[dBel84]

I am going to set up one of my tube amps to switch between a series and parallel 12.6VAC heater supply. I have looked at a few possible ways to switch them and think I have come up with the most simple solution but I need a sanity check. The diagram should be self explanatory , the switch is a dual pole on-on type switch. tia..dB

 

[fran]

but why?

 

[dBel84]

well, unless I am missing something else, so that I can use both 6.3V and 12.6V tubes in the same amp..dB

 

[luvdunhill]

are you switching the secondaries of the power supply? If so, it will work, just don't do it while the amp is on. Sorry, your diagram isn't that clear to me, plus I have no idea what noval tube you are using...

 

[dBel84]

Thanks and my bad. It was clear in my mind what I wanted to do and although intuitive if you are following the concept, not so clear as you point out. I actually hid the switch inside the chassis to avoid inadvertent switching.

I made the mod last night and was able to change tubes successfully. The basic premise was that the secondary AC supply for the heaters was 6.3-0-6.3 , and before someone bawls me out, when I originally built the amp I had no intention of using the centre tap and clipped it short ( hindsight is a wonderful thing) So, to do what I wanted to do with a 12.6VAC secondary was to run the secondaries in parallel for 12.6V heater tubes ( using pins 4 & 5 only ) and series for 6.3V heater tubes. The original tubes were 12AU7 type and I had a few other tubes that I wanted to try. It was well worth the effort as the new tubes show great promise. Now I just have to figure out why the heater bias I added is triggering my epsilon occasionally. ..dB

 

[luvdunhill]

Quote:

Originally Posted by dBel84 /img/forum/go_quote.gif I made the mod last night and was able to change tubes successfully.

cool. I'm doing a similar thing with switching DC heaters

 

[dBel84]

hope it goes as smoothly for you too.

..dB