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Old 18th January 2021, 02:12 PM   #1061
bobo le chat is offline bobo le chat  France
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No photo, card and power still on a board and not in a box before the next cards.
It is much more comfortable for modifications.

JLester
For the deletions of the ca3.6 and cb3.6 white Led version, am I correct?

ca3ca6cb3cb6.pdf

Roger
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Old 18th January 2021, 02:57 PM   #1062
JLesterP is offline JLesterP  Philippines
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Amplifier Modules and PCBs For Sale
Quote:
Originally Posted by stef1777 View Post
Bobo, do you have a picture?
Quote:
Originally Posted by bobo le chat View Post
No photo, card and power still on a board and not in a box before the next cards.
It is much more comfortable for modifications.

JLester
For the deletions of the ca3.6 and cb3.6 white Led version, am I correct?

Attachment 912983

Roger
Deletion of ca3.6 and cb3.6 is for Versions V1, V1A, V1B.

I'm using V1B and got shocking result (but you guys are not lol), so I think you also need to replace RA7 and RA8 to 2.2 ohms since it is default on V1A and V1B.

Regards,
Lester
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Old 18th January 2021, 03:14 PM   #1063
bobo le chat is offline bobo le chat  France
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Is it the capacitors with a red dot on my pdf?
Thanks
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Old 18th January 2021, 03:28 PM   #1064
JLesterP is offline JLesterP  Philippines
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Originally Posted by bobo le chat View Post
Is it the capacitors with a red dot on my pdf?
Thanks
Yes, correct
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Old 18th January 2021, 04:49 PM   #1065
commstech is offline commstech  Singapore
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Quote:
Originally Posted by JLesterP View Post
Deletion of ca3.6 and cb3.6 is for Versions V1, V1A, V1B.

I'm using V1B and got shocking result (but you guys are not lol), so I think you also need to replace RA7 and RA8 to 2.2 ohms since it is default on V1A and V1B.

Regards,
Lester
what is the purpose of reducing this resistance value? can i just short it out?
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Old 18th January 2021, 05:00 PM   #1066
JLesterP is offline JLesterP  Philippines
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Quote:
Originally Posted by commstech View Post
what is the purpose of reducing this resistance value? can i just short it out?
Using RA7/RA8 helps with stability (although the amp is still stable if we short them). Since we are using PFFB and have removed C_Op feedback caps, shorting out RA7, RA8 might make the amp unstable in some conditions (we have different setups so it's risky to recommend shorting them).

We are reducing the value to get optimum sound without compromising stability.

Add (or delete) resistors in series with opamp's power supply rails
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Old 19th January 2021, 05:39 PM   #1067
bobo le chat is offline bobo le chat  France
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Originally Posted by JLesterP View Post
My hunch is correct that the sound is being limited by the opamp feedback caps. Might be the group delay between the opamps are different.

In slaa788A, they increased it for stability from 22pF to 330pF (corner freq is ~48kHz in PFFB).

I think as long as the module is stable, the value can be decreased. In my module, the whole amp is stable even when the opamp feedback caps were removed (using LME49860).

-----------------------
Further upgrade is matching the resistors of SE to Diff buffer, as well as PFFB resistors. It will lower down the distortion further.
Hello
Aop input / output with 330pF 10kHz
Best regards
Roger
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File Type: jpg in-out-aop-10kHz-330pF.jpg (51.4 KB, 29 views)
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