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-   -   USSA-5 PCB GB (https://www.diyaudio.com/forums/group-buys/324459-ussa-5-pcb-gb.html)

fab 15th June 2018 05:19 AM

USSA-5 PCB GB
 
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.

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

************ note ************
This group buy was originally part of the following thread but specific posts were moved by an administrator of the forum. 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.

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 (20 to 50 for 8 ohms load at 100 Hz)
- 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

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 or USSA-5 and 5.1
- pcb almost compatible with USSA5B (reverse output transistors pin out)

See post # 346 for schematics of USSA5, USSA5.1 and USSA5B.
Differences between the USSA5 versions:
1) USSA5: using quad matched mosfet drivers now obsolete and harder to find. Exicon mosfet for output readily available.
2) USSA5.1: using non matched bjt drivers still in production. Also Exicon mosfet for output.
3) USSA5B: using non matched bjt drivers still in production. Using power bjt as output. This is the low cost version of USSA5 versions.


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.
- 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.
- the cost of several transistors ( mosfet drivers and/or Exicon mosfet) is relatively expensive.

Group buy conditions:
1) partial manual including BOM is provided after some communications by PM with me showing your real interest in building the amp in a timely manner so you are not a pcb collector- from my estimation roughly only 10% of pcb sold are really used for a real build within one year. Also to verify if this amp is really for you so you do not lose your time and money. Group buy is too much work to lose my time sending pcb with custom papers preparation....
2) once agreed by PM, your name is added on the official list and I send you the partial Manual at your email.
3) you provide your address so I can compute the shipment cost , then total cost
4) you pay me with PayPal as a gift at the address I give you
5) you provide a proof of either Mosfet drivers (or bjt drivers) and Mosfet output (or power bjt ) to show your good faith to build the amp since they are very costly.
6) once step 5 is done I provide the complete manual including adjustment instructions.
7) once all payments received, I order the pcb form manufacturer.
8) I ship the pcb to your provided address.


Fab

Samuel Jayaraj 15th June 2018 05:56 AM

1) Samuel Jayaraj, India - 1 set

jacques antoine 15th June 2018 07:46 AM

1) Samuel Jayaraj, India - 1 set
2) Jacques Antoine, France - 1 set

patriz 15th June 2018 08:02 AM

1) Samuel Jayaraj, India - 1 set
2) Jacques Antoine, France - 1 set[
3) Patriz 1 set

nfsgame 15th June 2018 10:20 AM

1) Samuel Jayaraj, India - 1 set
2) Jacques Antoine, France - 1 set[
3) Patriz 1 set
4) nfsgame, Germany - 2 sets

baswamin 15th June 2018 11:15 AM

1) Samuel Jayaraj, India - 1 set
2) Jacques Antoine, France - 1 set[
3) Patriz 1 set
4) nfsgame, Germany - 2 sets
5) baswamin, India - 1 set

thimios 15th June 2018 11:45 AM

1) Samuel Jayaraj, India - 1 set
2) Jacques Antoine, France - 1 set[
3) Patriz 1 set
4) nfsgame, Germany - 2 sets
5) baswamin, India - 1 set
6)Thimios-2 sets(4 pcb)

ravid 15th June 2018 01:31 PM

1) Samuel Jayaraj, India - 1 set
2) Jacques Antoine, France - 1 set[
3) Patriz 1 set
4) nfsgame, Germany - 2 sets
5) baswamin, India - 1 set
6)Thimios-2 sets(4 pcb)
7)ravid, India - 3 sets

baswamin 15th June 2018 02:26 PM

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

BDL 15th June 2018 04:20 PM

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
8) BDL, Romania - 1 set


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