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Chip Amps Amplifiers based on integrated circuits

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Old 27th July 2011, 01:06 PM   #11
Elvee is offline Elvee  Belgium
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Here is the updated circuit, including the stabilization components.

The top channel (R) has a power bandwidth of 40KHz, and the bottom one (L) only 20KHz.
Output power is 7W/ch.
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Old 27th July 2011, 01:10 PM   #12
AndrewT is offline AndrewT  Scotland
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C5 & C7 don't have a matching component in the other channel.
Could that go part way to explain the different performance?

The inverting amp is quite different from the non-inverting amp. Could that be another reason?
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Old 27th July 2011, 01:40 PM   #13
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This is cool!
I always wondered for years if this might work.
But never took the time to investegate it.
Have you tried a BTL configuration?
It looks like it may be very easy to do.

jer

Last edited by geraldfryjr; 27th July 2011 at 01:53 PM.
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Old 27th July 2011, 02:38 PM   #14
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by AndrewT View Post
C5 & C7 don't have a matching component in the other channel.
Could that go part way to explain the different performance?
It could


Quote:
The inverting amp is quite different from the non-inverting amp. Could that be another reason?
That's a possibility too.
There are other possible reasons:
-Difference of performance/behavior between the 317 and 337
-Middle regulator is a 317

I didn't investigate in details, and it is also probable that the compensations are suboptimal: I simply looked for stability, and did no tweaking for improved performance.

Quote:
Have you tried a BTL configuration?
It looks like it may be very easy to do.
No I didn't try that, but it would certainly work: basically, it's just two amps put side by side with some "electronic glue".
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Old 27th July 2011, 04:51 PM   #15
AndrewT is offline AndrewT  Scotland
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Default How does this amplifier work

Quote:
Now, the L-R correlation is used to modulate the current source, with L and R having opposite polarities (the loads must also have their polarities reversed).
Does the operation of this amplifier depend on the two channels being substantially in phase?
Stereo operation roughly meets that criterion.
Neither bridging nor out of phase operation meet it.
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Old 27th July 2011, 05:37 PM   #16
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by AndrewT View Post
Does the operation of this amplifier depend on the two channels being substantially in phase?
Stereo operation roughly meets that criterion.
Neither bridging nor out of phase operation meet it.
I just realized that in fact, this version has no advantage in terms of dissipation, regarding the correlation.
There is however an advantage for the BOM.

The previous version really had a reduced dissipation for a given output power, thanks to the correlation: the output power with totally uncorrelated signals would have been halved.

Quote:
Neither bridging nor out of phase operation meet it.
If you bridge it in stereo, it is possible, see figure below for the general scheme.
Additionally, for this version, it would be possible to make the bridging "vertically".

Here are some pics of the latest prototype.

I'll try to make more detailed measurements later.
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File Type: gif ChipBTL.gif (4.7 KB, 415 views)
File Type: jpg 104_4952.JPG (310.9 KB, 411 views)
File Type: jpg 104_4953.jpg (440.5 KB, 327 views)
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Old 27th July 2011, 09:58 PM   #17
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You guys are, wow, unbelievable !!!!

It NEVER came to my mind, a single second, using LM317 regulators as finals in an audio amplifier !!!!

Congratulations ! I like this site !!! I'm new here... (i'm more an RF and PIC guy than audio, but my interest in 20-20k is definitely rising.... my interest in LM3886 gainclones made me joining this, very interesting, site.).

I seriously think that i will learn a lot on audio here !!!!

Thank you !
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Old 29th July 2011, 02:53 PM   #18
Elvee is offline Elvee  Belgium
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Here is the circuit working in BTL.

As can be seen, no extra component is required, and it can work in mono.

As I said earlier, this amplifier doesn't do what I had in mind: I had hoped this one would be the Thevenin counterpart of the previous Norton one.

The nice thing about this circuit is its active current load, common to the two channels..

It could even be used by itself to boost a SE amplifier: the amplifier would remains SE (sort of), but with the assistance of the active load.
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Old 30th July 2011, 07:11 PM   #19
Elvee is offline Elvee  Belgium
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One more thing to say about those amplifiers: they are extremely easy to implement and live with:

Unlike many other class A amps, they tolerate ripple on the power supply, and they are thermally protected thanks to the voltage regulators: if the heatsink is too small, they simply shut down, without fuss or further problems (it happened to me more than once).

And despite their modest output power and performances, they are nevertheless real class A amplifiers, and deliver surprisingly good quality with very small means.

For this reason, they are ideally suited as class A introductory projects: they are on par with any chip-amp for simplicity, but with that little special thing brought by class A and SE.
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Old 9th August 2011, 04:46 AM   #20
Junm is offline Junm  Philippines
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Are +/-12,15,24v fixed regulators can also be used here or are they possible to use?
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