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Old 8th April 2013, 07:41 PM   #281
Luda is offline Luda  Germany
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Hi.

ZM, I hope it will

JimT and pidesd,I may try that. I'll probably build a version without gain first and then see what happens.



I started to look around for ways to get a regulated symmetric voltage with the parts I have and noticed that there is an error on passdiy.com
Quote:
"Regulation
much transformer and capacitor bank. The other intent is to physically and electrically isolate each power amplifier channel from every other,[...]"
seems to be incomplete.

I guess Click the image to open in full size.
might be OK, but I'll probably need P- and N-channel FETs to create symmetric voltages, which would be the BS250KL and the BS170.

Any objections?
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Old 8th April 2013, 07:49 PM   #282
pidesd is offline pidesd  Canada
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look at salas regulators. Unbeaten in my experience.

CLC is equally excellent(or even better) in my opinion but sounds different.

This beast however deserves batteries...with CL filters afterwards
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Old 8th April 2013, 09:27 PM   #283
Luda is offline Luda  Germany
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I don't have any inductors, and I don't want to use any parts I don't already have. Spare parts only. I may have to cheat a bit if I need a potentiometer for setting the working point of any FETs.

If I like the result, I may build a "better" version.
But for now: spare parts only.
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Old 8th April 2013, 10:19 PM   #284
Zen Mod is offline Zen Mod  Serbia
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my question was sort of comment , showing that I didn't get your question

however - put as many Jfets you have in parallel , as already written

there is no substitute for cubic ....... mA/V

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Old 9th April 2013, 09:00 PM   #285
Luda is offline Luda  Germany
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Hi.

Before I start soldering:

Is this correct?
Click the image to open in full size.


And could this work as a regulator? (EDIT: 12 V * sqrt(2) - 1,4 V = 15,6 V. I guess the difference is to low for this kind of regulator?)
Click the image to open in full size.

If the above is correct: Can I build a positive voltage regulator with the same parts, maybe like this:
http://www.abload.de/img/possup12xy01.png

or this?
http://www.abload.de/img/possup2cexpi.png

I have some L7812CV positiv voltage regulators.
I guess I could just use those for the postive and negative rails for testing...

Last edited by Luda; 9th April 2013 at 09:20 PM.
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Old 13th April 2013, 01:34 PM   #286
Luda is offline Luda  Germany
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Hi,

I measured the I_DSS of my 2Sk170 and 2SJ74:
HTML Code:
No	2SK170
10	10,74
16	10,58
19	10,48
18	10,08
11	9,76
9	9,35
17	8,92
12	8,75
21	8,69
20	8,27
15	7,96
14	7,89
22	7,89
13	7,75
25	7,73
26	7,65
23	7,38
24	7,09
27	7,08
28	6,92
7	6,6
3	6,25
5	6,03
8	5,97
1	5,73
4	5,56
2	5,26
6	4,93

No	2SJ74
1	6,27
8	5,91
7	5,57
2	5,36
3	5,25
5	4,96
6	3,82
4	3,51
And would choose:
HTML Code:
left:		
2SJ74		2SK170
6,27		6,25
5,25		5,26
--------------------
11,52		11,51 <-- Sum
		
right:		
2SJ74		2SK170
5,91		5,97
5,57		5,56
--------------------
11,48		11,53 <-- Sum
Is that OK?

The I_DSS-figures are quite low. This directly influences (lowers) the maximum output current and power, correct?

Last edited by Luda; 13th April 2013 at 01:36 PM.
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Old 13th April 2013, 03:20 PM   #287
Zen Mod is offline Zen Mod  Serbia
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correct
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Old 15th April 2013, 02:29 AM   #288
pidesd is offline pidesd  Canada
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Is a mini-Aleph using BF862 possible?

bottom of the page is a good exemple for PSU like you want to do
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Old 15th April 2013, 07:43 AM   #289
Luda is offline Luda  Germany
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Hi, that looks quite good, thank you very much.

I have build a board with two 7812s and some socket headers for the JFETs.

I hope I'll have time to test them this evening.

If I like the result, I'll upgrade (put in the other 2SJ74s and matching 2SK170s*, probably upgrade the PSUs to the design you just mentioned, get a toroidal transformer, ...

*my 2SJ74 have low I_DSS values.
Using 4 2SJ74s and only 3 2SK170s per channel would look strange, but should work fine as long as the I_DSS-figures match. Or maybe not?
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Old 13th May 2013, 08:12 AM   #290
Luda is offline Luda  Germany
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Quote:
Originally Posted by Luda View Post
Hi.

Before I start soldering:

Is this correct?
Click the image to open in full size.

[...]
I build the circuit shown above and get anything between 0.2 and 1 Volt Vout.

Due to the untimely death of my soldering station I'm not that motivated to go bug-hunting right now, but should I have used a 1k resistor for every pair of 2SK170/2SJ74 or even 1 for every FET?
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