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Old 10th October 2010, 10:12 PM   #31
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They should work fine. Phillips datasheet specifies 190MHz/NPN 160MHz/PNP, which is really good. I have been weary of these since for some reason the purveyors don't seem to think that stating the Ft or Cob on the datasheets would be a selling point. Phillips got smart, but even their datasheets don't state Cob.

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Old 12th October 2010, 09:18 AM   #32
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Keantoken,

Thanks a lot. I am as busy as usual but will send you a private email with a bit more information about the Marantz reg when I have the time in the coming couple of days. My current job is with a government department and they restrict forum access so I can only access the forum at night when the day is done.

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Old 18th October 2010, 04:48 AM   #33
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Default The K-Multiplier is born

Okay, here goes...

I have been consulting HiFi to create a preregulator that matches his application, and this is what I came up with. It is pretty much a Hi-fi C-multiplier. I call it the K-multiplier.

It will handle any load up to 1A, because the voltage across the outputs is limited to 2.7V - 1A*2.7=2.7W. I would not recommend drawing more than 200mA, since this gets into the outputs' low-beta region and performance will drop.

Voltage drop is about 2V. This can be decreased to about 1.3V if we bypass, say D5. However, a large drop in input will saturate the 2N5xx1 transistors.

This is designed as a prereg, not for high-ripple conditions. It is to improve the performance of later regulators. It will work in high-ripple situations, but you should add diodes to the string D1 and D5 depending on how much ripple you have.

HiFi encouraged me to post this here, and I might as well post the finished design, so someone can spot my errors...

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Old 18th October 2010, 07:45 AM   #34
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Hi keantoken,

Many thanks for all your work and simulations.

I have interrogation about using 1000F. Since this design is a capacitor multiplier, it will multiply everything coming from this capacitor. It will multiply good effects and bad effects (like coloratura, non linearity...!). Don't you think that using 100F or 10F might be more realistic?

Probably, it will be easier to find good 100F than good 1000F.

Thanks for all replies...
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Old 18th October 2010, 07:51 AM   #35
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There won't be any measurable degradation from using a 1000uF cap that I can see.

100uF is totally fine, the bass at audio frequencies will hardly be affected.

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Old 18th October 2010, 07:57 AM   #36
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Wait, the schematic had an error! Here is the correct schematic.

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Old 18th October 2010, 08:08 AM   #37
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Quote:
Originally Posted by keantoken View Post
There won't be any measurable degradation from using a 1000uF cap that I can see.
You could not see any coloratura in any simulator

This simulation goes to 1GHz. Do you think that 1000F is able to work at 1GHz?
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Old 18th October 2010, 09:08 AM   #38
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No, surely not, but I look anyways. You can always bypass that cap with smaller film caps.

The regulator should be decoupled by at least 10uF.

BTW, it is a joke to take credit for this circuit. Nothing special!

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Old 18th October 2010, 09:53 AM   #39
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reversing that diode seems to make a big phase difference.

Why is the PNP performing better this time over most of the frequency range?
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Old 18th October 2010, 10:12 AM   #40
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Beta characteristics of the master transistor will affect bass performance. Beta characteristics of the slave will affect output impedance.

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