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Old 4th January 2013, 02:58 PM   #261
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Nice one ! May-be it would-be a good idea to make a headphone amp from it ? With 30-600 ohms for load and +-18V of power supply ?
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Old 4th January 2013, 09:00 PM   #262
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Lazy Cat View Post
ALF pins connected to PCB with wires? Not very good idea.
ehh...why ?

btw, whats the deal with the ALF double mosfet ?
I thought it would have been more of a car-fi thing, with the advantage of being compact
I guess power/heat is not on the best side
or is there more to it than that ?
special tweeter amp ?
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Old 5th January 2013, 12:08 PM   #263
tinitus is offline tinitus  Europe
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Originally Posted by Lazy Cat View Post
... so still small separate on-board heatsink for VAS. I'm planning to go to the main heatsink with VAS, just like in my test setup.
yes, but I got the impression it was the optimal way
did I read somewhere else they shouldn't even share the same heatsink, but be completely seperated ?
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Old 5th January 2013, 12:44 PM   #264
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Quote:
Originally Posted by tinitus View Post
btw, whats the deal with the ALF double mosfet ?
I thought it would have been more of a car-fi thing, with the advantage of being compact
I guess power/heat is not on the best side
or is there more to it than that ?
special tweeter amp ?
So far as I tested ALF it acts more athletic (100 m) than any mosfet pair I tested so far.
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Old 5th January 2013, 12:54 PM   #265
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Quote:
Originally Posted by tinitus View Post
yes, but I got the impression it was the optimal way
Says who? There's no small heatsink or any other metal part on PCB at all. What could be more optimal than that?

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Originally Posted by tinitus View Post
did I read somewhere else they shouldn't even share the same heatsink, but be completely seperated ?
I'm here to break some rules. If you would carefully looked to VSSA pictures, you could notice VAS transistors on the same copper heatsink as ALF. It is on purpose copper and small to make as much as possible stress and fast transfer between both pairs. It is completely stable from 20°C to 75°C as I tested in reality. VAS bias goes from 10 mA to 16 mA, output bias fixed to 100 mA with help of TLVH431 set fixed to 1,565 V.
So there's no need for separate on-board VAS heatsinks as you can see.

Main purpose of this compact VSSA amp use is multichannel amp, active speakers, separate horn driver's amp, bookshelf speakers amp, comp amp etc.
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Old 5th January 2013, 01:41 PM   #266
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Originally Posted by Samuel Jayaraj View Post
LC, thank you for the schematic. Would you like to give a brief comparison of sound quality between VSSA, TSSA and SSA(IGBT)?
Bump.
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Old 5th January 2013, 03:37 PM   #267
tinitus is offline tinitus  Europe
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from your previous post I only thought it sounded like a compromise to have Vas drivers on main heatsink

anyway, I dont think it makes it easier to assemble with drivers on main heatsink
and since the ALF only needs one hole to drill, and thus no tricky allignment, that 'simplicity' would vanish with the drivers

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Originally Posted by Lazy Cat View Post
The only problem I noticed is thermal bias PTC because of VSA BJT's located on the same heatsink as the outputs. Solution is to use reference adjustable zener for bias spreader or relocation of 2SA/SC to separate heatsinks.
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Old 6th January 2013, 09:43 AM   #268
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Originally Posted by tinitus View Post
from your previous post I only thought it sounded like a compromise to have Vas drivers on main heatsink
On contrary, for an active speakers amp all heated parts should transfer the heat to outer heatsink, so chamber's inside is heated as little as possible. I extensively tested thermal conditions and with TLVH431 we get simple and reliable solution for perfect thermal stability. As bonus we get also lower THD because Vgg is constant, no matter of the amount of drive signal.

Three screws for transistors on the heatsink are also all fixation PCB needed to be completely stable. I'll definetely do it this way, others can do in a way as suits them most.
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Old 6th January 2013, 09:56 AM   #269
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Originally Posted by pergo View Post
With CRD or another CCS there's no variation at all.
With CRD the problem is Vk-knee voltage from where forward current becomes constant (Vk=2 V for 1 mA diode). It is just to high to be proper for 470 ohm replacement, since there's 0,8 V voltage drop on this resistor.
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Old 6th January 2013, 09:59 AM   #270
pergo is offline pergo  Italy
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you can use a simple CCS. CRDs are integrated jfet CCS.
Was only an example.
I know is more complicated and you want to maintain the design more simple as possible
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