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The Stax SRM-001 mod thread - Page 6

post #76 of 402
Quote:
really? the one I have here (from Larry) will not, the battery itself is longer than the bay -- the bay opening is 51mm, the battery is about 52mm.... can you post a picture of your ultrafire standing next to a AA alkaline? I wonder if they do design changes all the time.
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I measured the battery 51,8mm long (it is a trustfire I use not an ultrafire but just as long) . I have got a MK1 version of the SRM-001 so maybe that is why
I will take a picture later.
post #77 of 402
The one just modded is a Mk1 too.
post #78 of 402
Thread Starter 
Both the MK1 and MK2 has the same battery bay openning length, both 51mm.

I opened the protected cells and took out the circuit boards, then hard wired one board inside the 001 amp. here are some observations:
1) the ultrafire board cuts off at 3v, instead of the more common 2.5v. So you should always have good sound as long as the amp runs, until the amp turns itself off (then you get no sound at all ). Not sure how much battery life reduction this will cause, since the power is cut-off before the battery is fully depleted.

2) the protection board was designed to be hard wired onto the battery, it is designed to freak out when seeing 0 volt which means the battery is permernently dead. But in this case the circuit is installed in the amp (the load), the 0 volt situation happens when you take the batteries out of the battery bay during a battery change. Therefore, when changing batteries, you will have to leave the battery bay empty for a few minutes so the protection board can reset itself, before installing the fresh battery.
post #79 of 402
With Parallel Battery mod, can't you just swap one of the partially discharged batteries with a full one, then swap the other, so the protection board still sees 3V but just half the amperage for that 2-3 seconds?

Also, if I get horrible battery life, unprotected cells can be bought with more Mah than protected, right?

Lastly, peeps here should know that there was not enough room for a normal size protection board, so this was the only option to protect the cells. Otherwise, forgetting to shut it off when the batteries run low, like falling asleep while listening could harm the cells. AND, now the cells are not protected from overcharging unless you have a special Lithium battery charger (like mine).
post #80 of 402
Thread Starter 
Quote:
Originally Posted by HeadphoneAddict View Post
With Parallel Battery mod, can't you just swap one of the partially discharged batteries with a full one, then swap the other, so the protection board still sees 3V but just half the amperage for that 2-3 seconds?
NO NO NO! the two batteries recepticles are connected in paralle, if you take just one empty battery out and install a full one, the full one will have much higher voltage than the other empty one (still in the battery bay), so the full one will try very very hard to charge the empty one by sending tons of current, it is almost like a short, this will harm both batteries....now you know why I heatshrinked them two in red two in blue, so you won't mix the empty with the full by mistake.

Quote:
Originally Posted by HeadphoneAddict View Post
Also, if I get horrible battery life, unprotected cells can be bought with more Mah than protected, right?
I think they are the same.... unless you can find the Sony 1100mAH info-lithiums for a good price (and I don't remember the model # for the sony).
post #81 of 402
Great modding job Audiocats!

Here is the promised photo with the longer (51,3-51,8 mm) protected 14500 Li-ion battery
The tip of the battery is just small enough to squeeze in between. You have to roll the battery out so using more than one (only if you did the parallel batteries mod!) it is harder to get them out.
I still think you better use protected Li-ions; they shut down when they are getting low and you don't want to charge depleted Li-ions. Building a protection circuit inside is to much trouble for most.
These trustfires are also cheap ($6 shipped)



Although it is a MK1 set; My SRM-001 got a (T TA75062S .6G) in it and the mainboard is a PB-102 with the number 08444-00134 on it an with 03185 on the serial label. It seems like this is yet another variation.
post #82 of 402
Thread Starter 
Quote:
Originally Posted by pipoplus View Post
I still think you better use protected Li-ions; they shut down when they are getting low and you don't want to charge depleted Li-ions. Building a protection circuit inside is to much trouble for most.
These trustfires are also cheap ($6 shipped)
Thanks for the photo
agree, it is always better to have a protection board. That is why I squezzed in the ultrafire's protection board into the amp itself, so whatever is in the battery bay will be protected

by the way, if you like how your MK1 sounds, try some MK2 phones when you have a chance, you will be amazed
post #83 of 402
Quote:
Originally Posted by AudioCats View Post
NO NO NO! the two batteries recepticles are connected in paralle, if you take just one empty battery out and install a full one, the full one will have much higher voltage than the other empty one (still in the battery bay), so the full one will try very very hard to charge the empty one by sending tons of current, it is almost like a short, this will harm both batteries....now you know why I heatshrinked them two in red two in blue, so you won't mix the empty with the full by mistake.


I think they are the same.... unless you can find the Sony 1100mAH info-lithiums for a good price (and I don't remember the model # for the sony).
So, if you pull one discharged battery out you have to pull out the other, because if one unprotected-drained battery is still installed then it could be harmed if the full one is inserted first, even if the drained battery is removed within "a couple of seconds" of inserting the full one. Wow. That's crazy.

Anyway pipoplus, my SR-001 now has the protection circuit built-in, so the pair of batteries cannot be over-discharged below 3.0v, so I can use unprotected cells if I want to. I just have to be careful charging those cells in a proper charger, since they CAN be overcharged without the protection circuit that was pulled out of all of them (so they would fit).

The Ultrafire lithium battery charger that I have will not overcharge unprotected Lithium 14500 batteries. So, we should be good on that end too. My Ultrafire can even charge them in the car with the optional cable I have for it.
post #84 of 402
Thread Starter 
Update: battery life issue
just did the battery life test, the amp turns off at about 3 hours on a pair of freshly charged batteries. Current draw is about 480mA which is about the same as my modded MK2 board with 8599 installed. In theory a pair of 900mAH should last a little longer, like 3.5hr or so. Two factors can cause the shorter battery time:
1) the higher cut off voltage of ultrafire protection board. The power is cut off a little too early, before the battery is really depleted. Not much I can do about that, since the ultrafire board is the only one that can fit in (and even with that, I still had to fight to squeeze it in).

2)the rapid charger might not be fully charging the batteries. I have read the rapid chargers only do the stage-1 charging that is why it is so "rapid", and stage-1 only fill to about 70%. I am charging one pair of ultrafire in my "non-rapid" charger, will do the bettery life test on that pair tomorrow night and see if there is any difference....
post #85 of 402
One thing I can consider is that if the issue is the rapid charger, then I'll just buy a better charger that does a "more complete" job.

Likewise, if you guys can find protected cells that do fit two at a time, and they last longer than 3 hours in your units, then I could remove the protection board from the SR-001 Mk1 and buy those same protected batteries.

Or, I'll either search for lithium batteries with more than 900mah, or just live with 6 hours from 4 cells.
post #86 of 402
here you can find high grade Li-ion batteries. I also believe they sell protected 14500 in normal AA size and "real" 750mAh.
Having fitting 14500's is also a big issue in flashlight country
post #87 of 402
BatteryJunction.com has them in 900mah protected (52mm too long) but also 900mah unprotected (50mm which fit)
post #88 of 402
Thread Starter 
SFC update:
* the rapid charger is probably not the main problem on battery life issue. It took my slow charger over 10 hours to charge a pair of ultrafire, and the run time is 2 hour 50minutes, about the same as the rapid chargers.
Since you can use the unprotected cells in the battery bay, it is probably cheaper to just get one more pair of batteries.

* The amp is now pretty stable. It was quite warm for the first two days, I could feel it on both top and underside of the plastic case, which made me kind of worried because the +/- supply caps are right above the opamps and I think most of the heat came from teh opamp. High temperature is never a good thing for electrolytics. (though the UnitedChemicon PS caps are rated for 105C operation, so really there is no need to worry.) Now the case is only slightly warm, I think the burn-in of the opamp is nearly completed.

larry, the package will be sent back tomorrow afternoon. After receiving it, you probably still want to do two more days of burn in. It has about 60 hours on it right now, and according the AnalogDevice, BJT opamps need 70-100 hours to fully stablize. (I think the 8599's are BJT input, since the input impedance is quite low -- comparing to the FET input opamps it is).-- update: ok the 8599 is not BJT, it is still FET input, I got it mixed up with the 797 ... anyway, more burn-in won't hurt

by the way, I have put the original parts (taken off the MKI board) in the package too, and two of the ultrafire protection boards, just in case you might need them for whatever reason. I am keeping one ultrafire pretectin board, I will see if I can come up with a protection/dummy cell so you can use the lithiums in your stock MKII.
post #89 of 402
Quote:
Originally Posted by AudioCats View Post
SFC update:
* the rapid charger is probably not the main problem on battery life issue. It took my slow charger over 10 hours to charge a pair of ultrafire, and the run time is 2 hour 50minutes, about the same as the rapid chargers.
Since you can use the unprotected cells in the battery bay, it is probably cheaper to just get one more pair of batteries.

* The amp have become pretty stable. It was quite warm for the first two days, I could feel it on both top and the underside of the plastic case, which made me kind of worried since the +/- supply caps are right above the opamps and I am pretty sure most of the heat came from teh opamp, high temperature is never a good thing for electrolytics. (though the UnitedChemicon PS caps are rated for 105C operation, so really there is no need to worry.) Now the case is only getting slightly warm, I think the burn-in of the opamp is nearly completed.

larry, the package will be sent back tomorrow afternoon. After receiving it, you probably still want to do two more days of burn in. It has about 60 hours on it right now, and according the AnalogDevice, BJT opamps need 70-100 hours to fully stablize. (I think the 8599's are BJT input, since the input impedance is quite low -- comparing to the FET input opamps it is). So two more days should do it.

by the way, I have put the original parts (taken off the MKI board) in the package too, and two of the ultrafire protection boards, just in case you might need them for whatever reason. I am keeping one ultrafire pretectin board, I will see if I can come up with a protection/dummy cell so you can use the lithiums in your stock MKII.
Sounds like a plan. I would love a dummy protection cell for my stock Mk2!
post #90 of 402
Great work AudioCats.

I replaced input electrolytics with 47u/6.3 NX today. Difference is big. There is less distortion and details are coming in from darker background. I am awaiting AD8599s, some X2s and MKPs.

Have a nice day
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