This great amp was waiting for some TLC!
This is a Roy / Kitty Hawk 'The Kid' amp. A 18W 2x EL84 amplifier with a dedicated clean channel, a dedicated overdrive channel (called 'Lead') and a dedicated reverb. All crammed into one little box with a single Celestion speaker inside. And two 12AX7 preamp tubes.
The owner complained on the output. 'Is this amp really 18W?'
As you can spot this amp was build in 1984 by the Roy brothers. It was already recapped and someone added an FX loop to it.
The Sound
Connected one thing really stood out: this amp sounds incredible, but doens't put out the volume you'd expect from an amp like this. It is a pretty tame amp and even with the volume controles dimed the result was a reasonable volume but nothing really good. I wasn't expecting this.....
I checked and rechecked all the connections. I hoped to found a missing part, burnt resistor or just a bad tube. But no, there weren't any problems to be seen.
The sound is rather nice. The clean channel has a decent clean sound with a good and wide adjustable EQ and a decent reverb. The reverb though takes some volume to be heard and used. The 'Lead' channel can be switched by the onboard switch (or footswitch) and gives a nice overdrive that is pretty dynamic with the guitar. Lead setting 1 is a low gain transparant OD channel and Lead setting 2 adds a lot more mids to the signal. Even with this channel enganged, the volume was pretty tame.
The FX loop was placed just before the phase inverter. I 'think' the previous owner also got bummed on the volume issue and added a nice clean boost in the FX loop to compensate for this problem.
I checked the schematic:
The Fix
As you can spot, the amp only uses 2x 12AX7 tubes. The 'Lead' channel uses one extra half of the 12AX7 to get the gain going.
And this is where the problem starts. Following the clean channel, the signal is split into two to feed the reverb circuit. This was we lose a lot of volume in this channel. The most used cure for this, is adding a recovery tube stage; an added tube stage to make up for the volume lost in the reverb circuit (for example, look at the Fender Twin Reverb). This Kitty Hawk has no volume recovery stage and thus has a volume issue.
I asked the owner what he needed. He called and told me he didn't really need the overdrive channel. With that in mind I rewired the last part of the overdrive stage (removed three resistors, disabled one side of the relay) and now a recovery stage was introduced. I kept the volume control of the Lead channel to act like a 'Master volume'. And that seemed to do the trick.
Now the amp breathes fire! It is now a single channel amplifier with much more hair then the original! By keeping most of the Lead circuit intact, the switching still works so you can use the 'Overdrive' knob as a second gain knob. Also, the Lead 2 setting still gives much more mids, making it cutting through even easier.
It is now the amp that I though I started to work on. And am pretty happy!
Comments
Post a Comment