain. Pure clean boost of 70db. That should do it.

 

[ashbory]

An easy cheap way to boost the signal of any pre is to use an ART Tube MP mic pre in the chain. Pure clean boost of 70db. That should do it.

I don't know about that. I have one of those and it sounds good, but I wouldn't call it "pure and clean".

 

[Der Bluten Kat]

QSC PLX1804 11 lbs

 

[Der Bluten Kat]

oh and 900w/channel (2)

 

[Bob Lee (QSC)]

An easy cheap way to boost the signal of any pre is to use an ART Tube MP mic pre in the chain. Pure clean boost of 70db. That should do it.

I think 70 dB of boost would be way more than enough!

I think in most cases about 12 dB (the typical difference between consumer audio and pro audio "line" levels) should do; in extreme cases maybe up to about 20 dB. A Rolls ProMatch or similar device would be an inexpensive answer to having a preamp that you like but has a weak output capability.

 

[Turn Em Loose]

Seymour Duncan (sp?) makes a pedal called "The Pickup Booster". It's around 26 db of pure, uncolored gain. Works real well and is inexpensive. That should do the trick.

 

[knobbin]

What's the lightest "heavy" (ie not digital) poweramp out there?

I have a Focus SA and its great (cant rack mount it though), but I just want to see what's available for traditional poweramps that are less than 20LBS.

1000w preferable

I know of the stewart world 1.2 which is 11LBS, but the overheating/shutdown issue of this amp (seems to be common) makes me want to avoid it.

Others?

CROWN XTi series... 17 lbs(i think), super light, i have the 1000 which is plenty powerful at 1400 watts @4ohms, plenty of features, never heard of any crown products crapping out

 

[bongomania]

It's not about "poor gain matching" between preamp and power amps. It's just gain differences between one amp and another, but the gain controls on the front allow easy adjustment; that's what they're there for. For more oomph, turn up the gain, and/or put a hotter signal into the amp.

Hmmm... I don't understand the distinction you're making. If it's not a question of having the right output gain to best drive a given input sensitivity (AKA gain matching), but it is a question of increasing the output gain of the preamp (using an external device if necessary) in order to best drive the power amp... You get where I'm lost?

In the last thread where we discussed this, I said some "hot" things to you because I felt you weren't giving forth with a very simple piece of information. I apologise for speaking that way- and I hope you can spell this out in simple terms, if it really is that simple... since a significant number of people seem to not know the answer.

Are you saying the only difference between e.g. an AI or QSC and a CA-9 is how much gain they each have available? So given the same input level, the CA-9 just has the capability to amplify it more?