This amp uses the Fender 1.5K cathode resistor bypassed with a 25 µF electrolytic capacitor. The cap was changed to a 3 µF Aluminum in parallel with a 1 µF Tantalum ( why Tantalum? See here , 5th paragraph ). This brings the first gain stage frequencies up into the range of human hearing, and tames bass flabbiness.
The Conqueror uses the same Negative Feedback Scheme as the Fender Champ, with a 22K resistor between the output transformer secondary and the 2nd gain stage cathode. I used a push/pull switch on the Tone pot to turn the NFB off, by opening the NFB loop. This increases distortion and alters the tone somewhat. In a good way.
You could easily turn this NFB into a Presence control, but there's no room to put another knob. (sigh).
I can't believe that a modern amp design would use a first filter capacitor with only a 450 Volt rating. With modern wall voltage approaching 130 VAC, the potential at the first cap at turn-on can be 600 Volts. I recommend changing at least the first filter cap to at least a 500V rating. Your amp will thank you. I changed the 1st capacitor in the π filter to 10 µF and added a 4 Hy / 150 mA choke in place of the 10K Ω resistor. This modification is exactly what Leo did with the 5F2 Princeton - 8uf filter capacitors are a very important part of the character of the amp. The small capacitor is prone to sag. When pushed hard, the capacitor can't keep up - That is the clang, and jangle that people describe in the Princeton. It also tends to make the bass more "loose". The choke is required with a 10 µF 1st cap to keep the hum to a minimum.
NOTE: I ended up swapping the 10µF for a 22µF - the hum was just a bit much for me. The tone and behavior of the amp was much the same.
Tim Ward introduced me to this amplifier when he brought his over for me to play with. We both thought that the amp was dark sounding. The tone control doesn't seem to do much to the tone at all. Weird. Pairing a 5W Princeton circuit with a 12 inch speaker is a good idea, but Panama didn't quite get the circuit tuned to the speaker.
The 7-pin rectifier, 6Z4-J, is decidedly odd. It is functionally the same as the USA 6X4, but the pinout is different. So you would have to change the socket wiring to use a 6X4 (which might be worth doing, there are lots of NOS 6X4s out there). A better quality replacement is the Russian 6C4P-EV. This tube was initially designed for car radios; the filament is 6.3 Volts (the 5F2 uses a 5Y3GT, which operates at 5 V. By using the 6Z4-J, Panama could use a cheaper transformer (no 5VAC tap).
NOTE: rectifiers are constructed with very tight tolerances between the Anode and the Filament. On a very small diameter tube like this one, the distance between the elements is even smaller. A hard hit or a shock will cause this tube to short. Ask me how I know...
(refer to above schematic)
#1 FILTER CAP, CHOKE
V i n t a g e E l e c t r o n i c s
Panama departed from the Fender 5F1 Champ circuit in a few places: The filter caps are all 22 µF, instead of the 5F1's 16 µF, 8 µF, 8 µF, or the 5F2 Princeton's 8 µF, 8 µF, 8 µF. They removed one of the input jacks - there's only one on the Panama. They changed the 6V6 cathode resistor from 470 Ω to 330 Ω. The 5F1's 5Y3GT rectifier is changed to a weird Chinese 6Z4-J seven-pin miniature rectifier, and Panama added a tone control to the 5F1 circuit, as well as the 8Ω L-Pad. Everything else is pretty true to the 5F1 design (or the 5F2, whichever).
The L-Pad attenuator isn't very useful on this amp, and it does affect signal quality to the speaker. I disconnected it from the circuit and removed it from the amp. The result is improved tone (IMO). It also gave me a place to mount the FAT switch and the external speaker jack.
Panama got rid of one of the input jacks of the 5F1, which is fine, but they kept the 68K resistor, which is essentially the "Low Gain" input on Fender's amps. I changed this to 34K (okay, 33K) to duplicate the "High Gain" circuit of the 5F1.
The Conqueror features an attenuator in the form of an 8Ω L-Pad on the back of the amp. This is somewhat peculiar, since this amp only delivers 5 Watts, and certainly won't get loud enough to wake the neighbors. But, it's there, and it works well.
Panama does not publish the schematic of this amp. So I altered a 5F2 schematic which shows the suggested modifications.
I added a "FAT" switch to the second triode of the 12AX7. The switch, when "ON", adds a 25 µF capacitor in parallel with the second stage 1.5K cathode resistor. This modification significantly changes the gain of the section, and distorts easily. Use twisted pair here if you are mounting the switch at any distance from the circuit.
Panama added a one-knob tone control similar to the Fender 5F2 Princeton circuit, but they use a 1M pot, and it is not configured properly with the volume pot. I changed the tone pot to 250K, and added a 100K "bias" resistor to convince more of the signal to go through that tone control (as in the 5F2 Princeton). Later, I changed the pot back to 1M; it responds better.
The Panama Conqueror is a 5W combo amp made by Panama Guitars, in, you guessed it, Panama. The Amp is touted as being a tribute to the Fender Champ 5F1 circuit, but it is probably closer in circuit design to the 5F2 Princeton, since it has a tone control. Sells for less than $400; sometimes a lot less. I bought mine, new, for $250.
The Conqueror is enclosed in a handsome Spanish Cedar and Palo Mora Cabinet with removable front grill. With 12" aged V30 driver as standard.
Stunning Palo Mora tonewood baffle. Available as standard in Ivory White / Graphite, and special editions of Purpleheart and Emerald. Mine is purple. Excellent.
The Conqueror is hand-wired on an eyelet board, and is well made and very beautiful, especially with the grill cloth removed to display the gorgeous tonewood baffle.
The amp sounds good out of the box, but it is definitely dark, almost muddy sounding sometimes, and would benefit from some modification.
So modify it I did.