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HifiMAN HE-6 Planar Magnetic Headphone - Page 962

post #14416 of 16362
Quote:
Originally Posted by ohhgourami View Post


Same here! When my PC's PSU start buzzing and clicking, the voltage out the wall is about 1.5V higher.

Where do you hear this buzz?  The buzz is the 60Hz AC I'm sure.  You will hear it with amps with regulated supply when the toroid is not isolated well.  It's the magnetic field causing AC current signal.  Of couse if you hear it from phones it's probably the ground is not grounded well, but I've only picked this noise up with sensitive phones and the HE-6 is pretty stable since I believe this noise is well below what HE-t will pick up.

post #14417 of 16362
Luckily it only happens once in awhile for me. I'd go mad if it was as always like that.
post #14418 of 16362
Quote:
Originally Posted by ohhgourami View Post

Luckily it only happens once in awhile for me. I'd go mad if it was as always like that.

Could be one of the fans, but depends on how the noise is.  If it's a low frequency buzz, it's cyclic AC. If it's higher pitched buzz, there is some grounding issue somewhere.  Computer is full of noise.  Hard drive has a motor in it that can cause noise. 


Edited by SilverEars - 8/2/14 at 11:16am
post #14419 of 16362
Quote:
Originally Posted by wuwhere View Post

I live in S. Florida, FPL is terrible. Their power fluctuates a lot.

There are some power conditioners that will limit the power but they are pretty expensive, and the filtering in them hurts the dynamics (I use filtering on other stuff and prefer it, but I I think each component is different). I got a vintage general radio co variac off eBay because the dealer who built my amps said the transformers were good. He checked it out and replaced some things and added a decent power cord and it does work to lower the voltage and get rid of the hum. It was all quite reasonable, I think less than 300 in e whole thing.
post #14420 of 16362
Quote:
Originally Posted by SilverEars View Post
 

actually what wattage you need can be guessed based on the HE-6's SPL which is around 80dB/mW?   So, you pick louder than listenable dB level and can be estimated by taking the proportion of the power the resistor takes.  Of course this value if low enough not protect your phones from being blown from accidently raising the volume to extreme.  In order to make volume control more adjustable, decrease the resistance, but would there be resistor less than 10 that can withstand so much power?  I guess so since speaker wires take in lots of power.

Sorry, this is incorrect.  The speaker is the load, so the speaker uses the power.  If you use the speaker wire as resistance it will create a fire. LOL.  

post #14421 of 16362
Quote:
Originally Posted by SilverEars View Post
 

Could be one of the fans, but depends on how the noise is.  If it's a low frequency buzz, it's cyclic AC. If it's higher pitched buzz, there is some grounding issue somewhere.  Computer is full of noise.  Hard drive has a motor in it that can cause noise. 


4 fans spinning at 400rpm (inaudible)

Only SSDs so no moving parts

Fanless PSU

 

Spent a lot of time making sure no noise would be directly made by my PC. It's the damn AC power which seems out of my control.

post #14422 of 16362
Quote:
Originally Posted by SilverEars View Post
 

Not exactly.  There are two paths for the current to run.  Current runs most in the path of least resistance.  Voltage accross both are equal at the volume level.  The 10ohms will dissipate 5/6 of the total power to the both the resistor and the headphone. This means the heaphone is getting 1/6 of the power at the volume level, and with the 400watt capable amp, the total wattage drawn by the two loads is depends on the volume level.  whether if the HE-6 can be blown is dependent on the volume level and therefore how much is drawing at that level and the HE-6's power rating, but the resistor in paralell is taking 5/6 of the total output power.

And yet, it does NOTHING to protect the headphones EXCEPT in the case where the current through the resistor and the load combined exceed the current clipping point of the amplifier.  At that point, and ONLY at that point will the voltage sag and protect the headphones.

post #14423 of 16362
Quote:
Originally Posted by potterma View Post
 

And yet, it does NOTHING to protect the headphones EXCEPT in the case where the current through the resistor and the load combined exceed the current clipping point of the amplifier.  At that point, and ONLY at that point will the voltage sag and protect the headphones.

Point taken.  What I was meaning was that it prevents excessive power to the headphone by decreasing the majority of the power through the resistor.  In terms of directly connecting the headphones vs adding the resistor, the resistor is protecting the headphone by reducing the power to the headphone so depends on how you look at it.  But yeah, it's not a fuse for the headphone that's for sure.

post #14424 of 16362
Quote:
Originally Posted by ohhgourami View Post
 


4 fans spinning at 400rpm (inaudible)

Only SSDs so no moving parts

Fanless PSU

 

Spent a lot of time making sure no noise would be directly made by my PC. It's the damn AC power which seems out of my control.

I meant noise caused by the fans running and stopping.  The magnetic field from the fan motor causing the 400Hz noise being bled into the analog signal path.  As for the PS, it should be a 60Hz humm. 

post #14425 of 16362

The resistors in parallel do nothing to protect the headphone. The same amount of power will run through the headphone whether those resistors are there or not.

 

What will protect the headphone is a resistor in series and/or L-pad (resistor divider) configuration.

post #14426 of 16362
Quote:
Originally Posted by SilverEars View Post
 

Point taken.  What I was meaning was that it prevents excessive power to the headphone by decreasing the majority of the power through the resistor.  In terms of directly connecting the headphones vs adding the resistor, the resistor is protecting the headphone by reducing the power to the headphone so depends on how you look at it.  But yeah, it's not a fuse for the headphone that's for sure.

Lets take the series resistor out of the equation for a moment.  Now all we have is a 10 ohm resistor across the speaker out and a 50 ohm pair of HE-6's connected.

 

I'm not sure exactly how much power the HE-6 can handle, but just to stick a number on it, lets say its 10 W RMS.  That's about 0.45 A at about 22 VRMS or 0.64 A and 31.6 V peak.

 

Now, let's say I have an amp rated at 200 W into 8 ohms.  The minimum the amp can put out would then be 5 A at 40 V.  RMS.  That's 7 amps at 56.6 V peak.

Those are the MFR's rated min's.  At some THD or some such spec.  Its likely got some voltage headroom above that and if its a decent amp it should be easily able to deliver 2x 4x or 10x that current for short durations.

 

At our failure criteria for the HE-6, the cans are drawing 0.64 A.  That implies the resistor is carrying about 3.2 A peak for a total amplifier output of about 3.8 A peak.

 

Clearly well within the specs of this modest speaker amp.  Oh, by the way.  Your headphones just died.  Your resistor heated up, but it didn't protect you...

 

The point is, if you want to use a parallel resistor because it makes you feel good, or it does something to the sound you like, then by all means have at it.  But, don't fool yourself into thinking it is going to protect your cans.  If you want it to do that job, you need to determine how much current your amplifier puts out at maximum peak when the AC lines are running on the high side.  Then size that parallel resistor to drive the amp into its current limit before the voltage output can kill your headphones.

post #14427 of 16362
Quote:
Originally Posted by potterma View Post
 

Lets take the series resistor out of the equation for a moment.  Now all we have is a 10 ohm resistor across the speaker out and a 50 ohm pair of HE-6's connected.

 

I'm not sure exactly how much power the HE-6 can handle, but just to stick a number on it, lets say its 10 W RMS.  That's about 0.45 A at about 22 VRMS or 0.64 A and 31.6 V peak.

 

Now, let's say I have an amp rated at 200 W into 8 ohms.  The minimum the amp can put out would then be 5 A at 40 V.  RMS.  That's 7 amps at 56.6 V peak.

Those are the MFR's rated min's.  At some THD or some such spec.  Its likely got some voltage headroom above that and if its a decent amp it should be easily able to deliver 2x 4x or 10x that current for short durations.

 

At our failure criteria for the HE-6, the cans are drawing 0.64 A.  That implies the resistor is carrying about 3.2 A peak for a total amplifier output of about 3.8 A peak.

 

Clearly well within the specs of this modest speaker amp.  Oh, by the way.  Your headphones just died.  Your resistor heated up, but it didn't protect you...

 

The point is, if you want to use a parallel resistor because it makes you feel good, or it does something to the sound you like, then by all means have at it.  But, don't fool yourself into thinking it is going to protect your cans.  If you want it to do that job, you need to determine how much current your amplifier puts out at maximum peak when the AC lines are running on the high side.  Then size that parallel resistor to drive the amp into its current limit before the voltage output can kill your headphones.

Gotcha, I understand your concern, and everybody should head to this advice.  Although, It depends on the volume you have set at(actually, it volume will be very minimal).  If you have the volume pretty high before starting the music with a 400W amp, it will blow for sure.  Let's say it's 100Watts it certain volume level, That's 16Watts into a phone that 80dB/mW.  Probably would blow at that point.  

 

Also making sure that resistor is not reducing the total load value more than rated output is a good point.  If the amp is 400W at 8ohms, don't go below that for the total load, or the amp will overheat at max power.  Yeah, even with parallel resistor, a 400W  is pretty unsafe and high risk of blowing the headphones.  I just looked at a list of max SPL of phones is the highest I see is like 136.  So yeah, even 1W would blow the headphones.  

 

Yes, the paralllel resistors with speaker amps is uncool.  So, please becareful and do not use parallel wiring with HE-6 as you run the risk of blowing. We use headphone amps for a good reason. Please do not tap into speak amp's speaker terminal.  Please use the headphone out port.

 

I don't understand the 120ohm output impedance standard, and how it reduces the wattage to the phones if the amp is like 100watts.  


Edited by SilverEars - 8/2/14 at 2:13pm
post #14428 of 16362

I would rather use a very low wattage resistor in series for over-current protection.

post #14429 of 16362
Quote:
Originally Posted by Armaegis View Post
 

The resistors in parallel do nothing to protect the headphone. The same amount of power will run through the headphone whether those resistors are there or not.

 

What will protect the headphone is a resistor in series and/or L-pad (resistor divider) configuration.

Not true.  In parallel configuration, the current will flow more through the less resistive path, and drop more power there.  P=IV.  V is the same for both loads(the resistor and the headphone).  

 

I don't understand the purpose of even tapping into the speaker amp terminal and using resistors to attenuate. Headphones don't require more than minimal power.  Headphone jack does exactly what the resistor does by attenuating for the headphone input.  Even the series resistor is at a high risk unless everything is calculated out correctly.  I don't agree with all this big wattage amp is better argument now that I understand what it is essentially doing and the risks involved.


Edited by SilverEars - 8/2/14 at 1:59pm
post #14430 of 16362
Quote:
Originally Posted by SilverEars View Post
 

I don't understand the 120ohm output impedance standard, and how it reduces the wattage to the phones if the amp is like 100watts.  

 

It's a very old standard that's a holdover from transmission lines yadda yadda that had limitations we no longer need to be concerned about (especially not in the headphone world).

 

Some very old headphones actually had very high impedance ratings (2000+, etc). But these headphones were also used in situations where multiple units were plugged in parallel on a single amp, so this was to ease the load on the amp.

 

 

Quote:
Originally Posted by wuwhere View Post
 

I would rather use a very low wattage resistor in series for over-current protection.

 

Or just not use a ridiculously overpowered speaker amp to begin with :rolleyes:

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