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Speaker amps for headphones - Page 48

post #706 of 2933
Originally Posted by Gary in MD View Post

Flysweep:

 

You shouldn't use eneloops, they are only 1.2V, which isn't enough -- you end up with 1.2 x 8 = only 9.6V.  You need either alkalines or lithiums, as both are 1.5V, to get to the minimum recommended 12V total. 

 

Thanks for the heads up.. Eneloop is off the list, then.. any recommendations for a good lithium rechargeable?


Edited by FlySweep - 8/18/13 at 12:05am
post #707 of 2933

I couldn't find any lithium rechargeable AAs.  I have the non-rechargeable ones, which Jan said should last pretty long just driving headphones.  But if you want rechargeable lithium, you're going going to have to go to LiFePo.  They are available from hobby parts sites, but by the time you buy a charger and other connectors, you are up around $150. 

 

The other alternative is a 12v battery, available on Amazon.  With the addition of a charger and connections for the amp, you would still be waaay under $100 for 7-8 amp hours, and even if you doubled up and ran 2 in series to get 24v you could still probably stay around $100 or less.  Note that SLA's don't like to be discharged deeply (LiFePo's are better about that) so useable time from the 7-8 AH SLA might not be much more than what you can get from a 3.6AH LiFePo, without really shortening the life of the battery.  Of course you can get some really big universal 12v batteries (I saw one with 35 AH... and even it might not be the biggest available) that would last a long time driving the Millenia, even if you only discharged 33%.

post #708 of 2933

Here's a way to operate the MG3 at  25.2V while using only AA-sized batteries, internally:

 

If you want to get closer to the MG3's maximum permissible 27V, while using AA-sized batteries internally, you might consider researching 3.7V AA-sized Li-Ion "14500" batteries, similar to these made by Tenergy (a well-respected brand):

 

 

http://www.all-battery.com/6pcsLi-IonFlatTop14500_3.7V_800mAh_AA_RechargeableBatteries-39172.aspx

 

I am no longer suggesting we experiment with these batteries in the MG3.  Keep reading, but see the UPDATE below for a superior solution (in terms of safety).

 

 

 

And here's a smart charger that can charge "14500" Li-Ion batteries, but it only does four at a time:

 

 

http://www.batteryjunction.com/smx-intellicharge-i4.html

 

 

Li-Ion 14500 batteries are the exact same size as 1.5V AA Alkalines, but when fully charged, they will measure 4.2V each.  (3.7V is their nominal rating.)

 

The MG3 battery compartment holds 8 AA cells and it connects them serially (end-to-end), so if you were to load it up with eight of these Li-Ion 14500 batteries, you would get 33.6V, total - but we must not go past 27V. 

 

Solution:  Use 6 of the Li-Ion 14500 batteries shown at the link above (or their equivalent), for a total of 25.2V (the same, fully-charged voltage I'll be getting with the 6-Cell LiPo pack I've ordered).  

 

But how do you use six AA's in a battery compartment made for eight AA's?  Add two fake AA batteries!

 

http://www.ebay.com/itm/2-pcs-Pack-Dummy-Battery-AA-Conduct-Conductor-Electric-Current-Ultracell-plus-/271250525019

 

So, it's possible to run the MG3 at 25.2V, using internal AA batteries.

 

I might try this later on, but for now, I'll stick with the external LiPo pack approach.

 

Mike

 

UPDATE:  Don't run with this information without first reading this post, too!  tongue.gif


Edited by zilch0md - 8/20/13 at 9:11pm
post #709 of 2933

^ Mike, you're my hero. ^  Really appreciate the info.. I'll definitely pursue this option.  The battery pack is doable, but I'd like to keep the desktop space as clean as possible.. so these batteries will be excellent.

post #710 of 2933
Quote:
Originally Posted by FlySweep View Post

^ Mike, you're my hero. ^  Really appreciate the info.. I'll definitely pursue this option.  The battery pack is doable, but I'd like to keep the desktop space as clean as possible.. so these batteries will be excellent.

FlySweep,

We will be into some serious mutual admiration if you trail-blaze this! My last post was about a 3-hour effort, finding the best battery, the best charger, and a source for dummy batteries. I did my homework so I wouldn't have to do it later, but that effort is all for nought if no one uses it (not even me).

Thanks very much for taking the plunge!

Previously, I had made a tongue-in-cheek comment about how a 3800 mAh LiPo pack should last at least 0.9 hours given that the MG3's fuse would blow at 4000 mA, but just guessing, I suspect that the MG3 pulls something less than 500 mA, normally - one eighth the power required to blow the 4A fuse.

I'm basing this on two premises: The MG3 is a very efficient (doesn't get hot) Class D amp on a chip -AND- Jan Plummer wouldn't have designed it with a battery compartment to hold eight 2100 mAh alkalines - that would offer only 30 minutes of play time with a 4000 mA load. Pulling 500 mA, the MG3 could play for four hours on a set of eight AA alkalines - a more reasonable possibility. If the MG3 can play for longer than 4 hours on eight 2100 mAh AA alkalines, it must pull even less than 500mA. I wouldn't be surprised if that's the case.

I should just ask Jan Plummer how many mA the MG3 typically pulls and/or how long a set of AA alkalines last, but I don't want to wear him out with emails. ;-)

When you test the 25.2V solution, using six Tenergy 800 mAh Li-Ion 14500 batteries and two dummy batteries, the MG3 will be pulling a lot more current. Jan Plummer has said it's possible to blow the 4A fuse when supplying 27.5 volts. I'm just guessing, but I'd still be surprised to learn that the MG3 pulls more than about 2400 mA rms, as opposed to peak current demands. (Hint: RMS figures are typically 70% of peak.)

This is some really sloppy dead reckoning on my part, but if I cut that 2400 mA figure down by the ratio of 25.2V to 27.5v, I'm thinking the MG3 couldn't possibly pull more than 2200 mA rms at 25.2V. Keeping in mind that nearly all battery types suffer a non-linear capacity relative to linear changes in load (i.e. a battery that can deliver 2 hours of play with a 1 Amp load will give you far less than 1 hour of play with a 2 Amp load.) Sad, but true. The higher the current draw, the less proportional will be the play time.

So... I'm guestimating that the six 800 mAh Tenergy Li-Ion 14500 batteries, operating the MG3 at 25.2V when fully charged, pulling something less than 2400 mA rms (est.), might last only 15 minutes! (800 mAh / 2400 mA = 1/4 hour)

But that's my worst-case estimate. You might get an hour or more of play time using this 25.2V internal battery pack. Just a head's up, because when you start pulling lots of current, you'll pay the price in play time.

That's my only caveat, so go for it, FlySweep!

;-)

Mike
Edited by zilch0md - 8/18/13 at 8:32am
post #711 of 2933

Mike:

 

If I understand things correctly (not a given,but we'll try this anyway), if all we are doing is driving headphones with the amp it will use very little power, and the batteries will last a lot longer.  The LCD-3s, relatively inefficient planar headphones, take 1mW to get to 91 dBs.  Even running through the resistor box, I never have the volume past 9:30 on the dial, and I don't think it takes much power for its overhead and housekeeping (the thing is never even warm) so I doubt the Millenia is ever pulling >2 amps,  In fact, I'd be surprised if it was pulling even 1.


Edited by Gary in MD - 8/18/13 at 9:14am
post #712 of 2933

Here is the battery that Jan had recommended I try with the Millenia, along with a link to the adapter needed to plug it into the Millenia. Jan suggested I could strap two of these together to get 24volts, but that was getting too complicated for my situation (my set up is in my living room!), so I never tried it out. As I said in an earlier post, I agree that the battery route I did try (one 12 volt battery) provided a more transparent sound (needed to go back and forth a lot to determine that.....I agree with Gary, on ac it still sounds like the Millenia), but  that greater transparency makes my set up appear less full sounding. So, for now I'm sticking with ac. But that idea of getting the full power from internal batteries is intriguing..... Anyhow, sounds like you guys have the battery idea more than well covered, but just in case this is helpful, here are the links for Jan's recommendation:

 

Battery:

http://www.batteryspace.com/sealedleadacidbatterycombo12v75ah90whslabatteryinfannybag08asmartfastcharger.aspx

 

http://www.batteryspace.com/connectoradaptorcigarettemaleplugto55x25mmbarrelmale.aspx

post #713 of 2933

SMG:

 

Were you driving speakers with the Millenia on 12 volts?  If so, I'm guessing the "less full sound" you are getting could be tied to the fact that you only had 12 volts available, and even the most efficient speakers take a watt to get to ~100dBs, as opposed to <mW for most headphones.  The Millenia drops from ~30WPC to ~10WPC on 12 volts, leaving less headroom, and likely limiting the fullness of the sound. (My brain keeps repeating "sounds great, less filling" but I'm guessing only those of you above a certain age will get that).

 

If you have a chance, just take the battery out of your car and hook it up to your existing battery in series to get 24V, then see how it sounds.  You can explain this odd behavior to your significant other(s) as an urgent scientific experiment that could end up saving the world.  Or not.  biggrin.gif

post #714 of 2933
I hear you, Gary. I'm thinking its consumption could be more conservative still, as evidenced by my last post opening with a suggestion that the MG3 cruises along pulling "something less than 500 mA, normally - one eighth the power required to blow the 4A fuse." That was the limit of my optimistic thinking, before I then went on to estimate worst-case battery play times, pointing out that the relationship between battery capacity and load is not proportional, but I'm with you, here - play times are probably much better than my most pessimistic estimates.

I'm hoping FlySweep can get at least 4 hours of play time from the 25.2V Li-Ion AA solution, but I'm confident, if not certain, that he will enjoy a rock-bottom minimum of at least 15 minutes (working backwards from Jan saying the MG3 can blow a 4A fuse with a 27.5V supply.)

Enough with theorizing, eh? Let's test it. Go FlySweep! :-)

Mike
post #715 of 2933

I just wanted to say something about this whole power issue, as regards what the headphones actually need, vs what an amp can deliver. Of course technically speaking, the headphones we are using (unless we are talking about the HE-6 and the like) are not requiring anywhere near what something like the Millenia is putting out, even with the resistor box in place. But I believe that having more power "on tap" is impacting the sound, in a positive way (assuming again that the amp itself sounds good......I don't think power alone is the ultimate deciding factor). That is why it might be interesting for me to some day try using the full power the Millenia is capable of, but via battery power (still using the resistor box). Even with the resistor box, if the Millenia is able to provide its full power capability, the power out of the resistor box will be significantly greater than on just the 12 volts I have experimented with .......and yes, I realize that technically speaking, the headphones are not really using it, but I think having that extra power on tap  might still make a difference in headphone performance. (I could be wrong, though. smile.gif

 

Stew

post #716 of 2933
Quote:
Originally Posted by Gary in MD View Post

SMG:

 

Were you driving speakers with the Millenia on 12 volts?  If so, I'm guessing the "less full sound" you are getting could be tied to the fact that you only had 12 volts available, and even the most efficient speakers take a watt to get to ~100dBs, as opposed to <mW for most headphones.  The Millenia drops from ~30WPC to ~10WPC on 12 volts, leaving less headroom, and likely limiting the fullness of the sound. (My brain keeps repeating "sounds great, less filling" but I'm guessing only those of you above a certain age will get that).

 

If you have a chance, just take the battery out of your car and hook it up to your existing battery in series to get 24V, then see how it sounds.  You can explain this odd behavior to your significant other(s) as an urgent scientific experiment that could end up saving the world.  Or not.  biggrin.gif

No, never bothered to use the battery with the Millenia amp I am using with my speakers. The speakers I have are not that efficient. I was referring the headphones I am using (the Paradox). Of course, as with all things, it may be system dependent. I doubt the Paradox headphones are as full sounding as the Audeze to begin with. But, my experience with the battery pack was that the upper midrange and treble region were more transparent, more highlighted in a way, and that impacted - for me - the overall sonic picture. So in going back to the ac, even though that transparency was diminished somewhat, I preferred the 'fuller' sound.

 

You know, my wife - bless her soul - probably would shrug her shoulders and chuckle if she saw me lugging our car battery into the house......but the battery I have for the Millenia is already a 12 volt. I wonder about Mikes' internal battery idea, to get the full power out of the Millenia.....I still wonder if that would provide the transparency AND the fullness, in my instance. 

 

Stew

post #717 of 2933
Thanks for those Jan Plummer-supplied links, SMG52.

His choice of a 7.0 Ah battery gives us a benchmark of sorts, saying "7 Ah is enough to provide reasonable play times," whatever that may be. In other words, I can't imagine him recommending that battery for less than a couple of hours of play time.

Did he mention how many hours you might get with that battery? (At 7000 mAh, it has almost twice the capacity of the 3600 mAh LiPo pack I ordered and nearly nine times the capacity of the 25.2V Li-Ion AA contraption FlySweep is considering.)

Thanks!

Mike
post #718 of 2933
Quote:
Originally Posted by zilch0md View Post

Thanks for those Jan Plummer-supplied links, SMG52.

His choice of a 7.0 Ah battery gives us a benchmark of sorts, saying "7 Ah is enough to provide reasonable play times," whatever that may be. In other words, I can't imagine him recommending that battery for less than a couple of hours of play time.

Did he mention how many hours you might get with that battery? (At 7000 mAh, it has almost twice the capacity of the 3600 mAh LiPo pack I ordered and nearly nine times the capacity of the 25.2V Li-Ion AA contraption FlySweep is considering.)

Thanks!

Mike

 

I went through my emails with Jan, and I don't see anything about how long the external battery would last. But, it is so easy to recharge. I just had it plugged into an extension cord that had a switch on it, and then I could just swap cables to plug in the charger.....pretty simple, actually. 

post #719 of 2933
Quote:
Originally Posted by SMG52 View Post

No, never bothered to use the battery with the Millenia amp I am using with my speakers. The speakers I have are not that efficient. I was referring the headphones I am using (the Paradox). Of course, as with all things, it may be system dependent. I doubt the Paradox headphones are as full sounding as the Audeze to begin with. But, my experience with the battery pack was that the upper midrange and treble region were more transparent, more highlighted in a way, and that impacted - for me - the overall sonic picture. So in going back to the ac, even though that transparency was diminished somewhat, I preferred the 'fuller' sound.

 

You know, my wife - bless her soul - probably would shrug her shoulders and chuckle if she saw me lugging our car battery into the house......but the battery I have for the Millenia is already a 12 volt. I wonder about Mikes' internal battery idea, to get the full power out of the Millenia.....I still wonder if that would provide the transparency AND the fullness, in my instance. 

 

Stew

Oops, sorry.......you wanted me to hook up the car battery in line with the 12 volt I already have. Good idea, but, I am not that motivated. But thanks! 

post #720 of 2933

I've talked to Jan about battery life, and while I don't remember a specific number, he indicated that 7AH would allow the Millenia to drive headphones for a really long time.  Like weeks if not months.  Remember, though that SLAs do not like deep discharging, while LiFePo's apparently don't mind it.  So if you are going to use SLAs it would actually be better to have 2 batteries and use one for a couple of sessions while charging the other, so all you would have to do is swap them out.  Or try 4, using 2 while charging 2. 

 

Hmmm, 4 batteries... Stew, how many cars you got?  How about riding mowers? C'mon man, the world is depending on you!  (At least the small part of the Head-Fi world that is following this thread).

 

Wait a second...Come to think about it, I have about 6 12-volt batteries around here, if you include jump-starters... Oh, but I don't have the right connectors...

 

Annnnnd I'm not that motivated either -- I'm fine with the amp powered by Energizer lithiums or the AC adapter, at least for a while.

 

Never mind Stew, put the batteries back in the cars and lawn tractor...

 

biggrin.gif

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