@[USER=130048]Luckyadnan[/USER] & [USER=40807]pasarski[/USER]
Which tube do you have this time in your microphone?...
How much voltage (value) do you have at this time at your P.S.U. as HT Vb and how much voltage (value) do you have at this time at the pin 1 (Anode) of your tube?...
Are you sure that you properly connect the 200 MΩ resistor(s) comp. from pin 2 (Grid) to Ground?...
Do you have a certificated electronic engineer who can doing the soldering job for you and you can assume that he knows electronics, that he knows to follow properly the schematics and that he knows the dangers of working with high voltages you can change the B+ and see what it does to the sound?...
As I wrote to you before the «30MΩ to 200 MΩ Mod.» it is NOT the Premiere Mod. that you have to do, as changing the grid-leak resistor value you gain more extending bass response, but you also gain more Gain aka your microphone will sound more “Modern” or harsh…
This mod. comes as a side-change if you go from the 6072 – 12AY7 tube (μ Factor = 40) to the ECC82 – 12AU7 tube (μ Factor = 18) to get back up some of the gain that you lose by the change of the μ Factor of the tubes…
So the Premiere Mod. in any time is to choose firstly the “proper tube” that you like to work with it, then to properly re-biasing this tube with the proper Anode Resistor (RL) value to the proper Cathode Resistor (CR) value and the proper Cathode Capacitor value and then to mod. the Grid-leak Resistor if you think that you need it so…
Here are 2 F.R. pictures of the same RK-12 Capsule in 2 different 251 clone microphones…
The first one F.R. picture of the same RK-12 Capsule comes from a properly biasing 251 clone by a modified Apex microphone by Brian Fox of Fox Audio Research…
The 12+ and 251+ PE
https://foxaudioresearch.ca/CT12.htm
The second one F.R. picture of the same RK-12 Capsule comes from your (original) Warm Audio 251 microphone…
https://warmaudio.com/wa-251
As you can see there is a significant difference in these 2 Frequency Responses of the same RK-12 Capsule in 2 different 251 clone microphones and by the “traditional” change from the 6072 – 12AY7 to ECC81 – 12AT7 or even better to ECC82 – 12AU7 tube you can go to this “extended flat down” Frequency Response without to go to the “extreme to extreme” E88CC – 6922 tube which doesn’t have the same basing of the 12A*7 “family” and you will have some reliability problems with this tube in the ultra-high-impedance world of condenser microphones and without to use any led – diode solution as Cathode biasing, otherwise I could easily wrote to you:
“Wire 2 diodes 0.6 Volts in series from the pin 3 (Cathode) of your 6072 – 12AY7 in reverse pollarisation to ground and you will have a “Fixed Bias” like biasing response....”
There are many tricks under the belt in electronics and physics or if you like even better:
“There many ways to climb a mountain” as the legendary Miyamoto Musashi wrote, but in any time you have to consider that:
“There is no a free dinner for all the things in your life, you gain some – you lose some…”
