Power Amp Help...

[matthew90046]

I have yet to find a power amplifier that fits my criteria.  I am a MONO guy, keeping it simple is how I like play it.  Distillate to my F-1X to... (what I have is not what I want).  I want a single space power amp of top notch quality sound that can power my 4 ohm 2x15 cab to at least 600W.  As far as I can see the Stewart 1.2 bridged is the only candidate.  Is this all the industry has to offer?  (I have seen the Acoustic Image amp, but I want rack mount.)
 
When I do a search for mono power amps I am flooded with results for car audio power amps.  So here is the question... Why is it car audio folks can make power amps about the size of 1/2 rack space approaching 3000W and I cant find a 600W amp that weighs less than 30lbs.?  Is there some major difference between 110 AC and 12 volt DC?  
 
Cheers

[briant]

The Stewart World 1.2 is a good amp but you'll want to have an extra space between it and your F-1X for air flow - and maybe a small fan to point at it.  They have overheating problems due to the lack of built in fan.
 
Another single space option is the Peavey DPC-1400 - if you can find a used one.  Like all good Peavey products they discontinued it.  It does 1400W bridged at 4 Ohms.  And it is fan cooled and doesn't have overheating problems.
 
If you're willing to go to a 2 space power amp you'll have a lot more options - even if you're looking for light weight.  All the Stewart World amps are under 20 pounds.  I have a 1.6 and it just kicks all kinds of ass.

[keith_h]

Quote
Why is it car audio folks can make power amps about the size of 1/2 rack space approaching 3000W and I cant find a 600W amp that weighs less than 30lbs.? Is there some major difference between 110 AC and 12 volt DC?  
 
Yes there is a major difference between AC and DC. Power amps use DC. This means an AC unit must have a power supply to convert the AC to DC. The components to do this add considerable weight.  
 
If you would consider 2 rack space amplifiers you will find plenty that are below 30 lbs. All of my QSC PLX/PLX2 series amps come in around 21 lbs. QSC has many other amps that are fairly light weight. I have never used them but Crown has the XTI series that come in around 18.5 lbs. In both of these the biggest reason for them being two rack spaces is cooling. Two rack spaces allows for good airflow and ducting for the fans.  
 
One last thing is I would not get hung up on specs. While that 3000W auto amp sounds large it is most likely unusable wattage generated in a laboratory. I will say that QSC and Crown are generally conservative in their output specs and reflect more realistic values.  
 
Keith

[matthew90046]

Thanks for the input.  It's good food for thought.  
 
Currently I have a Sound Tech PS802 amp.  It is much like the Stewart 1.2, but the problem is that it can't go down to 4 ohms in bridged mono like the Stewart.  I am stuck using just one side of the amp rated at 400W this with this configuration.  If the stewart needs breathing room then I may as well open up to the idea of a 2 space power amp.  I just like how small and light my setup is now, just like a briefcase.  
 
This is how it looks now.
 

[David Houck]

If you like the amp, then another alternative would be to go with two 4 ohm cabs, one on each side.  400 watts per side into 4 ohms is pretty good power.  What kind of cab is that in the picture?

[hieronymous]

I don't have anything to add to the power-amp discussion, but I like your taste in basses!

[bsee]

Check some of the modern stereo power amps.  I use a PLX 2400 because I can run only one side.  There's so much juice there that there's no need to bridge it.  The sides are discreet enough that it's almost like carrying a backup amp.  If something goes in the side I am running, there's a fair chance that I can switch it over and run off the other side.  In other words, there might be enough benefit in carrying a 2U amp to make it worth your while.  
 
Certainly, I would expect that any single space unit is either going to require a second space kept open for heat dissipation or a very loud fan.

[matthew90046]

The cab is a early 1970's Sunn 215 that I found totally blown and I then loaded it with some Eminence drivers.  It's sounds really nice and I feel good about recycling the old gear.  I like it much more than the 4x10 BagEnd it replaced.  Krazie right!
 
On the left is a Distillate, on the right is a 1967 Gibson EB-0 with flats.

[dfung60]

The way that car audio amps generate 3000 watts is by lying about how much power they generate...  Watt=volts x amps, so at 13VDC (a lead acid battery is typically 13.8V, you'd be pulling 230 amps.  That's a lot of power, considering that most normal cars would probably be producing maybe 80 amps tops.  If you made 80 amps available to the sound system that would only be 1000 watts.  You can't actually take all the power from the alternator because you've got to give some to the engine so it can TURN the alternator.  And, even then, the amps aren't 100% efficient, so the numbers keep getting smaller and smaller.  If you see a 3000w car amp, it's probably designed to be in a car that sits on the car show floor plugged into a whole bunch of batteries that are being charged by a generator.  Or you're talking about one rockin' fire truck.
 
In fact, 3000w is even a problem for a 110VAC amp.  Again, you can't expect 100% efficiency, but it would require 27-30 amps.  You could get this sort of power on stage for your amp at the Staples Center, but the normal electrical service at the outlets in your home is only 20 amps.  
 
These modern lightweight amps use switching power supplies and might be 85% efficient (vs. old school transformer power supplies that were more like 50%).  I'm not sure that modern Class H-type amps can really produce their rated numbers on any sustained basis either.
 
I think the reason that you don't see a lot of single space power amps are that there's not much room in there for heat dissapation, even with cooling fans and other expensive solutions.  People will try to take the small amp in cram it into a small rack making the problem even worse.  A single slot fan makes a lot of noise to move any air compared to a 3 fan in a 2-slot chassis.  Guys who buy small amps are probably more likely to want it to be quiet rather than loud, so youv'e got a collision of all bad things here - expensive to make, noisy, and possibly less reliable under the conditions they really end up in.
 
Your best bet is probably a lightweight 2-slot amp.  It will be more reliable and should produce more power than your cabinet will ever be able to take.  If it won't handle a 4-ohm bridge load reliably, then you really could look at new speakers.  
 
Good luck,
 
David Fung

[gtrguy]

I sometimes use an older ADA B500B amp with my Alembic pre amp. It's a two space - two amp rig that sounds superb and is made for bass. It runs stereo which is great for an Alembic series, or you can use a mono bass out an F-1x to drive both sides. Since it has two amps built in, you can run mis-matched ohm cabs too! However, they are hard to find.
Dave

[jas]

dfung is dead right. The twits that buy apparently powerful car stereos are completely suckered. The manufacturers talk about peak music power, which is way over RMS (can't remember, twice or four times as much). It's just marketing - the amplifiers are likely to claim more power output than they can take from the power supply. Ignore the car stereo market completely.
Another trick is to multiply the number of output devices by their peak power rating and claim this as the output. If the power supply cannot deliver the current in bucketloads to the output devices, it's not going to manage to send the current to your speakers. Make no mistake, for high power systems, you need a REALLY serious power supply.
I use an old Amcron Crown DC-300A stereo power amp. It weighs a ton (big power supply) and is flat to 1/2 dB.
My esteemed colleagues here will advise better on specific bass amps, I just use industrial systems from the lab. Forget the car market, there's nothing there that would even make a passable fuzz box...
Happy days!
Jas

[keurosix]

Hey Matt,
Here's a thought:
Change the speaker wiring from parallel to series, and the load will be 16 ohms instead of 4 ohms (2x 8 ohm speakers). This will allow you to bridge your Sound Tech amp mono without killing either the amp or the speakers. You still might need more space for the amp to breathe though. If it isn't loud enough, then you'll need a bigger amp and rewire the cab back to parallel 4 ohms.
Kris
 
(Message edited by keurosix on May 27, 2008)

[0vid]

I have the PS802 Soundtech, and it works well but the stock fans make a racket. I changed the fans in mine,(bought a bunch of computer cooling fans and tried them to see which were quieter) to make them bearable at gigs. They would be useless in a studio.  
 
I  still use a slew of 1U amps with an F-1X in  my lighter 2U 'rig'. It varies from a Carver PM300, a Bryston 2BLP etc.. The Bryston is the meanest looking with the cooling fins on the front. It presently powers my studio monitors.  
I also use a Stewart P500 which is basically a World 600 but with a Chrome fascia plate. It is for sale if any one is interested, it is a US voltage spec and I am in the UK. Looks tres cool at gigs.
 
 
If you want higher power look in to;
 
www.d-amp.com
or
Powersoft DIGAM amps.
http://www.powersoft-audio.com/an_application_list.php?use_in=23&id_menu=194
 
There re also several manufactuers  such as C-Mark, Carlsboro,  etc who have 1U lightweight digital amps, mostly OEM'ed in china by companies such as:
 
http://www.madeinchina.com/2592271/P4857577/Digital-Power-Amplifier-Q2500.shtml
08)
 
(Message edited by 0vid on May 28, 2008)