KR-9600 DC Offset
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Sorry Bob, you're wrong. Lots of offset indicate an unbalanced input stage (usually) and lots more distortion products than should actually exist. Not to mention popping in the speakers on power-up and power-down. On many speakers with your theoretical 1/2 a volt the resulting 'thump!' would be quite a jarring event, not to mention the added distortion from cone displacement. Call me silly all you like, but you'll have to include the vast majority of amplifier designers when we say that offset should be as close to 0.000VDC as possible and any effort to get it there is not wasted at all.
RE: The KR-9600. Are his speakers in danger? Nope. Is the amp in danger? Nope. Are things working optimally? Nope.
The 9600 has no offset adjust (or bias adjust, for that matter) as the OP discovered. Curing offset issues on this one require the replacement of two transistors on each amp board (Qe1 & Qe2) with new high-gain matched pairs.
RE: The KR-9600. Are his speakers in danger? Nope. Is the amp in danger? Nope. Are things working optimally? Nope.
The 9600 has no offset adjust (or bias adjust, for that matter) as the OP discovered. Curing offset issues on this one require the replacement of two transistors on each amp board (Qe1 & Qe2) with new high-gain matched pairs.
Last edited:
Bigears
Manager of my own day
It's nice to know that my speakers are not in harms way with the un-optimum offset reading......the sound is still wonderfully warm and open.
I'd also love to hear that there are new output transistors of one sort or another available to fit the KR-9600
I've been through it a time or two with the KR-9600. There are no new "output" transistors for the KR-9600. The output stage uses an amp module that is long out of production. What EW suggests is a matched pair of driver transistors to address the DC offset issue, which IMHO, is the "warm" sound attributed to your receiver. That distortion from the excessive DC severely degrades its sound and adds significant upper frequency distortion and sloppy bass.
My experience with the KR-9600 is that eventually you will find that one day soon you will power it on and it will not output to the speakers because the protection circuit will not allow the speaker relay to close. At that point...you will have no choice but to address the DC issues.
This thread started by EW has opened many eyes to the issue. Suggested reading...
http://audiokarma.org/forums/showthread.php?t=5634
Yes, Bigears.
EchoWars' thread actually alerted me to DC offset readings before I measured this KR-9600 at 160 millivolts....my 9090db measured .003/.004 leading me to believe the 9600 was leaking lethal doses of DC,turning out to be not optimum but definately not lethal to equipment.
The sound produced by the KR-9600 is very similar to the Sansui 9090db, warm and open. Neither tubby nor too bright, just right vintage amplifier-wise
EchoWars' thread actually alerted me to DC offset readings before I measured this KR-9600 at 160 millivolts....my 9090db measured .003/.004 leading me to believe the 9600 was leaking lethal doses of DC,turning out to be not optimum but definately not lethal to equipment.
The sound produced by the KR-9600 is very similar to the Sansui 9090db, warm and open. Neither tubby nor too bright, just right vintage amplifier-wise
The 9600 has offset adjust (or bias adjust, for that matter) as the OP discovered. Curing offset issues on this one require the replacement of two transistors on each amp board (Qe1 & Qe2) with new high-gain matched pairs.[/QUOTE]
Pardon my ignorance, are you saying there are new replacement alternatives(" new high gain matched pairs") for the original output modules?..
Can you please tell me where to purchase them? Thanks!
Pardon my ignorance, are you saying there are new replacement alternatives(" new high gain matched pairs") for the original output modules?..
Can you please tell me where to purchase them? Thanks!
My statement should have read "The 9600 has no offset adjust (or bias adjust, for that matter)". Edited in my previous post now.
The output transistors are NOT responsible for offset. That is handled by feedback to the input (first stage) of the amp, where there are a pair of NPN small-signal transistors performing these duties. I even gave you the component designations on the PC board (Qe1 & Qe2). If you don't have the manual, go get it.
http://www.stereomanuals.com/
I usually use matched pairs of Zetex ZTX694B transistors on the 9600, but because Kenwood has the holes lined up in a row and the original transistors are BCE and the Zetex are CBE, they require a bit of thought and careful double-checking to install. Not really something a rookie ought to tackle.
The output transistors are NOT responsible for offset. That is handled by feedback to the input (first stage) of the amp, where there are a pair of NPN small-signal transistors performing these duties. I even gave you the component designations on the PC board (Qe1 & Qe2). If you don't have the manual, go get it.
http://www.stereomanuals.com/
I usually use matched pairs of Zetex ZTX694B transistors on the 9600, but because Kenwood has the holes lined up in a row and the original transistors are BCE and the Zetex are CBE, they require a bit of thought and careful double-checking to install. Not really something a rookie ought to tackle.