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Old 5th August 2009, 10:15 PM   #1
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Default velleman K8060

i have two velleman k8060's i was wandeing if i can bridge them??

if so how is it done?:S

i need help! :s

many thanks harry
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Old 6th August 2009, 12:07 AM   #2
Minion is offline Minion  Canada
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In theory it is possible but in Practice it might be quite difficult ....

I believe First you would need a Ballanced line driver as one amp would drive the Negitive part of the audio signal and the other amp would drive the positive and a Ballanced line driver will create a seperate negitive and a positive audio signal...

You can also use a Audio transformer to create a ballanced output for each amp ...

also each amp would have to have extremely closely matched components ( like resistors matched to 0.1% and closely matched transistors) because each amp has to have the same gain .....


Good luck
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Old 6th August 2009, 12:08 AM   #3
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You will need a phase splitter circuit to apply 2 signals 180 degrees out of phase with each other.
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Old 6th August 2009, 06:53 PM   #4
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im a bit new to this so could please explain this in real basics:S sorry x
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Old 6th August 2009, 07:18 PM   #5
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You just need a single op amp, configured as an inverter, driving one of the two amp modules. In the image below both resistors should be 10K.

You also need +/- 9 volts to +/- 15 volts to power the opamp. This is much less than the supply rails for the power amp modules. It can be obtained with dropping resistors and zener regulation or from a different power supply. You need bypass caps on the opamp power supply pins.

I'd use something like an LM833 or NE5532. Connect the unused opamp output to it's negative input and leave the positive input floating.

The only other trick is to get the grounding correct. Generally the positive input of the opamp needs to go to the quiet input ground of the module it feeds and/or the star ground point.

The speaker will then connect between the two positive outputs of the amp modules. I wouldn't suggest using anything less than an 8 ohm speaker as bridging makes it look like half the impedance. So with a 4 ohm speaker the amps would see a 2 ohm load and be very unhappy each having only a single pair of output transistors.

If the above is still too confusing, you might need to do some reading on basic op amp circuits, zener regulators, power supply design, good grounding practices, etc. Unfortunately I don't know of any ready-made boards/modules that will cleanly invert a signal, solve the power supply problem, etc.
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Old 6th August 2009, 08:19 PM   #6
jaycee is offline jaycee  United Kingdom
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To be honest, dont do it. The velleman amps only have a single pair of darlingtons as their output. Running them in bridge is just likely to toast them.
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Old 7th August 2009, 12:41 AM   #7
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Quote:
Originally posted by Minion
In theory it is possible but in Practice it might be quite difficult ....

I believe First you would need a Ballanced line driver as one amp would drive the Negitive part of the audio signal and the other amp would drive the positive and a Ballanced line driver will create a seperate negitive and a positive audio signal...

You can also use a Audio transformer to create a ballanced output for each amp ...

also each amp would have to have extremely closely matched components ( like resistors matched to 0.1% and closely matched transistors) because each amp has to have the same gain .....

Quote:
Originally posted by nigelwright7557
You will need a phase splitter circuit to apply 2 signals 180 degrees out of phase with each other.

Quote:
Originally posted by jaycee
To be honest, dont do it. The velleman amps only have a single pair of darlingtons as their output. Running them in bridge is just likely to toast them.
Yeah, to the last point above, depending on how aggressive the SOA protection is (if there is any?) in the amp modules, and how well heatsinked they are, their life may be shorter if bridged--especially if the amp is going to be used hard.

Relative to the two other posts, I was just trying to point out it's not really all that difficult in practice. You don't need any transformers, fancy phase splitters, 0.1% components, or "balanced line drivers". Lots of well respected amps offer bridging and use exactly one op-amp to do it.
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Old 7th August 2009, 02:31 PM   #8
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its obviously not jst a case of linking a few cables together i think i need to talk to someone and show them my setup:S

thanks anyway folks
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