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HE-500, LCD2, D5000, DT770, SR80, on a speaker amp (Emotiva mini-X A-100) Project - Page 187

post #2791 of 3790
Quote:
Originally Posted by Sonido View Post


In that case short is not the right word I'm using. There's no direct connection from + to -. Only a direct connection from the +'s to reach other before the headphone. I'll draw out a picture of the circuit when I get home.

My understanding was that when you connected the two + terminals on the same channel one driver is carrying all the current to the other side of the + terminal. This could blow the driver in some cases. The other headphone driver will just have the two grounds connected very little current will flow. Since the Mini-X does not have a earth ground connected to the chassis ground it is hard to tell what is all the possible current paths will be.

post #2792 of 3790
Quote:
Originally Posted by john57 View Post

My understanding was that when you connected the two + terminals on the same channel one driver is carrying all the current to the other side of the + terminal. This could blow the driver in some cases. The other headphone driver will just have the two grounds connected very little current will flow. Since the Mini-X does not have a earth ground connected to the chassis ground it is hard to tell what is all the possible current paths will be.
Not quite. I think that's how David blew one of his drivers. I'll provide a picture of the circuit later. It's a lot easier than explaining.
post #2793 of 3790
Quote:
Originally Posted by Sonido View Post
Not quite. I think that's how David blew one of his drivers. I'll provide a picture of the circuit later. It's a lot easier than explaining.

The other driver doesn't work either, yet it doesn't have a hole in it.

post #2794 of 3790

Ok guys. Here's what I did (third picture):

 

post #2795 of 3790

Just... nothing


Edited by davidsh - 12/18/13 at 4:59pm
post #2796 of 3790

Now had I reversed one channel but not the other, that would have caused a short in the amp for sure. Good thing I realized that it was not a simple reverse phasing due to the TRS. Had there not been a problem, I had been thinking about purposely reversing one channel, and not the other to see how sound waves cancel each other out. :D

 

Back home now, and good to report that everything is working fine.

post #2797 of 3790

Back on sound straight from Emotiva vs. through HE-Adapter. I could not hear a difference. Neither had noise floor problems at listening levels without Quickie. With Quickie, there was definitely a slight background noise when nothing was playing from straight from Emotiva. With HE-Adapter, there was no background noise even with Quickie.

 

On the topic of preamp/amp impedance matching, I got a response from the Bottlehead forums. The Quickie was designed for 40K ohm impedance amps. With the 10K ohm MiniX, they said there could a slight dip in the lowest bass. I tested this with a song with plenty of sub-bass, and sure enough with the Quickie in the chain there was a very slight drop, probably around 1 dB. It really only affects the 20-40 Hz range. I found higher frequencies (40-80 Hz) of bass sound better. Not more quantity, but encompassing or enveloping if that makes any sense. Still I would love to hear the sound it a well impedance matched amp with the Quickie.

post #2798 of 3790
Quote:
Originally Posted by Sonido View Post


In that case short is not the right word I'm using. There's no direct connection from + to -. Only a direct connection from the +'s to reach other before the headphone. I'll draw out a picture of the circuit when I get home.

Yes, exactly. The amp's + channels were combined at the TRS plug, traveled together along the headphone cable's shield, then half went in one driver and down its + wire to the amp, and the other half went through the other driver and down its + wire to the amp. 

 

When the two + signals combine they can work together like a push-pull amp to form very strong signals and work against each other to cancel out their waveforms so bad things can happen to your drivers but probably only at loud settings.


Edited by robrob - 12/18/13 at 7:34pm
post #2799 of 3790
Quote:
Originally Posted by davidsh View Post
 

Just... nothing

Yea, I saw it too and had a good chuckle. I'm thinking the drivers are cold.

post #2800 of 3790
Quote:
Originally Posted by robrob View Post
 

Yes, exactly. The amp's + channels were combined at the TRS plug, traveled together along the headphone cable's shield, then half went in one driver and down its + wire to the amp, and the other half went through the other driver and down its + wire to the amp. 


Out of curiosity and interest, what does this do exactly to the amp and headphones? I figure this is what caused the amp to shutdown, but it did run for 30 seconds before doing so. Also, while I did not pay close attention, the sound was not grossly distorted or anything I noticed immediately. Also I did not pay attention to difference in the channels, but because the +'s meet before going to the headphones, does the two channels get mixed, creating a single mono sound that goes to both sides of the headphone? One other question, does the + from either channel go directly to the + of the other channel since they are connected at the TRS? I would think this is what triggered the amp to shutdown.

post #2801 of 3790

Each stereo channel's + terminal is connected to an AC wave generator (amplifier). Normally when the wave is a positive voltage it wants to push electrons through the headphone + wire, through the drivers, then through the cable shield to ground. When the AC wave is negative the electrons are pulled in the opposite direction back to the wave generator (amplifier).

 

When you combine two AC wave generators at the TRS plug the the waves from each amplifier combine--two positive voltage waves will make a higher voltage, higher amplitude wave = more voltage and loudness at the drivers. All that positive voltage meets at the TRS plug and pushes together up the cable to the headphones and down to ground. All the electrons still want to flow to ground.

 

When a positive and negative voltage wave combine they weaken each other and if they're equal they will cancel themselves and the electrons will flow from the positive wave voltage to the negative wave--so electrons can flow from one + terminal to the other + terminal--shorting each other out and mostly bypassing the headphone drivers.

 

When two negative voltage waves meet it's basically the opposite of when two positives meet.

 

So what happens depends on the audio signal waves when they meet at the TRS plug.

post #2802 of 3790
Quote:
Originally Posted by robrob View Post
 

Each stereo channel's + terminal is connected to an AC wave generator (amplifier). Normally when the wave is a positive voltage it wants to push electrons through the headphone + wire, through the drivers, then through the cable shield to ground. When the AC wave is negative the electrons are pulled in the opposite direction back to the wave generator (amplifier).

 

When you combine two AC wave generators at the TRS plug the the waves from each amplifier combine--two positive voltage waves will make a higher voltage, higher amplitude wave = more voltage and loudness at the drivers. All that positive voltage meets at the TRS plug and pushes together up the cable to the headphones and down to ground. All the electrons still want to flow to ground.

 

When a positive and negative voltage wave combine they weaken each other and if they're equal they will cancel themselves and the electrons will flow from the positive wave voltage to the negative wave--so electrons can flow from one + terminal to the other + terminal--shorting each other out and mostly bypassing the headphone drivers.

 

When two negative voltage waves meet it's basically the opposite of when two positives meet.

 

So what happens depends on the audio signal waves when they meet at the TRS plug.


Thanks for that informative read. So it can create higher amplitudes (louder), and also short it at times. I guess that's what caused the amp to hit the kill switch. This is informative for those that choose to spend $20 on adapter cables from Amazon over making their own cables, especially when the +/- isn't in the standard red/black coloration.

 

For reference, I'm using these:

http://www.amazon.com/gp/product/B000068O5D

and 2 of http://www.amazon.com/gp/product/B0010CEIH8

 

The latter cable actually has a black and white wire sticking out on the other side. You can't see it in the picture. The black is ground and white is + in this case. I guess I plugged it in with the plastic plate facing up, thinking it wouldn't matter if I plugged it in backwards because I thought it would only be a simple phasing issue. I was close to plugging one side one way, and the other side the other way and letting my ears decide which phase was right. Luckily I did not do that.

post #2803 of 3790

Argh. Rob. No.

 

That's not... that's not how it works. I mean, there's a sort of rudimentary idea in there and I can see where you're trying to go, but... no.

 

I don't have the time to answer at this moment. Maybe someone else will jump in before I do.

post #2804 of 3790
Quote:
Originally Posted by Armaegis View Post
 

Argh. Rob. No.

 

That's not... that's not how it works. I mean, there's a sort of rudimentary idea in there and I can see where you're trying to go, but... no.

 

I don't have the time to answer at this moment. Maybe someone else will jump in before I do.


The plot thickens :evil:

 

:popcorn:

post #2805 of 3790
Hey guys, if I have the he500 and the emotiva, what dac would you recommend at around $100? Would you choose something between the modi, odac, or hrt music streamer II? I'm ok with getting used so if it can be found around $100 or less used that's fine.
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