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Author Topic: NPNG preamp  (Read 15635 times)

mixwell

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Re: NPNG preamp
« Reply #15 on: July 27, 2010, 12:35:41 pm »

Disclaimer - Adam sells NPNG preamps - and talks to Karl daily.  

In efforts to add information to this thread - which I hope the moderators will not frown upon given my relationship with Karl and his product - but here are the words from Karl himself about the QMP-4B that was recently up for sale on E-bay.

To whom it may concern. The QMP-4B for sale on E-Bay is in fact very close to the same circuit(s) as what is being produced today. There are differences in the way the output transformers are interfaced with the line amps. There are different devices used in the line amps themselves (but the circuit is the same). The output transformers are NOT Jensen but rather Reichenbach.  Which at the time, were being manufactured by a third party company (NOT Cinemag).  The reason I stopped producing the QMP-4Bs was due to a stability issue which I found out years later was the result of inconsistent manufacture of the output transformers. The QMP-4Bs (all 12) were produced in 1996. I have rebuilt and updated several 4s and 4Bs. The main problems associated with the units today are: They need a full retrofitting of the electrolytic capacitors, the output driver transistors should be updated, the isolation resistors should be removed and replaced with ferrite beads. And all the Molex connectors should be removed and point to point wiring should be employed. And I recommend loosing the insert points (it will also eliminate a stage of coupling capacitors). If all this is done you will have a unit that will sonically approach the sound of the 4NWs.  Another “issue” with the 4Bs is the all steel nickel plated chassis. Works great for fixed installations but put it in a road case and bounce it down the road….It will bend the rack face of the unit at the ears (the pre weighs at least 20 lbs).
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