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Some LME49600 implementations - Page 15

post #211 of 291

I've always been very happy with the sound quality.

It was just the heat that was worrying me.

 

It's just something to take into account for the next version.

 

Maybe I'll keep me eye open for a little stick on heat sink for the LME49990s.

 

 

Quote:
Originally Posted by wakibaki View Post

Thanks for making the effort. It seems the amp is working correctly, if running a bit hot.

 

I'm certainly not unhappy with the SQ of mine.

 

Hopefully someone else will complete one soon.

 

post #212 of 291
Hey Guys - just wanted to chime in and say I'm up for and excited for a build when it's 'soup'. I think you'll find quite a few chiming in once it's ready. I for one don't mind riding the edge, so toss me a board when you're ready.
Edited by Misterrogers - 7/16/12 at 6:57pm
post #213 of 291
Quote:
Originally Posted by Avro_Arrow View Post

I've always been very happy with the sound quality.

It was just the heat that was worrying me.

 

It's just something to take into account for the next version.

 

Maybe I'll keep me eye open for a little stick on heat sink for the LME49990s.

 

 

they make small, finned heatsinks for dip-16 chips, which are easily cut with a Dremel tool.  scuff the chip, and use 2-part epoxy to glue them down.  PITA, but works well, and looks kinda cool

post #214 of 291

I've been swamped at work, I'm still hoping to complete mine soon.

post #215 of 291

I got mine running and did a quick test.  It runs cool and has low dc offset.  I really didn't get a chance to give it much of a listen.  I am going on vacation for a week.  Will give a report on the sound when I get back.

post #216 of 291
Thread Starter 

Great! Looking forward to a more complete assessment.

 

w

post #217 of 291

I finished mine up over the weekend. It works and nothing blew up! I have the hum problem as well, but will rectify that the next time I visit my parents house to get my Dremel. Mine is uncased at the moment in an AC room the 49990 does get warm, but can pass the touching with finger test no problem.

post #218 of 291
Thread Starter 

Thanks J-Pak

 

I will order some boards in the next couple of days.

 

w

post #219 of 291
Quote:
Originally Posted by wakibaki View Post

Thanks J-Pak

 

I will order some boards in the next couple of days.

 

w

That's very good to hear! :-)

post #220 of 291

i'm using little copper bga sinks stuck on with sekisui thermal tape, commonly used by PC modders. the 49990 get hot no matter what they are used in, its normal it seems. for me its the LPUHP that puts out ~16WPC and the 49990 are still the hottest thing on the board. in this case there are 3 in close proximity for an instrumentation input and the ground plane is eroded away around them to lessen capacitive coupling, so they are even hotter; especially given they are running at +/-18vdc

post #221 of 291

If there are ever any modular boards made like the one A_A posted I would buy some (so I can build on balanced). Even with the hum I can tell this is a very nice sounding amp. I will post a more critical evaluation when I can get rid of it.

post #222 of 291

I've been quite happy with the sound quality of mine.

I can deal with the heat now that I know thats just how

it is and that it doesn't indicate a fault.

 

If there is enough interest in the module I posted earlier, I could

have some done...but I'm not in a financial position to make them

just for the fun of it.

 

What I really need is a partner. I can design, they can handle

the distribution and finance. All I'd ask is a couple of boards

for each design.

post #223 of 291
Thread Starter 

Thanks qusp for the input. The 49990s in this case have the groundplane removed in their immediate area for precisely the same reason, to reduce stray capacitance. It's a difficult balance to strike, making a compact board while at the same time having adequate cooling with a layout that doesn't create inadvertent feedback or crosstalk.

 

I ordered some Sekisui tape, and I've found some v. small heatsinks on Farnell.

 

I've just been checking out my TPA6120 design respin as I get a reduction for a bigger order, everything is looking good so far so I'll probably place the board order tomorrow.

 

w

post #224 of 291
Thread Starter 

Avro_Arrow,

 

I've just been looking at your circuit for the modular boards you were working on, the servo opamp has the inverting and non-inverting inputs swapped, if I'm not mistaken. The amp output should connect to the non-inverting input as the servo feedback goes to the amplifier proper's inverting input.

 

w

post #225 of 291

no worries wakibaki, I thought it best to chime in, as it worried me quite a bit initially too. I tried all sorts of wiring layouts to make sure I wasnt causing oscillation from RFI pickup with no success I conferred with opc and he confirmed its normal to get hot. lowering the heat in all honesty is probably more about us making ourselves feel better, going by the datasheet i'm pretty sure the chips are still well within SOA even when toasty to the human touch, the opa1632 is pretty hardcore like this too.

 

its still worthwhile checking that though if you havent already, are the inputs left floating when they are getting hot? ie. is this just during initial testing or in normal use with signal connected or inputs grounded? I did find that with the LPUHP one amp channel had a fair bit of offset (~3v) at the output (21db gain) with 30mV at the input. this completely disappeared when I grounded the inputs or applied signal and it seemed to be cooler to the touch too subjectively. the other channel was fine with only a few mV at the output whether floating or not.

 

both function perfectly with grounded inputs or signal, only when left floating (particularly because the LPUHP is completely floating including the PSU). I have some of those unfortunate high efficiency lightbulbs in my office, great for the electricity bill, **** for DC coupled floating wideband amplifier inputs...  it may well be that I just did the first channel test in the daytime, as ive struck this before in here.

 

I really need to get a scope …

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