Looking for a portable amp schematic.

[GuitarLord5000]

Also, what is the purpose of the .047 cap in the schem?  Would a .022 cap work in its place?

[javacody]

I'm not an expert, but using a smaller cap would probably filter some bass out.

Also, when removing parts from my perfboard, I found that I missed a connection from the 0.1 uF cap to ground. Doh!

[GuitarLord5000]

Ok, Im no expert either, but here goes.  The input cap is a .01 uf.  The output cap is a 220uf.  The .047 uf cap goes from Vout to ground with a 10 ohm resistor in line.  Im not really sure what that cap is there for, but if it DID remove some bass from the amp, wouldn't an increase in the input or output cap alleviate that?  Im just curious because I dont have any .047 uf caps and radio shack doesnt have any in stock.  If the .022 cap wont work in that location, im gonna have to order it.  I HATE waiting!

[javacody]

GuitarLord, do you happen to have two of those caps? You could use them in parallel to get 0.044 uF. That would get you close enough. Otherwise, just use the cap you have and upgrade later.

Ruby Build Report:

This amp smokes! It is better than the Gem, and way better than the design I came up with. It is very quiet and sounds awesome! Not to mention low parts count. Very good work B Tremblay!

[B Tremblay]

Ruby Build Report:

This amp smokes! It is better than the Gem, and way better than the design I came up with. It is very quiet and sounds awesome! Not to mention low parts count. Very good work B Tremblay!

Terrific!  That's great to hear.  In your opinion, should it replace the Little Gem?

[B Tremblay]

Ok, Im no expert either, but here goes.  The input cap is a .01 uf.  The output cap is a 220uf.  The .047 uf cap goes from Vout to ground with a 10 ohm resistor in line.  Im not really sure what that cap is there for, but if it DID remove some bass from the amp, wouldn't an increase in the input or output cap alleviate that?  Im just curious because I dont have any .047 uf caps and radio shack doesnt have any in stock.  If the .022 cap wont work in that location, im gonna have to order it.  I HATE waiting!

The .047uF and 10 ohm network increase stability (no oscillation) when the amp is set at higher gains.  I have seen a .022uF used there, so it shouldn't be a problem.

[javacody]

I would say that this would be a great replacement for the little gem, but I would leave them all up.

[smoguzbenjamin]

I'd say leave 'em all up too. Then you can choose what's best. But anyway, it isn't possible to use a .5W speaker in a 1W amp at full power and not blow it up if I'm correct... :roll:

[RDV]

I got the idea a while back to put an input buffer(I copied the one from the 'Grace') on the Little Gem cause it makes it work better with effects. Mine looks just like the 'Ruby' except for the input volume and I used a .001 for the input cap to un-muddy it. Thanks again for your gallant efforts!

Regards

RDV