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Old 12th November 2013, 12:54 PM   #161
rsavas is offline rsavas  Canada
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Hi guys/Owen,

? about insulators for LME49830 wire amp.
1) For the LME49830, do I need a insulator/thermal compound, (is the Ohmite HS isolated?) if so, what part #
2) LatFET, my HS's are not isolated from ground, so I need insulators, part number to use pls.
3) Owen do you have any LME49830 to sell me? Mouser/Digikey out of stock til Dec'13. Need up to 4 for the pcb's I have on order. I can add extra $ to my payment to you.

Thx
Rick
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Old 12th November 2013, 03:15 PM   #162
opc is offline opc  Canada
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Hi Rick,

You definitely will need an insulator between the heatsink and the LME49830 as the tab is at V- potential, and the heatsink is tied to ground.

I just use a standard adhesive back TO-220 isolator like the one listed on the LPUHP BOM, and cut it to size. Don't use the one listed in the PSU BOM as it's electrically conductive

As for the output devices, I know some people use Keratherm red with good results, but I tend to just use thin mica insulators with thermal grease, which has always worked well for me in the past.

Here's a link that might be of interest if there is any left:

http://www.diyaudio.com/forums/vendo...-ea-stock.html

I do have a 8 LME49830 ICs left over from the previous GB but I didn't offer them up as they are too thick to be shipped in a standard bubble pack. Since you're in Canada, it's not really a big deal so you're welcome to pick up 4 if you'd like. I think they go for $7 on Digikey, so let's call it $25 for 4 of them.

I also owe you an email, but I'm a bit backlogged until I get things sorted out with the orders. I will get back to you though.

Cheers,
Owen
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Old 12th November 2013, 03:37 PM   #163
rsavas is offline rsavas  Canada
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Owen, thx for your FB & offering me some LME49830, perfect I'll take 4 of them, pls add to my order of pcb's.
Take your time, I am in no rush, still have to order part & I am working on my Si4770 layout this week, want to get it out for fab ASAP. Decided to add a S/PDIF tx using a DIT4192.

Rick
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Old 12th November 2013, 04:54 PM   #164
UrSv is offline UrSv  Sweden
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If you do have something to ship those LME49830s in I'd be happy to buy two of them
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Old 12th November 2013, 08:41 PM   #165
opc is offline opc  Canada
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Default Lateral FET Amp

Hi Guys,

Attached are the measurements for the high power lateral FET amp.

These were all taken with dual regulated supplies feeding the amp. The PSU V2 was used at +/-24V to power the LME49830, and a LT1185 based supply fed the mosfets with +/-20V.

Power is obviously limited in this setup, but I was mostly just curious to see what the amp could do with lower noise supplies.

All measurements are done into an 8 ohm load, and the first set were done at 450mA bias.

I will also post a second set done at 900mA bias to show the improvement in distortion.

Cheers,
Owen
Attached Images
File Type: png FFT Spectrum Monitor no input.png (101.8 KB, 723 views)
File Type: png FR 1W 8R.png (65.5 KB, 693 views)
File Type: png FFT Spectrum Monitor 1W 8R.png (103.4 KB, 691 views)
File Type: png Distortion Product Ratio 1W 8R.png (48.7 KB, 674 views)
File Type: png THD Ratio 1W.png (66.3 KB, 660 views)
File Type: png Signal to Noise Ratio 1W 8R.png (45.2 KB, 100 views)
File Type: png Signal to Noise Ratio 10W 8R.png (45.5 KB, 85 views)
File Type: png DC offset - No Input.png (78.9 KB, 86 views)
File Type: png THD Ratio v freq.png (61.1 KB, 105 views)
File Type: png THD Ratio vs output power 8R.png (74.1 KB, 114 views)
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Old 12th November 2013, 08:43 PM   #166
opc is offline opc  Canada
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Default Lateral FET Amp

And here are the numbers for 900mA bias
Attached Images
File Type: png FFT Spectrum Monitor - 4W 900mA Bias.png (102.6 KB, 142 views)
File Type: png Distortion Product Ratio 4W 900mA bias.png (51.2 KB, 123 views)
File Type: png THD Ratio 4W 900mA bias.png (80.8 KB, 97 views)
File Type: png THD Ratio 450mA v 900mA.png (66.6 KB, 103 views)
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Old 12th November 2013, 09:44 PM   #167
BuildMeSomething is offline BuildMeSomething  United Kingdom
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Nice, I now have similar power supply needs for the two LME A/AB amps I already have built... something like +/-15V on the output side.

On the input side, would you recommend one PSU per amp, or should one be ok feeding the input of two LME's? Will be using two separate regulated 3A supplies for the outputs.

The two Class A/AB's will be powering a pair 8 Ohm Scan Speak woofers and the LPUHP's a pair of Mark Audio A7.3...

Paul
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Old 12th November 2013, 11:42 PM   #168
hochopeper is offline hochopeper  Australia
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Quote:
Originally Posted by opc View Post
Impressive observational skills Chris!

No oven yet... but some of the stuff I've been working on makes me wish I had one!

As for the bulbous solder joints, I blame my rushing, and the fact that I ran out of my favorite Cardas solder and am stuck using this odd radio shack stuff which isn't the best.

I had the solder wick out and started to clean up some of the joints, but then decided I'd have plenty of time to do that after I shipped out everyone's goodies

Thanks again to everyone here for all the support and positive comments, and I'm looking forward to shipping these out and having people build them all up!

Cheers,
Owen
I've got a toaster oven here half hacked to pieces waiting for me to install an SSR and hook it up to a little arduino controller to make a cheap SMT oven

With these regulator boards ... I've got a story and a question

1. I had been toying with the idea of looking at using a snubber between the rectifiers and the transformer for some DSP board layouts that I'm toying with. Looking at your measurements it seems these regulator's PSRR really take care of the issues at lower freq, above 1MHz on the datasheet the PSRR starts to drop away ... I wonder if for that freq range the issues are really more related to inductance in the connection from reg to load and the load's input decoupling. Just wanted to say thanks again for these measurements ... you've got me thinking and cleared my mind of a few issues that are sometimes hard to understand the magnitude of their impact in the real world.

2. I am in need of a dual +ve regulator. Hacking these to create dual +ve rails is going to be a no-go from my cursory glance right? Best case use the on board +ve reg and flick the diodes around and use the rect+filter section of the -ve half with an external regulator (say a super-reg). It's really not possible to isolate the two halves of this board though is it, the gnd plane will be connected at the output of the rectifiers? I'm just putting the ideas down now because I know someone else will be wondering too probably.


On the LME49830 amp ... I've had a quick glance at the DPS600 measurements (I've only got access to my dropbox on my phone though at the moment so small screen only) so these new regulated supplies are a small improvement on the DPS600 performance in noise floor and THD+N though in that case I think we're comparing 450mA to 600mA bias with the DPS600 tests so I'm allowing for that in the way I read these. One question, Owen, the distortion product ratios ... those values include noise, right?

Cheers,
Chris
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Old 12th November 2013, 11:46 PM   #169
hochopeper is offline hochopeper  Australia
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Quote:
Originally Posted by rsavas View Post
Si4770 layout this week, want to get it out for fab ASAP. Decided to add a S/PDIF tx using a DIT4192.
I was looking at an interface board design this morning before work, I was just about to start drawing up a part layout for the DIT4192 but alarm went off saying time to go and put an end to that
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Old 12th November 2013, 11:48 PM   #170
opc is offline opc  Canada
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Quote:
Originally Posted by BuildMeSomething View Post
Nice, I now have similar power supply needs for the two LME A/AB amps I already have built... something like +/-15V on the output side.

On the input side, would you recommend one PSU per amp, or should one be ok feeding the input of two LME's? Will be using two separate regulated 3A supplies for the outputs.

The two Class A/AB's will be powering a pair 8 Ohm Scan Speak woofers and the LPUHP's a pair of Mark Audio A7.3...

Paul
Hi Paul,

One supply shared by two amplifiers would be fine for the input stage. The LME has a very constant current draw, so there will not be any crosstalk issues with a setup like that.

As for the supply voltage, I would really suggest running it quite a bit higher than +/-15V for the output stage. At that rail level, the LPUHP will actually be the more powerful amplifier into 8 ohms, so you'd be better off using all LPUHP amps and reaping the performance advantage.

If I were to properly do a setup like the one you're describing, I would use something like a pair of LT1084 regulators set to roughly +/-28V along with a PSU V2 set to +/-32V for the front end. That will give you roughly 40W of output, and you can bias pretty high without dissipating too much power, while still having significantly more headroom than an LPUHP.

If you really don't need the power, then going with all LPUHP amps would be the better option. With a good 100VA transformer, you can expect about 18W of output before distortion rises above 1% thanks to the new regulators and the fact that the output buffers don't start current limiting until about 190-200mA RMS each. You can also push the supply voltage a little higher to +/-19 volts is you really want to push the limits.

Cheers,
Owen
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