Ruby Amp (ROG) ... complete! ... but very faint?

[Aurin]

I built a ruby with fetzer valve mod [ http://www.runoffgroove.com/fetzer-ruby.png ] and was quite pleased to find, when I had finished the last joint, that it worked. However it was VERY faint.... And the gain pot seemed to work backwards. (turning it clockwise turned the volume DOWN).

So I re-wired the pot and that seemed to help quite a lot. But it's still not very loud at all (barely above the volume of my electric's sound [without it being plugged in to anything]) . That's with the volume and gain pots turned ALL the way up.

So perhaps I'm reading something wrong on the schematic?

I figure I might've mis-wired the volume pot and possible the trimpot ... When I turn the trimpot full clockwise it totally kills the sound -- only at 1/2 rotation or less do I get any sound .

This is how I've got things setup (As I understand pots in schematics) :

Is that right?

If you have pictures of the underside of a working fetzer valve or ruby w/ fetzer valve that would be awesome....

[vanhansen]

Go from Pin 1 of the LM386 to lug 3 of the gain pot, then to lug 2.  Lug 1 goes to pin 8.
On the volume pot, come from the 22n cap of the Fetzer Valve to lug 3.  Lug 2 goes to pin 2 of the LM386.  Lug 1 to ground.
Yes, your diagram is correct.  You've got the pot lug order correct.

[Aurin]

Thanks for replying  =) Volume pot is wired correctly then....

I'll have to double check the gain pot when I get home... (After all I did end up switching things around a bit with that).

It could of course be the cruddy lil' speaker I'm using.... 4 Ohm 2.5 W 4" oval speaker that was harvested from an old TV (and I do mean old, didn't go above channel 13! heh heh).

[Steben]

A speaker with sensitivity of 100dB@Watt sounds double as loud as a speaker with 95dB@Watt. For example: My HiFi speakers (Wharfedale, not the worst around !) have 86dB@Watt !!! They sound 2x to 3x as quiet with the same input as a 100dB speaker!

[smashinator]

Is your speaker in a box?  If not, it will be much much softer because (if I remember this correctly) it phase cancels itself.

[Aurin]

Erm... no, no it isn't... I can't say as I've heard such a thing.... Guess I'll box it up and see!  Thanks for the suggestion.

I really want to get this thing rockin'

I'll also probably add a transfer jack so I can use the internal speaker or use it as just a head... Huzah for switchcraft's 13A =D .

[Aurin]

Stephen,

Ack! Don't know how I missed your post but... Good info =)  I hadn't even though of the dB sensitivity of the speaker.... Is there any "easy" way to guesstimate that value? Or would I need fancy equipment to make that calculation?

I really should try hooking up a real guitar speaker ...

[spudulike]

Check your fet pinout.

[Aurin]

I'm using an MPF 102 from small bear -- should be Gate, Source, Drain   when looking at the rounded part .... If I mixed up the source and drain connections I'll have to resolder a bit heh.... hopefully that's -not- the issue... We shall see, I suppose.
   
Thanks for the suggestion =).

[Connoisseur of Distortion]

with sensitivity, i am fairly sure that a 3 dB increase is perceived as a doubling in volume... but snesitivity can make or break your cab, yes

[Aurin]

Everything checks out --- it IS louder in a box rather than with the speaker on my work table.... Who knew? heh... When I put it in it's permanent home I'll have to take pictures... thanks for the suggestions all =).