[slokenafk]

Hi all. Quick lil question. I have some he-400s in the mail right now. Im considering getting into tube amps and im wondering what would be a nice and relatively affordable tube amp for these cans?

 

[henree]

I have the Little Dot Hybrid+. And depending on your tube choice it can sound fantastic. Amazing 3dimensional sound. The mids are amazing. I wish there was a little more bass though. 

 

[slokenafk]

Hm, Ive seen mention of the little dots. Correct me if Im wrong but an OTL tube amp would not be good for the he-400s due to low impedence?

 

[hodgjy]

  Hm, Ive seen mention of the little dots. Correct me if Im wrong but an OTL tube amp would not be good for the he-400s due to low impedence?

 
Thoughts are mixed on the use of OTL tube amps with planars, like the HE-400.  OTLs have high output impedance, which is not a good match for dynamic headphones because of the damping factor.  However, planars are purely resistive, so they don't have the same damping problems that dynamics have.  If that's the case, output impedance doesn't matter.  What matters is whether the OTL can push enough voltage for the low impedance headphones.

 

[slokenafk]

   
Thoughts are mixed on the use of OTL tube amps with planars, like the HE-400.  OTLs have high output impedance, which is not a good match for dynamic headphones because of the damping factor.  However, planars are purely resistive, so they don't have the same damping problems that dynamics have.  If that's the case, output impedance doesn't matter.  What matters is whether the OTL can push enough voltage for the low impedance headphones.

Thanks for the information. I have started to understand the sorcery that is planar magnetic headphones.

 

[ab initio]

   
Thoughts are mixed on the use of OTL tube amps with planars, like the HE-400.  OTLs have high output impedance, which is not a good match for dynamic headphones because of the damping factor.  However, planars are purely resistive, so they don't have the same damping problems that dynamics have.  If that's the case, output impedance doesn't matter.  What matters is whether the OTL can push enough voltage for the low impedance headphones.

 
This is not true.
 
Because they are mostly resistive, they are less susceptible to having the output impedance of the amplifier cause wonky changes in the speaker coils' RL filter characteristics. This has nothing to do with damping.
 
However, as far as damping is concerned. Damping results as the mechanical response of the transducer moves the driver coil (or the planar magnetics wire traces) through the magnetic field, a current is induced in coils which damps the transducer motion. The amount of current that flows is proportional to the damping and inversely proportional to the combined impedance of the headphone+amplifier. High amplifier output impedance limits how effectively the amplifier can control the transducer from free mechanical vibration.
 
having high output impedance will cause a difference in the damping of the transducer. Whether it is dynamic or orthodynamic is completely irrelevant. If the output impedance is too high, then the electrical damping will be low and the sound will be colored. This is bad if you want high fidelity sound reproduction, but some may find the distortion euphonic and pleasing.
 
Cheers

 

[DutchGFX]

The issue isn't voltage for low Z, its current. The reason tubes are used for High Z phones is because they are voltage gain stages. OTL amps are not good as they put out a ton of voltage and minimal current. Adding the output transformer converts this voltage into a current, which helps. You would be better off with a Hybrid, since they contain a voltage gain stage, AND usually a MOSFET current drive stage, which is beyond my knowledge.

The benefit of a hybrid is that it becomes a Power Amp, instead of a voltage amp or current amp alone, so it can be used with a variety of headphones.

I would go with a Lyr, its the best amp for planars in my opinion for under $500

Hope that helps!

 

[Xenophon]

   
This is not true.
 
Because they are mostly resistive, they are less susceptible to having the output impedance of the amplifier cause wonky changes in the speaker coils' RL filter characteristics. This has nothing to do with damping.
 
However, as far as damping is concerned. Damping results as the mechanical response of the transducer moves the driver coil (or the planar magnetics wire traces) through the magnetic field, a current is induced in coils which damps the transducer motion. The amount of current that flows is proportional to the damping and inversely proportional to the combined impedance of the headphone+amplifier. High amplifier output impedance limits how effectively the amplifier can control the transducer from free mechanical vibration.
 
having high output impedance will cause a difference in the damping of the transducer. Whether it is dynamic or orthodynamic is completely irrelevant. If the output impedance is too high, then the electrical damping will be low and the sound will be colored. This is bad if you want high fidelity sound reproduction, but some may find the distortion euphonic and pleasing.
 
Cheers

This is a very interesting argument and something I hadn't yet considered myself so thank you for that.  But I imagine the effect would be highly dependent on the structure, materials used in the traces, membrane thickness etc.  Are you aware of any efforts to quantify this effect and see to what extent it's relevant in the context of tube amplification which is intrinsically not exactly the sum mum of accuracy?
 
My high dollar solution would be to use a tube amp to feed a current buffer such as the Firstwatt F4 which is essentially a transparent window operating at unity gain (actually a bit less than unity).  But ok, not for <500 USD

 

[slokenafk]

The issue isn't voltage for low Z, its current. The reason tubes are used for High Z phones is because they are voltage gain stages. OTL amps are not good as they put out a ton of voltage and minimal current. Adding the output transformer converts this voltage into a current, which helps. You would be better off with a Hybrid, since they contain a voltage gain stage, AND usually a MOSFET current drive stage, which is beyond my knowledge.

The benefit of a hybrid is that it becomes a Power Amp, instead of a voltage amp or current amp alone, so it can be used with a variety of headphones.

I would go with a Lyr, its the best amp for planars in my opinion for under $500

Hope that helps!

It does thank you. Im still trying to justify spending more. My modest setup (magni + he-400) is still hard to justify to my SO. Ill have to give it some time before I spend even more.

Sent from my SCH-I535 using Tapatalk

 

[Xenophon]

The issue isn't voltage for low Z, its current. The reason tubes are used for High Z phones is because they are voltage gain stages. OTL amps are not good as they put out a ton of voltage and minimal current. Adding the output transformer converts this voltage into a current, which helps. You would be better off with a Hybrid, since they contain a voltage gain stage, AND usually a MOSFET current drive stage, which is beyond my knowledge.

The benefit of a hybrid is that it becomes a Power Amp, instead of a voltage amp or current amp alone, so it can be used with a variety of headphones.

I would go with a Lyr, its the best amp for planars in my opinion for under $500

Hope that helps!

You are absolutely, 100% right about what you say concerning OTL tube amps.  For low sensitivity, low impedance planars they must be the worst possible combo.  Just to say that I'm in complete agreement with you.
 
Yet, subjectively, when I listen to my HE-500 (38 Ohm if memory serves) connected to my DV 337 dual mono OTL tube amp that I purchased used for a song -but you don't want to know about what I spent on tubes so far- all I can say is that it sounds glorious and honestly, I don't think we're talking about some (to me) euphonic sounding distortion.