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RE: Croft Series X info

Posted by rogerh113 (A) on July 18, 2023 at 08:40:56

In Reply to: RE: Croft Series X info posted by bcarlos on July 18, 2023 at 07:43:33:

As a newbie, it is IMPORTANT to note that tube amps operate at high voltage that can fry you if you do not know what you are doing, and are not careful (even if you do know what you are doing).

If it is currently wired for 220v and you are using it with 120, it is effectively running at 1/2 power, which MIGHT explain the low volume. If it has 120 taps on the transformer, you might want to change the wiring from the 220 taps to the 120 taps.

The amp looks to be fairly clean, and may have been upgraded at some point in time. Likely the output is fairly low, on the order of 10W (see Croft Troubadour, which looks quite similar).

It seems that Croft used a capacitor to isolate each output side from the speaker, so blowing up the speakers is not so likely. You would have to trace the signal from the power tubes to the output lugs - the blue capacitors behind the power tubes might be isolating capacitors.

Not sure how to address the tube issue if you think they are not correct. You could look at other Croft OTL amps and see what tubes he used. Apparently Croft did not release schematics. The amp is wired point to point, so you could make a schematic yourself by mapping out the wiring.

Perhaps the amp will come up at 120V when wired for 120V, and all will be well. If not, then a deeper dive will be required. If you speakers will operate well with 10 watts, then it could be a fun project.

regards -- Roger

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