Bottlehead Forum

Bottlehead Kits => BeePre => Topic started by: Thermioniclife on February 28, 2021, 10:22:48 AM

Title: PB BeePre 1 to BeePre 2 output scheme
Post by: Thermioniclife on February 28, 2021, 10:22:48 AM

Hey PB, second question of the day. Do you see any problems with wiring a BeePre 1 in the manor of the BeePre 2 as far as having the grid run wide open and attenuating the plate. I would like to try it to see if it lessens the microphony. After looking at the schematic of my BP1 it seems like it should be possible, but I'm no EE. Do you sense danger? I think the c4s might not be happy on second thought.
Thanks,
Lee

Title: Re: PB BeePre 1 to BeePre 2 output scheme
Post by: Paul Birkeland on February 28, 2021, 12:29:57 PM

The BeePre 1 runs lower grid bias voltage than the BeePre 2, so I would not expect this to work well.  In order to get this to work satisfactorily, we had to abandon the filament bias and go with a more conventional bias scheme and less overall plate current. 

Title: Re: PB BeePre 1 to BeePre 2 output scheme
Post by: Thermioniclife on February 28, 2021, 02:04:09 PM

Thanks PB. I had an underlying sense of misunderstanding as this is a trait that has always followed me throughout life. Just when I think i am right I realize I'm wrong. Love the BP1 sonically and with o-rings and flask weights it is less sensitive but it still has microphony between tracks or when pausing tracks. I feel that the sound waves striking the tube envelope are causing this. I have tried moving the BP to different locations in my living room to try to find a null area in the room to no avail. Using 6a3's greatly improved this matter but they are lacking compared to the 300b Thanks again PB.
Regards,
Lee