In the past week I accidentally figured out a way to cancel nearly all noise from my line/mic amps. Using a pair of rectifier tubes wired up in an unconventional manner and combined with a pair of neon regulator tubes I was able to build an ultra low noise regulated tube power supply, which exceeds the performance of any audio gear in my studio racks. The new power supply combined with how the preamp tubes are wired up cancels out all of the heater filament hum (which was never more than subtle in the past) and also most noise that might be on the B+, which was in the past also very subtle. This means an overall reduction of about 6dB of noise. 6dB is very significant in this game of inches. I was considering going the more expensive route of solid state tube heaters, but that idea was thrown right out the window after testing the noiseless double rectifier double regulator power supply ("DRDR" - a Lightning Boy invention).
I have several projects on the bench, but today I'm starting work on a new version of the 1401 Stereo Mic Amp. I did some prototyping first and the new version will have a lot of really impressive things to offer. First off, some changes were made to the amplifier design that allowed me to coax 5 more dB of gain out of the amp. The only trade off is a slightly warmer sound. Win+Win! Also, a new feature is getting added to the preamp. Based on user feedback, there is now going to be a mic/line input switch on both channels. Another new feature is the treble control bypass, which is incorporated into the treble knob itself. A switch is built into the knob... turn it down all the way and then a little more until it clicks. Bypassing the treble control will allow for a couple more dB of gain and a gentle touch of brightness. Finally, it of course will incorporate the new LBA noiseless DRDR tube power supply.
New stats (based on prototype):
Noise Floor: -86dB
Gain: +45dB per channel or +47dB with treble bypassed.
Actual stats will be presented on the 1401 Preamp's product page after the completion of this first production version of Revision A.
About the Author
Mike Congilosi II, Owner/Designer/Electronics Engineer at Lightning Boy Audio and Owner/Audio Engineer/Music Producer at LBA Studios.