"All American Four" Guitar Amp

When you have a bunch of 'no value' AA5 radios, use the parts for a
nice 3W practice guitar amp. The bread tin chassis kept the prices low!

The large transformer is a 120/240 / 120 isolation transformer. This
amp was wired for 240 at the primary, as it will be a gift for a UK
friend when we meet at the Dayton Hamvention.

Joe

"Joe Bento" wrote in message
news:2009050415312243658-joseph@removespamkirtlandcom...
When you have a bunch of 'no value' AA5 radios, use the parts for a nice
3W practice guitar amp. The bread tin chassis kept the prices low!

The large transformer is a 120/240 / 120 isolation transformer. This amp
was wired for 240 at the primary, as it will be a gift for a UK friend
when we meet at the Dayton Hamvention.

Joe


Is there enough iron there for 50Hz mains??

On 2009-05-04 15:35:49 -0600, "Brenda Ann" said:


"Joe Bento" wrote in message
news:2009050415312243658-joseph@removespamkirtlandcom...
When you have a bunch of 'no value' AA5 radios, use the parts for a nice
3W practice guitar amp. The bread tin chassis kept the prices low!

The large transformer is a 120/240 / 120 isolation transformer. This amp
was wired for 240 at the primary, as it will be a gift for a UK friend
when we meet at the Dayton Hamvention.

Joe


Is there enough iron there for 50Hz mains??

The Transformer is a Triad N-N68X, which according to its published
specs is good for 120/240 50/60 Hz.

I have a 150VA transformer I wire in reverse to check out 240V
circuits, and this functioned well at 240V 60Hz.

Joe

In message 200905041533558930-joseph@removespamkirtlandcom, Joe Bento
writes

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Hum-wise, would there be any advantage in reversing the order of the
heaters for V1, 2 and 3, thus having the lower AC voltage at the lower
signal level stages?
--
Ian

On 2009-05-05 03:55:40 -0600, Ian Jackson
said:

In message 200905041533558930-joseph@removespamkirtlandcom, Joe Bento
writes

[ A MIME image / jpeg part was included here. ]


[ A MIME image / gif part was included here. ]

Hum-wise, would there be any advantage in reversing the order of the
heaters for V1, 2 and 3, thus having the lower AC voltage at the lower
signal level stages?

Ahhh.... I need to change the designations on the schematic. The
12AT6's are at the ground side of the string as wired in my amp.
Though not nonexistent, hum is very low level.

Joe

Corrected schematic to show actual wiring of heater string. First
12AT6 preamp heater is closest to ground.

In message 2009050508580977923-joseph@removespamkirtlandcom, Joe Bento
writes
Corrected schematic to show actual wiring of heater string. First
12AT6 preamp heater is closest to ground.

[ A MIME image / gif part was included here. ]

This arrangement might also help with reliability. The heater-cathode
breakdown rating of a 12AT6 might not be as high as a 50C5 (but I
haven't checked).
--
Ian

Joe,
Nice job on the AA4 amp, I have been thinking about drawing up a
schematic but you beat me to it.. :-)

I have some 50DC4 tubes, using that in place of a 35W4 you don't need a
filament dropping resistor.

Thanks,
Sal