NJL4302/4281 Discontinued. - Page 2 - diyAudio
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Old 16th June 2012, 02:05 AM   #11
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Quote:
Originally Posted by Bonsai View Post
It's very stable across temp and the response is fast. There's some more detail on th technique on pages 40 & 41 of my e-Amp write up.
Yes, I read and appreciated the write up. I like to learn from comparison of different methods so I was curious as to why you went that way. You think it superior to the ThermalTraks in performance? or because you had already developed it earlier so it was simpler just to reuse it? Or you didn't want to use a part without a second source

Best wishes
David

BTW In the earlier Ovation amp you mentioned later Miller Input Compensation trials. Any write-up on that?
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Old 16th June 2012, 03:29 AM   #12
Bonsai is offline Bonsai  Taiwan
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I just continued to use what I had found worked quite well on the Ovation 250, although at the upper end of the temp range it was not tight enough on that amp, hence the NTC solution. I have been considering the Thermal Trak, but this DOD announcement worries me a bit.

Re the MIC: no, I ended up going with TMC. On my next big amp, I will do MIC as A comp option sling with TMC and MC. Will all be relay switched though.
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Last edited by Bonsai; 16th June 2012 at 03:35 AM.
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Old 16th June 2012, 05:00 AM   #13
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Originally Posted by Bonsai View Post
but this DOD announcement...

Re the MIC: no, I ended up going with TMC. On my next big amp, I will do MIC as A comp option sling with TMC and MC. Will all be relay switched though.
DOD?
ThermalTrak should have better dynamic behaviour but your method looks exemplary in other respects so it may be an academic point.

...as A(a?) comp(ensation) option sling(link?)
TMC does not preclude MIC so you could have had even more to try! The combination looks to have promise. MIC is especially suited to the complementary symmetrical IPS that you prefer (me too).

Best wishes
David
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Old 16th June 2012, 07:17 AM   #14
Bonsai is offline Bonsai  Taiwan
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DOD = semiconductor industry terminology for end of life.

Thermal Trak should be very good. The sense diode is co-located on the header with the transistor die. However,I have not tried them.

Unfortunately, iPad spell checker is a bit too vigorous some times and I am lazy and don't read what I write before hitting the send button.

Should read "I will do MIC as a comp option along with TMC and MC"
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Old 16th June 2012, 09:40 AM   #15
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Originally Posted by jaycee View Post
I think its a very simple reason - the market is limited, high power amps are all going class D, and indeed a lot of the market is. The true hifi sector of the market is growing smaller all the time.
Yes. I think so, too.
Maybe only Semelab - the supplier for Naim Audio about
TT electronics Semelab
will offer audio power devices (both BjT and MOSFET) suited for analog audio amps (Class A and AB) for many years.
This means, I must delete post #1 about
bipolar (bjt) transistor families for audio power output stages
in few years.

Last edited by tiefbassuebertr; 16th June 2012 at 09:43 AM.
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Old 16th June 2012, 10:18 AM   #16
AndrewT is offline AndrewT  Scotland
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Originally Posted by Dave Zan View Post
.............. the NJL4*** ..................are the ones with best performance in every area. .........
you will find that the 4 series droop earlier as the IC increases.
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Old 16th June 2012, 11:16 AM   #17
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you will find that the 4 series droop earlier as the IC increases.
Yes, not much in it since the 4 series droop a little earlier but start a little better. So percent variation is a little worse but Hfe @ 25C dips below a convenient 100 at practically identical currents.
I plan to run a half dozen in parallel so I hadn't checked past 5 amps and when Hfe is so variable it's probably academic but I will stand corrected.
Probably should admit the 1/0 series, (not 3 series) are lower capacitance to avoid another comment.
So the 4 series are only faster, more robust, more gain and have lower thermal resistance for better thermal stability and power capacity.

Best wishes
David

Last edited by Dave Zan; 16th June 2012 at 11:22 AM.
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Old 16th June 2012, 11:27 AM   #18
AndrewT is offline AndrewT  Scotland
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Good indeed. That's why I bought 100prs 4281/4302 of non rohs when I thought the price was good.
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Old 16th June 2012, 12:04 PM   #19
hahfran is offline hahfran  Germany
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Quote:
Originally Posted by tiefbassuebertr View Post
Yes. I think so, too.
Maybe only Semelab - the supplier for Naim Audio about
TT electronics Semelab
will offer audio power devices (both BjT and MOSFET) suited for analog audio amps (Class A and AB) for many years.
This means, I must delete post #1 about
bipolar (bjt) transistor families for audio power output stages
in few years.
Indeed as class D is now available with feedforward correction ( with a 1 watt super low thd superfast class A) the linear power amps will become obsolete. A class D operating at at least 500 kHz sampling cannot produce non linear distortion rather distortion in class D are timing errors and at very low input inaccuracies ( overdrive must be prevented with limiters) insofar input noise produces not noise in output but distortion. This is cleverly compensated with feedforward. Another negative point is class D cannot have any CMRR. Nevertheless, the era of linear power amps is nearly over. Class D is so much cheaper and the only design objective is minimize timing error. nevertheless semiconductor is all about temperature and here class D has another advantage, there is for all semiconductors an optimum crystal temp where switching speed is a maximum. This is rather sharp for BJts and rather flat for FETs. Insofar, linear amps work best if junction temps were constant. As this is impossible to achieve , an approximation is operating setup constant. Insofar thermal trak should be better than the lagging thermal compensation. The very best is still the Quad 303 as it holds op constant on the fly there is no time lag.

Btw if anyone knows where to get a few NJL4302/4281 please let me know.
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Old 16th June 2012, 12:16 PM   #20
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Try Evette or Rudi Ratlos
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