AKG P414 - C414E preamp + U87 style DC converter strange voltages - any ideas?

[Khron]

"Can't use ltspice"? You only have a mac or something?

Can't really comment on Multisim - never used it, and never really had much reason to move away from Ltspice

I know i didn't use a zener - just for the hell of it, i figured i'd go with the way the BM600 dc-dc converter was done And whaddya know - it works

With a 60v zener model (1N5371B) and a 1nF output filter, the voltage got up to 38v at 10ms.

 

[ln76d]

Yuck for mac


I can't install ltspice - let say i have some problems with previous instalation and can't change system currently
I tried use in multisim 1n4148 with the same result  42V.

 

[Khron]

Previous installation... of Ltspice?

You sure have a looooot of secrets, man...

 

[ln76d]

Nah my head hurts so i have problems  on writing in english with sense
Yes previously installation.
I screwed up few things in registry etc. and i can't use installed ltspice, uninstall it and install new one.
I can't also restore system
Nothing exciting and nothing to brag about.

 

[Khron]

From what i can read, you'd have to force Ltspice (with a command line switch) to save user settings in the registry; otherwise, it has nothing to do with the registry.

Maybe something's screwed in your ltspice.ini file?

 

[ln76d]

Probably too
I screwed up many things on my system and tried many things
Before i don't finish mixing album, i can't touch it

 

[Khron]

https://www.youtube.com/watch?v=otCpCn0l4Wo ;D

 

[ln76d]

Exactly  ;D

 

[Khron]

Great minds think alike, hmm?

It'd be really weird to see your computer wear pants like that, though... :|

 

[ln76d]

It's enough to use win7 with aero skin

 

[ln76d]

Finally found the answer!

Yes, i will have to change zener

I bought another P100 to make a pair and checked converter - these f**kers are running capsule around 40V!
Nowdays AKG should't call itself AKG...

Input voltage going to the converter is around 24V.

 

[Tormy]

I really don't know what problems you guys had with simulating this circuit - it worked on the first attempt, for me.

See the screenshot

White trace = the node where L2 connects to D1/C4/C5
Blue trace = the node between D2 and R6 (the "load")

Yes, i know, there's no filter cap on the output - i was lazy ;D

Quick edit: Adding an output cap just makes the output rise slower. With 1nF, the blue trace gets to about 38v after 10ms. With 100nF, it only reaches about 1.5v after 10ms

And note, that's a plain old 1N4148, not a zener over there

Old post ut since I'm struggling with LTspice to make that oscillator working fine, Google finally returned me this post.
So, I see form your schematic you used a normal rectifier as for D1 = 1N4148 (connected as a zener?)
And for the 2 Coupled impedances the value of 220µH

But the Neumann schematics for the U87Ai reports as (D7 on their schematics indicated by 3 stars which suggest the code 8280500067) 62V Zener.

In the same schematics, somebody manually wrote different impedances for DR-1's windings.
There is also a kind of notation I think is in Norsk or Svenska but I can't fully read it, so I can't use any translator to get what's notated)

However it's written for the impedance DR-1
Pin 3 (GE) and Pin 1 (GN) Ground, I read 2.7mH
Pin 3 (GE) and Pin 2 (RT), I read 0.22mH > 200 µH
Pin 2 (RT) and Pin 1 (GN) Ground, I read 1.4mH

In both cases (your and the original schematics) is not indicated the dot on the windings
having said that, by putting that zener and that impedance values, I get a very strange behaviour on LTspice indeed ... I can't say "it works" because it doesn't. LTspice makes strange things

Even by putting a 1N4148 connected as you did it and 2 equal impedances and also to orient the dot on all the possible combinations: the behaviour is way strange.

If I give the directive K L1 L2 1 which is the coupling factor between the inductors: I get only DC (low voltage) without any oscillation.
As well as by adding "startup" into the directive ".trans 1s"

On the LTspice I've put all the Neumans values for all components, and since it is supplied at theoretical 46V from the emitter of T2 (capacitance multiplier and there are almost 2 volts drop from the Phantom), I just added a Cell of that value to supply it via the 39k resistor (R20 in the original schematic), but it doesn't work as it should.

I'm not able to make it work :-(
Where am I wrong?

 

[Khron]

I'm not able to make it work :-(
Where am I wrong?

Do you *NEED* to use strictly *THIS* particular circuit?

Go with Rogs' / the Rode-style 40106-based oscillator, it's much less finicky than any and all of these discrete circuits.

https://www.opic.jp137.com/index-ldc.html

 

[Tormy]

Do you *NEED* to use strictly *THIS* particular circuit?

Go with Rogs' / the Rode-style 40106-based oscillator, it's much less finicky than any and all of these discrete circuits.

https://www.opic.jp137.com/index-ldc.html

Yes I do. Not to build it, because I know it works. I wanted to use this schematics and to show the working to a couple of ppl i was explaining the U87 functioning, and i thought it could be very interesting to show, stage by stage, how it works through simulation.

Initially i doubted of the transistors model of LTSpice so I also went to looking for "more reliable" data but I got the same behaviour.
When today Google showed me this post, I went through all to check were and if I was wrong, but I didn't find the key point to make it work into LTspice.

So I asked here

 

[kingkorg]

Old post ut since I'm struggling with LTspice to make that oscillator working fine, Google finally returned me this post.
So, I see form your schematic you used a normal rectifier as for D1 = 1N4148 (connected as a zener?)
And for the 2 Coupled impedances the value of 220µH

But the Neumann schematics for the U87Ai reports as (D7 on their schematics indicated by 3 stars which suggest the code 8280500067) 62V Zener.

In the same schematics, somebody manually wrote different impedances for DR-1's windings.
There is also a kind of notation I think is in Norsk or Svenska but I can't fully read it, so I can't use any translator to get what's notated)

However it's written for the impedance DR-1
Pin 3 (GE) and Pin 1 (GN) Ground, I read 2.7mH
Pin 3 (GE) and Pin 2 (RT), I read 0.22mH > 200 µH
Pin 2 (RT) and Pin 1 (GN) Ground, I read 1.4mH

In both cases (your and the original schematics) is not indicated the dot on the windings
having said that, by putting that zener and that impedance values, I get a very strange behaviour on LTspice indeed ... I can't say "it works" because it doesn't. LTspice makes strange things

Even by putting a 1N4148 connected as you did it and 2 equal impedances and also to orient the dot on all the possible combinations: the behaviour is way strange.

If I give the directive K L1 L2 1 which is the coupling factor between the inductors: I get only DC (low voltage) without any oscillation.
As well as by adding "startup" into the directive ".trans 1s"

On the LTspice I've put all the Neumans values for all components, and since it is supplied at theoretical 46V from the emitter of T2 (capacitance multiplier and there are almost 2 volts drop from the Phantom), I just added a Cell of that value to supply it via the 39k resistor (R20 in the original schematic), but it doesn't work as it should.

I'm not able to make it work :-(
Where am I wrong?

I am not a LTSPICE expert, but i'm not sure Hartley oscillator can be simulated at all. I spent lots of time, but couldn't make it work. It can be tricky to pull off even in real life, it seems to have quite a temper.

 

[Tormy]

I am not a LTSPICE expert, but i'm not sure Hartley oscillator can be simulated at all. I spent lots of time, but couldn't make it work. It can be tricky to pull off even in real life, it seems to have quite a temper.

I was able to make this work fine. but it has not a JFET
Wo what I did is: to add a supply stage as for the one of the U87Ai second screenshot)
And it works. So I'm confused on how is it possible that this works and the other one not on LTspice.

 

[Khron]

I wanted to use this schematics and to show the working to a couple of ppl i was explaining the U87 functioning, and i thought it could be very interesting to show, stage by stage, how it works through simulation.

The oscillator for the capsule bias voltage is, in my opinion, pretty much irrelevant and unessential for the functioning of a microphone otherwise.

The only concerns might be economical (bill-of-materials costs etc), startup reliability... If it can put out the voltages the capsule needs, HOW it achieves that is entirely immaterial, as long as the resulting voltages are plenty clean, after filtering. But once again, that's just me...

I'm attaching the LTspice file, just change the extension from .txt to .asc; the BF245B model i got from here:
https://web.archive.org/web/2017082...zai/PHILIPS/models/spicespar/data/bf245a.html
Starts up just fine, oscillates at about 2.5MHz, and/but that's without any coupling factor between the two inductors (so, arguably, "worst case scenario"..?). Gets up to 45v or so after 50ms (couldn't be bothered to run the sim for longer).

 

[Tormy]

The oscillator for the capsule bias voltage is, in my opinion, pretty much irrelevant and unessential for the functioning of a microphone otherwise.

The only concerns might be economical (bill-of-materials costs etc), startup reliability... If it can put out the voltages the capsule needs, HOW it achieves that is entirely immaterial, as long as the resulting voltages are plenty clean, after filtering. But once again, that's just me...

I'm attaching the LTspice file, just change the extension from .txt to .asc; the BF245B model i got from here:
https://web.archive.org/web/2017082...zai/PHILIPS/models/spicespar/data/bf245a.html
Starts up just fine, oscillates at about 2.5MHz, and/but that's without any coupling factor between the two inductors (so, arguably, "worst case scenario"..?). Gets up to 45v or so after 50ms (couldn't be bothered to run the sim for longer).

Thank you so much. yes this is working. So at the end it was the semiconductor Spice Data that, in my case, were wrong ...