[millerdog]

Why aren't there tube amps for low impedence cans? AKA mapletree?
Is it a trend for headphone manufacturers to make these high imp. cans?
Certainly not Grado and Audio Technica?
Side note...what are the advantages of high or low imp. cans?
md

I was going to start a new thread but will edit this instead.
Why is there such a large gap in price in SS amps?
The Corda goes for $345, the next SS amps I find are the Sudgen and Adcom preamps for like $700.

 

[markjia]

I'm not electronics expert, so someone correct me if I'm wrong...

But from what I can remember, tube amps are inherintly better suited for high impedance amps (something about the properties of tubes themselves). As for the difference btw high and low impedance headphones, high impedance phones are harder to drive, but are less prone to distortion.

 

[zzz]

In a nutshell, tubes make excellent voltage amplifiers but are not so good at sourcing current. At the same power high-impedance headphones want voltage more than current, while low-impedance phones has opposite demands. So it's inherently harder to make a tubed amp for low-impedance phones.

One of the solutions is using a transformer to couple amplifier output to the headphone, which effectively reduces output impedance of the amplifier (at the same reducing the voltage swing too). But that has its own problems. Another (which is sometimes used in speaker amplifiers) is having many tubes in parallel as output devices, but that obviously has its own problems too

. Then come various clever OTL designs with [relatively] low output impedance but they are not ideal either.

And btw, high-impedance phones are not harder to drive. Maybe for voltage-limited portable amps, yeah, but for most stationary headamps this is not an issue.

 

[Hirsch]

what zzz said

The problem is actually easier for headphone amps than for speaker amps, which have to drive much lower impedance loads. The most elegant solution IMO is the Berning MicroZOTL, which apparently has a pseudo-transformer. This is an oversimplication (and a bad one) but it's able to use a transformer-type technology to reduce output impedance. It operates at radio frequencies (which are rather inaudible), unlike transformers that act directly on the audio signal. So, you get the benefits of an output transformer (output impedance of the ZOTL is below 2 ohms) without the sonic impact of the transformer.

Another solution, also with issues, is the use of solid-state output devices in hybrid amps (Melos, X-Can), that don't have the output impedance issues of tubes.

 

[millerdog]

thanks guys,
Been looking for info on this and have been kinda puzzled.
md

 

[Dusty Chalk]

Actually, there is one exception -- the EarMax Pro.