Hi.
I'm fairly new to this game.. and new on this forum
I've just finished building my first amp (a champ clone)
Now I want a real challenge, and I've talked to a friend about building him a c-lator, to fit with his brand new dumble-clone.
It looks like something I could do.
I'm looking at the schematics from this site and the one on ceriatone.
But what (reasonably priced) Transformer would you recommend for a 230v ?
If you go for 12.6VAC you will run the heaters of the two triodes in series (connect the 12.6VAC to pins 4 and 5 and leave pin 9 unconnected).
You need to drop 1.4VAC. Most likely you will need to drop a bit more since the transformer has 14VAC at 2A. At only 150mA (the current draw of one 12ax7 with series 12.6V heaters) transformer voltage will be higher than 14VAC.
R=U/I = 1.4/0.15 = 9,33 ohm
You could start with a single 10R or maybe 12R and check the voltage.
A 1W or 2W resistor should be fine (P=U*I= 1.4*0.15 = 0.21W).
Alternatively, if you wanted to go for DC heating (which might reduce hum) you could bridge rectify the 14VAC and use a LM317 wired as a current regulator to provide 150 mA DC.
For details see: http://www.tubecad.com/july2000/page6.html
35mm height might be too much for a 1U rack enlcosure.
I used the musikding transformer with 32 mm height in a Hammond 1U rack enclosure. Don't think 35 mm would fit into this enclosure. Might work for other 1U enclosures though.
Didn't see this one.
You could even use one of the other secondaries for a relay bypass.
Depending on the regulation of the heater winding (might be in the range of 10-15%) you might want to add a small dropping resistor (1R to 2R) for the heaters. Most likely it's not even needed.
Exactly
You can still include a couple 1R/2W resistors with your order at tube town in case you need/want to drop the heater voltage.
Besides, also with the Engl toroid you could do DC heaters using either the 6,4VAC or the 10VAC secondary winding.
Shouldn't cost you much more the € 5 for the parts.
Thanks.