TSSA - The Simplest Symmetrical Amplifier

[Joachim Gerhard]

Workarounds are my speciality

 

[Joachim Gerhard]

I will use BF246A to supply the Led.

 

[Lazy Cat]

I will use BF246A to supply the Led.

OK this one is from 30-80 mA, so may be that 2 k trimmer could not reach enough Ugs to go down to 2 mA. Than add serial resistor to set Id=2 mA

Ideally would be LED current equal Sziklai current, that means both CCS BJTs same current, same Ube characteristic, electricaly plus thermally (coupled together) makes CCS very stable.

P.S. BF246A Uds should be around 10 V for good regulation and AC suppression, if Rgs drops too much to get 2 mA, than lower 12 k to 10 k or less just to maintain Uds=10 Vmin

 

[Lazy Cat]

Workarounds are my speciality

Jack of all trades, master ... joke

Yes I see you're very capable and most handy, congratulations

 

[Joachim Gerhard]

My nickname is Joke by the way. Only my oldest friends know that.

 

[Joachim Gerhard]

It works without problem. 1,3mA in both channels right away.
Thats it for today.
Was fun, good night.

 

[Lazy Cat]

My nickname is Joke by the way. Only my oldest friends know that.

Thanks, the name's Lucky

Good night

 

[Joachim Gerhard]

Most components are on board. Some more wiring has to be done.

 

[Lazy Cat]

Most components are on board. Some more wiring has to be done.

Hi Gerhard

Three amp stages only (input, output, CCS) in TSSA but all black of small signal transistors on your PCBs. 6800 uF feedback elcos

Niceeee

 

[Joachim Gerhard]

Yes, i had them from another project, does not hurt.

 

[sonnya]

Good progress Joachim.

When i am done the gerber files, the BOM and the Pick and place data.

The board is made with SMT for the frontend.

I can produce the board with all SMT on them, but with above files i will upload everyone else can also.

Regarding the mosfet drivers. Is there an reliable source for 2SK216 and 2SJ79?? Or should wi install IRF instead???

 

[Lazy Cat]

Hi Sonnya

SMT parts are perfect choice here, since there are a lot small signal BJTs connected between themselves only. Try to make as compact PCB as possible.

There are few suppliers that can provide 2SJ79/2SK216. These are lateral mosfets (transconductance falls with higher temperature) so no problem with thermal runaway, also have integrated gate protection zeners - perfect drivers. Try to find these not IRFs.

I cannot wait to see your PCB

 

[Joachim Gerhard]

I can get them still although i think Renaisas stopped production of this transistors. Exicon makes laterals but not TO220. One solution is to use big ones for the drivers too.

 

[Lazy Cat]

Count me in for 2SJ79/2SK216, if you still can get them.

 

[Joachim Gerhard]

Sure, i use 2SJ77 and 2SK214. They can stand enough voltage. I really whould not like to go to hexfets. I think laterals sound better, especially when you go down the drain.
They are excellent constant current souces.

 

[Joachim Gerhard]

away goes trouble down the drain
LAST NIGHT A D.J. SAVED MY LIFE Lyrics INDEEP

 

[sonnya]

Sure, i use 2SJ77 and 2SK214. They can stand enough voltage. I really whould not like to go to hexfets. I think laterals sound better, especially when you go down the drain.
They are excellent constant current souces.

Last time the bag size was 500pcs and there also is a minimum buy.

 

[Joachim Gerhard]

For this few amps we will build i have enough, but maybe.....

 

[sonnya]

Second solution:

Raise frontend current 5x
Gateresistor reduced 5x
Maybe change the feedback network by reducing it 2x.

5mA in the front stage but still only 1mA in the input pair.

This Way the drive impedance for the mosfet is 5x lower. I Think this Will improve the thd performance simelar without the mosfet drivers.

 

[Joachim Gerhard]

Sure, that will work too. Nevertheless i build the version with driver first and then we can compare.