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Old 26th March 2010, 04:46 AM   #41
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Quote:
Originally Posted by tomchr View Post
Note that the ON Semi devices are single BJT's. No darlington here... Hence, the lower Hfe. So you'll need driver transistors. This will make the thermal system more complex.
I am studying this thermal system. 49811+driver+TT. Some results are presented here Compact Sized LME49810/11 +ThermalTrak Amp. Please comment.
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Old 26th March 2010, 04:55 AM   #42
tomchr is offline tomchr  United States
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Originally Posted by Sebastiaan View Post
don't you find it a bit tricky to run the amplifier without any Zobel on the outputs? Did u check for oscillations?

I suggest for extra stability safety margin you mount at least one 5W10R together with 100nF from output to ground.
Sorry, forgot to mention. I run the output of the amp board to another PCB that contains output relay, DC sense & protection circuitry, a Zobel network (10R+100nF), and the output terminals. I had to put this stuff on a separate PCB due to space constraints in the chassis I was reusing. I use 1/4" quick disconnect terminals and AWG 14 (2.5 sq mm) wire between boards both for output and supply.

I think the 0.1R could be the cause of your bias stability issues with Q current higher than 60 mA per device. I recall Douglas Self muttering about that in his amp design book.

I'm sure Sanken's distributor in your area will be able to refer you to a place where you can buy the devices. I have dealt with B&D Enterprises. They seem to have a good selection of hard-to-get devices and were able to provide what I needed. Not the cheapest, but if you need it, you need it...

~Tom
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Old 26th March 2010, 05:36 AM   #43
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Originally Posted by panson_hk View Post
This is volume price. You need to pay $2.9 per device for less than 100 pcs. Better to get free samples.
Actually, looks like $1.93 is a bug in ON's website. Volume pricing seems to be either 2.64 or 2.42. I'm with you on the samples.

Arrow quotes some good prices on the STD03s. No NPN parts in stock though.
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Old 26th March 2010, 04:27 PM   #44
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Tomchr, thanks for the testing results
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Old 26th March 2010, 06:39 PM   #45
Telstar is offline Telstar  Italy
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Originally Posted by twest820 View Post
B&D is one option.
Looks fine to me. To have enough to match i need at least 50 pieces anyway
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Old 26th March 2010, 10:24 PM   #46
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Originally Posted by tomchr View Post
Folks,

I have previously tried the LME49810 with 2SC3281, 2SA1216 output devices, MJE340/350 drivers and failed, I figured I should try the LME49811.
MJE340/350 don t suit at all as drivers, as they are limited
to 50mA maximum, and even at this current, they are not good...

Use 2SA1837/2SC4793 instead...

Another (very good) solution is to use Sanken s darlingtons
2SB1647/2SD2560 or 2SB1648/2SB2561.
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Old 27th March 2010, 06:57 PM   #47
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Originally Posted by Telstar View Post
Looks fine to me. To have enough to match i need at least 50 pieces anyway
I could be interested in your rejects if the price is right. I'll only be using one pair per channel.
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Old 27th March 2010, 07:02 PM   #48
Telstar is offline Telstar  Italy
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Originally Posted by twest820 View Post
I could be interested in your rejects if the price is right. I'll only be using one pair per channel.
Yeah, i'll put the extra transistors here for sale. There wont be only the STD03s
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Old 2nd April 2010, 04:34 PM   #49
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at what ampere the it will work efficiently(when bridged) (60-0-60 at 5 A is it enough?)
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Old 2nd April 2010, 11:20 PM   #50
tomchr is offline tomchr  United States
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Originally Posted by manun57 View Post
at what ampere the it will work efficiently(when bridged) (60-0-60 at 5 A is it enough?)
I'm not sure I fully understand the question. I'm guessing it relates to the recommended size of the power supply transformer.

Two channels bridged running at +/-60 V will output about 500~550 W comfortably into 8 ohm. While doing so, about 200 W will be dissipated as heat. So you'll need to provide 700~750 W of input power. Give or take... (750 W)/(2 * 60 V) = 6.25 A.

That is if you run the amp rail-to-rail into 8 ohms. Should you decide that 400 W of output power is enough for you - and honestly, the difference between 400 W and 500 W (1 dB difference) is barely audible - then your 2 x 60 V, 5 A transformer will do just fine.

BTW, I calculated the power dissipated in the heat sink as Pdiss = (Vsupply^2)/(2*(pi^2)*RL); where Vsupply is the total supply voltage (120 V); RL is the road resistance (8 ohm); and pi is the ratio of a circle's circumference to its diameter (3.1415926...).

~Tom
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