Samba : upload file fast but download file slow

Anyone can help me ?
I use my PC ( Linux ) act as File Server ( Samba )
But i have problem.

When i upload files to server via explorer . It's ok ( speed / fast ).
But when i download files from server to PC via explorer . It's not
ok ... It's very slow ....

Anyone have experience likte this. ?
How can i solve this problem ?
Anyone can guide me ?


Thank you very much
Pratchaya