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Old 19th September 2008, 02:26 PM   #1
mhtplsh is offline mhtplsh  India
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Default Help reqd - power bass for PA use

The amplifier is with heavy duty transformer & power supply. It is used for pa. But there is no powerful bass as required. What modifications might be required to get kick bass for PA use.
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Old 19th September 2008, 02:59 PM   #2
AndrewT is offline AndrewT  Scotland
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The first 5 opamps and the circuitry around them might give you a clue to the lost bass.
But PA/PRO amps are deliberately designed to remove the damaging low bass signal from the speaker terminals.
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Old 19th September 2008, 03:23 PM   #3
mhtplsh is offline mhtplsh  India
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Andrew T:
Quote:
The first 5 opamps and the circuitry around them might give you a clue to the lost bass. But PA/PRO amps are deliberately designed to remove the damaging low bass signal from the speaker terminals.
I too don't want low bass but i want more kick bass.
U hv mentioned about lost bass. Can u suggest how to change this?
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Old 19th September 2008, 03:31 PM   #4
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Buy a parametric equaliser and add boost around 80Hz.
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Old 19th September 2008, 03:46 PM   #5
mhtplsh is offline mhtplsh  India
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Quote:
Buy a parametric equaliser and add boost around 80Hz.
I know this.
But here the suggestion reqd is for getting more kick bass from the amp itself.
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Old 19th September 2008, 05:38 PM   #6
wg_ski is offline wg_ski  United States
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Add the EQ directly to the amp? Series RLC to GND directly from the - input of the 2nd op amp. 470 ohms, 3uF, and 1.3H. It's for 80 Hz, Q of about 1.4 (same as turning up that band of an ocatve EQ). The 1.3H can be synthesized with an op-amp circuit - I don't rememeber the exact circuit off the top of my head - but it's in most comprehensive op-amp data books and app notes.

Now why do you want to boost *80*? EEEEEEyuck!
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Old 20th September 2008, 01:59 AM   #7
mhtplsh is offline mhtplsh  India
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Quote:
Add the EQ directly to the amp? Series RLC to GND directly from the - input of the 2nd op amp. 470 ohms, 3uF, and 1.3H. It's for 80 Hz, Q of about 1.4 (same as turning up that band of an ocatve EQ). The 1.3H can be synthesized with an op-amp circuit - I don't rememeber the exact circuit off the top of my head - but it's in most comprehensive op-amp data books and app notes. Now why do you want to boost *80*? EEEEEEyuck!
The bass is loose. I wanted tight bass. Many say that higher damping factor gives tight bass.
in the following thread :
http://www.diyaudio.com/forums/showt...92#post1255792
djk said :
Try adding a pair of 47F at 63V (or higher) in parallel with the main filter caps. The bass will sound much tighter.

Here i want to say kick bass or more tighter bass. Sorry if misunderstood. Can the damping factor be improved?
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Old 20th September 2008, 03:34 AM   #8
wg_ski is offline wg_ski  United States
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"Tight" bass is the absence of all that excess 80 Hz goop. It's usually a function of the speakers. I would venture to say that any loose bass is not necessarily the amp's fault here. It has more than enough output transistors, 3 current gain stages, cascode VAS, and more filtering than they put in the QSCs and Crowns. At low frequency, the feedback factor is probably already to the point of diminishing returns. The only way the amp would be at fault is if they really did something wrong in the build or layout. That has more to do with it than you might think, and none of that is obvious from a schematic.
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Old 20th September 2008, 03:52 AM   #9
wg_ski is offline wg_ski  United States
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Personally, I would have used a darlington (C5200+predriver) in the driver stage of the high side banks. I did this with my S-Leach/class G experiment. I liked the SQ of the original class AB version better for driving top cabs, but for bass there isn't much difference going class G (other than how hot the amp and extension cord feeding it get). The MJE15033/032 pair will get pretty toasty like it is, and it won't handle 2 ohm loads as well as it should. But that will only affect behavior near clipping, and wouldn't be any worse than what the QSCs do.
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Old 20th September 2008, 04:59 AM   #10
mhtplsh is offline mhtplsh  India
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I got suggestion to hv 40~50 hz cutoff. If ok, then how to do this in the schematics or add another HP filter board? ?
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