QSC power amp

claudiomas · 15th July 2006, 07:41 AM

Hi! http://www.qscaudio.com/support/tech...rt/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

djk · 16th July 2006, 11:57 AM

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.

claudiomas · 16th July 2006, 05:58 PM

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 .

claudiomas · 16th July 2006, 08:06 PM

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 .

MikeBettinger · 17th July 2006, 02:38 AM

Is anyone aware of a source for a schematic. It sounds like an interesting design. Mike.

Enzo · 17th July 2006, 03:01 AM

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.

imix500 · 17th July 2006, 03:05 AM

Aren't the crown MA/MT series the same way? -The heatsinks are hot?

thejohn · 17th July 2006, 04:42 AM

Quite a few PA amps are designed this way. Apart from my QSC I know the there are a couple of Peavey's and I forget what else. QSC schematics are mostly available for free download from QSC website...

thejohn · 17th July 2006, 04:43 AM

...which is linked to in the first post!

MikeBettinger · 17th July 2006, 07:50 PM

Quote:

Originally posted by Enzo

The first post included a link to the QSC schematic collection.

I missed the link

, Thanks.

15th July 2006, 07:41 AM	#1
claudiomas diyAudio Member Join Date: Jul 2006	QSC power amp Hi! http://www.qscaudio.com/support/tech...rt/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 __________________ overbiased

16th July 2006, 05:58 PM	#3
claudiomas diyAudio Member Join Date: Jul 2006	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 . __________________ overbiased

16th July 2006, 08:06 PM	#4
claudiomas diyAudio Member Join Date: Jul 2006	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 . __________________ overbiased

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
40A 250V Schottky Power Diodes- Has anyone use in Power Amp to replace Diode Bridge?	dtm1962	Solid State	10	15th September 2011 07:38 PM
LTspice tool for power amp power supply component evaluation	andy_c	Software Tools	2	23rd August 2009 05:10 PM
Power transformers versus amplifier output power..what is your option?	destroyer X	Solid State	38	9th May 2009 05:23 PM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality	MARAVILLASAUDIO	Class D	1	5th November 2004 04:06 PM
power output calculations, rated power and required power output	metebalci	Tubes / Valves	7	22nd February 2004 05:49 PM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

16th July 2006, 11:57 AM	#2
djk diyAudio Member Join Date: Feb 2001 Location: USA	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.

17th July 2006, 02:38 AM	#5
MikeBettinger diyAudio Member Join Date: Jan 2006 Location: Virginia	Is anyone aware of a source for a schematic. It sounds like an interesting design. Mike.

17th July 2006, 03:01 AM	#6
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	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.

17th July 2006, 03:05 AM	#7
imix500 Proud Union Member diyAudio Member Join Date: Mar 2004 Location: Nashville, TN	Aren't the crown MA/MT series the same way? -The heatsinks are hot?

17th July 2006, 04:42 AM	#8
thejohn diyAudio Member Join Date: Mar 2005 Location: Cape Town, South Africa	Quite a few PA amps are designed this way. Apart from my QSC I know the there are a couple of Peavey's and I forget what else. QSC schematics are mostly available for free download from QSC website...

17th July 2006, 04:43 AM	#9
thejohn diyAudio Member Join Date: Mar 2005 Location: Cape Town, South Africa	...which is linked to in the first post!

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read