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Speaker amps for headphones - Page 124

post #1846 of 3116

The only time I will have really hot signal is when I connect a pro level outputs to a consumer level inputs sometimes when you interface pro equipment to consumer equipment. The only time I have use attenuators is on the outputs on OTL tube equipment for low impedance headphones. It did not work as well I hope. Some users like to use passive pre-amps but I do not like them either.

post #1847 of 3116
Quote:
Originally Posted by robrob View Post

Thanks potterma, I currently have 20*log(Rh/(R2+Rh)) which gives a negative number. It just seemed like R1 would add some attenuation, thanks for the clarification.

That formula is right, it should be a negative number........!
post #1848 of 3116
Quote:
Originally Posted by robrob View Post

Sorry Chris and everyone else.

I think I'll have a beer too. beerchug.gif

Which reminds me,

My apologies to Rob and everyone else!

Chris
post #1849 of 3116
Quote:
Originally Posted by brunk View Post
 
Quote:
Originally Posted by potterma View Post
 

No.  They attenuate the input signal.  They will not lower the noise floor, because the noise floor is a contribution from the amp itself, not the source.  Source noise is a different issue, and these won't help that, either.  The application for these devices is if you have a source with output signal too large for the amplifier (or whatever other components you are trying to connect).

The resistor network on the output reduces the signal amplitude (voltage) delivered to the load (headphone, for example).  It reduces the apparent noise floor of the amplifier because it is attenuating the signal.  The noise that is heard is typically from the gain stage(s) of the amplifier.  Since the gain is fixed, that noise is fixed.  Attenuating the output of the amplifier allows you to feed in a larger input signal for a given SPL out.

@manbear This right here. Further, those RCA attenuators are really the last thing you want to do. What you really want to do in your case is lower the gain of the amp, if you can't do that, then I suggest you may have the wrong amp for your drivers. If you have no other way possible then those are the way to go. You may also have a really hot signal voltage (uncommon unless it's from a hot preamp) that the amp can't handle, in which case you could switch DACs. Wasting so much signal voltage is a sad thing :( 


Thanks for the info guys. I have a working setup right now, but I'm just curious about other possibilities. The RCA attenuators would have been simple and unobtrusive if they were appropriate to use, but I see what you mean. They wouldn't be attenuating the noise itself...  I'm using 250 ohm series resistors on the output of my speaker amp right now. The Emotiva is a bit silly to use with the HE-400 (considering that the end result is ~170 mW into my headphones in this configuration), but I'm pretty happy with the sound. Plus, it looks cool and I can look forward to getting an HE-6 or something down the line. I'm gonna try some resistors that give me around 1 W next, and see if that sounds any different. 


Edited by manbear - 12/7/13 at 11:07am
post #1850 of 3116
Quote:
Originally Posted by Chris J View Post


That formula is right, it should be a negative number........!

If you are expressing V(out) with respect to V(in), I totally agree.  If, on the other hand you are trying to express attenuation, then I don't object to a positive number.

post #1851 of 3116
Quote:
Originally Posted by manbear View Post
 


Thanks for the info guys. I have a working setup right now, but I'm just curious about other possibilities. 

 

....snip.....

One other thing you may want to try is utilizing ReplayGain. JRiver Media Center has this functionality built-in. Matter of fact, it uses the latest R128. Download the trial version and see if it manages to help your situation :)

post #1852 of 3116
Quote:
Originally Posted by potterma View Post
 

If you are expressing V(out) with respect to V(in), I totally agree.  If, on the other hand you are trying to express attenuation, then I don't object to a positive number.

 

Yea, that makes sense because "attenuation" implies reduction so the negative sign is somewhat superfluous. 

post #1853 of 3116
Quote:
Originally Posted by robrob View Post
 

 

Yea, that makes sense because "attenuation" implies reduction so the negative sign is somewhat superfluous. 

If you want to get technical about it, negative attenuation would be gain....  

post #1854 of 3116
Quote:
Originally Posted by potterma View Post
 

If you are expressing V(out) with respect to V(in), I totally agree.  If, on the other hand you are trying to express attenuation, then I don't object to a positive number.

 

To express attenuation, a negative number is textbook perfect, you know: Voltage attenuation (or is it Voltage gain?) = -16.74328 dB.

Or -16.74328 dB of Voltage gain is 16.74328 dB of Voltage attenuation.....................nevermind...........:confused_face_2:

 

The most important thing is if you walk up to me while I'm walking down the street, tap me on the shoulder and say "when I put this magic box between my power amp and headphones I get 20 dB of attenuation" I know exactly what you mean!    :wink_face: 

But I might think you're a bit weird if you're standing on the street talking to people about attenuation.


Edited by Chris J - 12/8/13 at 7:51am
post #1855 of 3116
Quote:
Originally Posted by Chris J View Post
 

 

To express attenuation, a negative number is textbook perfect, you know: Voltage attenuation (or is it Voltage gain?) = -16.74328 dB.

Or -16.74328 dB of Voltage gain is 16.74328 dB of Voltage attenuation.....................nevermind...........:confused_face_2:

 

The most important thing is if you walk up to me while I'm walking down the street, tap me on the shoulder and say "when I put this magic box between my power amp and headphones I get 20 dB of attenuation" I know exactly what you mean!    :wink_face: 

But I might think you're a bit weird if you're standing on the street talking to people about attenuation.

Some people call it weird....  I just call it normal.... Of course, that's MY perspective....  It's the OTHER people who call it weird!

 

so, how's that attenuation going..... :blink:

post #1856 of 3116
Quote:
Originally Posted by potterma View Post
 

Some people call it weird....  I just call it normal.... Of course, that's MY perspective....  It's the OTHER people who call it weird!

 

so, how's that attenuation going..... :blink:

 

Actually, I would probably look at the attenuator circuit and say "nice workmanship!".

post #1857 of 3116

Question, I'm considering using the R1 and R2 resistors below with a switch to add or remove them from the circuit, to pair an amp with balanced output with single-ended headphones. Would these 3 ohm resistors protect a balanced amp? I know this box was used with an MG3 amp and had a distortion problem but I want to give it a try if it would safely allow connecting single-ended cans to a balanced speaker amp.

1000

post #1858 of 3116

If by balanced amp you mean the L- is inverted relative to L+ (and ditto for R)... don't do it. Don't connect them. Recable the headphones if you really want to use them with that amp.

 

Yes technically those resistors will protect the amp. Sort of. But... no. Even with a non-balanced amp you shouldn't ever use that arrangement.

 

Just no.

 

Please stop posting that diagram.


Edited by Armaegis - 12/9/13 at 10:35pm
post #1859 of 3116

Hey kids, be careful how you wire up your headphones. You don't want to blow them up...

 

http://www.head-fi.org/t/629352/he-500-lcd2-d5000-dt770-sr80-on-a-speaker-amp-emotiva-mini-x-a-100-project/2565#post_10048122

 

And yes, that's possible even with a resistor network. Possible with a low power amp too.


Edited by Armaegis - 12/9/13 at 10:49pm
post #1860 of 3116
Quote:
Originally Posted by Armaegis View Post
 

Hey kids, be careful how you wire up your headphones. You don't want to blow them up...

 

http://www.head-fi.org/t/629352/he-500-lcd2-d5000-dt770-sr80-on-a-speaker-amp-emotiva-mini-x-a-100-project/2565#post_10048122

 

And yes, that's possible even with a resistor network. Possible with a low power amp too.

Yea, I saw that post. He mixed up his headphone's banana plugs and connected the L+ and R+ amp out to one ear cup--boom. Destroyed headphone driver and a non-working amp (might be just a fuse).

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