I'd use a bipolar DC supply and connect their common to AC/RF ground. That way, you take care of common-mode noise, not just differential mode.
yeah, that makes sense. So, can you explain why DC heater doesn't need to be biased above ground, or would they still need to be?
Also, would a 2A slo-blo fuse be suitable?
Thanks again!
Also, would a 2A slo-blo fuse be suitable?
Thanks again!
It does need to be biased above ground to keep Vgk in bounds. It just needs to be at AC/RF ground, not DC ground.
In my case (I haven't used boards yet), bypassed to signal ground through the capacitor on the lower side of the divider and to RF ground by the two ceramic caps to the chassis.
ok, I understand now what you mean 🙂
In this case, perhaps we should do something like this on the board. In the middle of the input transformers, create an earth connection by using a really large ring on the PCB that could accommodate a #6 screw or something. This could be connected to the case via a standoff. Then, instead of routing the RF ground to the signal ground, as Jack did on the board (the center of the ceramic caps under the 6SN7, as well as the shield(s) on the input transformers), these would route back to this connection. Also, the XLR shields would connect here conceivably. Then add the two diodes and capacitor per the schematic, linking this node to the signal ground.
Essentially, the shield of the transformer will become a star ground point for these connections bypassed to signal ground on the PCB itself.
In this case, perhaps we should do something like this on the board. In the middle of the input transformers, create an earth connection by using a really large ring on the PCB that could accommodate a #6 screw or something. This could be connected to the case via a standoff. Then, instead of routing the RF ground to the signal ground, as Jack did on the board (the center of the ceramic caps under the 6SN7, as well as the shield(s) on the input transformers), these would route back to this connection. Also, the XLR shields would connect here conceivably. Then add the two diodes and capacitor per the schematic, linking this node to the signal ground.
Essentially, the shield of the transformer will become a star ground point for these connections bypassed to signal ground on the PCB itself.
I have variously connected the internal shield of the 6922 to the heater CT, to ground and let it float -- doesn't seem to matter.
I'm writing as fast as I can!😀 14 MOSFETs is an intriguing hint...
Just back from one trip, lawyers to be satisfied, then getting ready to leave again this weekend. All my music listening has been airport Muzak and Jerry Garcia bootlegs in the car.
Just back from one trip, lawyers to be satisfied, then getting ready to leave again this weekend. All my music listening has been airport Muzak and Jerry Garcia bootlegs in the car.
I changed the trace orientation for the outputs -- to conform with XLR Protocol:
An externally hosted image should be here but it was not working when we last tested it.
Re: Regulator
I still have a bunch of LastPas Regulator boards which I have used in the past -- search on DIYADUIO -- it's a very quiet regulator, but this first generation of lead-free zener diodes which are all you can get seem prone to failure (and when zeners fail, they fail as a short.)
I have a Maida which works OK, but Giame's MOSFET version seems to be more stable vs temperature.
Anyone who asks is free to get a drawing of the temperature compensated Maida regulator.
BDP said:
I still have a bunch of LastPas Regulator boards which I have used in the past -- search on DIYADUIO -- it's a very quiet regulator, but this first generation of lead-free zener diodes which are all you can get seem prone to failure (and when zeners fail, they fail as a short.)
I have a Maida which works OK, but Giame's MOSFET version seems to be more stable vs temperature.
Anyone who asks is free to get a drawing of the temperature compensated Maida regulator.
jackinnj [/i]to conform with XLR Protocol[/QUOTE] Looks more like the TRS protocol to me :) [QUOTE][i]Originally posted by jackinnj said:
If you send me the Gerbers, I'll have one made up.
schematic
I dont know where you guys found the schematic . I searched the http://www.audioxpress.com but could not find it
I dont know where you guys found the schematic . I searched the http://www.audioxpress.com but could not find it
Here's a suggestion for raising the DC potential on the filaments:
In real life, it isn't working as well as the simulation.
An externally hosted image should be here but it was not working when we last tested it.
In real life, it isn't working as well as the simulation.