Will removing a power tube cut my power in half?

You can't remove one of your power tubes in that amp. It only has two power tubes right?. I used to have an amp with four 6L6 power tubes, and your could either pull the inside two, or the outside two...but it was still very loud.

-SF

 

If your amp had a single ended class A output stage with 2 (or more) tubes in parallel, removing one tube would be ok because each tube is amplifying the full output signal. However, your DeVille has what's known as a class AB push-pull output stage....which means each output tube is amplifying roughly 1/2 of the output signal. So, if you remove one of your output tubes, about half of your output signal disappears, resulting in a very ugly sound.

 

How would a switch bypassing the P.I. to 1 output tube work?

 

Kevin O'Connor covers how to get single-ended tone from a push pull amp in his "The Ultimate Tone" book series. E-mail him and ask which book to buy.

 

still wouldnt work because the output transformer needs a push-pull (two tube) signal. Running a center tapped transformer as a single ended transformer is not a good idea.
In VaughnC's reply below he specifies a two tube amp running parrallel to a single ended OT... Thats a different amp from a more common push-pull.

 

Thanks! Would a multi-pole switch take care of the OT problem?

 

I don't think that would help. What you're doing is splitting the signal into tops and bottoms and sending 1/2 thru each 1/2 of the center tapped Tx. To use it as a single ended amp you'd have to run one of the output tubes in class a and send a full spectrum signal to just one side, otherwise the non-inverted signal going to both sides would cancel itself out. Running into just one side of the OT seems likely to expose the non-used side to flyback voltages that would likely be unhealty (unless you switched in a load in place of the non-functioning tube). Regardless, if you're just looking to drop the output power of the amp you could:
1. Add a switch for cathode bias
2. Add a switch for "triode mode)-together they'll cut the power in 1/2
3. Switch to yellowjacket adapters-another 50% drop
4. Add a switchable resistance in parallel with the speakers and equal to them (another 50% drop, we're now down to about 1/2 the percieved volume) or use an attenuator that'll let you drop down to 1/4 volume or less.

Of course all these'll change the tone and it's hard to know if you'll like the results...

 

Dr Bob.. Thanks kindly for the reply; great stuff but a couple of posts up i mentioned bypassing the P.I. first. My amp is not the same as loveanddag has, it is a YBA-3 with 4X6550s. Again thank You all.

 

bump

 

The point being that you cant bypass the PI and run one tube thru a push-pull OT. Either the amp has a single ended OT or not. If you have a push-pull OT you cant make it behave like a single ended OT... They are different circuits and not alike.

You definitely cannot do this with a YBA-3.

 

Thanks!