Woo Audio WA7 Fireflies Gen 3

Quick question: There is little stated on the internet about it that I could find. Is it fully tube amplified? Or hybrid SS and tube?

While I’m not fully sure, it looks like it’s tube drive not hybrid. It is a solid state power supply so not tube rectified, but the tubes drive the headphones, believe it’s transformer coupled

I do seem to remember reading about it being DC coupled to the transformer, yes. Thanks!

I remember the original fireflies were true transformer coupled tube amps (sans tube rectification), I’d say it’s pretty safe to assume the gen 3 is as well given the changes from 1-2 and 2-3. I just wish they would offer a version without the dac, as from my experience the internal dac on the gen 1 and gen 2 was pretty lackluster. Would have just rather pocketed the savings from not having a dac and gotten a nicer standalone dac. But could be better in the gen 3, won’t know until I try them lol

I couldn’t agree more. Supplement the dac with some XLR inputs instead. Then I can run my Ares II balanced into it.

I can sort of understand why they didn’t bother with xlr inputs, likely because the internal design of the amp isn’t balanced, and they just create a balanced out with taps on the output transformer. For a fully balanced design they would need 4 12au7 instead of two, otherwise in order to accommodate a balanced signal as it is now, they would need to add input transformers to convert to single ended internally, which would add unnecessary cost and complexity (also likely make the unit larger lol). Unless I’m misunderstanding how a balanced tube design actually works lol, the older firefiles weren’t balanced, so I’d be surprised if they redid the entire thing to make it balanced

If you wanted a balanced design from them, you’d have to step up to the WA22 as I believe that is fully balanced iirc (and also pretty great, nice step over the fireflies at least from gen 2)

Huh. Somehow I thought it was truly balanced. Isn’t the 12AU7 a dual triode? You could send plus to one side and negative to the other…

The marketing on the website indicates it is a Class-A balanced amp and DAC.

In theory yes, although it would depend on the overall topology of the amp, the amp could use both sides of the triode as push pull in opposite polarity, then add the signals back together when it reaches the transformer which acts as the common ground. Which wouldn’t be balanced (no separate ground for each channel at the end). Using the tubes in parallel would allow for more current overall, using both sides of each triode, but wouldn’t really be balanced either with a transformer coupled design. I’m not really the most educated on circuit design, but I do know there are tube designs which despite using a pair of double triodes, aren’t actually balanced for one reason or another. You’d really have to ask woo what parts of the amp are actually balanced to really know

Amps can be balanced on the output stage, but not balanced on the input stage, or vice versa, and also be balanced in the amplification stage, generally if something is balanced from start to finish throughout that would fall under fully balanced (or differential?), although I guess something only balanced on the output stage could also count as balanced, but not fully balanced. Can be confusing lol

It’s just weird that it’s noted as balanced, but not fully balanced like the wa22 or wa33.

Can be confusing lol, I guess if woo says it’s balanced then there’s a high chance of it being internally balanced lol, I just would have figured they’d give you a 4.4mm input if that were the case. Either way, not like it matters all too much as long as it sounds good

Yeah, there’s a subtle note in the marketing text that suggests it has a balanced output stage, and doesn’t indicate fully balanced, or otherwise balanced anywhere else. This is disappointing.

It could be fully balanced only if you’re using the built in dac, but I’m really not sure to be honest. Would really be a question for woo. I’m sure it sounds great regardless. A lot of this technical stuff goes over my head so just making guesses

Yeah. That’s the thing, I am betting they are sending the negative to one side of the tube and positive to the other, and balancing the output at the DAC. Still, I would like a fully balanced option for input, too. And at $1500, it doesn’t seem like a lot to ask for.