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Power Test SVT Pro 4

J

Joe Z

May 7, 2009
23
0
#1
I run my pro 4 in dual mono with 2 SVT 410hlf cabs, playing mostly in medium size clubs. I always thought it lacked the power it should have, although it sounds fine and is always perfectly clean - both of which were more important than whatever the "power" was.

Mostly out of curiosity, I brought it to a guy who was an authorized Ampeg repair shop and he put the head on his bench and showed 200 watts on each side into 8 ohm loads. Since my cabs are each 4 ohms, that should mean I draw 400 watts per side the way i am set up, which was up to spec, according to the tech. He reccomended no further investigation.

My understanding was that this thing should run 600 watts per side into 4 ohms, in the dual mono configuration.

First, is my info accurate? Have I misunderstood anything? Should I make any further investigations? If so, what should I look for?

As I mentioned, I'm not dissatisfied - but it's like, have you noticed how much better your car runs after you wash it? I'm sure I would be wondering less if I knew it was running up to spec the way it should be.

Thanx... Joe
 
#2
Hate to depress you on a Saturday, but power specs and bench power results are meaningless absent context, unless the results demonstrate a gross departure from spec. Some but not all context includes within what frequency range, or if not within a frequency range then at what frequency; one or both channels operating; at what distortion level; continuous or peak; ad nauseam. Also, if your operating environment is 4 ohms, then an 8-ohm test is of only academic value, since amp output power typically does not increase linearly with linearly-decreasing load impedance.

Now, having said that, there's a certain feel for an amp's potential power output capability that can be obtained from the specs, or maybe I should say that the specs can usually help you determine the amp's class of output capability: as in bedroom amp class, rehearsal amp class, club amp class, stadium amp class. Beyond that, however, almost everyone's playing games.

If your amp is doing the job you expect of it, if you're running it into the loads it was designed for, and if it's reliable, then I'd say just let it go.

Methinks you are experiencing the onset of GAS and are searching for a reason to whip out the plastic. :D
 
#5
ERRRRR,

I have covered this many times on here and a search would give you basically the same info I'm going to state again.

The ratings on the 4PRO are as follows, 300W continuous @ 8 ohms per channel, 490W into 4 ohms, and 600 watts into 2 ohms per channel. 900W continuous @ 8 ohms in the bridged mode and 1200W contiuous into 4 ohms bridged.

The tests I have run on the 4PRO are by metering the input drawn from the wall. This is because I needed to know the input current of these amps for my arena rig; I own TEN.

AT an extreme level of crank bridged mono into an 810 cab I was able to draw 15.2 amps out of the wall.

My line voltage here at the time was 124V, that calculates to 1884 watts drawn from the wall. The amp cannot operate continuously at this level of power. This is where the continuous specs are semi-bogus. The amp can hit peaks of 1200W without clipping or blowing up.

In the olden days when SS amps were a new thing, they rated the amps equivellent to tube amps. A 100 watt SS amp was as loud as a 100 w tube amp. Tube amps when ran at full crank compress and do nice distortion sounds, a SS amp when ran the same way EXPLODES and destroys componants. They require a 3-4 times power headroom to avoid clipping. Somewhere along the way MARKETING got involved and changed the rating on SS amps, and created all sorts of confusion. Because the amps will make the power, but not contiuously.

The 4 PRO is about as loud as a 400 Watt tube amplifier in the real world. The extra in the ratings is the headroom.

NOW, the amp will make 1200W out. BUt it is not continuous until the cows come home.

When you get to a single channel those 490W into 4 ohms is about like 100-125W toob amp.

There are some limitations and follow this. The power supply. There is only one inside the amp. It provides power to both channels. When in the bridged mono mode, one channel is the - channel and the other is the + channel. The - rail of the power supply feeds the - channel during the negative cycle and the + rail feeds the + side during the positive cycle. SO basically half of the supply is loaded half the time in layman's terms.

When in Dual Mono or stereo the power supply is feeding both channels at the same time in the same cycle. I was able to find power supply issues in one of my amps by running it in dual mono and heard distortion that wasn't there in bridged mono. I confirmed the theory with Jerrold and I replaced the caps and fixed the amp.

So the amp isn't as stellar a performer in dual mono or stereo as it is in bridged-mono.

Waleross is correct the amp will drive a pair of 810's to reasonable levels, however where we disagree is I feel the 810 needs to be hit harder to sound "right" than the amp can provide in that mode.

If you try and crank it up to the levels you can get in bridged, it will shut itself off, click.

That's why my arena rig has separate amps per cab.

I run the amp at 3/4 cranked up (3 O'Clock) on the preamp and 5/8th cranked (1:30) on the master to get max zoom per head in my rig.

ANYWAY, the 4PRO is a dog at 8ohms any way you look at it. It is not a good performer in dual mono, but it does OK with a couple 4HLF's to reasonable levels. I also own an HLF here. Just make sure you crank up the preamp gain until the red led flashes on every note, don't be afraid to turn it up to 3/4 if thats what you need, have your bass all the way up.

Do not try and run the 4PRO over 5/8th crank on the master in dual mono. It will shut itself off and it will get hot. Make sure your rack has good cooling.

If you have any further questions feel freee to PM me. Sometimes I don't make it back to some threads.

I am a huge supporter of these amps, and have a bunch of experience with them. They are a great box but need to be run within their abilities. They will let you down if you try and do something they don't like or they will put a huge smile on your face. You should be around when 6 of them are maxing out and vision is bluring from vibrating eyeballs.

My SVP1600's are the same amps sans preamps. The controls on the front of the 1600's are wide open, my SVPCL preamp puts out more voltage than the 4PRO's preamp. I just start cracking open the SVPCL and the amp is already cranking... Why you feel the amp needs to be cranked more than you should, is the preamp voltage. Just turn the knob up, numbers on the dial mean nothing, just turn until it does what you want. Just don't turn the master past 5/8th up in any mode; it will run at 5/8th forever and makes good power. I do leave the limiter engaged myself. They will run some additional power with the limiter off. I DO NOT recommend doing this in dual mono or stereo. The power supply being the limiter there again.

BOB
 
#6
Joe Z said:
I run my pro 4 in dual mono with 2 SVT 410hlf cabs, playing mostly in medium size clubs. I always thought it lacked the power it should have, although it sounds fine and is always perfectly clean - both of which were more important than whatever the "power" was.

Mostly out of curiosity, I brought it to a guy who was an authorized Ampeg repair shop and he put the head on his bench and showed 200 watts on each side into 8 ohm loads. Since my cabs are each 4 ohms, that should mean I draw 400 watts per side the way i am set up, which was up to spec, according to the tech. He reccomended no further investigation.

My understanding was that this thing should run 600 watts per side into 4 ohms, in the dual mono configuration.

First, is my info accurate? Have I misunderstood anything? Should I make any further investigations? If so, what should I look for?
Click to expand...

You have a bad spec understanding, and the guy who tested may not have 120V to his bench when the unit is drawing power.

The mains voltage drops under load, so the proper way is to adjust voltage and get 120V at the amp while the power is being drawn. Even though that may not be "reality" in every case, it is the "standard" way to measure power.

The 4PRO should give 300 per side, not 200, because 8 ohms is a lighter load than 4 ohms or 2 ohms, so the power supply voltage does not "fall" as far. That is just under 49V rms. His figure of 200W corresponds to only 40V rms.

At 4 ohms, you are mistaken, 490W, not 600, in dual mono, because as R Bonner mentioned, the load is heavier on the power supply for dual mono than bridge. That is 44.3 Vrms.

Depending on how the tech measured the power out, he may have gotten a lower number for any of a number of reasons, or he may simply have checked that he got 200W at 8 and so would expect to get 400 at 4.... (not true, by the way).

probably no problem, but it is not possible to know from what you say.

As far as the "feeling" of lower power, the power amp limiter is often the culprit. Turn it off and see what you get.

AND be sure you are driving the preamp hard... Really common problem. The red light should be on regularly. many are afraid of it, and don't turn up the preamp. You are expected to light that light, it is really more of an "I have enough signal" light, and not so much an "overload" light.
 
#7
guys - thanks for taking the time to make such thorough, thoughtful and helpful responses - RBonner, sorry I made you go thru it AGAIN - next time I'll look more carefully...my bad.

Craig.P, you called it - I know I was looking for a reason to shop, which I can't afford, shouldn't do and having carefully read the responses and made some adjustments, now will NOT do.

I may have been a little hung up on "knob position", which should be irrelevant, and I was VERY hung up on keeping the red clip lite OFF. I never had it over about 3-4 on a 10 scale and the lite only came on when I slapped an open E.

So I cranked up the gain a bit, played with the lite coming on (almost regularly) and 3 things happened: 1. it failed to explode, 2. it may have sounded a little better...more growl, and 3. any hang up with main volume knob position was gone because, obviously, it was now louder with less knob. I may not be ready to turn off the limiter, yet, however!

All that coupled with your corrections of my misunderstandings of the numbers made me recommitt to keeping the amp. You all probably know how important that can be to us.

Again, thanks alot....

Of all the forums I know, this one is always the most helpful with the smartest people!

regards...Joe
 
#9
I've had four 4-pro heads & multiple cabs over the past 11 years & here's the deal. If you run each side of the amp into two different cabs you run the amp weak!. If you run two 8 ohm cabs, each will get 300 watts RMS. If you run two 4 ohm cabs, each will get 490 watts RMS each. I two cabs for years till I decided to use one 8 ohm or 4 ohm cab "Mono-Bridged". Now you must rewire your speakon power cable (pin 1+ = “+”, pin 2+ = “–”) If you do not do this you will only be running one side of the 4 pro power amp! A regular speakon cable will work but it will only give you half power! Rewire "one end" (not both) of the speakon cable to (pin 1+ = “+”, pin 2+ = “–”) DO IT! Even the SVT 4 Pro owners manual tells you to do it. They even have a tutorial on youtube! Then hook the rewired end of your speakon to the 4 pro & the regular end to your cab & hold on to your Butt! If you run a 8 ohm cab make sure it can handle 900 watts RMS if you run a 4 ohm cab make sure it can handle 1200 watts RMS. You will be blown away by the shere power of this amp running full steam. I currently use my 4 pro with a 8 ohm Peavy tour 410. I'm pushing 900 watts RMS into it & I'm blowing away my entire band. I play Metal, 2 guitarist with Mesa tube half stacks & a loud as hell drummer. Not only can I hear myself very well they constantly tell me to turn it down. If your cliping your doing something wrong.
 

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