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Old 4th December 2011, 03:24 PM   #1621
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I like that design a lot to, from the beginning.
I sometimes need a small amp that is good, be it for active speakers or friends that just start into High End. This is then mostly for computer audio so when it is very compact that is good.
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Old 4th December 2011, 05:23 PM   #1622
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Quote:
Originally Posted by Idefixes View Post
Rhaaaaaa LC, do the #1615...i have to one more time to put my layout on eagle work bench......thanks for new schematic and "fonctionnel" confirmation.

Marc
It is basically the same as it was previously published, only some minor but necessary caps and trimmers added. At the end this is very high bandwidth design so the supply rails must be well decoupled at all crucial points. One of them is done by 1 uF cap as close to the output's collector pin as possible.

As you all guys already know I did a lot of extensive SSA testings and I am very familiar with this design, I know it better even than my pockets content, also all possible published versions are safely stored on my disks, so if somebody need certain info, just say it.

Today I finished the SSA BIGBT HP PCB layout & routing, so the files will be send to mine PCB manufacturer tomorrow morning. Only one question remains and still bothering me: which coating colour should I choose green, blue, red, white ... mhmmm

P.S. Maybe blue like my Projet Preamp PCB
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File Type: jpg Projet Preamp Module 013.jpg (628.3 KB, 582 views)

Last edited by Lazy Cat; 4th December 2011 at 05:29 PM.
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Old 4th December 2011, 05:51 PM   #1623
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Ok,
LC i don't want to add the input offset controle as i've been sure the offset flows out my preamp. So just an input cap for foreigner occosional preamp. What mod should i do on you latest schematic?

Marc
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Old 4th December 2011, 06:00 PM   #1624
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Quote:
Originally Posted by Idefixes View Post
Ok,
LC i don't want to add the input offset controle as i've been sure the offset flows out my preamp. So just an input cap for foreigner occosional preamp. What mod should i do on you latest schematic?

Marc
Compare both schs and add some decoupling caps if needed, otherwise I think your version is OK. Anyway, please post your latest sch suited to your last PCB version and I can comment.
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Old 4th December 2011, 06:12 PM   #1625
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Quote:
Originally Posted by Lazy Cat View Post
Anyway, please post your latest sch suited to your last PCB version and I can comment.
Here they are....
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File Type: jpg SSA_TT35_sch5.jpg (108.4 KB, 523 views)
File Type: jpg SSA_TT35_brd7.jpg (128.0 KB, 473 views)
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Old 4th December 2011, 08:48 PM   #1626
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Hi Idefixes

It will work with 2,2 kohm input impedance the same as with 10 kohm, depends only on your preamp's output current capability. Every value has its own benefits so you choose the one suits you the most, there is some room to experiment to get the best sounding solution in your system. I would certainly put two LEDs on board just to clearly see the normal operating conditions and/or fuses breakdown.

Input offset trimmer is almost a must if the amp is input DC coupled, so it serves to calibrate input offset (bases DC potential balanced to zero) when input is unconnected, so there is no change in an output DC offset if you short clamp the input or connect the zero DC low impedance source drive. We are speaking of some mV difference but anyway here's a possibility to trimm-out input DC offset completely to absolute zero conditions.

If you will use input coupling capacitor I have to inform you that it should be of high uF value at existing 2,2 kohm input to GND resistance. Just for an example input RC like 1 Mohm (input resistance to GND) and 1 uF (input coupling capacitor) means something like 1,6 Hz/-3 dB high-pass margin.

Also I would move 1 uF/0,1uF decoupling caps closer to the collector pins on PCB layout, just to prevent any HF ripple/oscillation loops over the supply rails. This is very important, cause I checked it just for the test purposes with my latest SSA HP VAS (small protoboard pictures) connected with 20 cm wires to the output stage. Immediately when I removed 1 uF decoupling caps near the outputs I got clear 17 MHz sine oscillation of several Vpp. This was also acid test cause I deliberately ran fully uncompensated amp on long VAS to output wires intentionally just to provoke all kinds of possible negative stuff to get the solution before PCB is made, so called stress tests.

All in all make small adjustments to PCB before going into production, now it is the time.

Regards, Andrej

Last edited by Lazy Cat; 4th December 2011 at 09:12 PM.
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Old 4th December 2011, 11:19 PM   #1627
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Here with some modifications.

Marc
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File Type: jpg SSA_TT35_brd8.jpg (127.3 KB, 412 views)
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Last edited by Idefixes; 4th December 2011 at 11:22 PM.
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Old 4th December 2011, 11:39 PM   #1628
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Quote:
Originally Posted by Lazy Cat View Post
Hi guitar

You can find all requested info in attached schematic. This one has all capacitors and other features needed for real world realization.
Thanks LC for the reply, but seems more things are added (as well as complexity)
what is the left top portion used for ? (Haven't saw such circuit before) and another set of voltage could be hard for me to achieve.
Could I ask why the you add another pair of 2.2k and 5k VR ?

The circuit main supply is written +-35V, is is compatible to +-40V too ?
What is the component labelled '5 A/T ', is it a fuse ?
I guess there are no special requirement for LED (even i can put RED, isn't it ? )
Do we need a input capacitor ? (seems most of the amp design have it )

If I were to make an power supply for it, at 40V how much capacity of reservoir should I prepare ? (asking for the power rating of this amplifier too)
So for those without voltage/power rating, I use above 50V & 0.5W is fine/sufficient ?

Just asking for fun, I have tons of BC550/560, could I make one SSA with all those ? (provided make it small output about 1W-5W)

Last edited by guitar89; 4th December 2011 at 11:43 PM.
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Old 5th December 2011, 12:09 AM   #1629
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Hi guitar

Quick answers:
- I am apologizing for that, no complexity, just well dressed TT version
- input DC offset nulling
- look very carefully +/- 15 V already present on both zeners
- fine adjustment for both halves - info on wikipedia
- it is
- 5 Ampere/Time lag fuse - info on wikipedia
- green LED colour means regular - normal operation, RED the opposite (alarm, faulty conditions, warning etc.)
- not mandatory
- calculate the Joules (energy), than calculate the Farrads (capacitance) - formula on wikipedia
- power ratings in Watt - formula on wikipedia
- different standards some 63 V, 0,66 W etc.
- yes you could
- BC-s are here because of their low noise, high hFE, high fT, etc. performance, not Watt-age, but you can try and smoke some plastic

Regards Andrej

Last edited by Lazy Cat; 5th December 2011 at 12:27 AM.
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Old 5th December 2011, 12:25 AM   #1630
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Quote:
Originally Posted by Lazy Cat View Post

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

I opt. finally for this Basic - MosFet version of the SSA-Bal. If You think there would be anything to add to this chosen final, for better and more natural sound of Yours basic SSA-Mosfet version, than I would be more than happy for any suggestion, otherwise the "masters" confirmation is on the wish list.

Thank You,

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