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Old 17th February 2003, 07:00 AM   #1
sangram is offline sangram  India
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Default Bridging inverted clone: Help! Keui?

Hi

I'm in the process of building a small amp for my computer speakers.

My question is: Is it possible to use inverted clones and bridge them in the conventional single-resistor bridging, or do I *have* to use opamps to split phase?

If I do use single resistor, my plan is:

Single resistor (=Rnfb) from output of one amp, to -ve input of the other. All other configurations remaining same, only -ve input of slave grounded. Do I use a cap or will a DC short do? I thought maybe a cap (~100 uF?) , But checking that anyways...

Will this configuration result in any danger for the amps?

BTW I'm using TDA 2030, this is also an experiment in frugality, not a final project. I plan to roll this out using TDA 7294 if this piece works...

Also I have separate supplies for the L/R channels and am planning on completely separated amp blocks - even the preamp and tone controls will have independent supplies for the two halves. I unfortunately have only one 12-0-12 VAC transformer, but I'll live with that... This is also a reason I do not want to go near an opamp.
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Old 17th February 2003, 08:28 AM   #2
Hamish is offline Hamish  Australia
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try this:
Bridgeclone
you get the bonus of running it balanced.
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Old 17th February 2003, 04:23 PM   #3
sangram is offline sangram  India
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Thanks.

DRV 134 not available in any store around here. There is TL074, which I can use, with a little more hassle - which I don't wanna take.

Or one resistor. Which I've succesfully used for non-inverting opamps, no problems.

Can I use the same the method for inverting opamps?
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Old 17th February 2003, 04:25 PM   #4
sangram is offline sangram  India
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BTW, how moronic can one be? I ask Kuei for help and I spell it Keui...

Sorry Mr. Kuei Yang Wang. Last time.
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Old 17th February 2003, 04:52 PM   #5
Hamish is offline Hamish  Australia
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maybe consider the sample program.

but you didn't hear it from me.........
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Old 17th February 2003, 05:15 PM   #6
Previously: Kuei Yang Wang
 
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Default Re: Bridging inverted clone: Help! Keui?

Hi,

Quote:

I'm in the process of building a small amp for my computer speakers.

My question is: Is it possible to use inverted clones and bridge them in the conventional single-resistor bridging, or do I *have* to use opamps to split phase?
Yes, it will do fine if sonic quality is of little concern.

Actually, if you bridge the thing you could get some of the single rail Chips intended for car radios. They are usually internally bridged, have low dropout voltages and can drive very low impedances and are just fine for a cheapskating PC Speaker Amp.

Using 2030 with voltages that low wastes a lot of power in the dropout voltagesof the output Transistors etc. Of course, if you want to use existing stuff.....

Sayonara
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Old 18th February 2003, 04:46 AM   #7
sangram is offline sangram  India
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Default Re: Re: Bridging inverted clone: Help! Keui?

Quote:
Originally posted by Kuei Yang Wang

Yes, it will do fine if sonic quality is of little concern.
Actually, I figured that the loss in sonic quality would be less than the loss if I was using a couple of opamps to split the signal, seeing that TL074/NE5534 are the only options around here. Also the bridge channel would be only driving a subwoofer. The fronts would still be driven by inverted standalone clones.

I will examine both options however, since you say there will be significant loss, I will have to try out opamps Vs. Resistors...

Quote:

Using 2030 with voltages that low wastes a lot of power in the dropout voltages of the output Transistors etc. Of course, if you want to use existing stuff.....
Could not understand, sorry. Do you mean the voltage should be higher?

I am using +/- 18 VDC (12-0-12VAC - should be around 16 VDC but actually gives a little higher voltage). Being a third world country the voltage at night creeps up to 21 volts per rail - just below the absolute max specified for the 2030..

That is slightly above the specified operating voltage for the chip, so there is some heat. I have also tried running the chip at +- 14 volts also, but no improvement/relaxation in the sound.

I do not like any of the single-rail car radio chips. The 2030 sounds much better than all of them - the closest is TDA2005. Not pleasant. The TDA 2009 is however a good option, decently specced, about 18 W RMS in bridge with 24 VDC rail, and pin-compatible with the TDA 2005 except for two pins, which is not a problem... But I still like the sound of the 2030 better...
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Old 18th February 2003, 06:57 AM   #8
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Quote:
Originally posted by sangram
Thanks.

DRV 134 not available in any store around here. There is TL074, which I can use, with a little more hassle - which I don't wanna take.

Or one resistor. Which I've succesfully used for non-inverting opamps, no problems.

Can I use the same the method for inverting opamps?
If by "one resistor method" you mean the method suggested by Rod Elliot on his site, that might not be good enough if you want good quality.

The proper way for bridging is using some way to send one signal in phase and another out of phase to separate power amps.

You can do a "balancing act" using a TLO74, implementing two chips per side for a balanced output.

Or you can try a transformer, which might be more available where you are.


Carlos
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Old 18th February 2003, 09:14 AM   #9
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Default Re: Re: Re: Bridging inverted clone: Help! Keui?

Hi,

Quote:

Actually, I figured that the loss in sonic quality would be less than the loss if I was using a couple of opamps to split the signal, seeing that TL074/NE5534 are the only options around here.
Sorry, but even the ones you mention probably make a fine phase inverter, better than re-amplifying the distortion of the other Amp, except of course....

Quote:

Also the bridge channel would be only driving a subwoofer.
In that case it will likely be "good enough". Just don't forget the resistor to ground from the negative input.

You may wish to consider using paralle/bridged TDA2030, as they do not have much dissipation.

Quote:

Could not understand, sorry. Do you mean the voltage should be higher?

I am using +/- 18 VDC (12-0-12VAC - should be around 16 VDC but actually gives a little higher voltage).
I read you message as meaning +/-12V....

Sayonara
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Old 19th February 2003, 04:22 AM   #10
sangram is offline sangram  India
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Default Re: Re: Re: Re: Bridging inverted clone: Help! Keui?

Quote:
Originally posted by Kuei Yang Wang
Hi,

Sorry, but even the ones you mention probably make a fine phase inverter, better than re-amplifying the distortion of the other Amp, except of course....
Thanks. Now I get why this form of bridging is not such a great idea in the first place. Never understood the reason why. Will give it a go.

Quote:
In that case it will likely be "good enough". Just don't forget the resistor to ground from the negative input.
Already done, Ive used a 100 uF/50V to ground the resistor, not sure if it can be grounded without the capacitor. Not willing to try, maybe I get high DC offset and ruin my speakers? I'm doing all my testing into live speakers.

Quote:
You may wish to consider using parallel/bridged TDA2030, as they do not have much dissipation.

I read you message as meaning +/-12V....

Sayonara


I do not have enough power to run more than 4 ICs, then also I'm stretching it a bit. Maybe 3 is better, as the transformer is only about 70 VA.

Thanks a lot for all your input.

Sayonara
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