USSA-5 PCB GB

[pinnocchio]

Hey Fab,

Please make sure you keep me a set!

Thanks
Do

 

[Oracle1]

Pcbs...

I also want a set ,(2 pcb ) to have a companion with my DCG3...

 

[Oracle1]

Fab, your inbox is full, i cannot send you a pm


Nestor

 

[fab]

My inbox is now ok.
Fab

 

[Oracle1]

Transformer question

About the transformer. I have this heatsink for each channel. Dimension 20X21.5X11.5 cm and weighs 6,3 kgr. (6.300gr). Safe choice is 2X18V, but can i choose something bigger ?


Thank you

 

[meanman1964]

Fab , can you give me info of the USSA 5.1 like schematic etc. ?

 

[manniraj]

Fab , can you give me info of the USSA 5.1 like schematic etc. ?

Here you go - USSA-5 PCB GB

 

[meanman1964]

Thanks!

 

[fab]

About the transformer. I have this heatsink for each channel. Dimension 20X21.5X11.5 cm and weighs 6,3 kgr. (6.300gr). Safe choice is 2X18V, but can i choose something bigger ?


Thank you

Hi Oracle1
I will suggest you stick with 2x18vac or use 2x 20vac max with your actual heatsinks if you want class A at 25Wrms into 8 ohms. Otherwise you will have turn down the bias current thus will reduce class A power. However you would have higher power in class AB mode. If you have 4 ohms speakers, to optimize class A you need more bias current so a reduced PSU voltage for same heatsink size.

Fab

 

[Oracle1]

Hallo Fab,
i have ordered all the components for the 5.1 (except the transformer). I will use the SLB PSU one for each channel.


So i am doing the one think that i hate most :
Patience !!!!

 

[fab]

Hello Oracle1

Good choice for the 5.1 version with no obsolete parts.

If you use the SLB please take into consideration that you will have probably 3vdc or so of voltage drop to the amp. if so you need about 2vac more (ex: 18 to 20) for the same desired voltage at the amp.
Unfortunately I was not able to ship your USSA5 pcb last week because of postal office reduced hours during confinement along with extended amount of work.... I have the envelope ready to ship since one week, so I am sorry. I will ensure to find a small window of time this week.

Same thing for the USSA5 pcbs of Nfsgame.

Fab

 

[fab]

Hello Oracle1
I forgot to consider that the SLB may have an ideal rectifier bridge. In this case you will get about 2vdc more. Thus I am not sure of the end voltage after voltage drop in transistors...you ate better asking peoples who have used the SLB because I have not.
Fab

 

[fab]

Pcbs shipped today for Oracle1 and Nfsgame.
Fab

 

[Oracle1]

BC quest ...

The journey for the correct BC's begins

 

[manniraj]

But on the USSA-5 amp the BC series transistors not required to be matched.

 

[nfsgame]

But it doesn't hurt to do so...

 

[Oracle1]

Exactly

 

[manniraj]

Oh yeah please go ahead, I just went as per the manual which I think says check the hFe value and use the highest on some position which I do not remember exactly

Thanks

 

[fab]

Oracle1
You do not have enough BCs....

Manual section 8.5.2.1:

Place higher HFE transistors in Q1 and Q2 position;
Match Q1 with Q2 (<= 30%)
Match Q3 with Q4 (<=50%);

Feel free to do better match but the match is optional anyway...


Fab

 

[Oracle1]

Bc's

Thanks Fab,
but the optional way is my way.
I have them, so i said why not? With the lockdown in my country i had plenty of time.