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Speaker amps for headphones - Page 109

post #1621 of 2665
Quote:
Originally Posted by robrob View Post
 

Wikipedia says this about power amplifier output impedance:

 

Do you guys agree with this? It would definitely simplify our calculations if I could just use 0.1 as a close approximation of amp output impedance.

I apologize for jumping in, I haven't read all the posts in this thread.

 

0.1 Ohm output impedance is a good enough approximation for almost any tube or SS amp.

 

I agree with SE, the four resistor network is needlessly over complicated.

Just stick with two.

post #1622 of 2665
Quote:
Originally Posted by Gary in MD View Post
 

 

 

It depends on who you believe, plus what your expectations are, I guess.  There was one blind comparison test in France that favored it over several dedicated (and much more expensive) amps, both Stax and 3rd party.  Others say it scales well with better amps. However, Spritzer thinks it's a piece of junk, and he is pretty high up in the Stax Mafia, so you ignore his opinions at some peril :normal_smile :.   So it really comes down to whether you want to try it for $500, hoping it will work with your amp(s) and that it won't blow up, or want to save your pennies (LOTS of them) and buy a real Stax amp.  I think I'm gonna try it (I'll also buy a nice fire extinguisher... and still be several thousand bucks ahead compared to a KG or Headamp unit...).

 

With respect, Spritzer can be rather black and white, either it's junk or it's amazing. 

post #1623 of 2665
Quote:
Originally Posted by Gary in MD View Post


It depends on who you believe, plus what your expectations are, I guess.  There was one blind comparison test in France that favored it over several dedicated (and much more expensive) amps, both Stax and 3rd party.  Others say it scales well with better amps. However, Spritzer thinks it's a piece of junk, and he is pretty high up in the Stax Mafia, so you ignore his opinions at some peril normal_smile%20.gif.   So it really comes down to whether you want to try it for $500, hoping it will work with your amp(s) and that it won't blow up, or want to save your pennies (LOTS of them) and buy a real Stax amp.  I think I'm gonna try it (I'll also buy a nice fire extinguisher... and still be several thousand bucks ahead compared to a KG or Headamp unit...).

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
post #1624 of 2665

Here's a screen capture of the network calculator. Please take a look at the formulas and let me know what should be changed:

 

 

The full size easily readable image is here: http://robrobinette.com/images/Audio/HeadphoneNetworkCalculatorScreen.jpg

 

Is there consensus the 2 or 3 resistor network is best?


Edited by robrob - 12/1/13 at 6:27am
post #1625 of 2665
Quote:
Originally Posted by Chris J View Post
 

Frankly, I have a certain amount of bias in this discussion.

I tried the headphone jack in my Bryston 2B-LP and found myself underwhelmed! frown.gif

 

BTW, I'm a big fan of Threshold and Bryston gear.

 

 

Hi Chris

 

The BHA-1 and the Bryston .4pre/2BLP pro combo share a lot of similarities,

CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 85

 

What did you use as a pre on the 2BLP or did you go direct and balanced or use an adapter "RCA to balanced" ( do not use a RCA to 1/4" as it stresses the amp:confused_face_2:), I'm using a properly wired RCA to XLR and it makes a huge difference. ;)

 

 

 

The noise floor of the BHA-1 appears non-existent, but as you mentioned in another thread there is some hiss with the 2BLP (it is a power amp not to forget), with most of my phones it's not an issue though and with so much reserve on hand IMHO it's great for inefficient phones, aka "K501s":smile: .

post #1626 of 2665

Would this type of two resistor network be better than the one in my spreadsheet? Is this the consensus "best headphone network" or is the three resistor network better if optimized to your amp and headphones?


Edited by robrob - 12/1/13 at 7:55am
post #1627 of 2665
This is what I do , it gives me the attenuation I want and the amp,s output is balanced to a load that it was designed for. I have been reading this thread and I can follow the designs
And know how to calculate the resister values. But for me unless there is a need for the complex arraignments you guys are so kind to design , like noise floor still,present or not enough attenuation. Great reading though.

I am a LISC electrical contractor and a LISC electrical PE. And at one time knew all of this in my head. Now a do google searches for formulas. What I did not know is what the theory behind the reasoning in using headphones on speaker amps . And this does touch on this a little .

One thing that was related but not discussed is why IEM!s are effected with amps that have a above 3 ohms output imp, where this effect does not take place with headphones.

The only answer I have found is the crossover is affected not the BA or dynamics drivers..

Al D
post #1628 of 2665
Quote:
Originally Posted by robrob View Post
 

Would this type of two resistor network be better than the one in my spreadsheet? Is this the consensus "best headphone network" or is the three resistor network better if optimized to your amp and headphones?

 

Hi Roberto, (makes you sound like a ladies man, yes?)

My opinion.................use the two resistor network.

I like the idea of resistor #3 in your diagram.

#2 gives you the attentuation you may need, #3 adds some damping to the system i.e. makes the amp output impedance appear to be low (in some respects).

Personally, I'm not a big fan of using an old receiver with a 120 Ohm (or 220 Ohm or whatever) between the headphones and the power amp, it's just not very versatile, with many headphones the interaction between the series resistor and the headphones can create frequency response aberations.

A properly chosen value for Resistor #3 greatly reduces that effect.

You guys already do all this when you chose R2 = 12 Ohms, R3 = 4 Ohms (for example)!

 

I may have "a bit of bias".......  :wink_face:

I've worked as a power Engineer for about 25 years, + I spent a year designing Analog Signal processing gear.


Edited by Chris J - 12/1/13 at 8:14am
post #1629 of 2665

FYI, here's Bryston's config on the 2BLP pro.

http://www.bryston.com/PDF/Schematics/2BLP_SCHEMATICS.pdf

 

 

post #1630 of 2665
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
post #1631 of 2665

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?

post #1632 of 2665
Quote:
Originally Posted by robrob View Post
 

Here's a screen capture of the network calculator. Please take a look at the formulas and let me know what should be changed:

 

 

The full size easily readable image is here: http://robrobinette.com/images/Audio/HeadphoneNetworkCalculatorScreen.jpg

 

Is there consensus the 2 or 3 resistor network is best?

 

Edit:   fixed my errors!

 

In the dual resistor example, the attenuation is 0.8

So if the amp outputs 1.0 Volt, the headphones see "0.8" Volts.

Problem is: to the headphones, the amplifiers output impedance now appears to be approx. 8 Ohms. 

 

I would call "Amplifier input impedance" the "Amplifier Load"


Edited by Chris J - 12/1/13 at 8:34am
post #1633 of 2665
Quote:
Originally Posted by Chris J View Post
 

 

Hi Roberto, (makes you sound like a ladies man, yes?)

My opinion.................use the two resistor network.

I like the idea of resistor #3 in your diagram.

#2 gives you the attentuation you may need, #3 adds some damping to the system i.e. makes the amp output impedance appear to be low (in some respects).

Personally, I'm not a big fan of using an old receiver with a 120 Ohm (or 220 Ohm or whatever) between the headphones and the power amp, it's just not very versatile, with many headphones the interaction between the series resistor and the headphones can create frequency response aberations.

A properly chosen value for Resistor #3 greatly reduces that effect.

You guys already do all this when you chose R2 = 12 Ohms, R3 = 4 Ohms (for example)!

 

I may have "a bit of bias".......  :wink_face:

I've worked as a power Engineer for about 25 years, + I spent a year designing Analog Signal processing gear.


Hi Chris

 

Have you tried this on the 2BLP pro?

 

Robert

post #1634 of 2665
Quote:
Originally Posted by Chris J View Post

 

I would call "Amplifier input impedance" the "Amplifier Load"

Will do.

post #1635 of 2665
Quote:
Originally Posted by m17xr2b View Post
 

Just wondering, would something like this make an improvement to the TBI? http://www.aloaudio.com/the-passport


It would probably be able to drive the Millenia, but there are lots of 12v options out there for less money -- as in buying lithium batteries., or the LiFePo batteries Mike (Zilch) has been using.  In addition, according to Jan Plummer and verified by various folks, including Mike, the amp really wants more than 12v.  There are also lots of options for more voltage, including the tried (by lots of folks on Audio Circle) and true approach of using a pair of SLA batteries in series, or LiFePo, or some of the lithium batteries for laptops.  And then there are linear power supplies.  All of these solutions can be had for <$200, i.e., less than the passport. 

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