Apex 460 mod question

[The Sugar Lion]

I was looking at the Fox Audio website and considering starting to work on the Mini-Mod that he has posted. I was hoping to just start with the very basic task of removing C9 & C10 to remove the 25K peak. My question is do I have to finish all the steps in the Mini-Mod for this to be safe or can I simply get rid of those two caps to start and continue using the mic?

Here is the step by step from his website for reference.

The FAR 460 Minimod
So what is the minimum you can do to make this mic. sound good? Turns out it's simple.
1. Remove C9 and C10 to remove the 25Khz peak resonance in the high end.
2. Change the caps in the signal path: Polystyrene input and 1uF polypropylene output (C8)
3. Change the tube to a 6072 or a very good 12AT7
4. Add a tiny EQ cap like that found in the ELA m251 design, between the Anode pin of the 1st stage tube and ground. ( I like 200pF myself but it depends on your capsule, sometimes 330pF is a better sound)

 

[Phrazemaster]

The pic shows up blank - it looks like it's a PDF when I click the link below it. You may need to make a jpeg out of it for it to work right here on the forum...

 

[midwayfair]

Yes, you can start with just removing the caps. There are no mods described that are dependent on others. But you might as well do #4 while you're in there. It's a huge improvement.

 

[The Sugar Lion]

The pic shows up blank - it looks like it's a PDF when I click the link below it. You may need to make a jpeg out of it for it to work right here on the forum...

Darn broken pictures!
And attachments as well for crying out loud.

 

[The Sugar Lion]

Yes, you can start with just removing the caps. There are no mods described that are dependent on others. But you might as well do #4 while you're in there. It's a huge improvement.

Thank you very much for the tip! I removed C9 & C10 with out any problems. I also put in a better 12AX7 tube I had sitting around not getting any use. So at least now it has a Russian made tube of decent quality in it.

I would like to do #4  as you suggest. I talked to a tek friend of mine and managed to get a 220pF Cap that I can use. I just don't know where to put it. "between the Anode pin of the 1st stage tube and ground" means nothing to me. I would be greatly appreciative if you could tell me what two points I need to solder that cap between. If it is easy enough to explain that is.

Thanks again!

 

[The Sugar Lion]

I decided to email Brian Fox and ask the man himself. He was very helpful.

The answer is simply put the cap between pin 1 and pin 9 on the tube socket itself. Took me all of a couple of min.

 

[micaddict]

Yes, Brian has a business, "but" he likes to share, too.

And he's got the bug for sure.

Does anyone know if he's a member here?

 

[granger.frederic]

hi,you can also:

-lower b+ to 120v
-remove c9,c10,c7,R8
-change c6 for an Elna Silmic 2 6.3v
-change c8 for a Paper in oil
-put a JJ ecc81 (don't forget to adjust the bias resistor )

you won't recognise it

regards

 

[The Sugar Lion]

hi,you can also:

-remove c9,c10,c7,R8

you won't recognise it

regards

That seems like a lot of removing. What would doing all that do to the sound?

I have removed C9 & C10, put in a 12AT7 as well as putting on a 220pF cap to tame the highs a little more. I might go with a slightly higher value there as it still seems bright. I can hear a difference but I would like to keep going. In #2 Brian suggests

"2. Change the caps in the signal path: Polystyrene input and 1uF polypropylene output (C8)"

The output is C8 but he does not say what the input cap number is. Anyone know the input cap number is?

Thanks again for any tips. I am operating on a very tight budget at the moment and would love to learn how to get the most out of these things while still doing it on my own. That way I could have at least a couple on hand

 

[moomilk]

Input cap from the capsule is C4 - in my mic it was already polystyrene there (TCM1050 - same circuit), while in early version of Apex 460 it  might not be so - check and replace if necessary,

Change the tube to 12AY7 \ 6072!

12ax7 really is not the best choice here,

6201 \ 12AT7 \ ECC81 also works great - with more gain and lower output impedance, but usually needs to be picked from several tubes for low noise,

And don't forget about the capsule 

And the transformer

BTW if you would change the capsule - EQ cap mod might become unnecessary,

Here is what I've done to mine - with M7 and 2461nico it sounds great:

*see attachment

C6 \ C7 - cathode bypass caps removal may be a bit controversial, so see for yourself, but in CCDA think it sounds nice without them with ECC81, while with 6072 - ~3-4db level drop might be less desirable.
Also with CCDA you can even use 3:1 \ 4:1 output transformer.
And certainly, if you would eventually decide to remove the cathode follower second tube stage - cathode bypass cap should remain in place and must not be removed.

 

[rock soderstrom]

Hi moomilk, thanks for your information but I can't see your attachment. Is it just me? Cheers

 

[The Sugar Lion]

I could see his attachments a couple of days ago but now I can't see them either.

 

[rock soderstrom]

...but now it works here. Strange! 

 

[The Sugar Lion]

And they are back!

 

[moomilk]

Yep, wanted to make a direct img link, but photo service got buggy, so got back to standard attachment.))

 

[The Sugar Lion]

I have managed to work my way through removing the 9&10 caps, adding the EQ cap, changing the cathode bias resister, change tube to 12AY7, removing the inner layers of screen, and changing the cathode bypass cap. All that remains is upgrading the audio path caps! I am not sure if I will bother with the damping resistor or not.

And go figure it sounds quite a bit different. And for the better. Glad I did it. One day I will do a second one so I have a pair. I would like to replace the capsules as well at some point but it is sounding pretty good as is. Thanks to everyone who commented on this thread and helped out.

 

[rockinrob86]

I forget what mods I did to mine, but I definitely did all of the fox ones and I want to say a few more - I ripped out the inner mesh as well, but still original capsule.  I added a NOS mullard 12ay7.  I haven't made the plunge into handmade capsules yet...

Used it for the vocals and drum room mic on this song over the weekend:
https://soundcloud.com/rockinrob86/the-invisible-strings