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Old 10th June 2012, 08:57 AM   #91
AndrewT is offline AndrewT  Scotland
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Look at the datasheet and see the problem.
Then decide what you as the designer can do to help the chipamp perform well.
If that means using a lower voltage to keep the chip cooler and using a lower voltage to reduce the current that will be demanded and using high efficiency speakers to reduce the current demand, then you can get good performance from chipamps.

Look at Peter Daniels results. He uses ~95dB/W 4ohm speaker. So it can be done, but you must inform yourself and then design for the chipamp limitations.

For me, the easy way is keep the chipamp cool and use 8ohms or higher speakers.
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Old 10th June 2012, 09:56 AM   #92
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Quote:
Originally Posted by SoIL4x4 View Post
I used a 22v transformer for my lm4780 build as recommended with the intention of using it with a 6ohm pair of speakers and a 4ohm pair. It seems to me Andrew is saying that these chips cannot be used with 4ohm speakers no matter what amount of voltage is applied.

P.s. I am listening to my lm4780 with 4ohm klipsch kg4s right now and it sounds delightful. Some more discussion or explanation of this topic would be appreciated.
Surely, if your power requirement is not too demanding, there is no reason why you cannot use the 4780 with 4R speakers.

Or if you need more power, use 2 in bridge or parallel mode.

I am intending to use 2 pairs of them driven differentially from the output of my dual differential tda1541a dac's Sowter I/V transformers. (This also removes any DAC output offsets.)

There are twin secondaries which will provide anti phase outputs so both amps are connected in non inverting mode with the speaker connected in bridge configuration.

For volume control I intend varying the gain - I always seem to listen with the volume control on my current setup rarely being adjusted, so the transformer secondaries will be directly coupled to the inputs, probably with a load resistor across them.

Ian
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Old 10th June 2012, 10:43 AM   #93
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by batteryman View Post
..............For volume control I intend varying the gain............
this changes the gain and phase margins.
That will change the output signal (it won't mimic the input signal) and could result in instability, or worse, oscillation.
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Old 10th June 2012, 12:17 PM   #94
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Originally Posted by AndrewT View Post
this changes the gain and phase margins.
That will change the output signal (it won't mimic the input signal) and could result in instability, or worse, oscillation.
You missed by point about only varying the gain a relatively small amount - far less than a conventional pot on the input would. The adjustment is more to cater for variations between CDs.

If I decide I need more volume adjustment then I'd use:-

SOWTER ATTENUATOR TRANSFORMERS TVC VOLUME CONTROL

I
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Old 11th June 2012, 04:56 PM   #95
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how about this amp when compared to LM3886 Amplifier Kit | Chipamp.com
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Old 11th June 2012, 07:06 PM   #96
wazzy is offline wazzy  Zimbabwe
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At the moment I have been using LM3886TF for more than two years, it has a 300va with 22 volt secondaries and 20000uF per rail, plenty loud for me and I'm playing through 88db/w 4ohm studio monitors.
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Old 12th June 2012, 01:46 PM   #97
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This apexaudio is not replying anything
whether the amp in this thread is working or not?
if its working can be used for Hi-Fi???
Is the circuit used in this PCB is same as in the Datasheet of LM3886? if not there would be any loss of quality of sound,power,frequency range etc

Last edited by charlestpt; 12th June 2012 at 01:50 PM.
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Old 12th June 2012, 03:03 PM   #98
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Quote:
Originally Posted by charlestpt View Post
This apexaudio is not replying anything
whether the amp in this thread is working or not?
if its working can be used for Hi-Fi???
Is the circuit used in this PCB is same as in the Datasheet of LM3886? if not there would be any loss of quality of sound,power,frequency range etc
post #57...
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Old 12th June 2012, 03:29 PM   #99
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Quote:
Originally Posted by apexaudio View Post
post #57...
Is the circuit used in this PCB is same as in the Datasheet of LM3886? if not there would be any loss of quality of sound,power,frequency range etc

can i use this speakers for home on this amplifier
http://www.indiajbl.com/CarAudioDesc.aspx?ID=110

Last edited by charlestpt; 12th June 2012 at 03:31 PM.
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Old 12th June 2012, 04:17 PM   #100
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Quote:
Originally Posted by charlestpt View Post
Is the circuit used in this PCB is same as in the Datasheet of LM3886? if not there would be any loss of quality of sound,power,frequency range etc

can i use this speakers for home on this amplifier
JBL GT6-S266
The pcb layout is not critical for audio circuits so there won't be any loss of quality if the schematic is not the same as the datasheet.

You might consider using two LM4780 dual chipamps which can be run with the amps paralleled for more current for 4ohm speakers.

Car speakers are designed for use in a small volume and will not be very good for home use unless your listening room is very small. You will also have to design a cabinet for them using the Thiele Small parameters which are not shown.
In a vehicle, you are actually sitting inside the louspeaker cabinet and it is the pressure changes that transmit much of the sound. (which is why you feel the bass in a car more than you do in your listening room).

Last edited by batteryman; 12th June 2012 at 04:21 PM.
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