Rebuild LM3886

[Philfr]

Hi,
I am rebuilding my LM3886. The goal is this one is to drive bass speakers (H frame with 2 Alpha15a per side, xover 12 db at 180 hz).

I changed toroid for a 300 Va (20 volt), add a safety loop breaker and checked the mounting of course !
I have LM3875 too, and for me it's sound more "warmer" than LM3886.
I do not say that it is the truth for everyone but maybe it depends of speakers, music, and taste.

I found this :
http://www.diyaudio.com/forums/pass-labs/103050-jfet-boz.html
jfet Boz small from Nelson Pass (mess 2). I have SJ74, so maybe I can use it ?

Or do you know another way to make LM3886 a little more "warmer" ?
Phil.

 

[Philfr]

An externally hosted image should be here but it was not working when we last tested it.

Other upgrade, change filtering caps, it's too big, 3x10000 uF per side !
Phil.

 

[abraxalito]

If your LM3886 needs more warmth, first thing to do is check the grounding and decoupling arrangements.

 

[Philfr]

Hi,
I think it's good about that :
http://www.diyaudio.com/forums/chip-amps/247535-lm3886-kit-am-3.html#post3744138
I remove also input cap (3,3 uF)..

Details about dac, it give 2,2 volts with 47 Ohm impedance, as brand said.
Phil.

 

[ivandezande]

An externally hosted image should be here but it was not working when we last tested it.

Other upgrade, change filtering caps, it's too big, 3x10000 uF per side !
Phil.

I have those same amp boards which omit a lot of stuff needed. Where is the complete Zobel?

 

[Philfr]

Hi ivandezande,
You are right, it has not zobel, only serial 0,1 Ohm at output..
But what would be the effect of a zobel circuit for low frequencies (35 to 300 hz in my use) ?
Phil.

 

[ivandezande]

Hi ivandezande,
You are right, it has not zobel, only serial 0,1 Ohm at output..
But what would be the effect of a zobel circuit for low frequencies (35 to 300 hz in my use) ?
Phil.

Good point, I did not catch that. However, in case you ever use it for full range, I would say it's good to make sure everything is there for stability in the future.