When I walked into N&L Oris’ room, I was intrigued by a banner which stated: “Break the tradition with multiple preamplifiers”. An accompanying diagram showed a source (CD player) connected to a preamp connected to a second preamp connected to a third preamp connected to a power amp. What kind of madness is this?
After a long discussion with the designer/inventor Jason Ngo from Penang, I found out that there was method in his madness.
If I am not wrong, a normal preamp has a certain amount of gain in stages to amplify the input voltage for output to the power amp.
What Jason has done is design external gain stages using tubes housed separately as low-gain preamps. The gain of his tube preamps ranges from 4X to 7.5X. He said his designs use direct heated tubes and no feedback. Tubes with their inherent harmonics will result in the effects that he is designing for and as for solid-state gain stages he has not tried them but feels the effects may not be optimal.
The output voltages of his preamps range from 3.8 V RMS to 7.5 V RMS. So his method is to connect one preamp to another to add up the output voltage to the correct amount for the power amp.
So does it work? He played a CD with a recording of a street scene and the sounds seemed to be coming from out of the speaker cabinets from somewhere to my left and right and I had to check the rear wall to see if there were any speakers set up there. A motorcycle sounded so realistic that when the biker rode off, he seemed to go around my shoulder. When he played a recording of thunder, the sound of the thunder seemed to roll towards my shoulders. The effect was a pretty weird sensurround kind of sensation.
Why and how using a chain of preamps can result in a sensurround effect is a mystery to me. Jason said that the effect will be heard only if the recording was done with an omni mike. If it is a normal studio album, his method will result in more depth and layering.
He has also designed a Class A hybrid power amp using 8 MOSFETS per channel.
For more details, you can call him at 012-3245521 or 013-2791219.
