Hi! http://www.qscaudio.com/support/technical_support/schems1.htm what do you think of QSC , very goods amps whit the main power 0 = OUTPUTS yes, hot speakers , all power transistors whit alls pnp and npn collectors grounded . you short the outputs no problem just change fuses . they can run a full power 24 hours a day and the sound its SUPERB
Glad you like yours.
Ways to improve your QSC:
Add power supply bypass caps, 22µF per rail makes the bass sound much tighter.
Add 0.1µF film bypass to all electrolytics in the signal path, bass sounds better, highs sound cleaner.
Remove current loading resistors on the output of the 5532 opamps, makes the amplifier sound much more dynamic. Be sure and use an external speaker fuse for protection against load faults.
There is still room for improvement, but these are the easy ones that make a big difference, and cost very little.
Ways to improve your QSC:
Add power supply bypass caps, 22µF per rail makes the bass sound much tighter.
Add 0.1µF film bypass to all electrolytics in the signal path, bass sounds better, highs sound cleaner.
Remove current loading resistors on the output of the 5532 opamps, makes the amplifier sound much more dynamic. Be sure and use an external speaker fuse for protection against load faults.
There is still room for improvement, but these are the easy ones that make a big difference, and cost very little.
i'm not allowed to do any modifications to my customers , repair this monsters means for olds equipements caps and for the new switching power supply amps complete main boards , for intermediates 50 Hz power supply models sometime few transistors and/or voltage amps modules . and often some little problem whit 15 Volts zeners diodes and resistors . but y use an USA 900 for test of TASCAM equipments and if you think your modifications will improve the superb sound of my amp y will tray to do it . tanks .
the main question : nobody built amps like this . all powers transistors collecteur grounded . no mica no compound . npn/pnp all toghether . you short outputs /no problem 24hday full power it's OK.linear amps plenty of bass and treble and medium as well .c'ant be . i now . need to try . yet still it mouve . eppur si muove .
Aroound here we call that "flying rails" and many amps are made that way. Even small Peavey solid state amps are often wired that way. Or at least grounded emitter.
If you would ground the emitter in a conventional PP output stage, why not reverse things and ground the collectors and run the rails to the emitters? Then the output xstrs can be grounded removing the need for insulators etc.
The first post included a link to the QSC schematic collection.
The EX, MX, and USA series are not all that old and are typical. the Powerlite and PLX series are switchers.
In their flying rail circuit, the speaker is between the main filter cap common and ground. The "output" of the power stage is also grounded.
To the uninitiated, this arrangement looks counterintuitive at first, but once you look at it a bit, the amp topology is not all that strange, and it is just a change of frame of reference.
If you would ground the emitter in a conventional PP output stage, why not reverse things and ground the collectors and run the rails to the emitters? Then the output xstrs can be grounded removing the need for insulators etc.
The first post included a link to the QSC schematic collection.
The EX, MX, and USA series are not all that old and are typical. the Powerlite and PLX series are switchers.
In their flying rail circuit, the speaker is between the main filter cap common and ground. The "output" of the power stage is also grounded.
To the uninitiated, this arrangement looks counterintuitive at first, but once you look at it a bit, the amp topology is not all that strange, and it is just a change of frame of reference.
, Thanks.
"QSC d'ont joke . alls power transistors collector ground main sink and +B-B to alls Emetteurs. never fail ."
Hey I know all that, I have a pile of broken QSC at home.
They are not the best sounding, or the best built amps.
Some of their models simply aren't worth fixing.
Of course that can be said about other brands and models too.
Hey I know all that, I have a pile of broken QSC at home.
They are not the best sounding, or the best built amps.
Some of their models simply aren't worth fixing.
Of course that can be said about other brands and models too.
Like every manufacturer they offer a range of product... what applies to the old USA series does not necessarily apply to the PL's and the same goes for everything else in between.
A couple of general rules that apply -
Musicians and nightclub DJ's can blow up any piece of audio gear regardless of how much it cost!
All repairs from above contain the sticky residue of an alcoholic beverage of some description!
Good quality pro gear -
Doesn't catch fire and burn to the ground when blowing up!
Has parts readily available (and schematics)!
Is easy to work on!
A couple of general rules that apply -
Musicians and nightclub DJ's can blow up any piece of audio gear regardless of how much it cost!
All repairs from above contain the sticky residue of an alcoholic beverage of some description!
Good quality pro gear -
Doesn't catch fire and burn to the ground when blowing up!
Has parts readily available (and schematics)!
Is easy to work on!
has anybody ever had the chance to compare the RMX Vs the PL2 line of their amps?
I'm looking for suggestions on a refference low ohm amp.
The Rmx is spec'd a bit better with lower distortion and slightly faltter response, however, the Pl2 is newer and would seem the newer tech would be benificial through its sound.
Thanks for any input.
Mule.
I'm looking for suggestions on a refference low ohm amp.
The Rmx is spec'd a bit better with lower distortion and slightly faltter response, however, the Pl2 is newer and would seem the newer tech would be benificial through its sound.
Thanks for any input.
Mule.
"Good quality pro gear -
Doesn't catch fire and burn to the ground when blowing up!
Has parts readily available (and schematics)!
Is easy to work on!"
Guess that leaves out both QSC and Crown.
No schematics, that leaves out Behringer.
"I'm looking for suggestions on a refference low ohm amp."
Buy twice as many Behringer and only run at 4 ohms, same price for two EP2500 or one RMX2450.
"The Rmx is spec'd a bit better with lower distortion and slightly faltter response, "
Meaningless. I have yet to find a correlation between specs and sound. Some Crown models test fantastic for distortion and yet sound nasty in the high end. I have an LSR&D 101 that can thump harder than a QSC MX2000, it's half the weight, and half the rated power, twice the sound.
Doesn't catch fire and burn to the ground when blowing up!
Has parts readily available (and schematics)!
Is easy to work on!"
Guess that leaves out both QSC and Crown.
No schematics, that leaves out Behringer.
"I'm looking for suggestions on a refference low ohm amp."
Buy twice as many Behringer and only run at 4 ohms, same price for two EP2500 or one RMX2450.
"The Rmx is spec'd a bit better with lower distortion and slightly faltter response, "
Meaningless. I have yet to find a correlation between specs and sound. Some Crown models test fantastic for distortion and yet sound nasty in the high end. I have an LSR&D 101 that can thump harder than a QSC MX2000, it's half the weight, and half the rated power, twice the sound.
Buy twice as many Behringer and only run at 4 ohms, same price for two EP2500 or one RMX2450.
not an option since behringer is neither a well regarded amp manufacturer and 2 ohms (more importantly stable into a theoretical short circuit) is what i'm looking for
"The Rmx is spec'd a bit better with lower distortion and slightly faltter response, "
Meaningless. I have yet to find a correlation between specs and sound. Some Crown models test fantastic for distortion and yet sound nasty in the high end. I have an LSR&D 101 that can thump harder than a QSC MX2000, it's half the weight, and half the rated power, twice the sound.
^^ hence why i'm looking for opinions.
Measurements have meaning in the sense that amps deliver their power within a given set of boundries. I have figured out those boundries...
however, as a reference. it also needs to sound as good (if not better) then the measurements would suggest.
P.S. Thanks claudio. That's exactly what i needed to know.
not an option since behringer is neither a well regarded amp manufacturer and 2 ohms (more importantly stable into a theoretical short circuit) is what i'm looking for
"The Rmx is spec'd a bit better with lower distortion and slightly faltter response, "
Meaningless. I have yet to find a correlation between specs and sound. Some Crown models test fantastic for distortion and yet sound nasty in the high end. I have an LSR&D 101 that can thump harder than a QSC MX2000, it's half the weight, and half the rated power, twice the sound.
^^ hence why i'm looking for opinions.
Measurements have meaning in the sense that amps deliver their power within a given set of boundries. I have figured out those boundries...
however, as a reference. it also needs to sound as good (if not better) then the measurements would suggest.
P.S. Thanks claudio. That's exactly what i needed to know.
"not an option since behringer is neither a well regarded amp manufacturer and 2 ohms (more importantly stable into a theoretical short circuit) is what i'm looking for"
And you think QSC is?
"Measurements have meaning in the sense that amps deliver their power within a given set of boundries. I have figured out those boundries..."
Maybe you should share it with us. I have a 160W amp (LSR&D) that will crush a 450W amp (QSC). The spec sheet is virtually meaningless, if you have figured it out, please share.
Sorry I can't tell you what you want to hear. QSC is near the bottom of my list for sound quality, reliability, servicability, and overall value.
And you think QSC is?
"Measurements have meaning in the sense that amps deliver their power within a given set of boundries. I have figured out those boundries..."
Maybe you should share it with us. I have a 160W amp (LSR&D) that will crush a 450W amp (QSC). The spec sheet is virtually meaningless, if you have figured it out, please share.
Sorry I can't tell you what you want to hear. QSC is near the bottom of my list for sound quality, reliability, servicability, and overall value.
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