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USSA-5 PCB GB

fab

Member
Joined 2004
Paid Member
PCB (1) will be less than 10$ US each + envelope +shipping (to be confirmed based on quantity). Price will decrease if the numbers of pcb increases. Therefore this is not commercial Diy...

Please write your name here and the quantity from the latest list in the thread.
1)
...

Hundreds of pcbs have been already delivered to Diy builders.

See more details about the USSA-5 here:

USSA-5 Build with Review


------------- added information ---------

USSA is a family of 20-25 Wrms (8 ohms) class A amplifiers depending on PSU and bias current.
For 4 ohms load it will give still about close to 20Wrms in class A (Square law effect) and up to 45-50 Wrms in class AB.

Design philosophy:
  • Current feedback type thus almost constant feedback factor amongst all the audio band.
  • only 2 stages (also with buffer stage for versions 3 to 5)
  • low/medium feedback factor (< 35db)
  • medium damping factor (25 to 70 for 8 ohms load at 100 Hz), depending on version
  • Square law effect maximizing class A for mosfet output versions (very low source resistor)
  • push-pull that allows to switch into class AB if maximum of class A is reached
  • THD is dominant 2nd and 3rd harmonics
  • Audio grade transistors only and operated in their more linear region
  • Soft clipping behaviour
  • main target is big soundstage, sound big (not thin) even at lower level, articulated bass, natural tonal balance (not artificially over bright), no extra sibilance and overall smoothness while being lively.

Pcb features:
  • output transistors optimally positioned for better heat distribution on heatsink;
  • carefull layout using ground plane, ground return scheme, reduced cross coupling of signals and proper feedback point
  • 2oz density copper trace
  • 2mm pcb thickness
  • gold immersion exposed traces
  • pcb compatible with either USSA-3, 3.1, 3.2 or USSA-5 , 5.1 , 5.2
  • pcb almost compatible with USSA3B or 3.xB and USSA5B or 5.xB (reverse output transistors pin out)
  • LATERAL fet ouputs for initial versions (except versions 7 and 8)
  • BJT ouput for B versions

See post # 346 for schematics of USSA5, USSA5.1 and USSA5B: USSA-5 PCB GB

For USSA3B and USSA3.1 see this thread:
USSA-3B new Version based on USSA-3
USSA3.2B: jfet input, using quad matched available mosfet drivers. Using power bjt as output.

Summary comparison table of USSA-X variations:

1646797737248.png

notes:
1) versions 7 and 8 are twin turbo class AB versions : +-/ 42VDC and double output. They are prototypes using a pcb meant for single output device thus needs wires to connect two pairs. There is no build manual and not supported for Diy. Special request can be submitted by personal message for USSA-8 for more experienced builders.
2) as a general note, for about the same damping factor, bass is tighter and snappy for mosfet output and less tight but maybe stronger for bjt output
3) damping factor may vary based on input stage current.
4) obviously, more details can be less forviving for bad recordings or low grade input source.
5) all class A designs have a more relaxed sound than the class AB in the table above. If high power is not mandatory, I personally recommend class A for better sound.

Documentation:
detailed manual including pictures at different steps and intermediate testing procedure at different phases of assembly to ensure fully working board at end of assembly.

Test equipment needed:
  • 2 x standard multimeters (precision 1mv) ( mandatory)
  • intelligent phone/pad sound generator application (optional)
  • 8-10 ohms 20W power resistor (optional)

Warnings:
  • If you are looking for a high power very bright sound this amp is not for you.
  • If you are listening mainly hard rock/metal music at high sound level this amp may not be for you. However, I mainly listen progressive rock at medium/high level and it sounds fine to me. Still my main amplifier.
  • if you want very tight /dry bass ( as opposed to articulated emotional big bass ) than this amp is not for you.
  • if you are not ready to manage the heat generated by class A than this amp is not for you.

Group buy conditions:
1) partial manual including BOM is provided (only adjustment instructions are missing) since from my estimation roughly only 10-15% of pcb sold are really used for a real build within one year...
2) once pcb are paid, I provide the complete manual including adjustment instructions.
3) once all payments received, I order the pcb from manufacturer.
4) I ship the pcb to your provided address.

Update on 2021/08/17:
Unfortunately the darlington bjt drivers used on USSA-5.1, 5B, 3.1 and 3B are now obsolete. For that reason. An alternate part for the driver is used. Thus this is a new version 5.2. Great sounding ! See post #701 and 702 for more details.

Fab
 

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Last edited:
Updating mine to 2 sets for another member.
------------------------------------------------------------------
1) Samuel Jayaraj, India - 1 set
2) Jacques Antoine, France - 1 set[
3) Patriz 1 set
4) nfsgame, Germany - 2 sets
5) baswamin, India - 2 sets
6)Thimios-2 sets(4 pcb)
7)ravid, India - 3 sets

Thanks
 
1) Jacques Antoine, France - 1 set
2) Patriz 1 set
3) nfsgame, Germany - 2 sets
4) baswamin, India - 3 sets (1 set each for baswamin, Samuel Jayaraj, Manniraj, common shipping to baswamin)
5)Thimios-2 sets(4 pcb)
6)ravid, India - 3 sets
7) BDL, Romania - 1 set
8) Luke - 2 sets
9) vvs07 - 2 sets
10) nounouchet - 1 set
11) PJN, US - 1 set

12) torb, Finland - 1 set
 
1) Jacques Antoine, France - 1 set
2) Patriz 1 set
3) nfsgame, Germany - 2 sets
4) baswamin, India - 3 sets (1 set each for baswamin, Samuel Jayaraj, Manniraj, common shipping to baswamin)
5)Thimios-2 sets(4 pcb)
6)ravid, India - 3 sets
7) BDL, Romania - 1 set
8) Luke - 2 sets
9) vvs07 - 2 sets
10) nounouchet - 1 set
11) PJN, US - 1 set

13) theoracle, New Zealand - 1 set
 
Why then register to buy a circuit board you do not know anything about it?

I was assuming (wrongly) this was a normal 'Solid State' thread in the long tradition of DiyAudio.
Regrettably, several posts here including yours show otherwise.
Therefore I changed my mind: I don't want to be part of this GO anymore.
Goodbye and good luck.


1) ------(no more)--------
2) Patriz 1 set
3) nfsgame, Germany - 2 sets
4) baswamin, India - 3 sets (1 set each for baswamin, Samuel Jayaraj, Manniraj, common shipping to baswamin)
5)Thimios-2 sets(4 pcb)
6)ravid, India - 3 sets
7) BDL, Romania - 1 set
8) Luke - 2 sets
9) vvs07 - 2 sets
10) nounouchet - 1 set
11) PJN, US - 1 set
 
1) Patriz 1 set
2) nfsgame, Germany - 2 sets
3) baswamin, India - 3 sets (1 set each for baswamin, Samuel Jayaraj, Manniraj, common shipping to baswamin)
4)Thimios-2 sets(4 pcb)
5)ravid, India - 3 sets
6) BDL, Romania - 1 set
7) Luke - 2 sets
8) vvs07 - 2 sets
9) nounouchet - 1 set
10) PJN, US - 1 set
11) torb, Finland - 1 set
12) theoracle, New Zealand - 1 set
 
1) Patriz 1 set
2) nfsgame, Germany - 2 sets
3) baswamin, India - 3 sets (1 set each for baswamin, Samuel Jayaraj, Manniraj, common shipping to baswamin)
4)Thimios-2 sets(4 pcb)
5)ravid, India - 3 sets
6) BDL, Romania - 1 set
7) Luke - 2 sets
8) vvs07 - 2 sets
9) nounouchet - 1 set
10) PJN, US - 1 set
11) torb, Finland - 1 set
12) theoracle, New Zealand - 1 set
13) JJGB, Finland - 1 set