FIIO EA13 "pure vacuum tube" integrated amplifier (?!)

[DanielT]

Yes. This claims to be class A, so hopefully crossover distortion is nonexistent.

A question from a non-tube expert: What exactly is a class A push-pull tube amplifier? That is what FIIO claims their EA13 tube amplifier is. Doesn't "push-pull" in the context of tube amps imply a class AB design?

Or do FIIO mean class A for the preamp section but Class AB for the power section?

By the way, aren't virtually all preamps class A designs? Both tube and solid-state ones, that is.

 

[fpitas]

A question from a non-tube expert: What exactly is a class A push-pull tube amplifier? That is what FIIO claims their EA13 tube amplifier is. Doesn't "push-pull" in the context of tube amps imply a class AB design?
View attachment 554686
Or do FIIO mean class A for the preamp section but Class AB for the power section?

By the way, aren't virtually all preamps class A designs? Both tube and solid-state ones, that is

No, not at all. The class is determined by how much of the wave cycle the devices conduct. For example, class C conducts less than a half cycle. Class A simply means both tubes conduct current the entire cycle. Push-pull class A used to be the choice when lowest distortion was desired back in the day. Push-pull triodes were the classic.

 

[DanielT]

No, not at all. The class is determined by how much of the wave cycle the devices conduct. For example, class C conducts less than a half cycle. Class A simply means both tubes conduct current the entire cycle. Push-pull class A used to be the choice when lowest distortion was desired back in the day. Push-pull triodes were the classic.

Interesting. I didn't know that.

In that case, EA13 might actually have decent potential and/or performance. It would be fun to see some measurements of it.

Paired with reasonably high-sensitivity speakers—and considering its low price compared to other tube amplifiers—it could be a good option for those wanting to try out or own a tube amp.

 

[fpitas]

Interesting. I didn't know that.

In that case, EA13 might actually have decent potential and/or performance. It would be fun to see some measurements of it.

Paired with reasonably high-sensitivity speakers—and considering its low price compared to other tube amplifiers—it could be a good option for those wanting to try out or own a tube amp.

There are worse choices. If you decide to tinker, there are a lot of tubers here that can help.

 

[DanielT]

There are worse choices. If you decide to tinker, there are a lot of tubers here that can help.

Thank you for the offer of help.

I view it as a complete old-school package—horn speakers and a tube amplifier. However, large horn speakers take up too much space in my small living room.

Perhaps a pair of Heco Aurora 700s or 1000s..

—which have reasonably high sensitivity—and letting a tube amp handle everything from around 300 Hz upwards (those speakers support bi-amping).

But $800 just to get tube glow. I don't know.
Plus I have, low/mid sensitivity speakers now that I'm happy with but it's always fun to think about new solutions.

 

[fpitas]

Thank you for the offer of help.

Oh, I'll help. But there are actual tube designers here.

 

[mhardy6647]

We've lost a couple of the best ones, though, over the years.
I mean from the forum, not from the planet -- although of course, time has passed.

 

[Ongii]

Fiio seems to have removed the wordings for headphone connections from their EA13 product page.
https://www.fiio.com/ea13
View attachment 554159

Is this requirement (connecting dummy loads) no longer applicable/ necessary?
It would be great to have an amp which can do the headphones amp by just plugging the headphones

 

[mhardy6647]

Is this requirement (connecting dummy loads) no longer applicable/ necessary?
It would be great to have an amp which can do the headphones amp by just plugging the headphones

As noted previously, two resistors and voila.

 

[Ongii]

Do ready to buy products exist for such a goal?
Any loudspeakers switch, for example?

 

[peng]

View attachment 553954

Adding a switch and a built-in load (couple of resistors) for transformer-coupled power amplifiers was a "solved problem" six or seven decades ago.
View attachment 553955
Fisher 500C schematic (detail) from Vacuum Tube Valley, vol. 6.
EDIT: Near the bottom right of the screenshot above. 330 ohm, 1 watt resistors serve to ensure a reasonable load for the OPTs in the Fisher 500C when headphones are used with it.
In full disclosure, I have a very nice 500C -- but I've never used it with headphones!

Can that headphone jack be modified for use as pre out? Or, without any mod, just use a jack to RCA to a power amp with 20 K or higher input impedance?

 

[JeffS7444]

Can that headphone jack be modified for use as pre out? Or, without any mod, just use a jack to RCA to a power amp with 20 K or higher input impedance?

That, or a simple speaker to line-level converter ought to work fine with a Fisher 500C.