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Old 13th March 2012, 04:03 AM   #2231
a1095us is offline a1095us  United States
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Quote:
Originally Posted by unsopa View Post
Nice work, a1095us,

thank you. I like those basic designs. And never have seen those "shared ic socket", good idea! But aren't you afraid of burning your headphones with DC without the protection circuit? I planned something you did a few weeks ago, but was warned to do here: #2143


What I meant by shared IC socket was nothing more than an 18 pin socket that mounts both 4556's. I am not using batteries or the battery charging circuit. I'm just utilizing the basic Op-amp circuit with my out-board regulated supply. No burning headphones here! I do remember to plug in the phones after power-up and remove them before power down. My power up spike measured a little lower than NwAvGuy's.
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Old 13th March 2012, 07:23 AM   #2232
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Quote:
Originally Posted by dook13 View Post
Greetings to all. New guy here. Caught the DIY bug with this amp. So thanks much for any help.
Welcome to diyAudio.
Quote:
I am looking to use 300mah 9v batteries (unless there are higher capacity battery options) and I'm considering changing the values of R1 & R2 as discussed in the blog with a 150ohm value..
There's virtually always options. I'd need to refresh my memory as to just what NwAvGuy wrote about them.
Before addressing your questions, I'd like to simplify things a bit by setting the regulated output at 12V, the shutoff at 6V, and the fully charged battery at 9V. And ignore the voltage drops of the steering diodes.
Quote:
My questions are:
Is it that slow to charge using the default value(220 ohm)? How long does take to charge?
The O2 has no provision for fast-charging batteries. At a 1/10th charge current it will take roughly 12-15 hours to fully charge (there's always losses, so it isn't simply 10 hours).
Quote:
Will going to the 150 ohm value be that much faster?
Not really enough to be significant.
Quote:
Do I have to worry about over charging with the 150 ohm value?
Possibly. The usual target is 1/10th primary charge current, and a 1/20th maintenance charge current. 300mA divided by 20 equals 15mA, while 3 volts divided by 150 ohms equals 20mA. (This is where I'm using the parameters I mentioned at the beginning.)
Quote:
What is the longest the O2 should be plugged in for with 150 ohm value?
I wouldn't worry for the first 10-12 hours. I'd definitely check them then to see if they're getting too warm.
Batteries that aren't made to fast-charge usually don't like to be fast-charged.
Quote:
Also could I use the SIP sockets used in the gain resistors for R1 & R2?
Not a problem.
Ideally, one wants to match the resistor value with the charge requirements of the battery (ie not those of the user, which is the undertone of your post IMO). You could obtain the real numbers for your situation to arrive at more accurate answers. But as it is, the only way to fast charge the O2 is by using human intervention of the charge cycle.

edit: "As it is" being that I'm not aware that any fast-charge mod for the O2 has surfaced.
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Last edited by sofaspud; 13th March 2012 at 07:50 AM.
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Old 13th March 2012, 08:42 AM   #2233
dook13 is offline dook13  United States
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Quote:
Originally Posted by sofaspud View Post

Not a problem.
Ideally, one wants to match the resistor value with the charge requirements of the battery (ie not those of the user, which is the undertone of your post IMO). You could obtain the real numbers for your situation to arrive at more accurate answers. But as it is, the only way to fast charge the O2 is by using human intervention of the charge cycle.
Thank you for your welome and reply. I've read some of your posts on the subject and was hopeful you would chime in.

When reading the notations in the blog and your posts I got the sense that the resistors and batteries where to be matched. I didn't take into account the batteries other specs. because I didn't know what to look for. Thats why I linked the battery and the resistor. Thought someone would see the specs and comment on whether it would match. Since i am clueless in this regard, my questions were not to task.

Quote:
Originally Posted by sofaspud View Post
There's virtually always options. I'd need to refresh my memory as to just what NwAvGuy wrote about them.
Before addressing your questions, I'd like to simplify things a bit by setting the regulated output at 12V, the shutoff at 6V, and the fully charged battery at 9V. And ignore the voltage drops of the steering diodes.
I will try to make sense of this. Again I'm not too savvy. I understand what your doing , just wouldn't know were to look. Will be leaving R1 & R2 alone until i figure out how to implement your suggestion. Better safe than sorry.
Again thank you for your reply. It was very helpful.
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Old 13th March 2012, 10:22 AM   #2234
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I only looked at the Amazon battery page. I didn't try to find a datasheet. Am I correct thinking you want to get as fast a charge as possible? Or just wanting bigger batteries?
I took a brief look at the resistor link. The purpose of R1 & R2 is only to limit the charging current, so anything will work.
As for the numbers I offered, the regulator output minus the voltage of the battery equals the voltage across the resistor. Ohm's Law then gives the current for charging the battery.
Ideally matched, yes. But the design and each implementation of it must take into account component and battery tolerances. A 1/20th final charge is chosen because a person can forget to unplug it and it's not likely to harm the batteries. A 200-ohm resistor would get you near the 15mA capacity/20 for the 300mAh batteries. You're on the right track; I wasn't meaning to dissuade you, only address your concerns.
A smart charge circuit could be added fairly easily via a dedicated charging connector on the rear of the unit.

While I'm on the subject, I plan to boost the battery capacity of my O2. I bought a front panel from Front Panel Express, and the B2 came with two, so I have an extra panel. I'm going to rivet a couple 9V battery holders onto it and parallel an extra set of batteries for 500mAh of O2 audio enjoyment. And still use the plain panel when size and weight have priority.
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Old 13th March 2012, 10:31 PM   #2235
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Many NiMH batteries simply lose their endurance by faster charging. So the life of a battery may be 500 charge cycles at a 200mA rate but only 175 charges at a 400mA rate. If you're way out of line, then you'd need a fan to take the heat off or you'd be in trouble. Anyway, Tenergy is a popular 9V (8.4V) supplier and they recommend 20mA nominal and 40mA for faster charging; very different from my 10x figures noted above which come from Sanyo and Energizer for their single cell products.

Now for the unknown-to-me parts. Is there any special math for this? In other words, if we had a single cell with certain charge ratings and grouped it together into a multi-cell product, what would the difference be in charge currents? I'd assume we'd divide the max current by the number of cells to ensure that by the time the feed has gone through the cells to the last one in line that it's not out of scope. So if we assumed 200mA per single cell, then we'd be at about 28.5mA for a 7-cell battery. Am I close or am I making the wrong assumptions?

Last edited by ethanolson; 13th March 2012 at 10:35 PM.
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Old 13th March 2012, 10:58 PM   #2236
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I'm sure there's special math for this. I couldn't tell you what it is, though. Cadex and Panasonic seem to have pretty good recharge docs and I may find it there. I'll have a look.
I'm not sure I understand your assumptions. For a series multi-cell battery the charge current is the same, and flows through each cell (which is actually the case for the 9V battery in the O2). For parallel cells, either the total current or the charge time can be doubled/tripled/etc. Balance between individual cells can probably never be completely disregarded, though.
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Old 15th March 2012, 04:54 PM   #2237
Fsatsil is offline Fsatsil  United States
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I received my enclosure and front panel from JDS Labs yesterday, my first O2 is officially finished and sounding great.
Click the image to open in full size.
Click the image to open in full size.
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Old 15th March 2012, 05:42 PM   #2238
BlueRob is offline BlueRob  Mexico
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Quote:
Originally Posted by sofaspud View Post
While I'm on the subject, I plan to boost the battery capacity of my O2. I bought a front panel from Front Panel Express, and the B2 came with two, so I have an extra panel. I'm going to rivet a couple 9V battery holders onto it and parallel an extra set of batteries for 500mAh of O2 audio enjoyment. And still use the plain panel when size and weight have priority.
Sound very interesting....keep us posted with the outcome
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Old 15th March 2012, 06:37 PM   #2239
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Originally Posted by Fsatsil View Post
I received my enclosure and front panel from JDS Labs yesterday, my first O2 is officially finished and sounding great.
Click the image to open in full size.
Click the image to open in full size.
Those JDS Labs front panels sure are purdy...
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Old 16th March 2012, 07:20 PM   #2240
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@Fsatsil, you gotta fix the date stamp on your camera.
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