Alto mac 2.3 hipass filter issue |
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Tonskulus
Registered User Joined: 15 September 2017 Location: Finland Status: Offline Points: 425 |
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Posted: 10 October 2017 at 7:20pm |
This thing is weird. In stereomode, hipass 30hz (switchable) is working properly, cutting down the low freqs for both channels. But if i switch this amp to a bridge mode, something weird is happening: hipass filter makes bass boost for ch2, ch1 stays unaffected. I noticed that while watching signal leds, ch2 channel blinks more than ch1. So I tested speaker for both channels and noticed that indeed there is much more bass in ch2.
As far as I know, both channels should give exactly the same signal in bridge mode (only polarity should be changed for another channel and this part is working properly).
What is that? :D |
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njw
Old Croc Joined: 26 March 2010 Location: S. Wales Status: Offline Points: 2572 |
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I have noticed that the signal leds do weird things on my 2.4's when in bridge mode and hi pass filter enabled, I've never actually tried connecting a speaker to each channel when in bridge to see what's going on, I just leave the hi pass switched off as the amps are always ran off an lms anyway.
I would also be quite interested to know what's going on here...
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valve head777
Old Croc Joined: 27 July 2012 Location: East Sussex Status: Offline Points: 1780 |
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Is it to do.with negative feedback being done differently while in bridge mode? Just a thought....
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Freedom of choice, choice of freedom.
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Tonskulus
Registered User Joined: 15 September 2017 Location: Finland Status: Offline Points: 425 |
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I don't know... should look for schematics to see how did they do that hi-pass..thing, but could not find any. I see this amp is definitely copied from QSC rmx somehow, but the input stage might be different. There is no DIP switch array like in QSC.
Maybe they missed something while copying the input stage, so it is just a bug :D I always test both channels separately @ bridge mode to make sure everything is ok. Edited by Tonskulus - 12 October 2017 at 6:26am |
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njw
Old Croc Joined: 26 March 2010 Location: S. Wales Status: Offline Points: 2572 |
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I know that on the QSC RMX and the Berry EP (RMX copy) that if the dip switches aren't set correctly then some very weird things can occur. I can only assume that Alto (or whoever the oem is!) missed a trick when they 'copied' the circuit but opted to use the three way mode switch rather than the dip switches.
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2515 |
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What does the owners manual say is the correct way to implement bridged operation? Should one or the other filters be disengaged? Should one of the gain controls be zero'd?
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Tonskulus
Registered User Joined: 15 September 2017 Location: Finland Status: Offline Points: 425 |
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From manual "Operate MAC 2 series in Bridged Mode
In this mode, the channel 1 input signal will be output from the bridge output
connectors. ( The 2 RED binding post ) In this case, use the channel 1 volume
control to adjust the volume, keep the volume control of channel 2 turned completely
down ( counter clockwise ). Bridged mode is intended for driving loads with a total
impedance of 4 ohms or greater. In Bridge Mode you will combine the power of both
channels into one speaker. You will have available massive amount of power so check
carefully the power handling of your speaker before operation." And that's how I did.. |
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2515 |
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I suspect the ch2 filter should be disengaged too, if it doesn't mention that in the bridged section maybe it does elsewhere.
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njw
Old Croc Joined: 26 March 2010 Location: S. Wales Status: Offline Points: 2572 |
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There is only one filter switch which operates on both channels....
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Conanski
Old Croc Joined: 26 January 2006 Location: Ottawa, Canada Status: Offline Points: 2515 |
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Ok.. well you didn't mention it yet but what does the bridged output look like?
Edited by Conanski - 17 October 2017 at 10:21pm |
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