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HE-500, LCD2, D5000, DT770, SR80, on a speaker amp (Emotiva mini-X A-100) Project - Page 246

post #3676 of 3684
Quote:
Originally Posted by Taowolf51 View Post
 
Quote:
Originally Posted by davidsh View Post

 

Perhaps the amp was turned on with the headphones plugged in or something.

Emotivas are usually very good about being safe when turned on. I can turn my XPA-200 on when my headphones are plugged in without issue, no popping.

 

I had no idea you ended up with a UPA-200! Any comments on it? Is there any hiss with headphones?

 

Sorry, this is from quite awhile ago, but I'm thinking about getting a UPA-200 or XPA-100 monoblock pair, and while googling this thread popped up! 

post #3677 of 3684
I destroyed my HE-500 with an upa-200. How is still a mystery to me. I think it might be because pre-amp was turned on while the headphones were connected.
post #3678 of 3684
Quote:
Originally Posted by wessabi View Post
 

 

I've been trying to figure out how to correct this. I've read a bit and I'm kind of confused on my options. I was recommended to get a ground loop isolator, but I've also seen resistor adapters, and remote amp level controllers. Then there's that resistor network and preamps. (Which I don't fully understand the function of)

 

My issues are, in order of importance- 

1. Constant light hiss

2. Volume maxes out at 9 o'clock. No wiggle room. 

3. Left and Right channels are unbalanced until about 8 o'clock.

 

So I can't listen at low volumes without reducing source volume (Does that make an audible difference in quality?) The hiss isn't really bad, and doesn't increase much until about 12 o'clock, but it would be nice to hear things go silent between songs or during a quiet section. For such clear, crisp headphones the hiss kind of dispels the magic a little bit.

 

Any way to fix this aside from spending a lot on another amp or performing surgery? And if I have to open up the mini, what tools would I need? I haven't messed with circuitry before but used a soldering gun once in high school. :P  Most of my skills I pick up from situations like this.

 

First, ground loops cause HUM, and a ground loop isolator can often reduce or eliminate this. Sometimes, if you have a situation where you can actually hear what your computer is doing as a sort of faint "chittering" noise, which is digital noise getting into the ground, a ground loop isolator can help that too. However, it will almost certainly have little or no effect on background hiss. Background hiss is simply the byproduct of current flow, and is present to some degree in all active circuitry. "Speaker amps", not being designed specifically for headphones, are designed to be quiet enough for speakers, but it's a lot easier to hear things through headphones (especially 'crisp clear" ones which probably emphasize high frequencies a little bit).

 

Since your hiss DOES increase when you turn the Mini-X's volume control up, it ISN'T coming from the Mini-X (the "background hiss" on the Mini-X itself won't increase much when you turn up the control). It is almost certainly coming in from the output circuitry of your source component - or is in the source material itself, and the Mini-X is boosting it along with the music. (To get one that would track well down very low, you would have to spend as much as the entire Mini-X costs, and it still wouldn't be perfect.)

 

All of this strongly suggests that simply adding a passive attenuator between your source and the Mini-X will help quite a bit.

 

 

 

Since your volume maxes out that early, that also suggests that your source component is putting out more output level than the Mini-X really needs (this isn't a problem per-se, but since the amount of noise is proportional to the maximum output level, it suggests the same issue).

 

All "audio taper" analog potentiometers fail to track perfectly at very low volume levels. While really expensive ones are better, none is perfect.

post #3679 of 3684
I doubt the noise is from the source per se. Didn't he say that the noise only increased when the volume was like 12 o'clock? Anyway, that is very easy to test. Just pull out the inputs.
post #3680 of 3684
Quote:
Originally Posted by davidsh View Post

I destroyed my HE-500 with an upa-200. How is still a mystery to me. I think it might be because pre-amp was turned on while the headphones were connected.

 

Well that's concerning. Since I'm not rocking a HE-6, maybe I won't throw my HE500s on one. The UPA-1L looks pretty damn sweet too. Really like the look of the newer updated Emotiva products. And they're having a sale right now to boot !

 

Quote:
Originally Posted by davidsh View Post

I doubt the noise is from the source per se. Didn't he say that the noise only increased when the volume was like 12 o'clock? Anyway, that is very easy to test. Just pull out the inputs.

 

Yup, just pull your RCAs out the back. Easy to figure out what the issue is. 

post #3681 of 3684
Quote:
Originally Posted by KeithEmo View Post
 

First, ground loops cause HUM, and a ground loop isolator can often reduce or eliminate this. Sometimes, if you have a situation where you can actually hear what your computer is doing as a sort of faint "chittering" noise, which is digital noise getting into the ground, a ground loop isolator can help that too. However, it will almost certainly have little or no effect on background hiss. Background hiss is simply the byproduct of current flow, and is present to some degree in all active circuitry. "Speaker amps", not being designed specifically for headphones, are designed to be quiet enough for speakers, but it's a lot easier to hear things through headphones (especially 'crisp clear" ones which probably emphasize high frequencies a little bit).

 

Since your hiss DOES increase when you turn the Mini-X's volume control up, it ISN'T coming from the Mini-X (the "background hiss" on the Mini-X itself won't increase much when you turn up the control). It is almost certainly coming in from the output circuitry of your source component - or is in the source material itself, and the Mini-X is boosting it along with the music. (To get one that would track well down very low, you would have to spend as much as the entire Mini-X costs, and it still wouldn't be perfect.)

 

All of this strongly suggests that simply adding a passive attenuator between your source and the Mini-X will help quite a bit.

 

 

 

Since your volume maxes out that early, that also suggests that your source component is putting out more output level than the Mini-X really needs (this isn't a problem per-se, but since the amount of noise is proportional to the maximum output level, it suggests the same issue).

 

All "audio taper" analog potentiometers fail to track perfectly at very low volume levels. While really expensive ones are better, none is perfect.

 

 

Awhile back Lonnie mentioned he would be willing to look into a "kick @$$" headamp. Any chance you've heard any rumblings about it? :D At this point I've become a bit of a silly emotiva fanboy (airmotivs, DC-1, A100)  so if he wants any feedback about features, etc people here would be more than willing. 

 

 

http://emotivalounge.proboards.com/post/613977/thread


Edited by elwappo99 - 2/3/15 at 2:50pm
post #3682 of 3684
Quote:
Originally Posted by elwappo99 View Post
 

 

 

Awhile back Lonnie mentioned he would be willing to look into a "kick @$$" headamp. Any chance you've heard any rumblings about it? :D At this point I've become a bit of a silly emotiva fanboy (airmotivs, DC-1, A100)  so if wants any feedback about features, etc people here would be more than willing. 

 

 

http://emotivalounge.proboards.com/post/613977/thread


No news yet, but I'll keep you in mind.

post #3683 of 3684
Quote:
Originally Posted by davidsh View Post

I doubt the noise is from the source per se. Didn't he say that the noise only increased when the volume was like 12 o'clock? Anyway, that is very easy to test. Just pull out the inputs.

 

Good point.... since the Mini-X is a fixed gain block fed by a potentiometer, odds are the fixed low level hiss (below where it starts to increase) is simply the inherent hiss on the amp itself, but once the hiss starts to increase, what you're then hearing is the source hiss multiplied by the gain of the amplifier. The problem is that adding a resistor divider to the output side of the amplifier is going to increase the output impedance - which sort of defeats the purpose of using a real "speaker amplifier". 

 

You could try a low impedance voltage divider on the output - possibly using a 20 ohm resistor and a 5 ohm resistor to ground on each channel. This would keep the output impedance somewhat low, but will dissipate a lot of power (you'd need big fat resistors and they'd get hot, which means choosing resistors carefully, and mounting or housing them carefully.)

 

However, if you do this, it's going to take significant work, and it will degrade the performance of the amp a bit.... I don't honestly think I could recommend that you do all that.... however, it should work....

post #3684 of 3684
I have done so with 6 and 2 ohm resistors. One can argue that the amp will see the impedance it was designed for in such a config.
In the end I don't think it really matters. At least audibly so. We aren't using multi armature IEMs, no?
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