Anyone know how to bridge the old school 1992 US Amps high current?

o. l. t. · 06:17 PM

I have an old 1992 model US Amps 50HCA and the neg wires are both at zero ohms between them leaving only the two positives.

This is confusing me.

L+ R+ = OPEN
L+ R- = OPEN
R+ R- = OPEN
L- R- = CLOSED ZERO

bob91343 · 4th June 2010, 06:50 PM

You can't bridge the output without inverting one input. Once you do that, you connect the load between R+ and L+ and leave the other connections open.

o. l. t. · 4th June 2010, 07:43 PM

You gotta be kidding.... I have to figure out a way to flip ONE rca polarity? I never remembered it being so much trouble back in 94 when I had this amp, but I don't remember much anyway..........

Perry Babin · 4th June 2010, 08:08 PM

Are you sure that the two shorted wires are the negative wires?

bob91343 · 4th June 2010, 09:50 PM

Well they aren't negative exactly; they are common, or returns. Yes they are tied together and are not part of the bridged circuit.

You do need to invert one signal; some amplifiers may have a switch for that. I did this with a guitar amplifier I made from an old stereo amplifier - I added an IC to invert one signal. Works great.

Perry Babin · 4th June 2010, 10:19 PM

Unless they're marked as the negative speaker wires, one may actually a positive speaker wire. For bridged amps, there are two common wires. One is used as a positive speaker wire and the other is used as a negative speaker wire. The two 'live' wires (one positive and one negative) are used for bridging.

o. l. t. · 5th June 2010, 01:00 AM

clearly marked on these old US Amps

US Amps 50HCA - Amp Guts

o. l. t. · 5th June 2010, 02:18 AM

The two + did not produce sound. Even with one inverted.

amc32 · 5th June 2010, 08:34 AM

These amps were designed by Rodney and Dirk. Inputs are inverted and should be able to bridge. They are a few that I have seen that were modded from the factory for competition. Does your amp have a 4 gang dip switch in the audio section or small headphone "like" jack mounted near the rca's?

amc32 · 5th June 2010, 08:44 AM

Even the older models that came before this version "KA50HC" were able to be bridge. Use a meter find the two speaker wires that are common,then use the tow wires that are remaining to connect to your speakers. This amp came wired using esoteric street wires for speaker wires,so you bridged output will be from a pair of wires. One will be round and the other one will be square in shape.

Hope this helps

4th June 2010, 06:13 PM	#1
o. l. t. diyAudio Member Join Date: Dec 2009	Anyone know how to bridge the old school 1992 US Amps high current? I have an old 1992 model US Amps 50HCA and the neg wires are both at zero ohms between them leaving only the two positives. This is confusing me. L+ R+ = OPEN L+ R- = OPEN R+ R- = OPEN L- R- = CLOSED ZERO Last edited by o. l. t.; 4th June 2010 at 06:17 PM.

4th June 2010, 08:08 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Are you sure that the two shorted wires are the negative wires? __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

4th June 2010, 10:19 PM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Unless they're marked as the negative speaker wires, one may actually a positive speaker wire. For bridged amps, there are two common wires. One is used as a positive speaker wire and the other is used as a negative speaker wire. The two 'live' wires (one positive and one negative) are used for bridging. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

5th June 2010, 08:34 AM	#9
amc32 diyAudio Member Join Date: Mar 2008	These amps were designed by Rodney and Dirk. Inputs are inverted and should be able to bridge. They are a few that I have seen that were modded from the factory for competition. Does your amp have a 4 gang dip switch in the audio section or small headphone "like" jack mounted near the rca's? __________________ ...............I Hear in color.................

5th June 2010, 08:44 AM	#10
amc32 diyAudio Member Join Date: Mar 2008	Even the older models that came before this version "KA50HC" were able to be bridge. Use a meter find the two speaker wires that are common,then use the tow wires that are remaining to connect to your speakers. This amp came wired using esoteric street wires for speaker wires,so you bridged output will be from a pair of wires. One will be round and the other one will be square in shape. Hope this helps __________________ ...............I Hear in color.................


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4th June 2010, 06:50 PM	#2
bob91343 diyAudio Member Join Date: Mar 2010	You can't bridge the output without inverting one input. Once you do that, you connect the load between R+ and L+ and leave the other connections open.

4th June 2010, 07:43 PM	#3
o. l. t. diyAudio Member Join Date: Dec 2009	You gotta be kidding.... I have to figure out a way to flip ONE rca polarity? I never remembered it being so much trouble back in 94 when I had this amp, but I don't remember much anyway..........

4th June 2010, 09:50 PM	#5
bob91343 diyAudio Member Join Date: Mar 2010	Well they aren't negative exactly; they are common, or returns. Yes they are tied together and are not part of the bridged circuit. You do need to invert one signal; some amplifiers may have a switch for that. I did this with a guitar amplifier I made from an old stereo amplifier - I added an IC to invert one signal. Works great.

5th June 2010, 01:00 AM	#7
o. l. t. diyAudio Member Join Date: Dec 2009	clearly marked on these old US Amps US Amps 50HCA - Amp Guts

5th June 2010, 02:18 AM	#8
o. l. t. diyAudio Member Join Date: Dec 2009	The two + did not produce sound. Even with one inverted.

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