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Old 16th March 2012, 09:00 AM   #11
Roushon is offline Roushon  India
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Thanks Andrew for the caution and thanks Kuldeep for
the nice reference.

I tried to make the amp PS as future proof as possible.
Each channel has its own PS. There are two toroidal
transformers. Each has 5Amp per rail and 2 x (0-33v).
There is filtering with enough electrolytic caps (around
14500uF per rail) and then regulated by LM338 to get +-
35v dc (which I can increase but this is optimal I think for
LM3886). So I guess bridge can be driven easily.

Regards
Roushon.
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Old 16th March 2012, 12:24 PM   #12
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Ya... its more than enough power.
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Old 17th March 2012, 03:47 PM   #13
Roushon is offline Roushon  India
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Default Polarity...

I am curious to know how does the polarity of the speaker is respected
in bridge amplifier. I guess inverted amp goes to - and non-inverted amp
to the + of the speaker. Is it correct or any polarity is OK.

Thanks
Roushon
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Old 22nd March 2012, 11:10 AM   #14
Roushon is offline Roushon  India
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Default A (possibly serious) question!

As I look at the application sheet AN-1192 I find that
in parallel of two LM3886 the feedback resistors are 20K,
on the other hand the same is about 47 and 51K in the
bridge of two LM3886. Why is this? My circuit is attached
in the parallel version. I thought I just have to exchange
the Amp input and the output of the AD8620 connection
to one of the LM3886. Do I have to change the feedback
resistors also.

Please let me know.

Thanks
Roushon.
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Old 22nd March 2012, 12:26 PM   #15
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formula to calculate gain differs for inverting and non-inverting input buddy
and polarity of speaker will also not matter in case of bridge. (thought you may have to check polarity if you have sub-woofer or other high powered woofers to match phase of output audio)
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Old 22nd March 2012, 12:38 PM   #16
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The 500R aggregate load on the OPA627 might well result in somewhat higher distortion than necessary. Also did you really intend to have gain > 100 ? If you cut out the T-network 1k resistor it'll be back down to X20 but I'd suggest raising the feedback network impedances by at least a factor of 2 to give the 627 an easier time.
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Old 22nd March 2012, 12:48 PM   #17
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if you use origin and expensive companents you'll hear good quality sound
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Old 22nd March 2012, 02:37 PM   #18
Roushon is offline Roushon  India
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Well, this thread is somewhat continuation of the earlier thread. Forgot to
mention that there is the stepped (10K) attenuator in between OPA627 and
the amp.

Abraxalito, you may (not) remember that that 1K T-network resistor was
suggested in the previous thread to match impedance as I was having
distortion.

Kuldeep, I did not mean why the inverted and non-inverted has different
feedback resistors, rather I wanted to know why the feedback resistors were
less than half value in the parallel case.

Please tell me to get a decent bridge what are the changes I should make
in the above circuit. I am planing to remove the buffer stage around OPA627,
but the stepped attenuator will be there.

Regards
Roushon
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Old 22nd March 2012, 06:10 PM   #19
Puffin is offline Puffin  United Kingdom
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Quote:
Originally Posted by kuldeepsingh View Post
formula to calculate gain differs for inverting and non-inverting input buddy
and polarity of speaker will also not matter in case of bridge. (thought you may have to check polarity if you have sub-woofer or other high powered woofers to match phase of output audio)
Yes.
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Old 24th March 2012, 01:34 PM   #20
Roushon is offline Roushon  India
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Default Answered!

I answered my questions. Lack of my basic knowledge. Just took a
revision....Will upload the final bridge circuit for advice...

Thanks
Roushon
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