CK12 Capsule Questions (for new DIY build & mod of WA251)

[Accelerator]

@Luckyadnan​

hi greeting from indonesia, ahh so i just only need to change the “yellow” electroltic capacitor? i mean the ridiculous 30ΜΩ Grid-leak Resistor is a “yellow” tantalum resistor? and just need to be replace with 200MΩ “yellow” tantalum resistor?

No, it is not that “easy”…

This “yellow” capacitor, which probable it is an electrolytic tantalum, probable it is the Cathode Bypass Capacitor…

You need firstly to decide before any replace:

Which tube you would like to use, so by choosing the tube that you like to use with the 100KΩ as RL (Anode Resistor) by the Ohm’s Low you will need to replace the Cathode Resistor to the spotted values that I wrote above…

Then only if you even like / need a more “bass heavy” operation of your microphone, you can granularly increase the Grid-leak Resistor from 30MΩ to 200MΩ which is the most “typical” AKG value…

(AKG C-12 VR, AKG-Siemens SM-203, AKG C-24, AKG Perception 820)

In simple words take as graded the tailor’s advice:

“Measure three times, cut once” and “One step at the time…”

 

[Luckyadnan]

@Luckyadnan​

No, it is not that “easy”…

This “yellow” capacitor, which probable it is an electrolytic tantalum, probable it is the Cathode Bypass Capacitor…

You need firstly to decide before any replace:

Which tube you would like to use, so by choosing the tube that you like to use with the 100KΩ as RL (Anode Resistor) by the Ohm’s Low you will need to replace the Cathode Resistor to the spotted values that I wrote above…

Then only if you even like / need a more “bass heavy” operation of your microphone, you can granularly increase the Grid-leak Resistor from 30MΩ to 200MΩ which is the most “typical” AKG value…

(AKG C-12 VR, AKG-Siemens SM-203, AKG C-24, AKG Perception 820)

In simple words take as graded the tailor’s advice:

“Measure three times, cut once” and “One step at the time…”

thankyou so much, but how to increase the Grid Leak Resistor? and how to know that default is 30Mega Ohm?

first my goals is getting more bass from wa251, because i feel that the low end of the mic is missing…

and second of my goals is to make it work with 12au7 and got that “neumann-ique”, because i already have a trying GE 6072A and i feel that the mid is to rumble and to cloudy. i wanna try the 12au7.

anyway do u have any picture of your mod? or type of part that u use for this mod? i want to try copy that.

thankyou so much..

 

[pasarski]

thankyou so much, but how to increase the Grid Leak Resistor? and how to know that default is 30Mega Ohm?

first my goals is getting more bass from wa251, because i feel that the low end of the mic is missing…

and second of my goals is to make it work with 12au7 and got that “neumann-ique”, because i already have a trying GE 6072A and i feel that the mid is to rumble and to cloudy. i wanna try the 12au7.

anyway do u have any picture of your mod? or type of part that u use for this mod? i want to try copy that.

thankyou so much..

IMO the biggest problem with this mic is how the high impedance area (where the wires from the capsule go) is constructed. There's some effort to the right direction, but it all falls short with the relays soldered directly to the PCB. I would try to clean the high impedance area with isopropyl alcohol before changing any parts. Lack of bass could very well be cured by that, or not if the contamination resides under the transparent stuff that's been sprinkled on the board (that stuff could very be the problem itself). I'm planning to re-build the whole high z area on my mic at some point but am not very thrilled to do that because it will not be a easy and nice task.

 

[Luckyadnan]

IMO the biggest problem with this mic is how the high impedance area (where the wires from the capsule go) is constructed. There's some effort to the right direction, but it all falls short with the relays soldered directly to the PCB. I would try to clean the high impedance area with isopropyl alcohol before changing any parts. Lack of bass could very well be cured by that, or not if the contamination resides under the transparent stuff that's been sprinkled on the board (that stuff could very be the problem itself). I'm planning to re-build the whole high z area on my mic at some point but am not very thrilled to do that because it will not be a easy and nice task.

can u share the photo after u do that? i want to make a copy of that. because dont understand some electronical stuff. what i read here i try to google it. i mean like default “30M Ohm” resistor. i try to find the picture on google to find what it is than look at inside my microphone if there is a part like that or not. then after i understand what is the part that u guys talk about i replace it. okay i will try to clean that with isopropyl alcohol..

 

[mihi_fuchs]

here‘s soundsamples for the 797 cy039. Back in the days my 797 costumer support said that’s the most similar in sound.

https://groupdiy.com/threads/c12-clone-in-t-bone-sct800-donor-body.81198/#post-1143227

The body should be the same.

 

[pasarski]

can u share the photo after u do that? i want to make a copy of that. because dont understand some electronical stuff. what i read here i try to google it. i mean like default “30M Ohm” resistor. i try to find the picture on google to find what it is than look at inside my microphone if there is a part like that or not. then after i understand what is the part that u guys talk about i replace it. okay i will try to clean that with isopropyl alcohol..

I will if I do it. So yeah, clean the upper part of the board. Don't leave any residues. Be careful not to clean these, they don't like isopropyl alcohol.

 

[pasarski]

Also check that this Teflon post is properly installed. In mine it was not attached to the board and the metal pin made contact to the board. (The 30 megaohm resistor is lurking just under it in the picture. Though in my mic it maybe wasn't even a resistor )

 

[Luckyadnan]

@pasarski @Accelerator guys please i need to ask about the 30mΩ resistor that i need to replace with 200mΩ resistor.


i just want to make sure is that the resistor on my picture (code yellow, gold, purple, green, red) is what you guys mean 30mΩ grid leak resistor.
that i mark in the photo.

can i replace it with 2x 100Mega Ohm 1/4 5% resistor in series? (in the 2nd picture)

ill mod my psu for drop B+ to 120v after replacing this resistor if you said this is what you guys mean.

 

[Luckyadnan]

Also check that this Teflon post is properly installed. In mine it was not attached to the board and the metal pin made contact to the board. (The 30 megaohm resistor is lurking just under it in the picture. Though in my mic it maybe wasn't even a resistor )

what the teflon use for? i already clean my board with a 96% alcohol. i will try my mic this night.

 

[Khron]

guys please i need to ask about the 30mΩ resistor that i need to replace with 200mΩ resistor.

Just a small nitpick - in the tech world, small "m" is the suffix for "milli", as in 1/1000th of whatever we're talking about, so what you wrote there was 30 milliohms (0.03 ohm) / 200 milliohms (0.2 ohm). Capital "M" is the suffix for "mega", as in one million units.

can i replace it with 2x 100Mega Ohm 1/4 5% resistor in series? (in the 2nd picture)

That should be fine.

 

[pasarski]

@pasarski @Accelerator guys please i need to ask about the 30mΩ resistor that i need to replace with 200mΩ resistor.


i just want to make sure is that the resistor on my picture (code yellow, gold, purple, green, red) is what you guys mean 30mΩ grid leak resistor.
that i mark in the photo.

can i replace it with 2x 100Mega Ohm 1/4 5% resistor in series? (in the 2nd picture)

ill mod my psu for drop B+ to 120v after replacing this resistor if you said this is what you guys mean.

Yup, that's the one. While we're at it, can someone look at the colored code?

Seems like your resistor has the same weird color code than mine. It reads 25,7ohm as five band resistor. As 4-band leaving out the yellow band it reads 250M. It measures larger that 30M so I suspect it really is a 250M (if it is there's no point substituting it to 200M). I lost mine the so I can't try to measure it better.

 

[Luckyadnan]

Just a small nitpick - in the tech world, small "m" is the suffix for "milli", as in 1/1000th of whatever we're talking about, so what you wrote there was 30 milliohms (0.03 ohm) / 200 milliohms (0.2 ohm). Capital "M" is the suffix for "mega", as in one million units.



That should be fine.

is that gonna make the mic sound like elam 250/251 with that single resistor replaced with 2pcs 100M resistor in series?

 

[Khron]

is that gonna make the mic sound like elam 250/251 with that single resistor replaced with 2pcs 100M resistor in series?

A single resistor value does not a microphone sound make...

It'll give you more low-end, but that's all i can personally say.

 

[pasarski]

I agree with the above opinion and add that the low end extension will happen in very low frequencies, probably will not be very noticeable with sources like vocals, and that the original elam used an 30meg grid to ground. If you want to get close to the "elam sound" you have to source an good brass CK12 or a proper re-creation. This subject have been discussed here many times before.

 

[Luckyadnan]

A single resistor value does not a microphone sound make...

It'll give you more low-end, but that's all i can personally say.

but i just not sure if this resistor is 30M ohm that mr @Accelerator mean about.

I agree with the above opinion and add that the low end extension will happen in very low frequencies, probably will not be very noticeable with sources like vocals, and that the original elam used an 30meg grid to ground. If you want to get close to the "elam sound" you have to source an good brass CK12 or a proper re-creation. This subject have been discussed here many times before.

i have vocal recorded on rent studio using u87 > chandler > UAD Apollo
it has a good low end and smooth vocal recording

now i try to build my vocal chain using
wa251 (GE 6072A) > PSU > Presonus Tubepre v2 JJ 12Ax7 & OPA BB 4134 > Alctron MP73EQV2 > DBX 266 XS > Alctron CP540V2 > Audient ID14 MKII (using xlr to TRS) without gain level, because it doesnt have line input

but the result is low end is missing, i dont know why, event i boost with preamp eq to match the u87 result its feels different.

is that if i change that resistor to 200M OHM will make a significant result?

 

[kingkorg]

but i just not sure if this resistor is 30M ohm that mr @Accelerator mean about.


i have vocal recorded on rent studio using u87 > chandler > UAD Apollo
it has a good low end and smooth vocal recording

now i try to build my vocal chain using
wa251 (GE 6072A) > PSU > Presonus Tubepre v2 JJ 12Ax7 & OPA BB 4134 > Alctron MP73EQV2 > DBX 266 XS > Alctron CP540V2 > Audient ID14 MKII (using xlr to TRS) without gain level, because it doesnt have line input

but the result is low end is missing, i dont know why, event i boost with preamp eq to match the u87 result its feels different.

is that if i change that resistor to 200M OHM will make a significant result?

You're trying to make apple juice taste like pizza you ate a year ago by adding some origano. Go back to the drawing board, read, read, read, and then again read. No one can really answer what you are asking because it doesn't make sense.

My honest advice is to leave that microphone alone, and please do not try to modify the PSU there are high voltages there.

 

[Accelerator]

@Luckyadnan, @Khron, @pasarski

A little bit of talk-to-talk “just to put the record straight” about these mods that I suggested…

I never owned or brought any Warm Audio product, as I never owned or brought any Telefunken Elecroacoustik USA product, as I will never own or buy any product from any major Chin-o-Canadian-American-whatever the fukk “globalization” mass production companies, because as it is odiously they “fukk it up” by “Cutting Coners” any time that they try to copy on or to be said more clearly to steal on from the heritage and the tradition of historical European Microphone Companies like AKG, like Neumann, like Schoeps…

This will be as stupid to me as if I had bought any Japanese Sony, Nikon, Canon Digital cameras and wait from any of them afterwards, to take pictures as good as my photos that I take with my "Made in Germany" Leica SL3 digital camera, regardless of any lens I should use ...

But let’s go back to the AKG-Telefunken AG GmbH ELA-M 250 & to the ELA-M 251E microphones…

First thing first, we have to understand that the AKG-Telefunken AG GmbH ELA-M 250 & to the ELA-M 251E microphones were not the “All Around” microphones like the AKG C-12, AKG C-12 VR, AKG-Siemens SM-203, AKG C-24, AKG Perception 820…

If the ELA-M 250/251E were “All Around” microphones as any other AKG Microphones they will had the 200MΩ Grid-leak Resistor, not the 8MΩ (AKG-Telefunken AG GmbH ELA-M 250 with AC701K) or nether the 30MΩ (AKG-Telefunken AG GmbH ELA-M 251E with 6072 – 12AY7) …

But, as I wrote before, Siemens, the leading Co. of the Telefunken AG GmBH Trast (group of companies) holded a grange against Neumann, so Siemens forced the AKG to make the ELA-M 250 & 251E as Anti-Neumann U-47 & M-49 microphone(s)…

So, both of these microphones (the AKG-Telefunken AG GmbH ELA-M 250 & the AKG-Telefunken AG GmbH ELA-M 251E microphones…) had been designed and made especially to be as an “One trick pony, but a good one”…

They are especially well made nearly "magical" for female radio speakers, female singers – songwriters…

In other words they are the “Next Diva’s best microphone choice” as they are working pretty “magical” with the female voice register(s) of any wannabe Lara Fabian, Rihanna, Celine Dion, Christina Aguilera, Demi Lovato …

So yeah, if you want an “One trick pony” microphone for female radio speakers, female soprano singers only or for mandolin players, violinists or for drums overheads don’t change anything, because even the bright sound / tone anemic Warm Audio WA-251 it is good enough “go too” for that…

Save you money, save your time, save your energy for the next best microphone, whatever it is, a condenser U-47 type microphone for male voices, a ribbon microphone for brass instruments, a dynamic microphone for your guitar – bass speaker cabinets, for your drums set etc. etc. etc.

In other words: “You can pick up your new (microphone) G.A.S. poison”…

But tell me whatever happens if this situation does not exist…

Tell me whatever happens if you are not a female radio speaker?

Tell me whatever happens if you are not a wannabe next Diva female soprano singer?...

Tell me whatever happens if you are not a worldwide “hit record” sound engineer – record producer with sexy female singers to make their “catwalk” in your studio?...

Tell me whatever happens if you are not a mandolin player or a violinist, tell me whatever happens if you are not a drummer?...

Hell, tell me whatever happens if you are not a “castrato” tenor?...

Well, in all of these situations we will have to consider that any Cathode Biased ELA-M 250 / ELA-M 251E microphone has 4 main filters…

1. The Combination Between the capsule capacitance and the grid-leak resistor as a Low-Cut / High Pass Filter…

2. The Combination between Cathode Resistor and Cathode Bypass Capacitor as a Low-Cut / High Pass Filter……

3. The Treble Cut Snubbing Anode Bypass Capacitor as a High Cut to cut-off the highs…

4. The Combination Between the valve’s Ra with the capacitance of the coupling Capacitor and the impedance of the output transformer, which all of this combination determinate the F.R. slop…

So, let’s see some of “my” Mods…

1. ECC81 – 12AT7 valve @ 120 DC Volts Vb, 100KΩ Anode Resistor, 2.7KΩ Cathode Resistor, 22μF Cathode Bypass Capacitor …

Well, well, well, surprise – surprise – surprise…

This mod has been done firstly by the Swiss Boutique P2P Microphone Company BSA Microphones for their BSA ELAM 250 Microphone (Price: CHF 2,985.00 aka €3,250.00) …

After BSA Microphones this same mod. has been done by the Telefunken Electroacoustik USA for their Alchemy Series TF51 (Price: $1,995.00 aka 2.399 €)...

How do I know it?...

I know it because I had read this Article – Review by Brian Fox of Fox Audio Research:

The Telefunken AR-51

Review by Fox Audio Research (part 1)

&

The Telefunken AR-51

Review by Fox Audio Research, Cont'd... (part 2)

So, by simply changing only the valve in the Warm Audio WA-251 (888 €) to the ECC81 / 12AT7 Gold Balanced JJ (€34,33) plus the changing of the Cathode Resistor to 2,7k RES-0,6W (€0,19) I can have an economical “upgrade” over € 1.511 to my pocket and off curse a sonically “upgrade” over the Alchemy Series TF51 (Price: $1,995.00 aka 2.399 € )

Now, let’s add the 200M, 2W (€0,21) grid-leak resistor in to the game…

Immediately everybody could tell that this Grid-leak Resistor value plus the Cathode Resistor – Cathode Bypass Capacitor value combination “look like” the AKG C-24 Stereo Microphone (EUR 31,570.39) with the only difference will be, that now we use the proper tube…

Well, I think that I can “take” these mods. to the Warm Audio WA-251 as an option and spend the rest of these € 30.688 EUR to hookers and drugs…

 

[pasarski]

but i just not sure if this resistor is 30M ohm that mr @Accelerator mean about.


i have vocal recorded on rent studio using u87 > chandler > UAD Apollo
it has a good low end and smooth vocal recording

now i try to build my vocal chain using
wa251 (GE 6072A) > PSU > Presonus Tubepre v2 JJ 12Ax7 & OPA BB 4134 > Alctron MP73EQV2 > DBX 266 XS > Alctron CP540V2 > Audient ID14 MKII (using xlr to TRS) without gain level, because it doesnt have line input

but the result is low end is missing, i dont know why, event i boost with preamp eq to match the u87 result its feels different.

is that if i change that resistor to 200M OHM will make a significant result?

Have you tried an other preamp? Presonus has quite low input impedance of 1.3k. In some spec sheets it's written that wa251 needs at least 2k.

 

[pasarski]

@Luckyadnan, @Khron, @pasarski

A little bit of talk-to-talk “just to put the record straight” about these mods that I suggested…

I never owned or brought any Warm Audio product, as I never owned or brought any Telefunken Elecroacoustik USA product, as I will never own or buy any product from any major Chin-o-Canadian-American-whatever the fukk “globalization” mass production companies, because as it is odiously they “fukk it up” by “Cutting Coners” any time that they try to copy on or to be said more clearly to steal on from the heritage and the tradition of historical European Microphone Companies like AKG, like Neumann, like Schoeps…

This will be as stupid to me as if I had bought any Japanese Sony, Nikon, Canon Digital cameras and wait from any of them afterwards, to take pictures as good as my photos that I take with "Made in Germany" Leica SL3 digital camera, regardless of any lens I should use ...

But let’s go back to the AKG-Telefunken AG GmbH ELA-M 250 & to the ELA-M 251E microphones…

First thing first, we have to understand that the AKG-Telefunken AG GmbH ELA-M 250 & to the ELA-M 251E microphones were not the “All Around” microphones like the AKG C-12, AKG C-12 VR, AKG-Siemens SM-203, AKG C-24, AKG Perception 820…

If the ELA-M 250/251E were “All Around” microphones as any other AKG Microphones they will had the 200MΩ Grid-leak Resistor, not the 8MΩ (AKG-Telefunken AG GmbH ELA-M 250 with AC701K) or nether the 30MΩ (AKG-Telefunken AG GmbH ELA-M 251E with 6072 – 12AY7) …

But, as I wrote before, Siemens, the leading Co. of the Telefunken GmBH Trast (group of companies holded a grange against Neumann, so Siemens forced the AKG to make the ELA-M 250 & 251E as Anti-Neumann U-47 & M-49 microphone(s)…

So, both of these microphones (the AKG-Telefunken AG GmbH ELA-M 250 & the AKG-Telefunken AG GmbH ELA-M 251E microphones…) had been designed and made especially to be as an “One trick pony, but a good one”…

They are especially well made nearly "magical" for female radio speakers, female singers – songwriters…

In other words they are the “Next Diva’s best microphone choice” as they are working pretty “magical” with the female voice register(s) of any wannabe Lara Fabian, Rihanna, Celine Dion, Christina Aguilera, Demi Lovato …

So yeah, if you want an “One trick pony” microphone for female radio speakers, female soprano singers only or for mandolin players, violinists or for drums overheads don’t change anything, because even the bright sound / tone anemic Warm Audio WA-251 it is good enough “go too” for that…

Save you money, save your time, save your energy for the next best microphone, whatever it is, a condenser U-47 type microphone for male voices, a ribbon microphone for brass instruments, a dynamic microphone for your guitar – bass speaker cabinets, for your drums set etc. etc. etc.

In other words: “You can pick up your new (microphone) G.A.S. poison”…

But tell me whatever happens if this situation does not exist…

Tell me whatever happens if you are not a female radio speaker?

Tell me whatever happens if you are not a wannabe next Diva female soprano singer?...

Tell me whatever happens if you are not a worldwide “hit record” sound engineer – record producer with sexy female singers to make their “catwalk” in your studio?...

Tell me whatever happens if you are not a mandolin player or a violinist, tell me whatever happens if you are not a drummer?...

Hell, tell me whatever happens if you are not a “castrato” tenor?...

Well, in all of these situations we will have to consider that any Cathode Biased ELA-M 250 / ELA-M 251E microphone has 4 main filters…

1. The Combination Between the capsule capacitance and the grid-leak resistor as a Low-Cut / High Pass Filter…

2. The Combination between Cathode Resistor and Cathode Bypass Capacitor as a Low-Cut / High Pass Filter……

3. The Treble Cut Snubbing Anode Bypass Capacitor as a High Cut to cut-off the highs…

4. The Combination Between the valve’s Ra with the capacitance of the coupling Capacitor and the impedance of the output transformer, which all of this combination determinate the F.R. slop…

So, let’s see some of “my” Mods…

1. ECC81 – 12AT7 valve @ 120 DC Volts Vb, 100KΩ Anode Resistor, 2.7KΩ Cathode Resistor, 22μF Cathode Bypass Capacitor …

Well, well, well, surprise – surprise – surprise…

This mod has been done firstly by the Swiss Boutique P2P Microphone Company BSA Microphones for their BSA ELAM 250 Microphone (Price: CHF 2,985.00 aka €3,250.00) …

After BSA Microphones this same mod. has been done by the Telefunken Electroacoustik USA for their Alchemy Series TF51 (Price: $1,995.00 aka 2.399 €)...

How do I know it?...

I know it because I had read this Article – Review by Brian Fox of Fox Audio Research:

The Telefunken AR-51

Review by Fox Audio Research (part 1)

&

The Telefunken AR-51

Review by Fox Audio Research, Cont'd... (part 2)

So, by simply changing only the valve in the Warm Audio WA-251 (888 €) to the ECC81 / 12AT7 Gold Balanced JJ (€34,33) plus the changing of the Cathode Resistor to 2,7k RES-0,6W (€0,19) I can have an economical “upgrade” over € 1.511 to my pocket and off curse a sonically “upgrade” over the Alchemy Series TF51 (Price: $1,995.00 aka 2.399 € )

Now, let’s add the 220k, 2W (€0,21) grid-leak resistor in to the game…

Immediately everybody could tell that this Grid-leak Resistor value plus the Cathode Resistor – Cathode Bypass Capacitor value combination “look like” the AKG C-24 Stereo Microphone (EUR 31,570.39) with the only difference will be, that now we use the proper tube…

Well, I think that I can “take” these mods. to the Warm Audio WA-251 as an option and spend the rest of these € 30.688 EUR to hookers and drugs…

These are fine mods. I myself quite like 12at7 in microphones. It will even drive OP's preamp better. I also removed the plate to ground cap, gaining air and maybe loosing some high frequency distortion.

Non of the mods will make the mic sound like an elam 251 though, with that k67 style capsule. One might get close to c800g/ref c territory with linear circuit and that capsule for sure.
With that k67 style capsule and straight

 

[Accelerator]

@pasarski

Non of the mods will make the mic sound like an elam 251 though, with that k67 style capsule. One might get close to c800g/ref c territory with linear circuit and that capsule for sure.
With that k67 style capsule and straight

Personally I can tell you that the only tube microphone with K67 style capsule that I had heard & like it, it was the Soyuz 017 Tube, but unfortunally with its price at 4.599 € it is stays out of my reach…

Then again, no schematic or layout of the Soyuz 017 Tube to copy it and it has custom unknown OEM toroid output transformers…