Harman/Kardon Receiver


Sometime ago I acquired for $75.00 a Harman/Kardon 430 receiver in exellent condition (all original) for a small bedroom system. After having it serviced, I have recently begun to use it, and I am astonished at how musical it sounds.  Associated equipment include Snell J IV speakers and a Cary 308-T cd player, interconnects are by The Cord Company and speaker cable is by NAIM.  The sound is so musical and satisfying that I can listen to it all day without any listener fatigue at all.  My question is if some of you experts on receivers could tell me why it sounds so good? I have no information at all about this receiver and would appreciate any insights the Audiogon family could provide.
For what it is worth, in the past I heard a Harman/Kardon 730 receiver and did not find it nearly as involving musically.
Thanks to all in advance and cheers.
Avondale
fuenteclara
i'm also a big fan of the hk x30 series and still own a 730 and 330, having also owned the 930 and 430 at various points. i've read that unlike everyone else, hk used very little negative feedback in their designs, which resulted in less interface and transient interface distortion (whatever those may be), which are supposed to much more audible than THD. i'm not sure about the tech stuff, but to my ears the hk always sounded more lifelike than the sansui, pioneer etc. of the same era.

Here's a picture showing the output transistors for the 430.

http://img.usaudiomart.com/uploads/large/553442-harman_kardon_430_twin_receiver.jpg

IMHO, that is one reason for the quality sound. I have had experience with many vintage units, and the ones using this type of output transistor always sound very good. BTW, same type of output transistor as the NAD 3020.


Thanks to all for you kind responses.  I am going to try to obtain an Owner's Manual for the unit. 
If I'm not mistaken, the 430 was part of their lineup that used separate power transformers for each channel. So its a dual-mono design in a single chassis. That is a good portion of why it does what it does.