hifonics viii bridged mono? rca q...

marko · 27th February 2009, 03:39 PM

i want to run a hifonics viii in bridged mono but need to know if i can just use either left or right input on the rca's. ideally i want to use just one input as i'm running a velodyne off it and they are very picky with rca's! the amp is a boltar and i'm currently running it off just one channel.

now when i test the amp on the bench with just a single rca the output didn't change wether bridged or left or right output...

also does anyone know where the subsonic filter cap is in a series viii amp? i need the amp to play down to below 5hz for the sub to calibrate correctly.

Perry Babin · 27th February 2009, 04:23 PM

With only one channel driven, the output will be the same as if it's driven off of only one channel.

If you drive only one channel with the amp bridged, you're likely to blow the channel with no signal.

Drive the amp with a 5Hz signal and follow it through the amp. If you get significant attenuation as it passes through a coupling capacitor, increase the value of that capacitor. Also check signal at the bypass capacitor in the feedback/gain circuit of the power amplifier. If you see increasing signal on that capacitor (the side that's NOT connected to signal ground) at the lowest frequencies, it needs to be larger also.

marko · 27th February 2009, 04:40 PM

so they're not like the old pg amps, i ran an ms2250 bridged using just the left rca input... maybe i should just use my old pg amps again!

i never had a problem with the pg amps and they turned on ok with the dd10 as well (other thread!). i just fancied running these old amps as you don't see them much these days, everyone runs genesis or dls so an install full of old school hifonics would of been cool

Perry Babin · 27th February 2009, 04:44 PM

I'm not sure how PG feeds both channels but many amps that can use only one input have switches built into the jacks. When no RCA connector is plugged in, two contacts short and the signal from the other channel is fed to the the channel with no plug.

marko · 27th February 2009, 05:10 PM

would be a shame to pull these sweet amps out after all the wiring i've done and getting them in there... i tried to run a velodyne off of one channel of the colossus but with no luck so i tried a boltar and that calibrated ok but off 1 channel only so not a lot of power on tap...

27th February 2009, 03:39 PM	#1
marko diyAudio Member Join Date: May 2004 Location: donnyuk	hifonics viii bridged mono? rca q... i want to run a hifonics viii in bridged mono but need to know if i can just use either left or right input on the rca's. ideally i want to use just one input as i'm running a velodyne off it and they are very picky with rca's! the amp is a boltar and i'm currently running it off just one channel. now when i test the amp on the bench with just a single rca the output didn't change wether bridged or left or right output... also does anyone know where the subsonic filter cap is in a series viii amp? i need the amp to play down to below 5hz for the sub to calibrate correctly.

27th February 2009, 04:23 PM	#2
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	With only one channel driven, the output will be the same as if it's driven off of only one channel. If you drive only one channel with the amp bridged, you're likely to blow the channel with no signal. Drive the amp with a 5Hz signal and follow it through the amp. If you get significant attenuation as it passes through a coupling capacitor, increase the value of that capacitor. Also check signal at the bypass capacitor in the feedback/gain circuit of the power amplifier. If you see increasing signal on that capacitor (the side that's NOT connected to signal ground) at the lowest frequencies, it needs to be larger also. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

27th February 2009, 04:44 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	I'm not sure how PG feeds both channels but many amps that can use only one input have switches built into the jacks. When no RCA connector is plugged in, two contacts short and the signal from the other channel is fed to the the channel with no plug. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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27th February 2009, 04:40 PM	#3
marko diyAudio Member Join Date: May 2004 Location: donnyuk	so they're not like the old pg amps, i ran an ms2250 bridged using just the left rca input... maybe i should just use my old pg amps again! i never had a problem with the pg amps and they turned on ok with the dd10 as well (other thread!). i just fancied running these old amps as you don't see them much these days, everyone runs genesis or dls so an install full of old school hifonics would of been cool

27th February 2009, 05:10 PM	#5
marko diyAudio Member Join Date: May 2004 Location: donnyuk	would be a shame to pull these sweet amps out after all the wiring i've done and getting them in there... i tried to run a velodyne off of one channel of the colossus but with no luck so i tried a boltar and that calibrated ok but off 1 channel only so not a lot of power on tap...

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