Head-Fi.org › Forums › Summit-Fi (High-End Audio) › High-end Audio Forum › Speaker amps for headphones
New Posts  All Forums:Forum Nav:

Speaker amps for headphones - Page 56

post #826 of 2542

Thanks for that Stew.  I get hiss to my 8-Ohm speakers with the MG3 using 24V power from either the AC adapter -OR- from my 25.2V LiPo battery pack.  And given that 12V power causes no hiss from either a battery on the external power jack or from internal AA batteries, I believe the problem is tied to how much voltage I'm using, independent of where it's coming from.  (So I don't think it's a grounding issue...)

 

I like brunk's suggestion, above, that we ask Jan if it's possible to adjust the MG3 gain, but again, I think we can trim that just by adjusting the voltage.  I will test with 16.8V four-cell LiPo batteries this evening, but I don't have any five-cell LiPo packs that could get me to 21.0V.  I'm resisting the urge to buy an variable-voltage DC power supply, because I would only use it for testing.  I'd much rather come up with a battery solution (at a voltage that doesn't induce hiss with my speakers).  For testing purposes, I can discharge the six cell pack no further than 18.0V, but the hiss might disappear somewhere along the way, between 25.2V and 18.0V.  I can also try my XP8000 with the inline voltage regulators (switch-mode) that allow me to select 15V, 16V, or 19V.  Test, test, test...  And then I'll have to find the ideal voltage all over again, for using the MG3 with the LCD-2 via the impedance match...

 

Mike


Edited by zilch0md - 8/23/13 at 4:06pm
post #827 of 2542
Quote:
Originally Posted by zilch0md View Post

Thanks for that Stew.  I get hiss to my 8-Ohm speakers with the MG3 using 24V power from either the AC adapter -OR- from my 25.2V LiPo battery pack.  And given that 12V power causes no hiss from either a battery on the external power jack or from internal AA batteries, I believe the problem is tied to how much voltage I'm using, independent of where it's coming from.  (So I don't think it's a grounding issue...)

 

I like brunk's suggestion, above, that we ask Jan if it's possible to adjust the MG3 gain, but again, I think we can trim that just by adjusting the voltage.

 

... snip ...

 

Mike

Interesting about the gain question.  I can see how that could happen with a variable input voltage and a Class D amplifier if the amplifier rail voltages are moving around with input voltage level.  For a given SPL level, is there a difference in the knob position between a 12 V supply and a 24 V supply?


Edited by potterma - 8/23/13 at 8:20pm
post #828 of 2542
Hi potterma,
Quote:
Originally Posted by potterma View Post

Interesting about the gain question.  I can see how that could happen with a variable input voltage and a Class D amplifier if the amplifier rail voltages are moving around with input voltage level.  For a given SPL level, is there a difference in the knob position between a 12 V supply and a 24 V supply?

Yes, indeed. When you switch the MG3 from using 24V to 12V, for example, you have to turn it down a bit.

I tested my 16.8V 4-cell LiPo pack tonight and noticed that I could still hear a tiny bit of hiss from my 8-Ohm speakers, at a distance of two feet. Not having a variable output power supply, I used my balance charger's discharge mode to pull the battery down fairly rapidly, stopping at 16, 15.5, 15, 14.5, and 14V to test it with the MG3. The hiss didn't disappear entirely until the voltage got down to 15V. Again, this is with my 8-Ohm speakers. At 15V, the SQ is better than at 12V, in my opinion and the black background makes it all the more enjoyable. Putting up with any amount of hiss just kills the realism this amp can produce.

Mike
post #829 of 2542
Quote:
Originally Posted by zilch0md View Post

Hi potterma,
Yes, indeed. When you switch the MG3 from using 24V to 12V, for example, you have to turn it down a bit.

I tested my 16.8V 4-cell LiPo pack tonight and noticed that I could still hear a tiny bit of hiss from my 8-Ohm speakers, at a distance of two feet. Not having a variable output power supply, I used my balance charger's discharge mode to pull the battery down fairly rapidly, stopping at 16, 15.5, 15, 14.5, and 14V to test it with the MG3. The hiss didn't disappear entirely until the voltage got down to 15V. Again, this is with my 8-Ohm speakers. At 15V, the SQ is better than at 12V, in my opinion and the black background makes it all the more enjoyable. Putting up with any amount of hiss just kills the realism this amp can produce.

Mike

Well, Mike, you are one patient guy. An audible hiss over the speakers that can be heard from several feet away would bother me. I haven't experienced it myself, nor have I read about it in any of the blogs where people have talked about the Millenia; It would have raised alarm bells before I even tried the amp out.  It is definitely something for Jan to explore. I assume you will let him know at some point.

post #830 of 2542

Mike:

 

How efficient are those speakers again?  TBI's Diamonds are listed at 87dB @1w/1m and I hear no hiss at normal listening levels.  I also hear no hiss with the LCDs through the resistor box.  It could be that your speakers are so efficient that they're picking up noise that most speakers won't.  Or maybe not.  In any case, it is worth talking to Jan about.

post #831 of 2542
Quote:
Originally Posted by zilch0md View Post

Hi potterma,
Yes, indeed. When you switch the MG3 from using 24V to 12V, for example, you have to turn it down a bit.

I tested my 16.8V 4-cell LiPo pack tonight and noticed that I could still hear a tiny bit of hiss from my 8-Ohm speakers, at a distance of two feet. Not having a variable output power supply, I used my balance charger's discharge mode to pull the battery down fairly rapidly, stopping at 16, 15.5, 15, 14.5, and 14V to test it with the MG3. The hiss didn't disappear entirely until the voltage got down to 15V. Again, this is with my 8-Ohm speakers. At 15V, the SQ is better than at 12V, in my opinion and the black background makes it all the more enjoyable. Putting up with any amount of hiss just kills the realism this amp can produce.

Mike

Just a thought to eliminate any variables in regards to hiss, have you tried re-seating your speaker wires? You know...oxidization etc., blah blah. Same for the ICs too. You're awesome for going through all those voltage options, my hats off to you!

beerchug.gif

post #832 of 2542
Quote:
Originally Posted by brunk View Post

Just a thought to eliminate any variables in regards to hiss, have you tried re-seating your speaker wires? You know...oxidization etc., blah blah. Same for the ICs too. You're awesome for going through all those voltage options, my hats off to you!

beerchug.gif

Yes, indeed!  Thanks!

post #833 of 2542

Hmm...  Thanks for the suggestion to seek Jan's advice, Stew, but I've honestly not felt any concern about returning the MG3 because I have from minute one assumed that at voltages higher than 15V, every MG3 out there would generate a detectable hiss with my Definitive Technology SM45 speakers.  I get a similar hiss with these same speakers when using the Emotiva Mini-X a-100, but it's more faint than with the MG3 on 24V power - and I never found a way to dial out the hiss coming from the Emotiva Mini-X a-100.  

 

I should emphasize that the hiss I hear from the MG3 into my speakers on 24V power is easily less than 10% as loud as the hiss I hear when using the MG3 with my LCD-2 in the absence of an impedance match.  That much louder hiss heard with the LCD-2, even when playing music, indeed sounds like the cassette tape hiss you once described (or was it Gary?)  The amount of hiss I can hear with my speakers from the MG3 on 24V isn't a problem when playing most tracks, as it can only be heard in those moments with some music where the absence of complete blackness is annoying because it can mask some of the very lowest level signals, stealing away the realism, but it's not constantly heard, as with the hiss I get using the LCD-2 without an impedance match.  

 

I'm probably beating this to death in my struggle to quantify the SPL of the hiss heard at 24V with my 8-Ohm speakers, but trust me when I say, it's very faint. My home is completely silent as a rule, but when the air conditioning cycles on, just the sound of the air rushing through the overhead vent (which itself isn't whistling or in any way annoying normally) is nearly loud enough to drown out the hiss I hear is at its loudest with the 8-Ohm speakers - when the MG3 is on 24V power.

 

All that said, I'm completely content with the MG3.  I really don't think it has a problem - especially given that I can extinguish that faint hiss completely by using 15V or less, and I rather like the sound I get at 15V.  

 

New topic...

 

On that point, every review I've ever read on the MG3 speaks of how different it sounds at 12V vs. 24V power.  I have solidly concluded that this has nothing to do with using a battery supply (internal or external) vs. the switch-mode AC adapter that comes with the MG3.  No.  It has everything to do with the voltage.  12V and 24V are simply two points on a sound-tailoring curve that runs from about 9V to 30V.  (9V is where a set of eight AA alkaline batteries would be fully discharged.)   At this point in time, I'm going to refrain from attempting to describe the audible changes that occur, but it's not subtle to my ears, nor those of several reviewers, but these sound signature differences lie along a continuum - where we are free to choose precisely the sound we want, just by selecting a particular voltage among an infinite number of points along the 9V to 30V curve - not that anyone is likely to detect a difference between 15.0000V and 15.0001V (or even between 15V and 16V), but the choices are indeed infinite between the two extremes. I'm encouraging people to abandon comparisons of only 12V vs. 24V - there's some good stuff happening in between!

 

While I'm on this soap box about supply voltage vs. sound signature, I feel compelled to point out something that's not at all profound - that the voltage coming from any battery pack will constantly decay during use - which, for the voltage-aware MG3, means (more profoundly) that the sound signature will constantly drift toward those traits that reviewers associate with 12V power.  No matter what voltage your battery pack starts at when fully charged, the sound signature will constantly drift during use - away from the sound signature associated with 30V power, toward that had at 9V.  With the 16,8V four-cell LiPo packs I've decided to use with the MG3 into my Definitive Technology SM45s, I'll be starting at 16.8V, with the 3-volt per cell audible alarm going off as a pack reaches 12V, but I don't think I'll want to wait that long to replace one LiPo pack with another fully charged pack, because I don't like the sound signature I get with 12V as much as I like the MG3 at around 15V!  

 

And thus... later today, I will be testing the MG3 with the five-cell Energizer XP8000 battery pack plus the XPAL Willy Cable WI15 - an inline voltage regulator that maintains a constant 15V output while the 21.0V  XP8000 discharges internally from 21V down to 15V, at which point, the regulator shuts down.  For the MG3, a constant voltage will translate to an unvarying sound signature.  In my experience and that of at least a dozen other Meier Stepdance owners, the XPAL Willy Cable WI15 voltage regulator injects absolutely no noise into an amp.  I've found that to be true with my DACmini CX and iBasso PB2 as well.  

 

 

 

 

More later...

 

Mike

(Control Freak)


Edited by zilch0md - 8/24/13 at 11:54am
post #834 of 2542

The American Heritage Dictionary:

 

feint mini-speaker.png (fānt)
Share: feint
n.
1.
a. A military attack or maneuver that is meant to divert attention away from a planned point of attack.
b. A body movement that is intended to divert another's attention, often by being deliberately left uncompleted: "The mongoose begins with a feint, which provokes the snake to strike" (Norbert Wiener).
2. A deceptive action calculated to divert attention from one's real purpose. 

 

 

faint mini-speaker.png (fānt)
Share: faint
adj. faint·erfaint·est
1.
a. Done with little strength or vigor; feeble: a faint attempt to apologize.
b. So weak as to be difficult to perceive; a faint light in the distance; a faint echo.
c. Lacking clarity or distinctness: a faint recollection.
d. Small in degree or amount; meager: faint chance of getting a raise.
2. Lacking conviction, boldness, or courage; timid: a tourist who is faint at heart.
3. Likely to fall into a faint; dizzy and weak: felt faint for a moment.

 

 

Sorry... tried to let it go... couldn't....

 

 

Excellent points about battery voltage droop with time and associated sound signature from the MG3!  Thanks for that!


Edited by potterma - 8/24/13 at 8:13am
post #835 of 2542

Folks:

 

If switching vs. linear power doesn't affect sound, another option would be a switching benchtop variable power supply (0-30V, 0-3 or 0-5 Amps).  The reason for using switching instead of linear is that the affordable ones don't need fans, whereas the cheap linear ones I've seen on Amazon and eBay all have really noisy fans (that would certainly drown out any hiss...).  To get a linear supply that has a big heat sink instead of a fan costs almost as much as the Millenia...  You can get a variable switching power supply for ~$80.  Of course that option isn't as portable as Mike's vast array of batteries, but for the times when we plan on using the amp at home (and the electricity is on), it seems to be a good way to find the Millenia's sweet spot. 

 

One other note:  It will be interesting to see if Mike hears the same significant difference in sound quality at various voltages on headphones as he did with the speakers, since the LCDs are going to be drawing so much less power.

post #836 of 2542
Quote:
Originally Posted by Gary in MD View Post

Folks:

 

If switching vs. linear power doesn't affect sound, another option would be a switching benchtop variable power supply (0-30V, 0-3 or 0-5 Amps).  The reason for using switching instead of linear is that the affordable ones don't need fans, whereas the cheap linear ones I've seen on Amazon and eBay all have really noisy fans (that would certainly drown out any hiss...).  To get a linear supply that has a big heat sink instead of a fan costs almost as much as the Millenia...  You can get a variable switching power supply for ~$80.  Of course that option isn't as portable as Mike's vast array of batteries, but for the times when we plan on using the amp at home (and the electricity is on), it seems to be a good way to find the Millenia's sweet spot. 

 

One other note:  It will be interesting to see if Mike hears the same significant difference in sound quality at various voltages on headphones as he did with the speakers, since the LCDs are going to be drawing so much less power.

+1 on the variable power supply, that is probably what i would use myself for ultimate versatility, then use a battery pack for a very nice transportable setup, unless the batteries really DO last that long.


Edited by brunk - 8/24/13 at 11:14am
post #837 of 2542
Thanks for the warning about cooling fans, Gary. I'd hate to have discovered that the hard way.
post #838 of 2542
And thanks potterma. I nearly feinted when I realised you was write! No prublem thow, I fissed it!
post #839 of 2542
Quote:
Originally Posted by zilch0md View Post

And thanks potterma. I nearly feinted when I realised you was write! No prublem thow, I fissed it!

Hey, weez gots tu stik tugedur u no!

 

 

 

 

michael

post #840 of 2542
Quote:
Originally Posted by zilch0md View Post

And thanks potterma. I nearly feinted when I realised you was write! No prublem thow, I fissed it!

rolleyes.gif

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: High-end Audio Forum
Head-Fi.org › Forums › Summit-Fi (High-End Audio) › High-end Audio Forum › Speaker amps for headphones