I have installed QSC amplifiers in large commercial systems. For the most part they usually don't blow up. They perform fairly well for what they are. They aren't the best sounding amplifiers either.
I'm talking large commercial systems here like football stadiums and civic centers where my average system power is in the neighborhood of 50,000 watts of power. The amplifiers I use will be driving 70 volt lines and others will be driving a 8 to 4 ohm load. No serious audio person will even consider trying to drive 2 ohm or lower loads even if the amplifier's manufacturer claims a 2 ohm or lower load capability.
It all boils down to realibility and you do not want to take chances. Oh, I have used all of the major brands of amplifiers in different systems and tend to stear away from Crown and the cheaper brands because they come apart. When we put a system together it comes with a warranty and we don't make any money if we have to chase back and forth changing amplifiers during the warranty. We don't have customers as repeat customers if we have a system that is costing them money because of cheap equipment we installed.
I'm sure that the cheap amplifiers will work fine in those little fly-by-night DJ systems that are a no-brainer to run. Run your 2 ohm loads here and replace the equipment yearly, that is if you can manage a years worth of usage from them.
I'm talking large commercial systems here like football stadiums and civic centers where my average system power is in the neighborhood of 50,000 watts of power. The amplifiers I use will be driving 70 volt lines and others will be driving a 8 to 4 ohm load. No serious audio person will even consider trying to drive 2 ohm or lower loads even if the amplifier's manufacturer claims a 2 ohm or lower load capability.
It all boils down to realibility and you do not want to take chances. Oh, I have used all of the major brands of amplifiers in different systems and tend to stear away from Crown and the cheaper brands because they come apart. When we put a system together it comes with a warranty and we don't make any money if we have to chase back and forth changing amplifiers during the warranty. We don't have customers as repeat customers if we have a system that is costing them money because of cheap equipment we installed.
I'm sure that the cheap amplifiers will work fine in those little fly-by-night DJ systems that are a no-brainer to run. Run your 2 ohm loads here and replace the equipment yearly, that is if you can manage a years worth of usage from them.
Well, some of Behringer and QSC amps are clones.
I do own a Behringer EP-1500 and everything corresponds in a perfect way to schematic of QSC RMX-1450 both of them running class AB. QSC RMX-2450 and Behringer EP-2500 also alike (class H). They commonly share "flying rail" topology.
I am interested to compare size of transformer in EP-1500 and RMX-1450. Does anybody here have a RMX-1450 and willing to take some photos or measure transformer dimensions?
I do own a Behringer EP-1500 and everything corresponds in a perfect way to schematic of QSC RMX-1450 both of them running class AB. QSC RMX-2450 and Behringer EP-2500 also alike (class H). They commonly share "flying rail" topology.
I am interested to compare size of transformer in EP-1500 and RMX-1450. Does anybody here have a RMX-1450 and willing to take some photos or measure transformer dimensions?
Mackie was kind enough to send me the schematics for their Tapco J-2500 made-in-China clone of the made-in-China QSC RMX 2450.
The schematic looks just like a QSC, even down to the patented (now expired) QSC limiter (which I don't like the sound of).
The Mackie unit weighs 12 lbs more than the QSC, and as a result is rated at 1.4KW per channel, both channels driven, 20hz~20Khz into 2 ohms, not at 1Khz only like the QSC and Behringer units.
Cost is about $70 more than the Behringer, and about $200 less than the QSC.
The schematic looks just like a QSC, even down to the patented (now expired) QSC limiter (which I don't like the sound of).
The Mackie unit weighs 12 lbs more than the QSC, and as a result is rated at 1.4KW per channel, both channels driven, 20hz~20Khz into 2 ohms, not at 1Khz only like the QSC and Behringer units.
Cost is about $70 more than the Behringer, and about $200 less than the QSC.
hmmm... I have to admit that i don't understand those schematics. There´s no center-tap on the main power transformer as we normally see in non-bridged amps . How does it "return power" to the transformer?
Clever to get rid of the mica washers. Great in terms of thermal efficiency and easy production.
Hope you guys can help me understand this.
Regards TroelsM
Clever to get rid of the mica washers. Great in terms of thermal efficiency and easy production.
Hope you guys can help me understand this.
Regards TroelsM
This module assembly is for an RMX2450 power amplifier and serves as channel 1. This is the RIGHT side PCB assembly, as viewed from the front, with gain pots (heat sink stamped "R").
There are many surface mount components on the bottom side of this assembly (not shown).
This assembly requires no solder connections for installation. There are two snap-in headers and four fast-on connectors for output and power connections. The amplifier's power supply does not reside on this assembly.
This assembly is manufactured in China and due to certain lead times, availability at any time may vary.
RMX2450 Spec Sheet (PDF)
RMX2450 Schematic (PDF)
PCB-QZ030C-PWR1$251.79
There are many surface mount components on the bottom side of this assembly (not shown).
This assembly requires no solder connections for installation. There are two snap-in headers and four fast-on connectors for output and power connections. The amplifier's power supply does not reside on this assembly.
This assembly is manufactured in China and due to certain lead times, availability at any time may vary.
RMX2450 Spec Sheet (PDF)
RMX2450 Schematic (PDF)
PCB-QZ030C-PWR1$251.79
Oh, did I mention that every reference designator for every part is exactly the same for the Tapco?
If you want to see the Tapco schematic, just download the QSC.
There are some component quality differences though. The main filter caps (C121~123) in the Tapco are rated at 80V, they're only 63V in the QSC.
If you want to see the Tapco schematic, just download the QSC.
There are some component quality differences though. The main filter caps (C121~123) in the Tapco are rated at 80V, they're only 63V in the QSC.
TroelsM said:
The power goes through center of caps at any audio frequency. Look at it as output transistor uses stored energy in cap to drive speaker.
Note that this amp could newer provide DC power to speaker.
So amp is totally dependeble on low reactance in filter caps.
Just as an amp with output capacitator.
Claudiomas,
Are you shure about that?
They may have licence to use the construction.
And if they did not, shouldn't they have been sued by now?
I agree that there may be some differences therefore I am asking about transformer size in QSC amp RMX-1450.
TroelsM,
Yes feedback takes care of it, otherwise output impedance would rise in lower frequencies. But some increase in capacitanse and quality of caps could not hurt I think.
By the way this has been discussed before here and one helpful member even did make a simplified circuit of this construction but I cannot find it anymore. I suggest a search maybe I missed it.
Are you shure about that?
They may have licence to use the construction.
And if they did not, shouldn't they have been sued by now?
I agree that there may be some differences therefore I am asking about transformer size in QSC amp RMX-1450.
TroelsM,
Yes feedback takes care of it, otherwise output impedance would rise in lower frequencies. But some increase in capacitanse and quality of caps could not hurt I think.
By the way this has been discussed before here and one helpful member even did make a simplified circuit of this construction but I cannot find it anymore. I suggest a search maybe I missed it.
QSC Schematics
QSC password their schematic page at times. Most of the schematics are available without a password at www.schematicsforfree.mattsoft.net in the audio section, pro audio sub section.
By the way Behringer copy from everybody. Most of their mixers were designed by Mackie. Just that Mackie got nothing for it. Now Mackie is copying QSC. I will almost guarantee you that QSC got nothing for it as well.
QSC for all their other faults, besides hiring away two of my technicians (I live 2 miles from them), at least do original design work of their own. While Mackie does most of their own original work (yes, I have visited Mackie's engineering dept. in Woodinvill WA and had lunch with several of their engineers), Behringer are the master copiers.
And yes, I have also seen Mr. Behringer. There is such a person. They do some original work in Germany but it does appear that most if their products are copies of other people's products. Usually about 85% as good and 60% of the price of the original. Maybe less. I have their DEQ2496 and that is an excellent product once I fixed the bad solder joint on the input XLR connector. One of the few that they seemed to have designed themselves.
And the other person is right about running a 2 ohm load. If you expect reliability, never run 2 ohms in a pro installation. 2 ohms is for car audio where you don't have a lot of voltage but do have a lot of current available.
I also hear that Behringer is on the prowl to buy other pro audio companies and may be putting together their own conglomerate soon the way that Harmon did with JBL, dbX, Crown, etc.
I also hear that Mackie in the Seattle area and Niles Audio in Miami are looking for experienced audio design engineers.
QSC password their schematic page at times. Most of the schematics are available without a password at www.schematicsforfree.mattsoft.net in the audio section, pro audio sub section.
By the way Behringer copy from everybody. Most of their mixers were designed by Mackie. Just that Mackie got nothing for it. Now Mackie is copying QSC. I will almost guarantee you that QSC got nothing for it as well.
QSC for all their other faults, besides hiring away two of my technicians (I live 2 miles from them), at least do original design work of their own. While Mackie does most of their own original work (yes, I have visited Mackie's engineering dept. in Woodinvill WA and had lunch with several of their engineers), Behringer are the master copiers.
And yes, I have also seen Mr. Behringer. There is such a person. They do some original work in Germany but it does appear that most if their products are copies of other people's products. Usually about 85% as good and 60% of the price of the original. Maybe less. I have their DEQ2496 and that is an excellent product once I fixed the bad solder joint on the input XLR connector. One of the few that they seemed to have designed themselves.
And the other person is right about running a 2 ohm load. If you expect reliability, never run 2 ohms in a pro installation. 2 ohms is for car audio where you don't have a lot of voltage but do have a lot of current available.
I also hear that Behringer is on the prowl to buy other pro audio companies and may be putting together their own conglomerate soon the way that Harmon did with JBL, dbX, Crown, etc.
I also hear that Mackie in the Seattle area and Niles Audio in Miami are looking for experienced audio design engineers.
QSC SCHEMATICS
http://www.qscaudio.com/support/technical_support/schems1.htm
HERE all schematics free all time . fees only for complete service manual including detailed tecnicals descriptions and bias andshort limit setup . BOB LEE , QSC engineer said behringer are unauthorized copies.
4fun i'm in holyday but if you wont some QSC detailed photos first send your behringer photos.
http://www.qscaudio.com/support/technical_support/schems1.htm
HERE all schematics free all time . fees only for complete service manual including detailed tecnicals descriptions and bias andshort limit setup . BOB LEE , QSC engineer said behringer are unauthorized copies.
4fun i'm in holyday but if you wont some QSC detailed photos first send your behringer photos.
Claudiomas,
If that's true regarding copying then I am sorry for QSC, however does not QSC protect themselves from copying?
Anyway here is one lowres pic of Behringer EP 1500 that should at least show dimensions of transformer and general layout.
If we are going to exchange big high res pics we have to mail.
If that's true regarding copying then I am sorry for QSC, however does not QSC protect themselves from copying?
Anyway here is one lowres pic of Behringer EP 1500 that should at least show dimensions of transformer and general layout.
If we are going to exchange big high res pics we have to mail.
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