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Old 23rd May 2013, 06:34 AM   #21
Alfonz is offline Alfonz  Bulgaria
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Try another circuit! This is a good guide to p2p wiring(for example) or just try another working circuit from website.

And don't forget to post pictures of your progress!
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Old 23rd May 2013, 07:31 AM   #22
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No, do NOT build that Mick Feuerbacher thing! That is a prime example of an amp that is incomplete and prone to problems that could lead to much dissapointment, like ruined speakers. I always recommend reading and following the details in the data sheet paying close attention to the components on the schematic listed as "optional", they are not optional, except for very specific cases where it is known for sure how the amp will be used, otherwise all of those components should be included so the amp will be stable under all conditions.

Mike
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Old 23rd May 2013, 10:26 AM   #23
AndrewT is offline AndrewT  Scotland
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check your +ve supply voltage to Centre tap and -ve supply voltage to centre tap and -ve to +ve voltage.
check the voltage on pin 8 to centre tap.

Add a Zin resistor to allow the input offset current a route to escape. Otherwise you will cripple the opamp/chipamp if the input is DC blocked.
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Old 23rd May 2013, 08:45 PM   #24
Alfonz is offline Alfonz  Bulgaria
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Excuse me for posting that project Michael. Never tried it, but I've met some good feedback.
As for me I wouldn't try the author's circuit. May be a Zobel network will help.
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Old 24th May 2013, 04:40 AM   #25
sangram is online now sangram  India
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Quote:
Originally Posted by AndrewT View Post
Add a Zin resistor to allow the input offset current a route to escape. Otherwise you will cripple the opamp/chipamp if the input is DC blocked.
Quote:
Originally Posted by overall feedback View Post
...try with resistor to gnd and another source.
Quote:
Originally Posted by Michael Bean View Post
Once again, does the non-inverting (+)input have a dc-ground referance connection somehow? If there isn't a DC path for the input bias currents to follow, no, it won't work.
Quote:
Originally Posted by volume knob View Post
You need a resistor from pin 10 (Vin+) to ground
This is why we want pictures, could have avoided all the nonsense over PM.

What is the DC reading on the output?
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Old 24th May 2013, 09:44 AM   #26
AndrewT is offline AndrewT  Scotland
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San,
there are pics in posts 11 & 13.
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Old 30th May 2013, 10:01 AM   #27
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Quote:
Originally Posted by Michael Bean View Post
Once again, does the non-inverting (+)input have a dc-ground referance connection somehow? If there isn't a DC path for the input bias currents to follow, no, it won't work.

Mike
so are u saying if i feed input directly from headphone jack to pin 10, it wont work and i have to attach 1k series with 20k parallel to gnd for reference?

(...bcoz lately, i ve skipped 1k on input+).
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Old 30th May 2013, 10:06 AM   #28
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Quote:
Originally Posted by sangram View Post
What is the DC reading on the output?
18.1-0-18.6v dc, when not connected to ic.
and when connected, it drops around 0.6v on both rails.
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Old 30th May 2013, 01:07 PM   #29
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Quote:
so are u saying if i feed input directly from headphone jack to pin 10, it wont work and i have to attach 1k series with 20k parallel to gnd for reference?
Yes, most (might as well assume all) opamp inputs (both the inverting and non-inverting) need a DC path to a low resistance node. A signal source may or may not provide that path for you, so you should include one yourself to be sure. The 1k resistor in series with the non-inverting input is usually there to limit current for reducing the turn-on and turn-off thumps and noises, so isn't really necessary for proper operation.

Mike
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Old 30th May 2013, 02:50 PM   #30
sangram is online now sangram  India
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Quote:
Originally Posted by AndrewT View Post
San,
there are pics in posts 11 & 13.
Sorry, should have been clearer - the OP has been on PMs with me for a month now and has stubbornly refused to every request to provide pictures and a schematic, even after me saying that it was not possible to remotely troubleshoot without a schematic.

It was once we saw the pics that things became clear to me

It wasn't possible to help him at one point without seeing this, and when I told him to open a thread, he assumed it was because I was being difficult, and even messaged me something about the tone. I chose to ignore that. I can't help those who will not help me help them :S

Last edited by sangram; 30th May 2013 at 02:55 PM.
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