PINT Problem

[[AK]Zip]

Quote:

Originally Posted by mb3k I finally got a steady 50mA current draw somehow, and I didn't even touch the circuit, but now there's no sound from either channels. My best guess is the op amps finally fried. Frustrating. What's everybody's opinion on C6?

I have built quite a few of these and on a few of them I left C6 off to try and it worked just fine without it.

-Alex-

 

[cire]

i've built two minified PINTs so far and zero issues with populating everything.

after playing with my PINT powered by my digital variable PSU, i've come to a couple conclusions when it comes to considering voltage (keep in mind, i used crappy sony cans):

-audible distortion starts at about 3v. its pretty slight at that voltage, but as you go lower, it gets more and more crackly, like bad AM reception. the thing pretty much dies at 2.3v

-current draw is constantly ~50ma from 18v down to 4.5v. lower than 4.5v, the draw shoots the hell up to 180ma, but when voltage drops to 3.2, the current also drops to a low 20ma

 

[kklee]

Quote:

Originally Posted by cire -current draw is constantly ~50ma from 18v down to 4.5v. lower than 4.5v, the draw shoots the hell up to 180ma, but when voltage drops to 3.2, the current also drops to a low 20ma

Now that you mention it, I noticed the same thing. I turned on my power supply at 0V and turned it up watching the current draw. At first I thought something was wrong when I saw that it rose to ~180mA at 4.5V, but as I kept turning up the voltage (expecting smoke at any second!), it dropped down to ~50mA and stayed there all the way to 18V.

 

[NeilR]

Just to add a data point here, I built up my first Pint last night, Mini3-fied, and it fired right up, drawing about 51mA. The chips get very hot by my way of thinking and I thought I might have had a problem, but there are no oscillations on the scope and it sounds great.

The SMD work was very interesting with all the different SMD bits that went into it.

Thanks to Tangent and all the contributors to this and other threads. Especially AMB foir the Mini3 mod.

Now I just have to decide on a case....

Regards,
Neil

 

[Filburt]

Quote:

Originally Posted by NeilR Just to add a data point here, I built up my first Pint last night, Mini3-fied, and it fired right up, drawing about 51mA. The chips get very hot by my way of thinking and I thought I might have had a problem, but there are no oscillations on the scope and it sounds great. The SMD work was very interesting with all the different SMD bits that went into it. Thanks to Tangent and all the contributors to this and other threads. Especially AMB foir the Mini3 mod. Now I just have to decide on a case.... Regards, Neil

Did you include C6?

 

[NeilR]

Quote:

Originally Posted by Filburt Did you include C6?

Yes, I did. Tangent's specified part.

I made a decision to run this with 1 9V rechargeable. With that battery, I am drawing 44ma, which is a little better than the 51-52ma I drew at around 22V. The chips also run much cooler, of course. That decision had more to do with casing considerations than anything else.

 

[threepointone]

Hey, I was just thinking--If we're using the PINT for low impedance IEMs, current is more important than voltage, correct? So it'd probably be better for me to maybe use two 9Vs in parallel for longer battery run time? Can you charge batteries in parallel with simple modifications to this charging circuit, or are there more problems to be considered in this configuration?

 

[cetoole]

Quote:

Originally Posted by threepointone Hey, I was just thinking--If we're using the PINT for low impedance IEMs, current is more important than voltage, correct? So it'd probably be better for me to maybe use two 9Vs in parallel for longer battery run time? Can you charge batteries in parallel with simple modifications to this charging circuit, or are there more problems to be considered in this configuration?

It is not a good idea to have NiMH batteries in parallel. It would be a better idea to have 8 or so NiMH AAA batteries in series, which would also give you far superior battery life (900-1000mAH for the best NiMH AAA, compared to ~270mAH for the best NiMH 9v PP3 battery), and not take up too much additional room. Doubt it would fit a mint tin, but I havnt actually used one ever, and there are other casing options around.

 

[cire]

the problem with running NiMH batteries in parallel is that they have low impedence, so the higher voltage one essentially ends up feeding current into the lesser voltage one. this problem doesn't arise for alkaline batteries because their impedences are high enough to prevent it.

 

[Filburt]

Quote:

Originally Posted by NeilR Yes, I did. Tangent's specified part. I made a decision to run this with 1 9V rechargeable. With that battery, I am drawing 44ma, which is a little better than the 51-52ma I drew at around 22V. The chips also run much cooler, of course. That decision had more to do with casing considerations than anything else.

Okay, I was just asking. C6 seems to really help quell oscillations in the mini3 config, then. I don't have C6 installed and the best I could pull off was about 56mA, which from what I've gathered is quite low w/ C6 omitted. I had to do everything practically flawlessly to get it there

I may just start installing C6 and making it easier on myself, if I build any more

 

[amb]

Quote:

Originally Posted by Filburt Okay, I was just asking. C6 seems to really help quell oscillations in the mini3 config, then. ... I may just start installing C6 and making it easier on myself, if I build any more

My Mini³fied PINT does not have C6 installed, and it is stable. The reason why C6 was omitted was because in the current "real" Mini³ prototype there is no such capacitor, and my Mini³fied PINT was serving as a test mule where I wanted to test the Mini³ circuit on the PINT pcb layout for comparison purposes, so aside from the battery charging circuit, everything else was made to be identical to the Mini³ to avoid introducing other variables.

That said, however, I don't see any reason why you shouldn't install C6. It is simply some extra supply rail decoupling with a different capacitor type.

 

[threepointone]

I was just wondering, has anyone with problems tried cleaning the flux off the board to see if that helps at all? The only reference to flux and PINT in these forums is in a FS post by someone who couldn't get theirs to work and didn't have a flux cleaner. And of course, tangent cleans all his boards with isopropyl alcohol. I know it's a unlikely, but maybe this is why some people have misbehaving PINTs while it seems like most of tangent's own PINTs are fine?

and also, what's the typical current draw of a PINT? (2x AD8397 configuration)

 

[cire]

Quote:

Originally Posted by threepointone and also, what's the typical current draw of a PINT? (2x AD8397 configuration)

depends on the voltage:
~4.5 to 24v = ~50ma
~3.2 to ~4.4v = ~180ma
~2.5 to ~3.1v = ~20ma

 

[cmirza]

Quote:

Originally Posted by cire depends on the voltage: ~4.5 to 24v = ~50ma ~3.2 to ~4.4v = ~180ma ~2.5 to ~3.1v = ~20ma

Im still pretty new to DIY stuff. So if you have a draw of ~50ma and use a battery with ~250mah capacity, you should expect ~5 hours of usage from the device?

 

[cire]

that would be true if only companies didn't exaggerate their specs