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Old 14th September 2012, 06:48 PM   #3041
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Originally Posted by Samuel Jayaraj View Post
Any reason for not using BF245B and 2N5486 JFETs in the SSA BIGBT HP? Just asking as I have them, as well as 2N5462. Moreover, the voltage rating of 2N5459 is lesser than 2N5486.
SSA is predecessor of TSSA, j-fets were implemented much later to possibly improve the design, speaking of sound quality. More about this could be told later on, after CSA's listening tests will be performed.

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Originally Posted by Samuel Jayaraj View Post
Although this question belongs to the TSSA thread, is the 10K NTC the only heat sensing device in TSSA BIGBT HP?

Thanks.
Yes, it will be precisely tuned to correct tempco with serial and parallel resistors. Major improvement is its capacitance to the heat sink, which will be few pF only.
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Old 14th September 2012, 06:50 PM   #3042
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Originally Posted by shaan View Post
I tried to draw a PCB which will look like the attachment.

Dimensions:- 3.5" X 2.8"

Currently rendering the bottom artwork for toner transfer process. Will upload once done and checked for errors.

Nice drawing Shaan

What about CCS-s? Wouldn't it be nice to have them onboard?
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Old 14th September 2012, 06:55 PM   #3043
Salas is offline Salas  Greece
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I wish we had such nice toroids available here.

Well there is hope, as the net says, some companies have started mass production and soon the story is going to turn better...
You have SHILCHAR R-Core made in India. Betters any toroid in any respect.
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Old 14th September 2012, 11:14 PM   #3044
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Originally Posted by Lazy Cat View Post
What about CCS-s? Wouldn't it be nice to have them onboard?
Yes.
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Old 15th September 2012, 04:22 AM   #3045
Harry3 is offline Harry3  Australia
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Yes from me too - Having everything on the one PCB would give consistent results. Hint to anyone who has board lay out skills.
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Old 15th September 2012, 06:12 PM   #3046
naf is offline naf  Indonesia
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yes! please Shaan.. include CCS onboard.
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Old 15th September 2012, 07:38 PM   #3047
shaan is offline shaan  India
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Quote:
Originally Posted by Lazy Cat View Post
What about CCS-s? Wouldn't it be nice to have them onboard?
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Originally Posted by Harry3 View Post
Yes from me too - Having everything on the one PCB would give consistent results. Hint to anyone who has board lay out skills.
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Originally Posted by naf View Post
yes! please Shaan.. include CCS onboard.
Yes the BJT CCS has an instant effect on the amplifier from thermal stability to noise performance. But, for long hours of listening, NO GOOD.

For me, the CCS fed SSA sounds noticeably more crisp than the resistor fed SSA. But after a while it makes the music sound strange(!). "Clinical" would be the closest word to my feelings, although I suspect high order harmonics too. I don't have o'scope and other sophisticated instruments for juggling with it in a "standard" way, so it was simply removed from the board and the resistors were re-placed. Then-and-there the pleasing and enchanting SSA sound was re-established. The CCS was re-connected again a few days later and the fatigue came back. Interesting, but not a happy experience. As a result it was permanently removed.

Still, I do not discourage anybody to use it; I just expressed my experience with it, the case may be different with others.

Perhaps LC's well-tested jFET+SSM+TLC based CCS is the only sonically superior alternative to the resistor.





BTW, The layout for my pee-cee-bee (or whatever it may look like) is ready and will be uploaded shortly.
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Old 15th September 2012, 08:24 PM   #3048
shaan is offline shaan  India
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Smile Rookie job, please be gentle...

Some mods:

1. There's an input cap, everybody knows why. It's an electro ; but trust me once the SSA is up and running, it vanishes.
2. Fixed FET bias of ~150mA with two 1N4148(only 1058/162 tested, ECX not).
3. 10ohm after 1N4007; apparently lowers turn-on thump/hum.
4. 1K+22pF input RF filter.
5. Couldn't eliminate the only one jumper. Sowy.
6. Simple potentiometers; no multiturn. As I found it unnecessary for setting the offset.
7. 1K in series with pots to protect them in case accidentally both set to lowest resistance.
8. Zobel added(of course ).
9. 1M before input cap removed. Pretty unnecessary if you ask me.
10. Front end and VAS bias can be varied with changing 1K2 resistor's value, but if the specified BJT's are used then it should not be necessary. Bias with 1K2 measures 4.5mA through inputs and 15mA through VAS.

Both layouts are the same, but the one in the right is a little style-ish having fancy pads and lots of copper.

Comments welcome.

PS. The zip contains higher resolution pics of the layout in PNG format.
Attached Images
File Type: png SSA_PEECEEBEE_PARTS.PNG (67.1 KB, 871 views)
File Type: jpg SSA_BOTTOM_TOPVIEW_1.jpg (174.5 KB, 763 views)
File Type: jpg SSA_BOTTOM_TOPVIEW_2.jpg (182.6 KB, 724 views)
Attached Files
File Type: zip SSA_PEECEEBEE.zip (688.1 KB, 226 views)
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Old 15th September 2012, 09:49 PM   #3049
shaan is offline shaan  India
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There was an error on the parts print. 1K at the input. Repaired. Apologies.
Attached Images
File Type: png SSA_PEECEEBEE_PARTS_.PNG (67.2 KB, 709 views)
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Old 15th September 2012, 10:46 PM   #3050
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Quote:
Originally Posted by shaan View Post
For me, the CCS fed SSA sounds noticeably more crisp than the resistor fed SSA. But after a while it makes the music sound strange(!). "Clinical" would be the closest word to my feelings, although I suspect high order harmonics too.
If on the oscilloscope, the current is flat whatever the signal level, there is no question to ask. Whatever it sound "clinical" or not, that is the way it *has* to sound.

Just measure the current, and, if the measures are good, it it the resistor version witch has a problem.
May-be, too, the problem is the wiring lengths between the CSS and the board ? CSS are high impedance by definition.
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