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Old 18th January 2012, 09:10 PM   #1711
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Hi guys

Here's my output binding posts with DC sense circuit. It triggers at +/-1,2 Vdc sending signal to SSA Soft Start C7, C8 pins, which in a case of being triggered instantly shuts down the amp's channels (high Zout), plus cuts off the power. Hopefully just won't ever happen ...
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File Type: jpg 2.jpg (563.8 KB, 526 views)
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Old 18th January 2012, 09:18 PM   #1712
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Quote:
Originally Posted by Thomas_2-love View Post
@Salas, did you make any progress on your version? I liked your approach.

LC: any chance your build will be measured? I'm interested in distortion and noise. Before going to build anything I do want to know if it will be in "my ballpark"
Hi Thomas

Now I'm soldering the second SSA BIGBT HP channel and this one will be measured to the last detail, so wait a little more for the specs. But as for now I can tell you there's no noise at the output at all, dead silent. I put my ear on tweeter's dome and heard no noise, hiss or whatever at all. Also no power on/off sounds, no notification from speaker, so only power LED-s on PCB or music sounds tells you the amp is on ...
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Old 18th January 2012, 09:25 PM   #1713
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Quote:
Originally Posted by igor0203 View Post
LC, I'm wondering what's in that beautiful enclosure behind speaker?

Click the image to open in full size.
That's my StereoLith amp from 2002. In short dual mono, symmetrical LTP's VAS, 4 pairs BIGBT output, +/-80V output rails, 800VA toroid per channel. The only amp I retained for myself, all others named MonoLith (more than 20 monoblocks) were sold to my friends.
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Old 18th January 2012, 09:53 PM   #1714
Salas is online now Salas  Greece
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Quote:
Originally Posted by Thomas_2-love View Post
@Salas, did you make any progress on your version? I liked your approach.
Been playing very nicely but I want to see if it ''tunes up'' any further. Soon.
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Old 19th January 2012, 04:40 AM   #1715
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Quote:
Originally Posted by Lazy Cat View Post
Hi guys

Here's my output binding posts with DC sense circuit. It triggers at +/-1,2 Vdc sending signal to SSA Soft Start C7, C8 pins, which in a case of being triggered instantly shuts down the amp's channels (high Zout), plus cuts off the power. Hopefully just won't ever happen ...
You never stop to amaze us...
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Old 19th January 2012, 01:41 PM   #1716
maxente is offline maxente  Romania
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Hi LC
Tell me if i understand correctly i must match those two bjt transistor for close hFE from the picture below?
What about those irf's i must match them to?
Sorry if you have mentioned in other post (to mutch to read ) but how mutch power do you expect from your final version that you are building now at what load?
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Old 19th January 2012, 02:16 PM   #1717
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Exactly, 2SA/SC transistors should be hFE (current gain) matched inside +/-5% or even within tighter tolerance if possible but +/-5% is mandatory for good performance ie. fifty-fifty load current split between them.

Regarding IRF's matching procedure I usually perform two brief very simple measurements. First, set variable DC power supply connected to the Gate and Source of a N-channel mosfet (watch the polarity, gate is positive and source is negative) to potential that Ugs voltage causes 100 ohm Rds resistance between Source and Drain (measured with digital ohm-meter). Keep this DC Ugs voltage value to test P-channel mosfet (reverse the polarity to Gate and Source) and find the ones closest to 100 ohm Rds. Second, repeat the procedure at 10 ohm Rds among initial mosfet's selection for both channels with the same procedure like described before. What's left on the table are closely matched mosfet N-P channel pairs.

P.S. Be very careful, your body static electricity potential could easily break gate junction, +/-20V is usual Ugs max potential allowed.

Last edited by Lazy Cat; 19th January 2012 at 02:30 PM.
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Old 19th January 2012, 02:29 PM   #1718
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Quote:
Originally Posted by maxente View Post
Sorry if you have mentioned in other post (to mutch to read ) but how mutch power do you expect from your final version that you are building now at what load?
SSA BIGBT HP with +/-60V on the output stage will give something around 150W/8ohm and 250W/4ohm.
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Old 19th January 2012, 02:32 PM   #1719
maxente is offline maxente  Romania
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Thank you for answers !
If i don't have IRF610, IRF9610 what should i put instead, are those vertical?
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Old 19th January 2012, 02:39 PM   #1720
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Yes they're vertical. You could try to use 2SJ79 and 2SK216 pair but these two have lower Ugs threshold voltage, different layout, plus they have negative tempco and integrated input protection zeners, but anyway it is good exchange with the same matching procedure.
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File Type: pdf 2SJ79.pdf (57.5 KB, 65 views)
File Type: pdf 2SK216.pdf (57.3 KB, 20 views)

Last edited by Lazy Cat; 19th January 2012 at 02:43 PM.
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