I will be using this preamp to feed the power amp section of a Harman Kardon hk990
Danoroo, hate to be the bearer of bad news but looking at this your HK990 intergrated doesn't have poweramp inputs, just preamp outputs.
http://www.studio-22.com/harman-kardon/images/harman-kardon-hk990-back.jpg
Cheers George