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Amplifiers Rescue Gods |
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Earplug ![]() Old Croc ![]() Joined: 03 January 2012 Location: Europe Status: Offline Points: 7006 |
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Those old Peaveys are bloody tanks! ![]() Well worth fixing. ![]() |
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Earplugs Are For Wimps!
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EmPro ![]() Registered User ![]() ![]() Joined: 26 June 2020 Status: Offline Points: 356 |
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I like the're so easy to fix,if you have the parts you need is a 30min job
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EmPro Audio
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EmPro ![]() Registered User ![]() ![]() Joined: 26 June 2020 Status: Offline Points: 356 |
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EmPro Audio
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shaun1264 ![]() Registered User ![]() ![]() Joined: 06 September 2013 Location: Surrey Status: Offline Points: 242 |
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Chance buy on a Crown D75... Pleasant surprise someone changed the mechanical buzzing transformer to a torriod. Typical cooking PCB from the 320ohm resistor complete with vaporised tracks. Upgraded R1 910 resistor to a 5watt and relocated to the side of the PCB board. (sorry no pic), changed the 10v zener diodes for the opamps supply, new caps, put back together, power up, several hundred mV DC offset on both channels!!. re-examine board and find two more broken tracks. ... fixed them and power up and now perfect. Adjusted bias as manual states. Very low THD. ![]() ![]() ![]() |
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luton_soundman ![]() Old Croc ![]() ![]() Joined: 03 August 2010 Location: Bedfordshire Status: Offline Points: 4472 |
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Very nice
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Sound Hire/Sales new/used equipment.
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EmPro ![]() Registered User ![]() ![]() Joined: 26 June 2020 Status: Offline Points: 356 |
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EmPro Audio
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EmPro ![]() Registered User ![]() ![]() Joined: 26 June 2020 Status: Offline Points: 356 |
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However i bought mine without ear racks..and never found ones to buy for it....
![]() ![]() Edited by EmPro - 25 March 2023 at 9:05pm |
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EmPro Audio
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shaun1264 ![]() Registered User ![]() ![]() Joined: 06 September 2013 Location: Surrey Status: Offline Points: 242 |
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Another one of Gerald Stanley's patent topology designs. Class AB+B. Very large amounts of negative feedback to get THD down very low.
A little bit of info here for the technical minded... When TIM distortion was discovered by Matti Otala back in the 70s he incorrectly blamed too much negative feedback as the cause.. infact, it's actually caused by not enough feedback and slow semiconductors back then. ...slew induced distortion. This gave Crown a bit of bad rap way back then as people knew Crown used large amounts of negative feedback... Audiophiles still believe in this myth! Infact Crown amps never had any TIM distortion. They all measured well.
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EmPro ![]() Registered User ![]() ![]() Joined: 26 June 2020 Status: Offline Points: 356 |
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Clever design,basicaly on low power the output transistors are off...is working on the drivers,no bias thru outputs...as you rise the volume the power outputs will kick in and take the heavy load further...nice one..and helps a lot with thermal stability.
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EmPro Audio
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shaun1264 ![]() Registered User ![]() ![]() Joined: 06 September 2013 Location: Surrey Status: Offline Points: 242 |
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Absolutely correct. pre drivers act as class A, drivers act as class AB and output act as class B. Driver and pre drivers have good fast speed and outputs lower speed (much more stable and durable) outputs act as boosters. Crossover notch is literally non existent.
Idle power much lower too! |
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EmPro ![]() Registered User ![]() ![]() Joined: 26 June 2020 Status: Offline Points: 356 |
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Indeed,my one was faulty,one output transistor shorted and the ch was off,no other faults apart from that,i replaced all 4 outputs just in case with MJ15024....and rock and roll since
![]() Edited by EmPro - 26 March 2023 at 12:04pm |
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EmPro Audio
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EmPro ![]() Registered User ![]() ![]() Joined: 26 June 2020 Status: Offline Points: 356 |
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EmPro Audio
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