"The Wire AMP" Class A/AB Power Amplifier based on the LME49830 with Lateral Mosfets - Page 199 - diyAudio
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Old 7th November 2012, 04:22 PM   #1981
rsavas is offline rsavas  Canada
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Location: Ontario
Owen, good stuff, you're all over it. I wonder if they (LCBO) (our gov. run liquor store) take Paypal and offer pickup &/or delivery? :-) Still looking for the shopping cart.
I see lots of stock in Ottawa, which one Nepean? and you have a Paypal account? I am a sport, I'd follow through on my offer, its only a silly beer or 2 or ...
TRIPEL KARMELIET
LCBO 287490 | 330 mL bottle
Price: $ 3.00

The Quantity on Hand displayed is as of the Inventory Date indicated. Please contact the store to confirm quantity.

Rick

Last edited by rsavas; 7th November 2012 at 04:34 PM.
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Old 13th November 2012, 07:50 AM   #1982
kiwik is offline kiwik  Estonia
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Yeah, my first DIY project in last 20 years.
Finished one channel and powered up. At the moment bias is 300mA, will do some tests with higher bias later, to see if there will be danger of overheating. I'm using heatsinks and power supply from old soviet-time Amfiton 50-YM104 amp, not sure how much power these heatsinks can handle.
At the moment LME and fets are powered by +-33V unregulated. Hooked up my old-timer Korvet 35AC-028 speaker. The sound was far better than i could expect. Have tried the same source and preamp (Amfiton YP-003) with different end-amps and same speakers before, i was pretty sure these speakers are crap. Have to rethink regarding speakers, they sound descently good with theWire amp.
Have to say, design of PCB is excellent, it's doable even if not having any experience with SMD parts. Assembly manual was a great help also.

wb Margus
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Old 13th November 2012, 02:35 PM   #1983
opc is offline opc  Canada
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Hi Guys,

Glad to hear more and more people are getting this done! I'd love to see more pictures if people get the chance.

I'm currently looking at building up my messy implementation in a proper chassis, so I'll be posting some pictures of that endeavor over the next little while.

rsavas:

Sorry for leaving you hanging... for some reason I didn't get a notification for your reply, but I did get one this morning for the note from kiwik.

Your offer for the beer is very kind, but no worries... as a happy side effect of our talk, I ended up checking stock on that beer and found that they did indeed have it in stock at the store near my work, so I quickly ran out at lunch and grabbed a dozen of them

kiwik:

Your implementation sounds really neat... you should post some pictures if you get a chance!

At +/- 33V rails, you should be more than safe to turn the bias up a little unless the heatsinks are really really tiny.

If the heatsink and power supply are up for it, I would push for around 600mA and see how things look. That's only about 40W of dissipation per channel which should be manageable, and basically puts you in class A operation for a good majority of typical listening.

Cheers,
Owen
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Old 14th November 2012, 06:19 AM   #1984
kiwik is offline kiwik  Estonia
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kiwik:

Your implementation sounds really neat... you should post some pictures if you get a chance!

At +/- 33V rails, you should be more than safe to turn the bias up a little unless the heatsinks are really really tiny.

If the heatsink and power supply are up for it, I would push for around 600mA and see how things look. That's only about 40W of dissipation per channel which should be manageable, and basically puts you in class A operation for a good majority of typical listening.

Cheers,
Owen[/QUOTE]

Thanks for advice!
Heatsink itself is probably big enough, i'm not sure if thermal conductance between fets and sink is sufficient.
Still have a plan to use separate PSU for LME-s, with some 40-45V voltage. But it's over my skills to build one from scrach, if anyone have a good suggestion where i can find one?
Amp is all over my table now, will take some pics when heatsink is mounted to the frame.

wb Margus
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Old 15th November 2012, 12:29 AM   #1985
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Default Potentially stupid question alert ...

Just wanted to check something ...

1. bias trimmer at 5k = 1A bias current (with 10V between pin 11 and 12 on LME chip, 2mA flowing through 5kR ...)

2. bias trimmer at 0R = 0 bias current (with 0V between pin 11 and 12 on LME chip)

linear in between these points?

Last edited by hochopeper; 15th November 2012 at 12:35 AM.
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Old 15th November 2012, 02:12 AM   #1986
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Ignore the above ... please! Reading the FET datasheet now ... bias voltage is linear, not current.

Last edited by hochopeper; 15th November 2012 at 02:15 AM.
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Old 15th November 2012, 02:04 PM   #1987
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Quote:
Originally Posted by HYPERTUNE View Post
I Want:

8 - PCB's without part kits.

Owen: I have a 60v smps I'd like to use (Connexelectronic SMPS800). What's your opinion in this application?
They look really nice, I use a similar one from Coldamp and it's first rate - absolutely no hum at all, which is fab. Greatly improves the amps bass as well of course. At that price you could use one for the LME and one for the output.
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Old 16th November 2012, 08:33 PM   #1988
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Owen I need some catalogue help. My first implimentation of the Lme boards is in an old kenwood Km106 chasis. The rails for the LMe chip are +/-75 and the fet's +/- 68. The lme chip runs hot to touch. ie I can't keep my fingers on the chip/heatsiink for more than a few seconds. I was looking through the Digi-key catalogue and i found some Avid heatsinks similar to the ones you used but about twice as tall. Mounting is different for the chip, bolts not spring clip. Using your vast resourses and knoweledge can you recomend an alternative heat sink for me that will fit the board.
For anyone that is interested I am still testing with a high Z load ie 1000ohms, output voltage is 45 volts RMS just before clipping. My tagret is 35vrms with an 8ohm load. The original kenwood was able to put out 38vrms in an 8ohm load. Pretty good for an amp that was rated at only 130Watts.
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Old 16th November 2012, 09:32 PM   #1989
IanAS is offline IanAS  England
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Quote:
Originally Posted by multisync View Post
Digi-key catalogue .... Avid heatsinks
Could you post the part number for those please? What's the C/W rating?

I need to buy two such heat sinks. I plan to go nearer to 100 across the LME.
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Old 18th November 2012, 05:17 PM   #1990
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I think this is the heat sink for the LME chip

digikey WA-T247-101E-ND
Length 1.260" (32.00mm)
Width 0.921" (23.40mm)
Height Off Base (Height of Fin) 0.630" (16.00mm)
Power Dissipation @ Temperature Rise 1W @ 20C
Thermal Resistance @ Forced Air Flow 8C/W @ 500 LFM
Thermal Resistance @ Natural 7C/W

I found this one at digikey

Digi-Key Part Number CR517-ND
Length 2.000" (50.80mm)
Width 0.650" (16.51mm)
Height Off Base (Height of Fin) 0.630" (16.00mm)
Power Dissipation @ Temperature Rise 1.5W @ 20C
Thermal Resistance @ Forced Air Flow 2C/W @ 800 LFM

looks like it can disapate more heat, except digikey does not have a price or stock


for the current build I will cut up some old motherboard heatsinks and epoxy them onto the side of the supplied heat sink, won't be pretty and hopefully I won't loose any fingers on the table saw
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