Paleo-Electronics Blog

I guess before I dived into the requirements, I should have talked a bit more about the amps upon which I am basing the Songbird.

Unsurprisingly, I am starting with a Gibson Skylark.   To be specific, I am starting with the pre-crestline GA-5.   This is a lovely little class A, single ended amp, rated at about 5 watts.   She uses a 12AX7 as a pre-amp, 6V6 power tube and a 5Y3 rectifier.

This was a student model amp, and a direct competitor with the Fender “Champ” amps.  Fender started making the champs in ’48 (I’d kill for a 5B1 schematic, but I’ll bet it’s damn close the ’52 Les Paul amp).    By the early to mid 50′s these student models were all pretty damn similar.

To the left is a  classic Fender Champ 5E1 schematic.  12AX7, 6V6, 5Y3 and almost the exact same thing as the  …

… Champ 5F1 schematic.   In fact, the choke has been replaced with a resistor (much cheaper) and the bypass cap has been removed from the 1st stage preamp cathode.  If you look carefully, you can see that the cap was simply erased, as the dots are still there.

And here is the GA-5 Skylark schematic that I will be using for a baseline.  There is really almost no difference.   Fender has a 1MΩ resistor at the input, the bias resistors are slightly different on the preamp…    just little stuff mostly.    However, don’t think you can just swap the OTs on these things.    Fender uses 3.2 or 4 Ω speakers and Gibson almost always uses 8 Ω speakers.    The GA-5 also uses 10 and 20 μf capacitors for power conditioning compared to 8s and 16s in the Fenders.   I’ve read that this is expected to mellow out the highs.   I don’t disagree, I just doubt that I would notice.   Who knows though?   There is never any trouble getting ampophiles to argue over which part is most important.

A little caution is in order when discussing the Gibson Schematic.  They are prone to small errors.   Note that V3 is listed as a 6Y3  or arguably a 6V3 if you want to be kind, but either way, it’s actually a 6V6 of course.

Why the Gibson?

To my ear, the Gibson sounds just a little warmer, and the Fender is a bit harsher.   Some ears will prefer the earlier transition to overdrive/distortion on the Fender.   I prefer that ‘barely holding it together’ feeling I get from the Skylarks.   When you back off with the pick it’s plenty smooth, but hit it hard and it will bite back.

Since these are all 5 watt amps, they can reasonably be dimed in the studio (or your garage).   Try bringing your Marshall stack into a little studio and see what happens.   The Skylarks I play at home right now are 8-9 watts and Push-Pull instead of SE.   This Skylark will give me more overdrive at even lower volumes.

Later on, when I discuss power tubes in more detail I’ll drag in the Gibsonette schematic, which just uses two 6V6′s in a class A, SE configuration.   This could give more power .. although I’m not really sure that is a goal.

So.. to wrap it up.. these are classic Studio/Bedroom amps.   Great tone and the ability to push it hard even with the kids in bed.   This is what I want to build.