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HE-500, LCD2, D5000, DT770, SR80, on a speaker amp (Emotiva mini-X A-100) Project - Page 168

post #2506 of 3792
Quote:
Originally Posted by Drsparis View Post


Omg I have a resistor box made by TBI that has interference issues for piano notes and other high frequency noises. I believe it is based on the first Picture and I believe it is bare wire for the ground. Could this be my problem? I even sent the box back cause it has been bugging the heck out of me.

All I need is a cable shield? Omg:-D

This diagram is only for an unbalanced "single ended" headphone cable.

post #2507 of 3792

I believe these would be the formulas for the unbalanced 2 resistor network:

 

post #2508 of 3792
Quote:
Originally Posted by robrob View Post

This diagram is only for an unbalanced "single ended" headphone cable.

Yup it was originally for my unbalanced he 500 on a TBI millenia mg3 . I have a balanced code x on its way I'm hoping that bypassing the ground of the resistor box might solve it. But I would like my other headphones to be usable too..
Edited by Drsparis - 12/5/13 at 10:31am
post #2509 of 3792
Quote:
Originally Posted by Drsparis View Post


Yup it was originally for my unbalanced he 500 on a TBI millenia mg3 . I have a balanced code x on its way I'm hoping that bypassing the ground of the resistor box might solve it. But I would like my other headphones to be usable too..


Not sure if I understand your issue.  You said something about interference issues for piano notes and other high frequency noises. The Emotiva Mini-X  uses singled ended outputs. Not sure what issue you are having would a balanced cable will solve?

post #2510 of 3792
Quote:
Originally Posted by john57 View Post


Not sure if I understand your issue.  You said something about interference issues for piano notes and other high frequency noises. The Emotiva Mini-X  uses singled ended outputs. Not sure what issue you are having would a balanced cable will solve?

Well it was a resistor box made for a balanced amp to a) fuse the negative terminals and b) lower noise floor via resistors.

I have not used it with the emotiva (getting it next week)

The way the resistor box was set up was to have 4 inputs and 4 outputs (although the grounds crossed so we're essentially the same wire). This allows me to use speaker taps for a balanced phone and put the 2 positives in the box and the 2 negatives directly in the amp. Hopefully this will solve my issue.

This gave me interferance on certain notes. Notably St Luis blues by Hugh Laurie (the first 2 seconds have awful interferance in the left channel whereas the notes should be coming out of the right channel. I believe this to be a crossover problem of the grounds...
post #2511 of 3792
Quote:
Originally Posted by Drsparis View Post


Well it was a resistor box made for a balanced amp to a) fuse the negative terminals and b) lower noise floor via resistors.

I have not used it with the emotiva (getting it next week)

The way the resistor box was set up was to have 4 inputs and 4 outputs (although the grounds crossed so we're essentially the same wire). This allows me to use speaker taps for a balanced phone and put the 2 positives in the box and the 2 negatives directly in the amp. Hopefully this will solve my issue.

This gave me interferance on certain notes. Notably St Luis blues by Hugh Laurie (the first 2 seconds have awful interferance in the left channel whereas the notes should be coming out of the right channel. I believe this to be a crossover problem of the grounds...


It sounds to me you are trying to say that there is a resistor is in parallel with the two channels on the balanced outs. I would have not done that with a balanced amp without knowing its topology. Balanced outputs can mean different things to different people. This would especially true if the stereo amp is using bridged mode output for each channel. The fact you are hearing awful interference in the left channel whereas the notes should be coming out of the right channel tells you something is very wrong with the resistor box design for that amp. With a few speakers amp designs the designer is excepting that the speakers ground are isolated from each other. With the Emotiva Mini-X that is not an issue. I would like a better a better understanding on why it did not work before I would move forward with another amp but that just me. Without more details I am limited in what I can say.

post #2512 of 3792

Drsparis, since the Emotiva Mini-x has common ground black speaker terminals you can safely remove the interface box's two resistors from the headphone common negative return (shown on my diagram as R5).

 

I agree with john57 that your resistor box isn't working right with the MG3 amp's output circuit.

 

Quote:
 The way the resistor box was set up was to have 4 inputs and 4 outputs (although the grounds crossed so we're essentially the same wire). This allows me to use speaker taps for a balanced phone and put the 2 positives in the box and the 2 negatives directly in the amp. Hopefully this will solve my issue.

 

With your balanced headphones connected like that then the left and right + leads are connected together through 4 series resistors (R3-R5-R5-R3. These resistors are not connected to ground). That doesn't sound like a good idea.


Edited by robrob - 12/5/13 at 2:55pm
post #2513 of 3792
Thanks for all the help guys. I think I will use the frame and connectors and make my own inside network of resistors (even though I'm not quite sure what I'm doing lol) . Seems like a simple diagram.

It sucks because it was made for the HE 500 by the guy that makes the mg3.i even sent it back and he couldn't identify the problem. :-(

So I realised this doesn't really have anything to do with the original thread, I feel bad. I will continue this in PM lol.
Edited by Drsparis - 12/5/13 at 3:34pm
post #2514 of 3792

Sorry I miss that you were talking about the TBI millenia mg3 amp. I miss that obvious point in your post. According to the designer the TBI millenia mg3 does not use common ground. Are you saying the designer can not duplicate the problem or can not find a solution?  That certainly does not sound good. I noticed that all of this was talked about on posts 1023-1026 on this thread. I think that you will have less issues with the Emotiva.

post #2515 of 3792

After getting feedback from the gurus it seems the good old two resistor "Preferred Headphone Interface" will work fine with unbalanced "single-ended" headphones:

Just make sure your amp has its black speaker terminals tied together. If they're not you could damage your amp.

post #2516 of 3792
Quote:
Originally Posted by robrob View Post

 

Just make sure your amp has its black speaker terminals tied together. If they're not you could damage your amp.

Really, it would be that simple when using my MG3 with Single ended headphones? and remove the wire when with balanced headphones....

post #2517 of 3792
Quote:
Originally Posted by robrob View Post
 

After getting feedback from the gurus it seems the good old two resistor "Preferred Headphone Interface" will work fine with unbalanced "single-ended" headphones:

Just make sure your amp has its black speaker terminals tied together. If they're not you could damage your amp.


Great! per channel!

post #2518 of 3792
Quote:
Originally Posted by Drsparis View Post
 

Really, it would be that simple when using my MG3 with Single ended headphones? and remove the wire when with balanced headphones....

 

Use a multimeter's continuity to verify your MG3's black speaker terminals really are tied together, if yes then you could install a switch in your interface box to disconnect the joined negative lines. You could install a 4-pin XLR for balanced headphones then flip the switch and use the TRS jack for unbalanced headphones.

post #2519 of 3792
Quote:
Originally Posted by robrob View Post
 

Use a multimeter's continuity to verify your MG3's black speaker terminals really are tied together, if yes then you could install a switch in your interface box to disconnect the joined negative lines. You could install a 4-pin XLR for balanced headphones then flip the switch and use the TRS jack for unbalanced headphones.


Should the amplifier be powered on or off?

post #2520 of 3792

off

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