Noob needs recommendation for a brighter tube

Is the Ember set to low output R ?
should not matter much with LCD2 tonally except that the tube is driven a bit louder giving more harmonics/tube sound.
With the V8 drivers there may be a bass boost when the output R is set to mid or high and recommend low setting for this one.

Have you played around with the input cap settings ?

The frequency response should be ruler flat from 10Hz to well above 20kHz with the majority of the tubes.

Have to address the hum first.
Shouldn't be audible.

Does the Ember stand on top or very close to other equipment ?

test this by using the Ember set alone on a table with only the amp connected to the mains with the vol switch turned down and only a headphone plugged in (low output R)
When the hum is not present move the amp around and see where the hum becomes audible.
Most likely a magnetic field.

When the hum is only heard when connected to other gear it may be a ground loop.

When the hum increases with the volpot it may be a cable with poor screening.

After it is determined where the hum comes from and is dealt with try listening to the amp with low output R.

Looks like a grounding issue mostly.

The fact that some tubes pick up more hum or have more noise originates from their gain and the anode current it operates on.
The same goes for roll-off in the treble which goes hand in hand with lower currents and higher gain tubes.

You could try the following:
use a piece of wire and run it from the shield of one of the RCA connectors to a known 'ground'.
This can be copper waterpiping in the room (where it is not painted) or central heating connected with metal piping (also a non painted patch needed) or a ground lug from an AC outlet. Ensure you NEVER connect it to the live or neutral wire.
See if the amp becomes silent.

In that case the easiest way is to connect a piece of wire between the RCA output shield for instance and a 'known' ground.
When this works it is simply a matter of the connection a bit more permanent.
Sometimes a safety ground is connected to gear that has a 3 prong cable and is connected to a 3prong socket.
In that case an extra wire between line out and an unused input of said device can help.

Not being able to actually see the circumstances it is difficult to give proper advice.
In any case... the Ember should not show an audible hum.

A great tube, one of my favs of the miniatures is the E80CC - features phenomenal clarity that makes many other tubes sound dull and bassy. The Tungsram E80CC is the best value. The pinched waist Phillips are crazy $$$ now.

You could also try a few tubes from the 6CG7/6FQ7 family - similar to the 12BH7s, but often without the prominent bass. The most balanced 6CG7 I've used is a Canadian Westinghouse 6CG7 - tough to find. The Sylvania 6CG7s from the 1950s are pretty well balanced as well.

Would suggest a Telefunken 6922, but over-priced and not as good as the E80CC in my indefatigable opinion. ;-)

In the 12AU7 family, a vintage RCA 5814A is one of the best balanced I've used - a Telefunken 12AU7 is very good as well (and not stupid $$$). Still does not deliver the clarity of the E80CC.

If you were to use G1217's great 6SN7 to 9pin adapter, it opens up the vast range of 6SN7s tubes. With some rolling, expect you will find some 6SN7s that suit your desired flavour. This is the beauty of the G1217 amps - they're not a tonal destination - they're the rolling train across the sonic scenery. The journey is destination.

My G1217 Solstice lives in an RFI infestated office, so most tubes require some sort of screening to reduce hum and noise. If the noise is not too loud, then a solid copper spiral connected to rear thumscrew  does the trick.

Shown wrapping around a Sylvania 12SN7.

Other tubes in my always expanding collection can require more shielding -  then I make an RF cone-of-silence from copper RFI sheilding sheets. A copper lead from the shield is connected to a thumbscrew.

Since we aren't hearing your gear with our ears, can't suggest definitive options. Other than getting a Solstice, an adapter and a Tungsol 12AH7. That tube combo slices off the bass almost as well as a stock pair of Grados ;-)

Perhaps Frans could suggest a passive line level filter inserted between the DAC and Ember. Or you could go old skool and use a schiit loki and eq like it's 1959!

Proper grounding isn't always easy. Most outlets in living rooms do not have safety earth (at least where I live).
In those cases running a wire to a grounded point, central heating (with metal piping) should always be grounded. Remove some paint and tape some wire to it.
Another option is (copper) water piping, Should also be grounded and the same paint things apply.

In most of the cases the amps are silent by themselves and don't need grounding at all. In some cases there might be a real need for it.

Keep going. It seems to be a grounding issue. Frans has always been of great help with these issues. If grounding is an issue with your house a lot of other tube amps or even SS may have problems. I have all grounded sockets (now) the one socket in the entire house that wasn’t grounded, a mistake by the builder, I pluged my subwoofer into. It took a lot to figure out the hum.

Doesn’t seem to be bad tubes. The Ember is a very quiet amp.