Pre- amp gain and LM3886

[decky]

I did not have time yesterday - I was answering the posts LOL!

However - I will definetely cut the gain on the gainclone to 22 with a 1k resistor. For the preamp I will see how it goes. I have a guy at work that might be willing to help and scope the output to check for any oscillations. This is only if the amp sounds OK after the mod.

The second option is to follow my initial thought and Andrew's suggestion regarding the headphone amp and puting a unity gain buffer in the preamp box. I might lay my hands on a MF X buffer.

Andrew can you give me a link to Nuuk's site?

 

[seventenths]

http://myweb.tiscali.co.uk/nuukspot/decdun/

 

[AndrewT]

http://myweb.tiscali.co.uk/nuukspot/decdun/gainclone2.html for the specific page.

 

[BWRX]

Have you tried turning down the amp gain like BWRX and I both mentioned? Okay, its really weird that he and I agreed on something, especially the same gain setting.

I was going to suggest lowering the amp gain to around 11V/V but I don't know if the LM3886 will be stable on the chip amp PCBs with the gain that low, plus no one else seems to like (or have tried) the LM chips with gain that low.

 

[danielwritesbac]

I was going to suggest lowering the amp gain to around 11V/V but I don't know if the LM3886 will be stable on the chip amp PCBs with the gain that low, plus no one else seems to like (or have tried) the LM chips with gain that low.

Hi man! I think you're right (again!) Looking at the smaller than normal 100uf caps aboard the amplifier PCB's, its seems designed to tolerate low gain settings (lower than most kits). In observation, lower gains did work better on the chipamp kit.

I think that 1k or 1.1k may be optimal for low DC offset, but that one could change the 22k out for some lower figure. What do you think?

My guess (and this is just a guess):
_NFB
1.1k Ri
15k Rf
60uF Ci
_Input
1k Rb
13k Rin
2.2uF Cin

Any good?