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Old 13th March 2012, 04:23 PM   #271
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Quote:
Originally Posted by panson_hk View Post
Hi,

You can add zener diodes as simple regulator. If I were adding a regulator for the front end, I will use linear regulator.

Do you use conventional output devices instead of ThermalTrak? Vbe multiplier can be MJE15030.

Why do you use small cap for C8?
Well, I'd prefer a linear regulator as well but that would be messy to add to the board. I prefer neat and orderly over messy and complicated.

I'm going to use the output transistors that you recommend, which I guess are the Thermal Trak. Are you saying that if I use the TT, outputs I don't need a Vbe multiplier? I'm not very experienced with all of this so pardon my confusion.

As for C8, bypassing a zener diode in a simple regulator circuit with a capacitor usually has the function of shorting the high frequency noise from the zener to ground. A big electrolytic is going to have too much inductance at high frequencies to effectively shunt the zener noise to ground. Normally, a small ceramic or mica capacitor is better at this kind of function. This may not be a big deal in the +5volt circuit but I'm just stating generalities here.
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Old 13th March 2012, 04:34 PM   #272
atupi is offline atupi  Romania
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Originally Posted by panson_hk View Post
Hi, One pair ThermalTrak NJL3281D/1302D is enough for 50 W / 8 Ohms. Very safe for driving reactive loads as well. You need to adjust bias setting, nothing more. Are you doing stereo amp?
Yes i want a stereo version for listening on medium audio levels in my livingroom.
Please be aware that my speakers are 4ohm bookshelfs.
If it's suitable i would like to reuse a toroid transformer 2x40V big enough.
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Old 13th March 2012, 04:50 PM   #273
AndrewT is offline AndrewT  Scotland
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40Vac+40Vac is going to give +-58Vdc, or more, for the supply rails.
Expect ~300W into 4r0 from that, requiring a 600VA to 1200VA transformer to power a stereo amplifier.
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Old 13th March 2012, 06:11 PM   #274
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I couldn't find dimensions for the boards on the website. Can you provide them please? I can wait I suppose until they arrive, but I'd like to start planning before then.
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Old 14th March 2012, 11:18 AM   #275
AndrewT is offline AndrewT  Scotland
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wait till you have a working and tested assembly laid out before you.

Then work out how to package all those modules and build/buy a chassis to suit.
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Old 28th August 2012, 04:58 PM   #276
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Originally Posted by panson_hk View Post
Hi, One pair ThermalTrak NJL3281D/1302D is enough for 50 W / 8 Ohms. Very safe for driving reactive loads as well. You need to adjust bias setting, nothing more. Are you doing stereo amp?
How is the performance into 4 ohms? I don't see any data on that.

Also, how many ThermalTrak output devices do I have to buy to get a matched pair?
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Old 28th August 2012, 04:59 PM   #277
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wait till you have a working and tested assembly laid out before you.

Then work out how to package all those modules and build/buy a chassis to suit.
No, all I need are the boards, the transformer, and the big capacitors and I have enough information to decide on the box size.
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Old 28th August 2012, 07:16 PM   #278
klewis is offline klewis  United States
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Originally Posted by dirkwright View Post

Also, how many ThermalTrak output devices do I have to buy to get a matched pair?
You probably won't come up with a matched pair. Just adjust the Re resistors to get a reasonable balance between the p and n.
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Old 28th August 2012, 07:47 PM   #279
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I have matched pairs of ThermalTraks on my webstore
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Old 28th August 2012, 07:58 PM   #280
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I have matched pairs of ThermalTraks on my webstore
I don't see NJL3281 and NJL1302 on your site.
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