Lowering Tube power amp output

On my Fender Twin Reverb I can remove either the two outer tubes or the two inner tubes ( four 6L6GC's in a row) to reduce power by half. You can probably do the same on your amp. Contact Rogue to find out which pair to remove.

Even if you are able to remove tubes and reduce power, this will often impact the impedance, which may cause other issues.

Why are you looking to do this, and what do you want to accomplish?

Agree with contacting Rogue and getting a direct response/recommendation. This avoids any unintended or unforeseen problems.

Charles 

If you don't want or need that brute, sell it and buy a more modest amp. 

No other way to reduce heat generation other than remove some tubes but I don’t know if your amp supports that. Likely this won’t work because of bias circuits that depend on two tubes to compare. You need someone that understands the amp well.

I have an Ayon amp with 4 x 6c33c tubes and makes 400 watts of heat. cant use it in the summer. In the summer I use my Decware. I’ve got it to dialed in I may end up selling the Ayon rather than switching back in the winter.

Jerry

Just a thought, you can replace the KT88s with KT77s. I believe that will drop the power to about 50W. I have Rogue M-180s. They were loaned to me to audition for a month. The owner was using KT88s in them and frankly they sounded great to me. I bought a new set of KT120s, installed them and set the bias. Big difference in many things including heat generation. But like someone already said, call or email Rogue and see what your functional options are. They are great people to deal with.

Call Rogue audio!! The only audio amps I know of that you can remove some power tubes reduce output power without issue or damage is Atma-Sphere amps.

Mike

probably off my rocker here,  "but"

i sometime mess around with some older(50's/60's) lower power tube pcs, and when first start up i always start with a variac. slow, low power. i started to realize that most all tube amps will generate sounds at a lower power. some actually start to generate music at 70/75 volts,(not a perfect sound) but good enough to tell that the unit was going to work without the magic smoke . i realized that around 100vac the beginning sound was good enough to sound ok for my old snuff box ears(older folks might get this) also actually drops transformer temperature, and i feel with less trans stress. oh, less heat by far. with a pair 6l6 amps, 50w quad each running at 100v did make a lot of difference in room temp. but still these are my winter amps, they will come down in the spring. 

you can hang me if i am wrong. so far it has worked for me. my opinion less power in, cooler internal parts, maybe even longer tube life, a lot less heat. i have been doing this for a few years with no noticeable difference in sound quality (snuff box/can) 

by the way usually i don't push the amps very hard, most time at lower volumes.

16x16 room, between 85 / 100db as loud as i like it, until after a little numbing then sometime move volume up a little. that is a lot of talking too much but(lucy said splain yourself).

sorry for being long winded  

Lowering voltage might do the trick without causing any damage.  In some applications, under-voltage could be harmful to transistors, but, I doubt that there is a problem with tube gear.  Does anyone know if the lower voltage might reduce the cathode/heater emissions to the point where cathode stripping might occur?

Personally, I would sell the amp and look for a lower powered amp if you determine that you really don't need that much power.  Two hundred watts is usually way more than one really needs for almost any speaker.  I generally don't like the sound of higher powered tube amps that are running a multitude of high-powered tubes, like KT88, KT120, and KT150.  These types of amps tend to be "hard" or "harsh" sounding compared to lower powered amps running the likes of 6L6 or KT66 tubes.  I would take a 40 watt KT66 or an even smaller 6L6 amp any day over a high-powered tube brute.

@tubelvr1 The more powerful you make a tube amp (unless its an OTL) the more limited its bandwidth becomes, due to the output transformer.

What this means is that for the most part smaller tube amps sound better (except for OTLs where bigger ones sound better).

So rather than remove tubes to reduce power getting a smaller amp is good advice. FWIW the output transformer is designed to provide a certain load for the power tubes provided its output is loaded correctly (for example an 8Ohm speaker is connected to the 8Ohm taps). When you remove tubes that load that the transformer provides will change and so the remaining tubes won't be loaded correctly and most likely will be too low of a load for the remaining tubes. This will lead to excess distortion, the tubes running hotter and their reliability compromised.

So don't do it!!

Drop in some Kt-77's  There cheap now also

I’ve heard you can start removing push-pull pairs on each side (normally 3 push-pull pairs per side), but as noted this will be suboptimal. You’ll have to re-bias if you do this. You can also just drop the tube biases down from the standard 40mA to say 35mA, for a slight reduction in heat. Rogue is great to chat with if you want their guidance on this. 

If you’re concerned about heat dissipation, an amp with a dozen KT88 and 6 small tubes is not a great match. As others have suggested, it’s probably a good idea to trade the amp in. Many audiophiles without heat concerns would love to have that amp!

Electric cost your concern for ac? 

It is frequently over 90 degrees outside… my partner is disabled and uncomfortable so I keep the house at 70 degrees. Even so, my electric bill (with 100 hours of 36 tubes… 8 KT150s running) is less than my Verizon bill, insurance bill, property tax bill, Comcast bill… How is this an issue? Too much bass?

It is frequently over 90 degrees outside… my partner is disabled and uncomfortable so I keep the house at 70 degrees. Even so, my electric bill (with 100 hours of 36 tubes… 8 KT150s running) is less than my Verizon bill, insurance bill, property tax bill, Comcast bill… How is this an issue? Too much bass?

I don't get it either. No problem running tube amps during summer here in GA, even with my AC slightly underpowered. Electricity cost is not really a concern on a $10K tube amp?

Just run the tube amp when you're listening, and turn it off when done. I've yet to experience any tube component that doesn't sound great after just a couple minutes warm up. By contrast, some of those solid state components need to be kept on for hours before they get into a good place.