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Speaker amps for headphones - Page 10

post #136 of 2719
Quote:
Originally Posted by wuwhere View Post

 

My gut guess is because only a few bothered to try and with the AKG K1000 mostly and with a not too powerful speaker amps. With the arrival of HiFiMan's HE-6 all that changed. Even Fang used an old Threshold T400 to demo his HE-6. The price of the new higher end HP amps is going up, some here have discovered that vintage receivers sound good too. More options to power your HP which is good.

makes sense, good points. 

post #137 of 2719
Quote:
Originally Posted by wuwhere View Post

True, a typical audio amp is a voltage amplifier. Let's take a case of just a parallel 10 ohm resistor rated at 10 watts with a 50 ohm HP and for some reason the 10 ohm resistor blows. What will happen to the 50 ohm load rated at say 5 watts?

I assume you are referring to a 50 Ohm headphone with 5 Watt rating.

What happens to the other loads in your household wiring when you plug and unplug something?
When you turn your vacuum cleaner on and off.
I've never heard of any equipment in a house being damaged because a vacuum cleaner was being turned on and off.

OTOH, when output transistors blow, headphones or speakers may be damaged by the DC pulse.
Edited by Chris J - 4/17/13 at 9:19am
post #138 of 2719
Quote:
Originally Posted by Chris J View Post


What happens to the other loads in your household wiring when you plug and unplug something?
When you turn your vacuum cleaner on and off.
I've never heard of any equipment in a house being damaged because a vacuum cleaner was being turned on and off.

 

 

What if a single parallel resistor (for one channel only) were to fault. I'm thinking of the HE adapter box configuration. In that case the entire circuit wouldn't be broken.

 

Would that result in the corresponding side of the headphone (the right or the left) becoming louder ?

post #139 of 2719
Quote:
Originally Posted by alan s View Post

 

What if a single parallel resistor (for one channel only) were to fault. I'm thinking of the HE adapter box configuration. In that case the entire circuit wouldn't be broken.

 

Would that result in the corresponding side of the headphone (the right or the left) becoming louder ?

 

If I understand you correctly:

 

assume this is a solid state amp with a very low output impedance (this is a fair assumption!)

 

assume each channel has an 8 Ohm resistor in parallel with it's output

 

assume each channel is also loaded down with a 100 Ohm resistor in series with a 60 Ohm headphone

 

now if in one channel only the parallel 8 Ohm resistor fails so that it looks like the resistor is removed (this is called open circuit), then the difference in volume should be negligible.

reason:

your power amplifier probably has an output impedance of approx. 0.05 Ohms, maybe 0.1 Ohms (basically a very low value)

 

so if you remove or delete one of the 8 Ohm resistors, you may not even notice the difference in volume from channel to channel (i.e. right versus left).  The channel without the 8 Ohm resistor MAY sound very slightly louder.

 

However, if the 8 Ohm resistor faults so that the resistance is now 0 Ohms (this is called short circuit)................well, let's hope we didn't destroy the corresponding amp channel! frown.gif

 

OTOH

If the power amp is a tube amp with a relatively high output impedance, if one channel has the 8 Ohm loading resistor and the other one does not, then the one without the loading resistor would probably be noticeably louderredface.gif

 

 

BTW, I'm not trying to talking anyone into using or not using a loading resistor.


Edited by Chris J - 4/17/13 at 9:40am
post #140 of 2719
Quote:
Originally Posted by Chris J View Post


I assume you are referring to a 50 Ohm headphone with 5 Watt rating.

What happens to the other loads in your household wiring when you plug and unplug something?
When you turn your vacuum cleaner on and off.
I've never heard of any equipment in a house being damaged because a vacuum cleaner was being turned on and off.

OTOH, when output transistors blow, headphones or speakers may be damaged by the DC pulse.

 

Or to put this another way,

in your household wiring, when you turn a toaster or a tea kettle or a vacuum cleaner ON and OFF (i.e  very large loads are turning ON and OFF) the Voltage at the receptacle in the wall remains approx. 120 Vac.

 

You will get the same result from a SS power amp, the output voltage will not be affected very much by removing and adding an 8 Ohm loading resistor.

The headphones will NOT draw any extra current if you delete the 8 Ohm resistor.

 

You light bulbs in your house do not draw extra current when you turn a toaster ON and OFF.

 

BTW, I guess most people know that the light's in your house flicker when you turn a vacuum cleaner ON because the vacuum cleaner motor draws a lot of current for approx. 1/2 second to get the motor spinning. So the 120 vac line drops for a split second because the motor may draw 8 times it's normal running current to get up and running.

post #141 of 2719
Quote:
Originally Posted by Mambosenior View Post


Did you ever hook HPs to the speaker taps of the Bryston with a balanced cable?

 

BTW,

 

Just thought I would bore everyone with some math......tongue.gif

 

My cute little Bryston 2B-LP outputs 60 Watts into an 8 Ohms........i.e. 60 Watts is the onset of clipping.mad.gif

So the amp outputs a maximum of 22 Volts.

22 Volts into my ancient Senn HD424 'phones works out to 0.242 Watts at clipping. They are 2,000 Ohm 'phones.

 

So I ain't too worried, as long as I keep the volume down to a reasonable level.   But then we always do that when we use loudspeakers anyway!


Edited by Chris J - 4/17/13 at 2:10pm
post #142 of 2719
Thread Starter 

Very nice example of real numbers..

post #143 of 2719
Hey, thanks!

BTW, tried driving the Senn HD424 directly from a Pass Labs X-150 last night.
This is a balanced output, SS power amplifier, rated at 150 Watts per channel into 8 Ohms.

A very tight, punchy, clean, dynamic sound! The headphone cable used was the original skinny little cable.

The two best sounding "headphone amplifiers" for my HD424 headphones are the power amp and the balanced outputs on my pre-amp.
These headphones are 33 years old.
Edited by Chris J - 4/18/13 at 4:02am
post #144 of 2719

Can I attach the following headphones (HE-500) directly to the speaker terminals of the following SS amp without the need for resistors etc.?

 

Amp:  Emotiva mini-X a-100.  Solid state. 50 watts/ch into 8 ohms

 

Phones:  HiFiman HE-500, orthos, efficiency 89dB, impedance measures 40-50 ohms (purely resistive)

post #145 of 2719
Quote:
Originally Posted by Headphoner View Post

Can I attach the following headphones (HE-500) directly to the speaker terminals of the following SS amp without the need for resistors etc.?

Amp:  Emotiva mini-X a-100.  Solid state. 50 watts/ch into 8 ohms

Phones:  HiFiman HE-500, orthos, efficiency 89dB, impedance measures 40-50 ohms (purely resistive)
http://www.head-fi.org/t/629352/he-500-lcd2-d5000-dt770-sr80-on-a-speaker-amp-emotiva-mini-x-a-100-project
post #146 of 2719

What an attractive (looks and price) amp!

post #147 of 2719

Thanks, I am familiar with the thread you recommended.  But some of the contributors to the present thread seem to know more about using resistors with headphones and speaker amps.  So I was hoping to get opinions from contributors to the present thread about the need for resistors when using the HE-500 with the Emotiva mini.

post #148 of 2719
Quote:
Originally Posted by Headphoner View Post

Can I attach the following headphones (HE-500) directly to the speaker terminals of the following SS amp without the need for resistors etc.?

Amp:  Emotiva mini-X a-100.  Solid state. 50 watts/ch into 8 ohms

Phones:  HiFiman HE-500, orthos, efficiency 89dB, impedance measures 40-50 ohms (purely resistive)

Assuming your headphones are 50 Ohms:

the Emotiva can output up to 8 Watts into your headphone at clipping.

if you add a 50 Ohm series resistor then the Emotiva can deliver 2 Watts into your 'phones at clipping.

If you want to try it without the resistor, then start with the volume at zero and increase the volume to a comforatble level. This will not damage your headphones.

If you do choose to use the 50 Ohm series resistor, only you can decide if you prefer the sound of the added resistor. Some people like the added series resistor for the safety factor it adds.

In theory, adding an 8 Ohm resistor in parallel with the output may actually add distortion, or may decrease distortion. Try it with and without the parallel resistor, see what you prefer.
post #149 of 2719
You have no need for a resistor with that amp. It's power is about perfect for the HE-500. The protection of adding a parallel resistor was to help output transformer coupled speaker amps see a 8 ohm load. Anything over 80 w the factory recommended their load box in case of an accidental full volume condition with too powerful of an amp. Responsible management of the volume/signal strength lessens the risk of this happening. I know of members running 200wpc amps without problems. I've been running 125wpc amps for 3 years and had one mistake that blew my 6s. I sent a 50db+ signal to the amp by mistake and it popped the tracer to the driver. Professional gear has different needs and I was ignorant of the DAC's function. Anyway, if you put your HE on an amp and have very little movement before getting too loud, you may want to consider the adapter box. If you have some travel on the volume before getting loud, you should be fine. IMO
post #150 of 2719

It's nice to put some numbers to some of this stuff:

 

for reference, you probably output an average of 1 Volt into a pair of loudspeakers when you listen at a moderate volume.:

 

a wee little headphone amp like a Matrix M Stage will output approx. 8 volts maximum into your favourite 'phones

 

a "real man's" headphone amp like a Bryston HPA-1 will output approx. 15 Volts max into your favourite 'phones

 

The 50 Watt Emotiva will output a maximum of approx. 20 Volts into a pair of 'phones.

 

A 125 Watt power amp like Mr. Happy Camper's will output approx. 32 Volt max.

 

As our Happy Camper points out, just keep a sharp eye on your volume control! 

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