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Old 23rd November 2011, 01:03 PM   #1481
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Originally Posted by Lazy Cat View Post
Hi igor0203

Yes of course, maybe even GB if there will be some interest shown here.
I think this won't be a problem...
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Old 23rd November 2011, 02:30 PM   #1482
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Just a little teaser

The SSA BIGBT HP PCB is almost ready to be published. I will be the first one to build this version on a new shiny PCB which will be prepared by master Alex. Hardly wait to get a Christmas gift

Hi Andrej,

That's awesome!!! Put me on your list for the GB.
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Old 23rd November 2011, 05:41 PM   #1483
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I made some little modification to alow the use of 3.5°K/W driver heatsink (cf picture) for the twice drivers, and swap to 5 1r2 1w 1% resistor instead one 0r22 5w (question of localy ordering).
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File Type: jpg dissp driver.jpg (14.4 KB, 516 views)
File Type: jpg SSA_TT35_brd2.jpg (122.3 KB, 519 views)
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Old 23rd November 2011, 06:00 PM   #1484
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Originally Posted by Lazy Cat View Post
Hi igor0203

Yes of course, maybe even GB if there will be some interest shown here.
Ohhh yes...sounds great, I might be in also so keep us posted.

BTW, I'm curious about the implemtation on those boxes of yours for the BIGBT's
can you show us the inside? need the power resistors be non inductive? its only 0.22 Ohms so I think it wont matter at all.

Cheers, Tony
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Old 23rd November 2011, 06:11 PM   #1485
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For BIGBT people should keep in mind NPN/PNP hfe matching. In my 100 MJL3281 and 100 MJL1302 batch i can only have 4 good NPN/PNP pair

Marc
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Old 23rd November 2011, 07:33 PM   #1486
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Some more little arragement on my SSA ThermalTrack 35V rail version
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Old 23rd November 2011, 11:22 PM   #1487
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Question N & P-BIGMT ?

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Originally Posted by Lazy Cat View Post
Hi Sound Rays

The same issues remains with T9,10,13,14 as before.

Please read my corrections again.

Regards, Andrej
LC,
Hurry is never good at all, You are right, I did foreseen the most important details of Yours suggestions, hopefully now solved + I add an option for possible realization of Yours BIGMT module in post #458.
I hope that I redraw it correctly... Yours proposed SCH, please correct it if any errors. This is is also what I wonder to try, would the output be similar near to the rails as with this present OP stage ?
I have a 750W toroid with 4 separate sec. winding 30V AC. This would be enough for driving low imped. speakers.
Any additional kind suggestion for the best sound outcome from this simple SSA bal-fet version would be much appreciated.

Thank You,

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Old 24th November 2011, 01:09 AM   #1488
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Hi Sound Rays

Khmm, new sch of yours, khmm, new comments (cannot just say confirmed ):
- correct T1, T4, T6, T7 to BC560C, it's a must
- correct T2, T3, T5, T8 to BC550C, it's a must
- if you will use T13 as 2SK216 and T14 as 2SJ79 than T11 is BC550C mounted on a PCB (not on the main heatsink), because of the negative tempco of 2SK216/2SJ79. If you will use IRF's as drivers than T11 is BD411 on the heatsink, period.
- T15, T17 are P-channel mosfets, so you must reverse diode orientation. It should be exactly the same as it is drawn inside T14 symbol (the same P-channel mosfet). Please Sound Ray, electronics is suppose to be very exact science and you have major discrepancy here.
- T15, T17 are 2SJ162 not 2SJ62, correct it please
- omitt D3, D4 completely, you don't need them because mosfet symbol shows you that these diodes are already incorporated inside both mosfet channels
- C26 is 0,1 uF
- you will need extra P1, C1, Rx for the negative input DC offset calibration

Regarding all mosfet BIGBT (Balanced Insulated Gate Bipolar Transistor) my opinion is that it can work but very hardly to be balanced ever, even if you trimmed R38, R39 to 50-50 output drain currents. If it would ever work than also the name would change into BIGMT as you already stated. Bipolar transistors works as a current gain devices so inside BIGBT, mosfet driver runs only one base current for both BJT's all the time and if hFE's are equal, thus naturally forces outputs to the exactly equal collector currents. By mosfets as balanced outputs, Vgs among both channels are so different through the whole range of transconductance, that balanced operation would be simply mission impossible.

Please repost all-corrected sch for the last inspection, regards, Andrej

Last edited by Lazy Cat; 24th November 2011 at 01:19 AM.
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Old 24th November 2011, 01:36 AM   #1489
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Originally Posted by SOUND_Rays View Post
I have a 750W toroid with 4 separate sec. winding 30V AC. This would be enough for driving low imped. speakers.

Thank You,

750 VA/4 x 30 V transformer would satisfy the power consumption of two channels (stereo amplifier) for 4 ohm speaker loads. Lower speaker impedance than that would demand more transformer's VA. Let say 2 ohm speaker loads doubles the power needs into 1,5 kVA and so on ...

Last edited by Lazy Cat; 24th November 2011 at 01:39 AM.
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Old 24th November 2011, 01:47 AM   #1490
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Hi Andrej,

That's awesome!!! Put me on your list for the GB.
OK thanks, confirmed
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