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Tread power supply has high ripple - Page 2

post #16 of 20
9/5/10 at 2:21am

Firstly, avoid shorting the output.

 

What the fuse will do is blow if and only if the draw of the circuit as a whole reaches its threshold. If everything goes cabbages, the current draw for the whole thing is going to try to do a runner, causing the fuse to blow. Ideally, this will happen before the sudden excessive power dissipation causes anything else to release the magic smoke and or catch on fire. Practically...a fuse is a precautionary device to reduce the likelihood of dangerous failure, not a foolproof solution, and not always a solution which prevents circuit-damaging failure.

 

Fusing the output isn't going to help, isn't necessary, is redundant, and possibly makes it more likely that Weird Things Will Happen if it ever goes cabbages (i.e. fire). So do not do that. On the other hand, do fuse the input if you're going AC (unless you like fires), and do be aware that fuses are precaution and not a foolproof solution.

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post #17 of 20
9/5/10 at 8:19am

The LM317 protects itself against some shorts, though I've noticed that different brands and grades do so to varying degrees.

 

If the cap banks around the regulator are too big, they can eventually kill the protection diodes (D1 and D2).  On the next power cycle, you're likely to kill the LM317.

 

The fuse on the input is more to protect the downstream circuit in case it experiences some kind of short, preventing the power supply from trying to supply it infinite current.

 

You should read your regulator IC's datasheet.

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post #18 of 20
9/5/10 at 9:32am
Thread Starter 

Well, the regulator is from the kit I bought from Tangent's shop. So, it should be of a kind well known to Tangent... ;)

Of course I do not want to short the output, and will avoid it as well as I can. However, on of the uses of this standalone kit I have built is that I will power my CMoy from it by hooking the battery clips with some crocodile thingies (whatever they are called in english :)) that are fed from a pair of binding posts on the power supply. So accidentaly I might be misfortunate enough to short the inputs, and want to secure the device as well as possible from any damage.

 

And, I am aware of Tangent's precautions to not use a Tread as a lab power. I will be very careful.

 

Some pictures of this device will be posted ASAP so you know what it is.

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post #19 of 20
9/5/10 at 12:16pm

Alligator clips. And if you don't want to wire the circuits together more permanently, have you considered installing some sort of jack? (Me, I'm a fan of desoldering.)

 

I think the "you should read the datasheet" comment was more of a "for your information and edification" thing. He selected it, yes, so we can be fairly confident that it's compatible...but that's not the point of reading it. And anyway, why wouldn't you want to at least glance over the datasheets for the parts you're using?

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post #20 of 20
9/6/10 at 12:53am
Thread Starter 

Alligator clips it is . They are called crocodile clips in Sweden. We don't have either crocodiles or alligators here so the name stem from the more impressive species I guess. In the US there is alligators so of course your clips are alligator clips.

 

Yes, I have considered soldering a power inlet to the case, and it might just work. I will look into it again, but the space is veeery limited indeed. I use a case like this: http://www.hammondmfg.com/pdf/1553B_BAT.pdf.

A very nice case for a CMoy IMHO. Highly recommended, There is a belt clip as accessory, and obviously even a proto board that fits perfectly as an accessory. I did actually snip off the board mounts to have my strip board sit as low as possible. That enabled me to fit a volume pot on-board and fit 4 x 470 uF caps. The height is just enough. I will post a few pics of this one too.

 

I've also built a very small device around a little PIC processor that senses the battery power and blink a led as a battery warning. That too I hope to squeeze into the case. It will be much tougher to fix... It uses a LM2936 in a TO-92 package as a regulator. And I read that spec very thoroughly. I will probably post about this DIY project in its own thread once I have confirmed it works as expected... . So far it has been tried in a breadboard. It is soldered down, but so far not tested in real life.

 

It felt like an Ok workaround to use alligator clips on the CMoy as I have it on my desk at work. I have a Pimeta in the works that will replace the CMoy as a desk solution as soon as it is done. That assembly will include another Tread in a metallic Hammond case and be fed by an AC/AC walwart. That assembly will also include a grubDAC, so to be the perfect desk computer headphone amp . I hope...

 

Well, that's enough of OT for now.

 

Btw, yes I will definitively read the specs on that specific LM317 included in the kit to learn all about it. Especially as I use as a simple lab power. I know that Tangent wants his users/customers to understand and learn about the specifics themselves as far as possible, and I respect that. In this case however I thought I had a distinct question that had a distinct answer. The reality is seldom distinct though...

 

EDIT: I just hooked up the power supply set to 18 V with alligator clips to the CMoy, which is a standard Tangent design with a modified virtual ground using TLE 2446, and a hefty caps bank as mention above. OPA2132 op-amp. My god what an improvement with that voltage! I have only used it with 9V battery before, and thought the sound was top notch then! I am an audiophile, always on the lookout for affordable ways to achieve sound nirvana. Finding expensive stuff sounding great is not difficult. Doing it the affordable way is much more rewarding, And I can tell you that this combo, The CMoy at 18 V+ (tread supplied) with the modifications mentioned and Koss Porta Pros is a perfect match. I can not believe the kind of sound possible at this low budget solution. It is hooked up to an old Creative SB Audigy of the first generation. I am impressed.

Next step is to turn the power up to 24 V. And, what can the Pimeta bring...

 

The power supply introduced a little hum when I had the CMoy on top of it, I guess because I use a plastic shell, which provides no shielding. However, placing the CMoy 1-2 inches to the side of the power supply reduced the hum to zero. Dead silent! No noise, just dead silent even with higher volume settings. Great!


Edited by barsk - 9/6/10 at 1:45am
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