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Speaker amps for headphones - Page 110

post #1636 of 3116
Quote:
Originally Posted by manbear View Post
 

In what situations are these different network designs most appropriate? I know that we want to make sure dynamic headphones see a low enough impedance for the correct damping factor, and that we want to make sure tube amps see either a 4 or 8 ohm load so as not to ruin them. But what about running orthos from a solid state amp -- is there any reason I shouldn't just use series resistors? Does anyone know if the Emotiva performs better if I trick it into seeing an 8 ohm load instead of something much higher?

 

A tube amp will NOT be damaged if it doesn't see a 4 OR 8 Ohm load.

In Rob's spread sheet, in the three resistor version, you could allow R1 to be infinite (i.e just omit it).

If the tube amp sees a load of 8 Ohms or higher (say approx. 32 or 50 Ohm or 64 Ohms or 43.73945 Ohms), it should be OK.  Almost any SS amp should be rather indifferent to a higher or lower load impedance, just don't go TOO LOW.

 

As an example, R2 = 12 Ohms and R3 = 4 Ohms would be OK  for dynamics,

from the headphone's point of view, the output impedance is less than 4 Ohms, so we have good damping 

form the amp's point of view, the load is approx. 16 Ohms. A tube amp or SS amp would be OK with this.

Attentuation is approx. 12 dB, so hiss is reduced, if you need to reduce hiss!?

hiss can be reduced more by increasing R2.

 

But it's all a trade off:     if R2 = 12 Ohms and R3 = 4 Ohms, you also have to be comfortable with the travel of your volume control, i.e. for your system would this avoid having all volume control travel between 8:30 and 9:00 o'clock?  Hopefully the resistor network would also get the travel more between 9:00 and 1:00 o'clock.

 

With headphones and a power amp and a resistor network it's all a compromise between reducing the hiss and improving the volume control travel.

Don't over think it, folks.

post #1637 of 3116
Quote:
Originally Posted by ALRAINBOW View Post

Chris

Thanks for the reply. How about the IEM. Low freq cutoff with a amp that has a higher than normal output imp

I really would like another persons view on this

Thanks
Al D

 

Hi Al,

I'm pretty certain that most headphone designers design headphones with the assumption that the headphone amp will have a very low output impedance.

Same for speakers: the basic assumption when designing crssovers that the crossover and drives will be driven by an almost ideal voltage source, meaning amp output impedance is almost zero.

So..............

 

If the IEMs have a very low impedance and a built in crossover and/or an impedance that varies with frequency, then, yes:   The lower the AMP's output impedance the better.

Reason, you may get undesireable frequency response interaction between the amp and your headphones.

You should get a flatter frequency response from your headphones using an amp with a lower output impedance.

 

The other point of view you will hear is that if the headphone has a very flat impedance WRT frequency, then it doesn't matter if the amp output impedance is high.

True, but not all my headphones have a flat impedance curve WRT frequency.

An amp with a low output impedance gives me one less thing to agonize over.

 

Chris


Edited by Chris J - 12/1/13 at 9:15am
post #1638 of 3116
Quote:
Originally Posted by gjc11028 View Post


Can you explain the blow up part? I have read some reviews and some threads but missed that. I understand that the wee cannot be used with amps with that have balanced output (both binding posts with signal) like pass labs (I think) or the blue circle I have, but is there more than that? Thanks


The Wee can't be used with amps that have bridged outputs. 

 

My comment about blowing up was in reference to some of the negative opinions voiced by others regarding the quality of the components in the Wee, particularly the transformer.  I personally don't know enough to determine whether the components are high quality or low quality, but any time you are working with high voltages, it pays to be a bit careful.

post #1639 of 3116
Quote:
Originally Posted by Rob80b View Post
 


Hi Chris

 

Have you tried this on the 2BLP pro?

 

Robert

 

Hi Robert,

No, I've never opened up the 2B-LP Pro and started messing around with headphone jack values.

To be honest, the 2B-LP is not in an optimum place for headphone listening unless I want to either lay on the floor or put a chair in the middle of the "TV Room". LOL!

I really bought it to drive the rear channels in my surround sound system plus I wanted balanced inputs.

Chris

post #1640 of 3116
Big thanks to chris.

The ohms law formulas I used recently actually hurt my brain it's been so long . But It did come back to me once I seen them. Google is really a cool thing. Anyway thanks all of you guys collectively I feel I am further into this now and although some of what I say is conjecture it is because of testing and not hearing negative effects even if the setup is not ideal .

Great reading and I am sorry if I have offended anyone here with my arrogance or ignorance. I did not mean to...

Al D
post #1641 of 3116
Quote:
Originally Posted by Gary in MD View Post


The Wee can't be used with amps that have bridged outputs. 

My comment about blowing up was in reference to some of the negative opinions voiced by others regarding the quality of the components in the Wee, particularly the transformer.  I personally don't know enough to determine whether the components are high quality or low quality, but any time you are working with high voltages, it pays to be a bit careful.

Thanks. I appreciate the point about bridged amps, but the point I made about the balanced output is also true; confirmed by email with woo audio
post #1642 of 3116

Balanced outputs as in common ground?

post #1643 of 3116
Quote:
Originally Posted by Gary in MD View Post
 

Balanced outputs as in common ground?

I would be surprised if it was otherwise, not many head amps these days have separate grounds, hence the 4-pin XLR.

post #1644 of 3116
Quote:
Originally Posted by Gary in MD View Post
 

Balanced outputs as in common ground?

 

Wha?

Now I'm confused........kidding!

 

If a power amp has "balanced outputs" (basically the same as bridged outputs), the amp left and right will still have a "common ground", but that is internal. and is not the BLACK ternimals.

 

Anyway, the BLACK speaker terminals are not a "common ground", they are independent "inverting outputs".  Some people call them negative because they are the opposite of the RED terminals. 

You can't tie the two BLACK terminals together.

post #1645 of 3116
I concur sir. But maybe one of the amp design guys can way in. If an amp has separate power supplies as in a real bal amp I am guessing no. But I do agree with the 4 pin XlR.

But keep in mind here as we are using a speaker amp not a headphone amp.

Al d
post #1646 of 3116
Quote:
Originally Posted by ALRAINBOW View Post

I concur sir. But maybe one of the amp design guys can way in. If an amp has separate power supplies as in a real bal amp I am guessing no. But I do agree with the 4 pin XlR.

But keep in mind here as we are using a speaker amp not a headphone amp.

Al d

 

Ya got a point there!.

The power supplies may be totally separate, but even then, the signal common (signal ground) has to be common throughout the whole system.

 

I'm referencing a few bridged power amp (i.e balanced power amp) schematics I have.......Pass Labs, Sumo.............and the Bryston BHA-1.

I think I have some on .pdf if you are curious.

PM me and I can e-mail them to you.

Really just for fun, I'm not trying to hammer the point home! :o

post #1647 of 3116
Quote:
 The power supplies may be totally separate, but even then, the signal common (signal ground) has to be common throughout the whole system.

Not for a "balanced" headphone amp. You can use two completely separate amps to drive each stereo channel.

 

An amp with balanced input, "balanced" push-pull amplification and non-common ground on the headphone/speaker side of the output transformer doesn't have a common signal ground. In the schematic below I do not consider the zero volt reference grounds of the input and output transformers and the ground near "Vcc" to be in the "direct" signal path.

 

post #1648 of 3116
Quote:
Originally Posted by robrob View Post
 

Not for a "balanced" headphone amp. You can use two completely separate amps to drive each stereo channel.

 

An amp with balanced input, "balanced" push-pull amplification and non-common ground on the headphone/speaker side of the output transformer doesn't have a common signal ground. In the schematic below I do not consider the zero volt reference grounds of the input and output transformers and the ground near "Vcc" to be in the "direct" signal path.

 

 

Right.

I hadn't thought of transformer coupling.

Too much Solid State "no transformers in the signal path" amplifiers in my brain!

 

Mind you, that's an extremely atypical headphone amp, balanced or unbalanced.


Edited by Chris J - 12/1/13 at 12:55pm
post #1649 of 3116
Quote:
Originally Posted by Gary in MD View Post
 


The Wee can't be used with amps that have bridged outputs. 

 

 

 

I sent a message to Woo a few weeks ago about the WEE and bridged amps and this was his reply...

 

Quote:
 A bridged/balanced spk amp can be used for WEE.

Thanks,
Jack
--------------------------
www.WooAudio.com
Twitter.com/WooAudio
post #1650 of 3116
Quote:
Originally Posted by Armaegis View Post
 

 

I sent a message to Woo a few weeks ago about the WEE and bridged amps and this was his reply...

 

Okay... then I give up? :blink:  The Wee will not blow up due to the type of amp used.  I was probably going to get one anyway.  :biggrin:.

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