[nailbunny7]

If I'm not mistaken, the 1250, like many receivers of the day, drives the headphone output off the speaker outputs through a series resistor. No need for the mess of a speaker tap adapter.

se

That would make me so happy

 

[Steve Eddy]

That would make me so happy

Post a query over in the "Calling All 'Vintage' Integrated/Receiver Owners" thread in the full size headphone amps forum. I'm sure someone there can give you a confirmation on that for the 1250.

se

 

[Happy Camper]

Thanks!
Can you give me a rule of thumb as to when to use the resistor?

HiFiMan suggests using the parallel resistor for transformer coupled output amps not rated for 50 ohms. They also recommend using a series resistor on amps above 80 watts.

Experience says be careful with the volume control and you can use them on any amp within reason and responsibility. I have ran mine on 40 to 400 w speaker amps.

 

[LarsHP]

Isn't the resistor on the speaker output (inside vintage type amps) going to add to the output impedance quite a bit? This will then make a poor damping factor.

My Leben CS300 has such a headphone output (it uses a 270 Ohm resistor), and I think I hear that poor damping factor in the bass. I am getting resistors for speaker tap output to my HE-6.

 

[Steve Eddy]

Isn't the resistor on the speaker output (inside vintage type amps) going to add to the output impedance quite a bit? This will then make a poor damping factor.

My Leben CS300 has such a headphone output (it uses a 270 Ohm resistor), and I think I hear that poor damping factor in the bass. I am getting resistors for speaker tap output to my HE-6.

Orthos like the HE-6 are virtually a purely resistive load so the whole notion of "damping factor" is meaningless.

se

 

[Clemmaster]

Quote:

Orthos like the HE-6 are virtually a purely resistive load so the whole notion of "damping factor" is meaningless.

se

 
No, the electrical damping factor determines the degree of "control" the amp has over the drivers and it is true for any type of load.
 
Planar drivers are immune to frequency response alteration because their impedance across the spectrum is flat so they all respond the same way to the amp's output impedance. 

 

[LarsHP]

Quote:

No, the electrical damping factor determines the degree of "control" the amp has over the drivers and it is true for any type of load.
 
Planar drivers are immune to frequency response alteration because their impedance across the spectrum is flat so they all respond the same way to the amp's output impedance. 

You express my understanding of this exactly - and would like to add that the control is specifically important regarding bass quality.

 

[Steve Eddy]

No, the electrical damping factor determines the degree of "control" the amp has over the drivers and it is true for any type of load.

No, "damping factor" has everything to do with reonance, and comes from the world of dynamic loudspeakers.

If you look at the impedance plot of a typical dynamic loudspeaker, you'll see that it has a peak at the low end of its frequency range (dynamic headphone drivers also exhibit this same basic characteristic). Where this curve peaks represents the driver's resonant frequency and relates to the driver's low frequency response.

This resonance is the result of the reactive elements of a loudspeaker driver, which are capacitance and inductance in the electrical domain and mass and compliance ("springiness") in the mechanical domain.

The character of this resonance is described by "Q," which in driver specs is given as "Qts." Qts is a composite of the driver's electrical resonance (Qes) and its mechanical resonance (Qms).

A Q of 0.5 is what's called "critically damped," meaning you'll get the flattest low frequency response without any ringing or overshoot. A Q below 0.5 is called "overdamped," and while there is no overshoot or ringing, low frequency response will be diminished. A Q above 0.5 is called "underdamped," and results in varying degrees of ringing and overshoot as well a a peaking in the low frequency response.

There is a common compromise that shoots for a damping factor of 0.707. The "give" is that there will be a small amount of ringing and overshoot, but the "take" is that you get the flattest, lowest extending low frequency response.

If you put a driver of a given Qts in a sealed box, you end up with a higher overall Q (called Qtc). How much higher depends on the size of the box. Smaller boxes will raise Qtc to a greater degree than a larger box.

When when designing loudspeakers, it's assumed that the loudspeaker will be driven by a voltage source, which ideally means an output impedance of zero.

And now here is where damping factor comes in.

If you have a loudspeaker that you have designed to have a Qtc when driven by a zero or very low output impedance, as you increase the output impedance, you raise the overall Q, just as you would if you decreased the size of the box, and this means you will begin to get more and more ringing and overshoot, as well as a peak in the low frequency response.

Basically what happens is the higher output impedance diminishes electrical Q and the resonant behavior begins to resemble the driver's mechanical Q which is typically rather high.

Anyway, the salient point I'm trying to make here is that damping (and hence "damping factor") has everything to do with resonant behavior. And if you're driving a purely resistive load with no resonance, "damping factor" is meaningless.

se

 

[Steve Eddy]

You express my understanding of this exactly - and would like to add that the control is specifically important regarding bass quality.

Only when you're dealing with a resonant system like a dynamic loudspeaker or headphone driver. Not when you're dealing with orthos which have no resonance in the low frequencies as witnessed by their flat, virtually purely resistive impedance curves. The ortho driver is "controlled" just fine even when driven from high source impedances.

se

 

[khaine1711]

Quote:

Only when you're dealing with a resonant system like a dynamic loudspeaker or headphone driver. Not when you're dealing with orthos which have no resonance in the low frequencies as witnessed by their flat, virtually purely resistive impedance curves. The ortho driver is "controlled" just fine even when driven from high source impedances.

se

Thanks for the detailed technical post Steve. Explain why the He-6 sounds pretty much the same out of different impedance tap on my amp.
 
Still does output impedance affect orthos in anyway?

 

[Steve Eddy]

Thanks for the detailed technical post Steve. Explain why the He-6 sounds pretty much the same out of different impedance tap on my amp.

Still does output impedance affect orthos in anyway?

Well,you'll get attenuation due to the voltage divider formed by the amp's output impedance and the impedance of the headphones. As a simple example, if the source impedance is 50 ohms, and the headphones are 50 ohms, the voltage across the headphones would be half what it would be if the source impedance were zero.

se

 

[Clemmaster]

Quote:

No, "damping factor" has everything to do with reonance, and comes from the world of dynamic loudspeakers.

If you look at the impedance plot of a typical dynamic loudspeaker, you'll see that it has a peak at the low end of its frequency range (dynamic headphone drivers also exhibit this same basic characteristic). Where this curve peaks represents the driver's resonant frequency and relates to the driver's low frequency response.

This resonance is the result of the reactive elements of a loudspeaker driver, which are capacitance and inductance in the electrical domain and mass and compliance ("springiness") in the mechanical domain.

The character of this resonance is described by "Q," which in driver specs is given as "Qts." Qts is a composite of the driver's electrical resonance (Qes) and its mechanical resonance (Qms).

A Q of 0.5 is what's called "critically damped," meaning you'll get the flattest low frequency response without any ringing or overshoot. A Q below 0.5 is called "overdamped," and while there is no overshoot or ringing, low frequency response will be diminished. A Q above 0.5 is called "underdamped," and results in varying degrees of ringing and overshoot as well a a peaking in the low frequency response.

There is a common compromise that shoots for a damping factor of 0.707. The "give" is that there will be a small amount of ringing and overshoot, but the "take" is that you get the flattest, lowest extending low frequency response.

If you put a driver of a given Qts in a sealed box, you end up with a higher overall Q (called Qtc). How much higher depends on the size of the box. Smaller boxes will raise Qtc to a greater degree than a larger box.

When when designing loudspeakers, it's assumed that the loudspeaker will be driven by a voltage source, which ideally means an output impedance of zero.

And now here is where damping factor comes in.

If you have a loudspeaker that you have designed to have a Qtc when driven by a zero or very low output impedance, as you increase the output impedance, you raise the overall Q, just as you would if you decreased the size of the box, and this means you will begin to get more and more ringing and overshoot, as well as a peak in the low frequency response.

Basically what happens is the higher output impedance diminishes electrical Q and the resonant behavior begins to resemble the driver's mechanical Q which is typically rather high.

Anyway, the salient point I'm trying to make here is that damping (and hence "damping factor") has everything to do with resonant behavior. And if you're driving a purely resistive load with no resonance, "damping factor" is meaningless.

se

 
You surely know your schiit 

Thanks for the details!

 

[LarsHP]

Thanks, Steve Eddy, for your detailed explanation. However, my ears tell me easily, that the bass is tighter on both my SS amps, which has less than 1 Ohm output impedance, than through my tube amps headphone output, which has a quite high output impedance.

If it isn't the difference in output impedance making the bass thight on my SS amps and clearly less so on the tube amp, what makes the difference then?

 

[khaine1711]

Quote:

Thanks, Steve Eddy, for your detailed explanation. However, my ears tell me easily, that the bass is tighter on both my SS amps, which has less than 1 Ohm output impedance, than through my tube amps headphone output, which has a quite high output impedance.

If it isn't the difference in output impedance making the bass thight on my SS amps and clearly less so on the tube amp, what makes the difference then?

The amps themselves?
 
You're talking about two different amps, one SS one tube even. Not saying ss have better bass than tube or anything like that. Just that different amps are ... different.

 

[Steve Eddy]

Quote:

You surely know your schiit 

Thanks for the details!

 
I know a little Schiit (glancing over at the Magni on my desk).

 
No problem. There's a lot of apocryphal information floating around the audio world that keeps getting passed along as Gospel so it's often hard to separate the wheat from the chaff.
 
se