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USSA-5 PCB GB

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#742
I already have built and using USSA-5 but always intended to build USSA-3 using Sanken BJTs and Exicon combos as getting matched 2SK2013/313 is now becoming too too difficult 🙂

Guyome 1 paire
baggerbole 2 paire
detdur 1 paire
G600 1 paire
Norgaard 2 paires
rebone 2 pairs
manniraj 1 pair (USSA-3) - @fab not sure if this group buy includes the version 3.x also
 
#752
Good finding Nikodemuzz 👍 for the FQP3N30, Farnell has also FQP3P20 so mosfet driver issue is resolved (for now…).

For darlington bjt, the complementary general purpose amplifier transistors TIP111 and TIP116 (Mouser has many) appear good candidate to replace the Sanken. Sanken HFE slope Curve is more linear high high current than the TIP one but as a driver in the USSA amplifier the current never will exceed more than 200ma (even dynamically) where the HFE slope is still straight for both Sanken and TIP.
I have about 6 pairs of TIP111/116 that I can eventually test in one of my board but no worry it will work. Worst case situation is that there may be a a change in base resistors value - if any- for optimization.

if you are worry about the sound difference, here my observations based on all my USSA-3.x and USSA-5.x variations. The most contributing factor in this same topology is by order of importance:
1) output transistors ( bjt or mosfet, type of mosfet)
2) input stage transistor (bjt CFP, jfet )
3) drivers (darlington bjt, mosfet, mosfet type)

Items 1 and 2 have similar effect but number 3 has less impact (and especially if you change transistors part number of the same type : bjt or mosfet) except that bjt driver allows a lower maximum amplifier damping factor compared to mosfet driver.
if you change 2 out of 3 above items than it can make an important difference in sound. Not better or worse just different but you may prefer one more than the other….

if you compare 2 USSA variations with the 3 items being different than there is a major impact in sound. I recommend doing so if you are willing to build 2 variations so you choose the one you like the best in the end or you swap them from time to time like I do if you like both 😉

Please reconfirm your pcb buy in. Already with this number of pcbs, price is going down….🙂

Fab
 
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#755
I found J313 and K2013 (from Prakit), and I know two others on the list have also managed to find these.

Perfectly fine for me that the PCB's are green, it is the easiest color to spot problems on - and that is the reason most PCB's are produced in green .
I prefer that the PCB's are not gold immersion, while it looks nice it's really only great if you need long storage times - and despite the rather large line-up of projects, I do not plan on that 😊

Thanks a lot Fab!

Guyome 2 pairs - confirmed
baggerbole 2 paire
detdur 2 paire
G600 1 paire
Norgaard 2 pairs - confirmed
rebone 2 pairs
manniraj 1 pair (USSA-3)
Nikodemuzz 1 pair
 
#757
Hi Norgaard
thanks to let me know that some of you have found the good mosfet audio pair from original USSA-5.0. This is excellent.

as for the others, if not already done, please re-confirm your buy in before I order the PCBs….

I will try to post a table using my personal very subjective observations between each variations that I have built but have in mind that it is in my own audio system….

Fab
 
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