Dual Ruby builders

[bdevlin]

Anyone use this layout?
http://home.comcast.net/~chrisbaer/dual_ruby.pdf

If so, did you find any necessary modifications to it.  Am I correct in interpreting that the speaker - connection is not attached to ground?  That of course is unlike the single Ruby schematic.

[mdh]

I seem to recall someone having trouble with that layout in the past. It is true that the speaker is not connected to ground, as the amplifiers are in a bridged configuration (see http://en.wikipedia.org/wiki/Bridged_amplifier), but I think there were some other problems with it. If I were you, I would put the runoffgroove Ruby and Little Gem MkII schematics side by side, and reconcile how to replace the Little Gem MkII input buffer with the Ruby input buffer. That's what I did a little over a year ago when I built a bridged Ruby on perf.

As for that particular layout, I think I actually do see a problem. Numbering the ICs left to right, it looks like pin 2 of IC1 should be grounded, and pin 3 of IC1 connected to the wiper of the volume pot. IIRC, we had the last guy who tried to use this layout cutting traces and soldering flying leads. I would just perf it or draw a new layout.

[pyrop]

As for that particular layout, I think I actually do see a problem. Numbering the ICs left to right, it looks like pin 2 of IC1 should be grounded, and pin 3 of IC1 connected to the wiper of the volume pot. IIRC, we had the last guy who tried to use this layout cutting traces and soldering flying leads. I would just perf it or draw a new layout.

Yep that is the fix for the error in that layout...

paulw

[bdevlin]

I got that correction worked in with pins 2 & 3.  I still have no signal at SPKR out.  I got the audio probe out and I have signal on pins 1,3,5,7, & 8 on IC1(Left) with the expected high signal on pin 5.  BUT, on IC2(Right), I only have signal on pins 1,2, & 8 and the signal on pins 1 & 2 is much lower than it is on IC1.  All the voltages to all the pins look fine and I tested the IC's and they are good.

[mdh]

Well, since IC1 pin 3 should be connected directly to IC2 pin 2, if you're seeing less signal at IC2 pin 2 than IC1 pin 3, maybe you should check for a cold solder in that area.  Or just preemptively reflow those joints.

[bdevlin]

I got this working with the suggested corrections and fixing a missing solder joint .  It does not have the gain that my single Ruby has.  I'll have to investigate (transistor differences and component values).  The other thing is that I need to test the battery drain on this Dual Ruby.  I had a used 9 volt get funky pretty fast on me.

[squidsquad]

I think Ruby DOES use a lotta juice...so 2 would be LOTS.  Try using a 12v wallwort....you'll get a bit more headroom.

[bdevlin]

As for that particular layout, I think I actually do see a problem. Numbering the ICs left to right, it looks like pin 2 of IC1 should be grounded, and pin 3 of IC1 connected to the wiper of the volume pot. IIRC, we had the last guy who tried to use this layout cutting traces and soldering flying leads. I would just perf it or draw a new layout.

Actually this correction is not necessary.  I tried the circuit with the correction suggested above and without.  Both work, and, although I only did a VERY breif comparison.  The sound was comparable if not the same.