A tube 'red plates' when too much voltage is applied to the plate. You will see a red or orange glow...not a good thing.

I'm using a 5W4GT with the 6K6's. It is a low power 5Y3.

Those are different drivers than I've been using and from what Dennis supplied. Different enough that the design of our amps may be different. Mine uses the wide range of 6922 type tubes. I'm currently using the vintage Russian 6N23P. If I recall from my Cary preamp days, the 6SN7 is quite a bit bigger. My experience might therefore vary from yours.

In terms of power tubes, I've not found any current production that come close to several vintage flavors I've tried. Current favorite is the 6K6GT - Visseaux or RCA (1940's and 50's). Others I've liked a lot along the way - all vintage: GEC KT77, Visseaux 6V6GT (Pope second fav 6V6).

The 6K6GT's seem best with a 5Z4GY rectifier. I've liked the British (Mullard, Osram, Cossor, etc., all the same) "fat bottle" CV378/GZ37/53KU rectifier for all other power tube types.

Yes, doesn't sound good. Does it happen with both 6K6 tubes? Do you have another pair to try, maybe different brand?

I'm using the 5Z4G rectifier. The chart you linked to describes it as "low voltage drop 5Y3. As you say, the 5W4GT is described as "low power 5Y3". The specs are different. Do you have a 5Z4 to try by chance? I think I have a 5W4 I can try to see what it does. I'll check and let you know.

Edit: The 5W4G I have is a British "ST" type or coke bottle shape. After running 15 min or so, no red plating I can see in the 6K6's.

You will notice a greater variety in tone/sound using different driver tubes moreso than power tubes. After all, the quality of the signal that comes out of them is what gets amplified by the power tubes and sent to your loudspeakers.

The Brimar tubes you've listed are great. You might want to try the Sylvanias as I think they are some of the best examples.

Power tubes do have a distinct signature of their own, but affect overall sound to a lesser degree. It's the driver/powertube combo that counts. When you find the right combo it can be quite exciting.

The Tung Sol 6L6G is an excellent tube. In the right configuration it rivals NOS. It is actually uprated to 6L6GC spec. Pretty balanced tonally with very good bass characteristics.

The GL KT77 is another excellent tube with great midrange and bass. Mellower topend.

The GL KT88 is a stellar performer. Reliable bass and midrange with a very nice topend.

When it comes to rectifiers, a change in voltage & current alters everything about how an amp will perform.

When you take all of these variables into consideration you understand why Dennis calls them a tube rollers dream... or nightmare depending on your frame of mind.

You've got a nice set of tubes to play with. Have fun with it.

My amp uses octal based drivers as I asked Dennis to make that accommodation. (I have many, many NOS variants to choose from in my stash) Very little difference in the overall design of the amp from the 9pin driver version.

Are you saying the 6K6 and 5Z4GT does not sound good? Being a low voltage drop rectifier it is applying more voltage to the 6K6 and that may be why it does not sound good. 5W4GT's are very inexpensive.

Nice set to start with and the 5U4G is good to go with all of them. If you get 6V6G tubes you will need to use a 5Y3 (RCA or Sylvania are good choices) with them. A big plus is that only one driver tube is needed and excellent single tubes are easier to find than pairs. My amp uses 6SN7 and 6SL7's also. I agree with Twanny about getting a Sylvania 6SL7 or 6SN7. A 5AR4 rectifier would be good to have too. The new production Gold Lion has been well received and is reasonably priced.

No, I was empathizing about your describing the red plating as not sounding good.

For me the 5Z4G and 6K6 seem to be the best combo I've found to date.

Thanks, I have a Brimar 5z4g and will give it a go.

Thanks guys, I really appreciate your input on the tubes. Having a selection of tubes supplied by Dennis specifically for the amp was a big attraction in buying this amp because I have very little experience with tubes (and all of that with guitar amps).

Any thoughts on using the Dared preamp with this power amp vs. seeking a purpose built one from Dennis? Obviously, the latter would be preferred. But how well have you all found your Inspire amps to pair with non-Had preamps?