[mesaboogie]

I have been around hifi and pro audio but headphones I never got into. I have acquired a pair of Audeze LCD 3 headphones and I am googling the devil out of the impedance matching. I am not seeing a clear understandable explanation of why these (headphones in general) don’t require a match the way speakers do. We should use the impedance of the headphone divided by 25 for the amps output impedance? Mind->blown.

I have built a few tube guitar amps and own a nice hifi tube power amp and that just seems completely counter everything I have ever known.

So question
1) if a company like Woo Audio lists the output at 8-600 ohms, are they saying it’s okay for use with headphones rated between that? Their hi z/lo z switch sets it to two settings that accommodate with approve mismatch anything between there? Would it stand that 8ohm is one of the OT taps, or would it be more likely higher and they say it will work with a 8ohm headphone?

2) from the above, if listing 8-600 ohm, are they saying the headphones actual rating? Or is that for the amps impedance after you do the math of 110/25?

3) LCD 3 is 110ohm. So I want about a 4.4ohm output transformer?

I have heard them with the WA7 fireflies and while the Hiz setting initially sounded more immediate, the loZ setting was more pleasant after a short time. Still trying to determine if I want to buy a tube or SS, or if there is a true audiophile level kit/layout; build my own.
The WA7 with the LCD3 was a hair warm on the top end. Far from bad though. I heard the Focal Utopias thru it though and they have the top end. So maybe part the headphone and a slightly brighter amp is what I need.

 

[Dulalala]

1) if a company like Woo Audio lists the output at 8-600 ohms, are they saying it’s okay for use with headphones rated between that? Their hi z/lo z switch sets it to two settings that accommodate with approve mismatch anything between there? Would it stand that 8ohm is one of the OT taps, or would it be more likely higher and they say it will work with a 8ohm headphone?

It would work, but you might have issues like impedance mismatching. Really depends on the actual specifications of the amp, the 8-600 ohms is just a general rules thing.

2) from the above, if listing 8-600 ohm, are they saying the headphones actual rating? Or is that for the amps impedance after you do the math of 110/25?

I've never heard of the /25 rule? It's usually 1/8. The reason you want an output impedance of less than 1/8 of the impedance of the driver is to make sure that you have sufficient electrical damping.
The 8-600 ohm refers to the impedance of the headphones.

3) LCD 3 is 110ohm. So I want about a 4.4ohm output transformer?

I don't know what you mean by 4.4 ohm transformer? But anything with an output impedance with less than 14 ohms should be fine regardless. You'd be hard pressed to find a headphone amp with a higher output impedance than that anyways with the exception of an OTL tube amp.

 

[mesaboogie]

That was my 110/25 equaling 4.4. I must have misread that somewhere about dividing by 25. Even the 1/8th still gets me why they want dampening rather than perfect match, other than I guess headphone makers not using a set of standard impedance numbers?

 

[Dulalala]

That was my 110/25 equaling 4.4. I must have misread that somewhere about dividing by 25. Even the 1/8th still gets me why they want dampening rather than perfect match, other than I guess headphone makers not using a set of standard impedance numbers?

I mean what you meant by "output transformer".

You might want to read this...

https://en.wikipedia.org/wiki/Damping_factor

Especially the "in practice section".

 

[mesaboogie]

I will read that in a bit. Thanks. I was referencing the output impedance of the secondary on the OT. So with 1/8 of the 110 ohms the secondary would ideally be wound at 14ohm from what I am gathering.

 

[Me x3]

The higher the damping factor the more the amp will be able to transfer its power to the headphone.
If the amp has an output impedance of 110 Ohm and your headphone has an impedance of 110 Ohm then you won't be able to use the amplifier's full power.
(In some cases you might not need it anyway)

When it comes to dynamic (moving coil) drivers, damping factor can be of importance because they have a winding impedance curve.
When paired with an amplifier with low damping factor the sound gets coloured in the shape of the impedance curve.

Your planar has a flat impedance curve (same impedance for all frequencies) then it won't become coloured with a low damping factor.
According to some tests and measurements we've accomplish, distortion doesn't increase either. So there's little to worry about when you're using a planar magnetic headphone with flat impedance.

A detailed neutralish solid state amplifier might be the most balanced match for your Audezes.
Most of them have very little output impedance so damping factor will be great anyway.

 

[MindsMirror]

Most headphone amp's don't use output transformers. An output transformer is used to drive a low impedance load from a high output impedance source. A headphone impedance is typically sufficiently higher than the amp's output impedance, so no transformer is needed.

As far as I'm aware, hi-fi integrated amps don't use output transformers either, so even with hi-fi speakers you don't want to match the speaker and output impedance, you want as low output impedance as possible.

The only amps I'm aware of that commonly use output transformers these days are guitar amplifiers. Guitar amp's often still use tubes and and have too high output impedance to drive the speakers directly without a transformer. Also high fidelity is not a concern for guitar amps, a colored or distorted sound is desirable.

 

[buke9]

My Amps and Sound Kenzie has a output transformer.

 

[mesaboogie]

Most headphone amp's don't use output transformers. An output transformer is used to drive a low impedance load from a high output impedance source. A headphone impedance is typically sufficiently higher than the amp's output impedance, so no transformer is needed.

As far as I'm aware, hi-fi integrated amps don't use output transformers either, so even with hi-fi speakers you don't want to match the speaker and output impedance, you want as low output impedance as possible.

The only amps I'm aware of that commonly use output transformers these days are guitar amplifiers. Guitar amp's often still use tubes and and have too high output impedance to drive the speakers directly without a transformer. Also high fidelity is not a concern for guitar amps, a colored or distorted sound is desirable.

I don’t know about integrated as I don’t pay much attention to those, but almost every hifi tube power amp I have looked at has an output transformer unless it’s an OTL, and those are generally not as well regarded for their versatility with loads, even when supplying ample WPC. Great amps maybe, but picky with loads. But OTL is rare for hifi tube power amps.

Good to know that OTL is common in headphones. I was noticing a higher percentage saying OTL than I am used to running into with normal HiFi power amps.

But I am a fan of high end tube gear. It’s my first choice, but I can appreciate SS too. My phono pre is an Avid Pulsus, solid state, and fantastic. I have heard enough Pass equipment to know I wouldn’t feel bad with their stuff either.

 

[buke9]

There are some OTL's that have no problems with low impedance Planars also the LTA Microzotl 2 is one.