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Grounding issues

Posted by bpur (M) on March 11, 2007 at 22:59:28

In Reply to: Re: Karna vs Amity posted by KurtP on March 11, 2007 at 21:40:23:

Most of the horror facing Gary Pimm, while constructing the Karna's, came from having two chassis, with power mostly on one and signal and the tubes on the other. There are so many tubes and transformers that even one gigantic box would not have held them all. The entire ground scheme was made from Nylon selvage covered Litz wire and if you copy nothing else in your instrumentation grounding scheme, copy that.

Gianluca is absolutely correct about the interstage being the key to the amps performance. These amps are just so revealing that even the deservedly well thought of original interstage's, were found to be wanting. Took me several iterations before learning how to balance low permeability gain and this unusual sensitivity to the internal coil capacitance's.

The current units in Lynn's amps, being level three on our performance chart are ruler flat to 20k and then climb to +6 dB at 35 k. Too many turns within the same winding space. So, it will take a larger unit to flatten the highs while keeping the permeability increase to a minimum and so controlling the overall distortion, but specifically where the core becomes permeable, 1 kHz and lower. Level one interstage's do not have this problem with skewed performance, but they are not as revealing either.

I agree with most folks here that a triode connected PP with perhaps a SE driver stage to a voltage splitting transformer coupled interstage will be good enough to soothe the need for music and dynamics from what are some of the best speakers available.

My personal amps are input splitter transformer to PP parallel 7119,s to an 1.414 to 1 PP step down interstage to eight EL 34's in PP paralell to a 1560 z ohm output we originally supplied to Cary for their 6 pac amps. Very noble, powerful, amazingly detailed sound. The only passive components are the grid blockers.

So, don't just look at the DHT amps, as other tubes and topologies are actually equaling that delightful performance and providing power to boot.

Bud

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