Lme49810 with 2SC3263 & 2SA1294 output HELP!!! - Page 3 - diyAudio
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Old 6th November 2013, 10:06 AM   #21
basi is offline basi  Croatia
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Location: Novska
Hi to all!!!

I buy some 2sb649/d669 yesterday and i change VR on bias to 500ohm.
This is my new schematic.

Click the image to open in full size.


Btw this amp will be use for Subwoofer i expect around 120w at 8 ohm.
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Last edited by basi; 6th November 2013 at 10:09 AM.
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Old 6th November 2013, 11:11 AM   #22
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Are the 220R base resistors necessary for the driver stage?
Do you not need 55V rails for 120W/8ohm output?

Edit:
And 57V for the chip?

Last edited by palstanturhin; 6th November 2013 at 11:26 AM.
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Old 6th November 2013, 12:02 PM   #23
AndrewT is offline AndrewT  Scotland
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35Vac will give ~+-50Vdc when the amp is idling
This will sag to ~+-46Vdc when delivering full power.
That will usually get 100W to 120W of maximum sinewave power into 8r0 dummy test load.

+-47Vdc seems about right for the fully loaded condition while delivering 120W into 8r0.
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Old 6th November 2013, 01:38 PM   #24
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I get only 93W to 8ohm from 46V rails???
And -4V off, 49810 not able to deliver rail to rail output, I get only 78W???
Maybe something wrong with my calculations, need to check them...

Edit:
Yes, Andrew is right (as always)...
With 46V rails you will get 102.5W
And with 50V rails you will get the required 123.8W

Sorry, completely misscalculated everything first...

Last edited by palstanturhin; 6th November 2013 at 02:02 PM.
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Old 6th November 2013, 02:51 PM   #25
rsavas is offline rsavas  Canada
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Location: Ontario
Quote:
Maybe something wrong with my calculations, need to check them...
Or methods/instrumentation?
Monitor DC supply(droop) with a DMM and a scope.
Monitor AC o/p with a DMM and a scope.
See where the amp clips, what clips, how it clips, the LME49810 or the bjts.
I(other's) design PA's with a separate PS for the fornt-end (LME) and the o/p bjt's. Having a variable supply for the
fornt-end gives you more headroom(important for MOSFET's) and control of drive strength, where the amp clips.
Having a separate PS for the fornt-end (LME) while you are developing , with I current limited, helps too. The 49810 has the baker clamp!!
I have not done enough testing on the LME yet, but you have to determine what do you want to clip first, the LME or the o/p's. For MOSFET's(Lateral) I would think that you want the FET's to clip first due their soft saturation(tube) like characteristics..
For bjt o/p, I/you need to test/listen.
I posted a front-end PS at,
Dual high V tracking linear regulator for review
Warning it is only simulated, not fab'd or fully tested but is based on Pioneer/Sansui designs, using new available parts.

Cheers
Rick
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