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Old 24th July 2012, 06:04 PM   #401
RNMarsh is offline RNMarsh  United States
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One characteristic I place some high importance on - more than most others - is how flat the hfe curve is with varying Ic. If you have a pair that are as flat and the Vbe is .72 v AND the hfe match and the temp coeff are complimentary, then they are better.

The power supply IS important. 3-terminal regs are the minimum performance. And, in this app dont need to be pre-loaded to get the regulation to work best. But you should strive for better. Shunt reg is my preferred method. To get up and runnning, the 3-term gets you there quickly.

-Richard Marsh

Last edited by RNMarsh; 24th July 2012 at 06:25 PM. Reason: details
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Old 24th July 2012, 06:12 PM   #402
sonidos is offline sonidos  United States
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Yes, anatech, a mod on this forum, helped give me input on my Adcom amp rebuild. He pointed out to me to pull up the datasheets and note the flatness of hfe curve. There are still some good Japanese transistors out there.
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Old 24th July 2012, 06:16 PM   #403
Unomas is online now Unomas  Spain
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Quote:
Originally Posted by homemodder View Post
Those BDs are fine to use, get the highest hfe ones, these parts will be far superior to the mje200s in this application. They are faster, have much lower parasitic capacitances and as the amp probably runs on higher than 10v their SOA figures are fine.
Another alternatives is MJE172/182, or 2sa1930/2sc5171.
Hi homemodder, thanks for your comments.
I agree with you about the MJE172/182 but unfortunately I have not have any of them. Regarding the 2sa1930/2sc5171, they are quite similar to the ones I mentioned in my previous post, 2sa1306/2sc3298 so they have similar problems: different body, different pin-out and quite dissimilar electrical characteristics. But there are ways to use them: for instance I can mount them on the bottom of the PCB, but I still have to conform the pins as they measure differently.

In conclusion, I think my best option is the BD139/140.

Javier
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Old 24th July 2012, 07:09 PM   #404
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Originally Posted by sonidos View Post
For PSU regulation, I'll go with the good ol' fashioned 317/337 combo for now. I know you (and other designers like JC) say topology, topology, and topology are important. How much emphasis do you give on PSU performance in this circuit?
Pulllleeeaaase, try the LT1963A/LT3015 -- this is the best sounding pair of OEM regulators, hands down.
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Old 24th July 2012, 07:36 PM   #405
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Pulllleeeaaase, try the LT1963A/LT3015 -- this is the best sounding pair of OEM regulators, hands down.
well....since you asked nicely..
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Old 24th July 2012, 08:36 PM   #406
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dual secondaries allow using the same Vreg part type for plus and minus - you can use the better reg (lower noise, better ripple rejection, load step recovery...) for both, in duplicate reg circuits

cuts the number of different part types, you only have to "optimize", characterize one circuit design instead of 2

Last edited by jcx; 24th July 2012 at 08:45 PM.
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Old 24th July 2012, 08:46 PM   #407
sonidos is offline sonidos  United States
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Originally Posted by jcx View Post
dual secondaries allow using the same Vreg part type for plus and minus - you can use the better reg (lower noise, better ripple rejection, load step recovery...) for both, in duplicate reg circuits

cuts the number of different part types, you only have to "optimize", characterize one circuit design instead of 2
Tell me if I'm all wet, but 317 vs. 337, the output impedance behaves differently for each reg from what I read on the jbau thread. Does using the same reg for both give consistent output impedance on both rails?

Last edited by sonidos; 24th July 2012 at 09:05 PM. Reason: clarification required
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Old 25th July 2012, 02:52 AM   #408
RNMarsh is offline RNMarsh  United States
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Originally Posted by sonidos View Post
Tell me if I'm all wet, but 317 vs. 337, the output impedance behaves differently for each reg from what I read on the jbau thread. Does using the same reg for both give consistent output impedance on both rails?
Dont bother with the 317/337 at all. Use the Linear Technology for 3-terminal regulators for thier convenience/simplicity of built.... and better performance.
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Old 25th July 2012, 06:53 AM   #409
RNMarsh is offline RNMarsh  United States
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I bought about 20 each of the Hitachi 2SD669A/2SB649A devices. Very consistant... They both test .72v and Hfe within 5% of compliment right out of the box. They look good down to 30 Ohm loads. I havent tried them in amp but should be a drop-in replacement.

[the MJE-xxx can go down to lower Z loads than 30 Ohms, if that is important to you.] -RNM

Last edited by RNMarsh; 25th July 2012 at 06:58 AM. Reason: Alternate output devices-
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Old 25th July 2012, 02:02 PM   #410
sonidos is offline sonidos  United States
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Can anyone comment if Sanyo 2SD600/2SB631 combo a good alternative? I also have a good amount of these in my spare parts bin.
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