[Schnarpf]

First of all, thank you for this thread. I have connected my Audeze to my Shindo by using a Hifiman adapter. When I read about connecting headphones to speaker amps I was curious if that could work. I didn't want to build a Robinette box by myself, because I don't trust myself in succeeding and I would't like an exploding amp or phone, so I got the adapter. I also got a Hifiman HE6 from my very generous dealer. Unfortunately, I didn't like its sound as much as the LCD2. What is really interesting is that my Shindo sounds completely different now. Connected to my speakers, Audio Note E, it sounds delicate, fast and sparkling with enormous quantities of information in the upper registers and lots of dynamic punch. Btw, why do so many people complain that tube amps are "mellow sounding"? I never heard such an amp.
Now the music is presented a lot darker with weight down in the lower registers, but in a way that, just now, sounds even better than with my speakers. There is more density, less delicacy, a little more what I see as euphony. Compared to my DAC/headamp, an Eximus, there is different presentation. Where the Eximus is a little pale, the Shindo, fed by the Eximus DAC, gives you colourful sound. Maybe not the last word in extreme precision, but strings sound big, I'm listening to Dvoraks String Quintet op. 97 right now. Beautiful!

 

[Armaegis]

  Need some help from the experts here please!  I have Alpha Dogs and LCD 3 running of speaker taps on my Integrated Tube Amp.  The output off of the speaker taps is rated at 5 wpc and I have 10 ohm wirewound resistors across the speaker taps as a load.  How can I determine the power in watts that is being input to my LCD 3 that are 110 ohms impedance with 93db sensitivity?  The headphones sound very good, but I would like to compare the power to my other Denon amps that output 110 wpc and 125 wpc off of the speaker taps on those.  Can someone help with the confusion?  It would be much appreciated!

Is your tube amp's rated 5 wpc into a 4ohm or 8ohm load (or something else?). Let' s just assume 4ohm for now.
 
Power is calculated as P = V^2/R
so holding the voltage swing the same but increasing impedance
we drop power by a factor of 4/110... which gives you ~182 mW
 
That's still enough to get you to roughly 115dB.
 
That all said, it'll probably get louder than that. The calculations all assume that you're at the voltage limit of the amp, whereas in most cases you're actually hitting a current limit which is no longer a concern when you switch to headphones so they can in fact push highher.

 

[Terja]

@cute - The combined resistance for your set up with the LCD3  is 9.17 ohms (10ohms x 110ohms / 10 + 110) or (CR=R1xR2 / R1+R2).
 
With an amp rated at 5 watts, of that, the 10 ohm resistor is chewing up 4.58 watts ( 5wpc x 9.17ohms / 10ohms), which means only 0.42 watts are available for the LCD3, or based on calculation (5wpc x 9.17ohms / 110ohms = 0.417 watts).
 
If you use a higher value resistor, say 15 ohms, you will increase the amount of power available to the headphone.

 

[Chris J]

@cute - The combined resistance for your set up with the LCD3  is 9.17 ohms (10ohms x 110ohms / 10 + 110) or (CR=R1xR2 / R1+R2).

With an amp rated at 5 watts, of that, the 10 ohm resistor is chewing up 4.58 watts ( 5wpc x 9.17ohms / 10ohms), which means only 0.42 watts are available for the LCD3, or based on calculation (5wpc x 9.17ohms / 110ohms = 0.417 watts).

If you use a higher value resistor, say 15 ohms, you will increase the amount of power available to the headphone.

It depends on the output impedance of the amp, but the difference will be academic.
Assuming the amp is rated for 5 Watts @ 8 Ohms, and you are not loading the amp done excessively, increasing the parallel resistor from 10 Ohms to 15 Ohms will make very little difference.
The main thing is: the headphones will still present a 110 Ohm load to the amp.

 

[davidsh]

This is also highly dependent on the amp itself. Generally tube amps are good at great voltage swings, not so much at delivering current, meaning it might deliver quite a lot of power to your headphones if you had no parallel resistor across the terminals. Unless it has an output transformer, then things get wonky I think?
 
But you do have a parallel resistor, meaning @Terja is correct in his calculations.
 
Is the amp OTL or does it have a output transformer?

 

[cute]

It has an output transformer!

 

[Chris J]

This is also highly dependent on the amp itself. Generally tube amps are good at great voltage swings, not so much at delivering current, meaning it might deliver quite a lot of power to your headphones if you had no parallel resistor across the terminals. Unless it has an output transformer, then things get wonky I think?

But you do have a parallel resistor, meaning @Terja
 is correct in his calculations.

Is the amp OTL or does it have a output transformer?

Let's just assume you have:
An amp with zero output impedance.
Let's also assume:
You are not in voltage or current clipping.
Let's also assume the amplifier is designed as a voltage source (a very reasonable assumption).
Adding or taking away the 10 Ohm resistor will have no effect on how much power the 110 Ohm headphones can draw.


Edited, I performed some calculations, see below....
Since this is a tube amp, which has an output transformer, the output impedance will not be close to zero, but the output impedance will only make a slight difference.

 

[doyouknowSBmean]

how is an A-GD master 10 for a he6 or hd800. a 500 watt monster @4 ohm.

 

[Chris J]

  @cute - The combined resistance for your set up with the LCD3  is 9.17 ohms (10ohms x 110ohms / 10 + 110) or (CR=R1xR2 / R1+R2).
 
With an amp rated at 5 watts, of that, the 10 ohm resistor is chewing up 4.58 watts ( 5wpc x 9.17ohms / 10ohms), which means only 0.42 watts are available for the LCD3, or based on calculation (5wpc x 9.17ohms / 110ohms = 0.417 watts).
 
If you use a higher value resistor, say 15 ohms, you will increase the amount of power available to the headphone.

 
Let's assume the tube amp outputs 5 Watts @ 8 Ohms
and let's assume the output impedance of the amp is 0.5 Ohms
 
Output voltage into an 8 Ohm load would be 6.32 Volts @ 5 Watts.
Using the voltage divider principle, the output voltage would be 6.36 Volts into a 9.17 Ohm load (the 10 Ohm resistor in parallel with the 110 Ohm headphone).
The amp would output 4.41 Watts into the 9.17 Ohm load, the headphones would receive 368 milliWatts, the 10 Ohm resistor would receive approx. 4.04 Watts.
 
If the 10 Ohm resistor was changed to 15 Ohms:
Total load impedance is 13.2 Ohms
Output voltage is 6,47 Volts.
Output power is 3.17 Watts
Power into the headphones is 380 milliWatts, into the 15 Ohm resistor 2.79 Watts
 
So even with a 0.5 Ohm output impedance the difference between loading the amp with either a 10 Ohm resistor or a 15 Ohm resistor is trivial:  368 milliWatts vs. 380 milliWatts.

 

[Rossliew]

First of all, thank you for this thread. I have connected my Audeze to my Shindo by using a Hifiman adapter. When I read about connecting headphones to speaker amps I was curious if that could work. I didn't want to build a Robinette box by myself, because I don't trust myself in succeeding and I would't like an exploding amp or phone, so I got the adapter. I also got a Hifiman HE6 from my very generous dealer. Unfortunately, I didn't like its sound as much as the LCD2. What is really interesting is that my Shindo sounds completely different now. Connected to my speakers, Audio Note E, it sounds delicate, fast and sparkling with enormous quantities of information in the upper registers and lots of dynamic punch. Btw, why do so many people complain that tube amps are "mellow sounding"? I never heard such an amp.
Now the music is presented a lot darker with weight down in the lower registers, but in a way that, just now, sounds even better than with my speakers. There is more density, less delicacy, a little more what I see as euphony. Compared to my DAC/headamp, an Eximus, there is different presentation. Where the Eximus is a little pale, the Shindo, fed by the Eximus DAC, gives you colourful sound. Maybe not the last word in extreme precision, but strings sound big, I'm listening to Dvoraks String Quintet op. 97 right now. Beautiful!

My guess is you are hearing the sound signature of the LCD-2, which is dark and warm...tube-like i suppose.

 

[Schnarpf]

Thanks. This needs further investigation! I will try other speaker amps as well.

 

[potterma]

Let's assume the tube amp outputs 5 Watts @ 8 Ohms
and let's assume the output impedance of the amp is 0.5 Ohms

Output voltage into an 8 Ohm load would be 6.32 Volts @ 5 Watts.
Using the voltage divider principle, the output voltage would be 6.36 Volts into a 9.17 Ohm load (the 10 Ohm resistor in parallel with the 110 Ohm headphone).
The amp would output 4.41 Watts into the 9.17 Ohm load, the headphones would receive 368 milliWatts, the 10 Ohm resistor would receive approx. 4.04 Watts.

If the 10 Ohm resistor was changed to 15 Ohms:
Total load impedance is 13.2 Ohms
Output voltage is 6,47 Volts.
Output power is 3.17 Watts
Power into the headphones is 380 milliWatts, into the 15 Ohm resistor 2.79 Watts

So even with a 0.5 Ohm output impedance the difference between loading the amp with either a 10 Ohm resistor or a 15 Ohm resistor is trivial:  368 milliWatts vs. 380 milliWatts.

Actually, if the resistor is in parallel, then the voltage out of the amplifier = the voltage across the resistor = the voltage across the headphones. There is no voltage divider. There is a current divider but that has ZERO effect on the power delivered to the headphones. The parallel load resistance does NOTHING to the power to or the current through the headphones.

 

[Chris J]

Actually, if the resistor is in parallel, then the voltage out of the amplifier = the voltage across the resistor = the voltage across the headphones. There is no voltage divider. There is a current divider but that has ZERO effect on the power delivered to the headphones. The parallel load resistance does NOTHING to the power to or the current through the headphones.

 


As I said, assuming the amplifier has an output impedance of 0.5 Ohms (or has a non-zero output impedance).
Since all voltage amplifiers (i.e. the typical audio power amp) have some output impedance, there will be a voltage divider effect between the output impedance and the load impedance.

I didn't make those numbers up.

But you are partially correct:
the voltage across the 10 or 15 Ohm resistor will be the same as the voltage across the headphone.

You have neglected the effect of the tube amplifier's output impedance.

 

[Redcarmoose]

First of all, thank you for this thread. I have connected my Audeze to my Shindo by using a Hifiman adapter. When I read about connecting headphones to speaker amps I was curious if that could work. I didn't want to build a Robinette box by myself, because I don't trust myself in succeeding and I would't like an exploding amp or phone, so I got the adapter. I also got a Hifiman HE6 from my very generous dealer. Unfortunately, I didn't like its sound as much as the LCD2. What is really interesting is that my Shindo sounds completely different now. Connected to my speakers, Audio Note E, it sounds delicate, fast and sparkling with enormous quantities of information in the upper registers and lots of dynamic punch. Btw, why do so many people complain that tube amps are "mellow sounding"? I never heard such an amp.
Now the music is presented a lot darker with weight down in the lower registers, but in a way that, just now, sounds even better than with my speakers. There is more density, less delicacy, a little more what I see as euphony. Compared to my DAC/headamp, an Eximus, there is different presentation. Where the Eximus is a little pale, the Shindo, fed by the Eximus DAC, gives you colourful sound. Maybe not the last word in extreme precision, but strings sound big, I'm listening to Dvoraks String Quintet op. 97 right now. Beautiful!

High power tube amps always have punch. It is the low power ones that caused the rumor.

 

[potterma]

 

Actually, if the resistor is in parallel, then the voltage out of the amplifier = the voltage across the resistor = the voltage across the headphones. There is no voltage divider. There is a current divider but that has ZERO effect on the power delivered to the headphones. The parallel load resistance does NOTHING to the power to or the current through the headphones.

 


As I said, assuming the amplifier has an output impedance of 0.5 Ohms (or has a non-zero output impedance).
Since all voltage amplifiers (i.e. the typical audio power amp) have some output impedance, there will be a voltage divider effect between the output impedance and the load impedance.

I didn't make those numbers up.

But you are partially correct:
the voltage across the 10 or 15 Ohm resistor will be the same as the voltage across the headphone.

You have neglected the effect of the tube amplifier's output impedance.

No, I haven't.   Unless you are measuring the voltage out of the amplifier with no load connected (how would you know your load wasn't driving your amp into current clipping?)  So, if you measure the output voltage with the load attached, what I said above is exactly true.  Ohms law doesn't lie.