E50+L50 Stack Questions / Tube Amp recommendations?

[t08!0]

Proud new owner of the Topping E50 / L50 stack!

Headphones I have (for now) are:
Edition XS (balanced), Sivga 21(balanced)
Grado 80, Senn HD280.
A few other randos in the house I'll be pulling out, like Koss KSC75, HyperX, etc.
I will probably be adding to this list through the year.

At the moment, it's simply Macbook Pro -> E50 Balanced -> L50 Balanced. I have a Topping MX3 connected to some speakers that I don't really care about. I know I can go E50 RCA -> MX3, but I'm simplifying by just switching between DACs when I want to listen to speakers or not.

From what I understand you should not connect unbalanced headphones to a balanced chain. From what I also understand, the L50's amp is electrically unbalanced regardless of the headphones output (sad-face, did not know this). With the L50 set to Balanced inputs, both headphone outputs work.

L50 Question: I'm assuming in this case, since the amp is electrically unbalanced, it's OK to connect unbalanced headphones to either headphones output regardless of the inputs?

E50 Question: There are three different filters. I've seen the graphs, but it's not clear to me which I should use.

Tube Question: I'm so ridiculously impressed by the crystal clean sound coming out of this stack, but I want to play a bit and I've never played with tube amps. Given my current stack / headphones, any recommendations for a starter amp and tubes, under $150? I've been eyeballing these cheapos that would keep me in a fully balanced chain, but as far as I can tell, still be able to use both balanced and unbalanced headphones:
Loxjie P20 (ASR review)
Douk H2 / Suca Audio Tube-T2 Pro.
Douk T8 is also interesting, particularly to add tone control, but I'm assuming the headphone output is not balanced? Or perhaps the Douk T8 Pro, but then I have no headphone out.

I would perhaps jump on the xDuoo 604, but I wouldn't be able to use unbalanced headphones with it.

 

[staticV3]

Hi @t08!0! Welcome to ASR.

From what I also understand, the L50's amp is electrically unbalanced regardless of the headphones output (sad-face, did not know this).

No need to be sad. Balanced (differential) headphone output is pointless for Desktop Headphone Amps. There's no advantage in sound quality.

I'd be happy instead, as it means that I can utilize the L50's full output power even with fixed 3.5/6.35mm headphones

L50 Question: I'm assuming in this case, since the amp is electrically unbalanced, it's OK to connect unbalanced headphones to either headphones output regardless of the inputs?

Since the L50's 4pin XLR and 6.35mm TRS outputs perform identically, there's no point in spending money on XLR->3.5mm converters so that you can plug your unbalanced headphone into the "balanced" output.

In fact, these adapters always bear the risk of poor connections or faulty construction, so I just wouldn't bother.

For single-ended headphones, use the single-ended output.
For 4pin XLR headphones, use the 4pin XLR output.

For any other headphones, convert them to whatever port's more convenient to you.

E50 Question: There are three different filters. I've seen the graphs, but it's not clear to me which I should use.

Try all three.
If you can't hear a difference, then F3 is safe choice as it'll prevent aliasing.

 

[DVDdoug]

Tube Question: I'm so ridiculously impressed by the crystal clean sound coming out of this stack, but I want to play a bit and I've never played with tube amps.

There is no advantage to 1950's technology. It's just more expensive to make a good tube amplifier. Tube power amplifiers are especially expensive because they need an output transformer. If you want "tube sound" (distortion?) you'll have to listen to the particular amplifier to decide if the distortion is kind of distortion you want, and in the amount you want. (There is no one tube sound, and like good solid state amps, good tube amps don't have any particular sound of their own.)

"All else being equal", a balanced headphone amplifier can put-out twice the voltage for 4 times the power, or 6dB louder. But there are easier ways to get double the voltage (or more) and you don't need special headphones.

Balanced microphone connections are used because it helps with noise immunity. Microphone preamps typically have a gain of 100 or 1000 and noise gets amplified too. Line level connections are not as sensitive to noise, but if you have long cable runs or a ground loop, then balanced line connections can help. In a pro recording studio the microphone and line connections are both balanced. As a bonus, they can use the same cables for both.

Speaker & headphone wiring/connections can't pick-up enough energy to get noise out of the transducer so noise isn't a problem. But balanced (AKA bridged) outputs are sometimes used on power amplifiers (for more power). Unlike headphones the speaker itself doesn't have a ground or a common connection between left & right, so balanced/bridge amplifiers can be used with any speaker. That also means you can't have a ground loop.