Just from searching (since I have the pre-amp and amp), not from experience)
https://audioproz.com/AP.php?Article=64https://audioproz.com/AP.php?Article=95
https://quirkaudio.com/?page_id=895https://quirkaudio.com/?page_id=952https://quirkaudio.com/?p=936
https://audioproz.com/AP.php?Article=64https://audioproz.com/AP.php?Article=95
https://quirkaudio.com/?page_id=895https://quirkaudio.com/?page_id=952https://quirkaudio.com/?p=936