Apex 435 mods, anyone?

[rmaier]

Hi all,

I recently completed modding a pair of Apex 460s after following several threads here and at a few other sites, and was so encouraged by the results that I decided to grab an Apex 435 to see if it would benefit from a few simple mods.

At this point, I've removed the innermost layer of mesh from the headbasket and was pleased with the result (more open, less internal reflection), so I'll probably go ahead and remove the second layer since it helped to open up the 460.

As far as components go, C7, C8 and C9 look like the same brand of cheap electrolytics found in the 460, and I'll probably go ahead and replace them with Black Gates of the same value.

So what else would help this mic?

Ralph

[dkelley]

Originally Posted by rmaier

Hi all,

I recently completed modding a pair of Apex 460s after following several threads here and at a few other sites, and was so encouraged by the results that I decided to grab an Apex 435 to see if it would benefit from a few simple mods.

At this point, I've removed the innermost layer of mesh from the headbasket and was pleased with the result (more open, less internal reflection), so I'll probably go ahead and remove the second layer since it helped to open up the 460.

As far as components go, C7, C8 and C9 look like the same brand of cheap electrolytics found in the 460, and I'll probably go ahead and replace them with Black Gates of the same value.

So what else would help this mic?

Ralph

the output transformer sucks in the 435, and it has some body resonances that should be reduced somehow. I personally would like to figure out some sort of diffuser or some that could go in front of the capsules in 435s and 460 (and many other similar mics from the same factory) to reduce a bit of the 8khz peak in the capsule a bit.

I mod my own 460s and 435s now for fun, just got into it recently, and have decided that there are frequency response problems with the capsules that can probably be corrected using either physical damping like that or some sort of eq circuit added to the main circuit. I'm working on it but don't have much time these days so it'll take me a long time to get any circuit designs worked out at this rate. It's really more of a theory at the moment.

Cheers,
Don

[dgatwood]

Originally Posted by dkelley

the output transformer sucks in the 435, and it has some body resonances that should be reduced somehow. I personally would like to figure out some sort of diffuser or some that could go in front of the capsules in 435s and 460 (and many other similar mics from the same factory) to reduce a bit of the 8khz peak in the capsule a bit.

Are you sure you aren't thinking of the 415? Unless I'm missing some microscopic transformer hiding between the two circuit boards, my 435 doesn't have an output transformer, nor is there room for one.

[rmaier]

No traffo on mine either...

Ralph

[PhilGood]

Originally Posted by rmaier

Hi all,

I recently completed modding a pair of Apex 460s after following several threads here and at a few other sites, and was so encouraged by the results that I decided to grab an Apex 435 to see if it would benefit from a few simple mods.

At this point, I've removed the innermost layer of mesh from the headbasket and was pleased with the result (more open, less internal reflection), so I'll probably go ahead and remove the second layer since it helped to open up the 460.

As far as components go, C7, C8 and C9 look like the same brand of cheap electrolytics found in the 460, and I'll probably go ahead and replace them with Black Gates of the same value.

So what else would help this mic?

Ralph

What are the values on C7, C8, and C9?

Black Gates are somewhat expensive and hard to come by, so it might be better to replace the lower value ones with film capacitors. There is probably also a small cap up by the capsule, probably around 1000pF that could be replaced with a polystyrene of the same value if its a ceramic or tantalium cap.

Photos or a schematic would help.

[rmaier]

Good to have you aboard Philgood. Thanks for your input on the 460s in previous threads.

C8 and C9 are 220uf 16v. C7 is 47uf 50v. The parts are available at partsconnexion.com for $2-$3 a piece. I'll let you know how they sound.

Sadly, the schematic on the apexelectronics.com website (for the Apex 430 wide diaphram) doesn't jive with the 435 I have. I'll try to scrounge up a schematic, but maybe these jpegs will suffice for now.

Like the 460, C1 on the 435 is tucked behind one of the PCBs. I'm not sure what the value is. The cap reads 102...

Am I right in assuming that the transistors in this mic are doing the job of the tube in the 460, and if so, would it make sense to upgrade these components as well?

Ralph

[PhilGood]

Really would be helpful to have a schematic, as C7, C8 and C9 might not even be in the signal path. If so, upgrading would be a waste for the most part.

Can you describe the capacitor on the backside of the circuit board close to the capsule?

Photo's would also be very helpful

[PhilGood]

OK. Just looked at the JPGs. I wouldn't worry about C7, C8 and C9 as those look to be on the power side of the board.

Look at the other side. The B side. THESE are the caps that need to be replaced. You see the 4 yellow lumpy ones and the 2 light green ones? Those are dipped tantalium caps, and they are HORRIBLE for sound. (some of those look like they might just be filter caps, like the two at the bottom) Replace those with good film caps. If the cap on the backside of the board by the capsule looks like any of those, replace it with a good polystyrene or mylar.

[rmaier]

Okay, how about this:

-replace C3, C4 (224 - 0.22uf) with Orange Drop (200v?);

-replace C15 (to capsule), C16, C17 (all 102 - 1000pf) with either Orange Drops or Nichicon foil polyester depending on what will fit;

-possibly replace C1, C2 (223 - 0.022uf at the bottom) with Orange Drop (200v?)

Thanks.

Ralph

BTW, has anyone put a Peluso in one of these? I will phone Long&McQuade tommorrow and see if their tech has a schematic that I could post.

[PhilGood]

Peluso replacement would be the biggest improvement. Second would be replacing C15, 16 and 17 with polystyrene 1000pF caps.

[rmaier]

Thanks. A goodie bag from Mouser is on the way . The goodie bag from Peluso will have to wait.

Ralph

[rmaier]

It’s been a while …

After going too far with one of these mics, I think I can offer a few comments on what works and what doesn’t.

Replacing C15, C16, and C17 with Xicon Polystyrene film caps (50v .001uf) really helped to clean up the upper mid honk that this mic normally has. Additionally, replacing C3 and C4 with Black Gate non-polarized electrolytics (50v 1uf) helped open up the bottom end. I would have liked to try a few Solens, but the interior is too tight.

Removing one of the inner layers of mesh also helped to open up the top end, but I after taking out the second one, I wished I hadn’t. The mic sounded harsh and seemed to be much more prone to reflections. I’m not sure what exactly was going on, but it wasn’t pretty.

Knowing when to stop …… I tried replacing a few more tantalum caps with some big Orage Drop polypropylenes, and now I have a snazzy paperweight… (Oh well, I’ve been wanting to try a breadboard project for a while now). So I bought a couple more…

When I compared the modded mic with a stock one, the difference was huge. I will soon have a pair of usable condensers for about $130 Cnd. The kicker was when I compared the modded Apex to an AT 4033a, a mic that I seem to recall paying close to $600 for. The negligible difference in sound between the two was hardly worth the difference in price. While neither the modded 435 or for that matter the 4033a would qualify as my “go-to” mics, the Apex strikes me as a hell of a deal if you’re willing to spend a bit of time with it, and a relatively painless way to expand you toolbox.

Bottom line: replace C15,16,17 with polystyrenes; replace C3,4 with Black Gates; remove 1 layer of mesh (if you still feel like you need more air).

[Gus]

first picture looks like the DC to Dc converter

the other
one fet and two pnps?

might be a china take on the schoeps circuit.

boring no transformer

[craigmorris74]

Before and after (or modded vs unmodded) clips would be awesome.

Craig

[antichef]

While we're on the subject -- I have the Apex 430, which I think is one of the candidates for the Scott Dorsey mod. I paid about $20 for it, it's stock, and it sounds awful -- the perfect canvas for the novice tinkerer. I've been searching and searching, and all paths have led to the [quite reasonable] instruction to get the proper back issue of the magazine in which it was published. Problem is, the back issue - Jan, 2002 Recording Magazine - is and has been completely sold out from the publisher, as far as I can tell. Is there any other source for this info or something similar (or a source for the magazine)? I've heard that the mod involves replacing the circuit boards -- if that's true, I'd also be interested in less intrusive approaches that only require replacing caps, etc.

[crazydoc]

Originally Posted by antichef

While we're on the subject -- I have the Apex 430, which I think is one of the candidates for the Scott Dorsey mod. I paid about $20 for it, it's stock, and it sounds awful -- the perfect canvas for the novice tinkerer. I've been searching and searching, and all paths have led to the [quite reasonable] instruction to get the proper back issue of the magazine in which it was published. Problem is, the back issue - Jan, 2002 Recording Magazine - is and has been completely sold out from the publisher, as far as I can tell. Is there any other source for this info or something similar (or a source for the magazine)? I've heard that the mod involves replacing the circuit boards -- if that's true, I'd also be interested in less intrusive approaches that only require replacing caps, etc.

Here's a link for an abridged version. Some parts of the discussion, and the layout of the new circuit board have been edited out. It does have the circuit schematic, however.

http://www.pfarrell.com/music/shanghaimic.html

[antichef]

Originally Posted by crazydoc

http://www.pfarrell.com/music/shanghaimic.html

Thanks - I should have mentioned that I saw that, but the edits (and references to the magazine) scared me off -- but it provides enough info?

[mshilarious]

Read this thread with respect to the Dorsey mod:

http://www.homerecording.com/bbs/sho...d.php?t=219124

Now if the Apex 430's capsule is indeed happy at 35V, it's a relatively simple matter to bias the FET so it doesn't overload as easily, you just need to create a voltage reference with a divider (probably a trimpot would be handy) off the 12V rail, and connect the R10 1G resistor to that instead of ground.

Also I don't know the specs on 2SK170 very well, but I think it could do with less current than that, especially if you bias its input, so I would try increasing R1 and R2. 2.2K is a value set for electret capsules with internal FETs, and even then that is low if there is a following buffer stage. 2SK170 is discontinued but there are still stocks; however I've picked up some FJN598s to play with, but haven't done much with as of yet. KSK30 looks similar to 2SK170, but I don't have those.

Finally, in my experience 12V zeners are too noisy to rely on the 10uF tant cap. Notice how there is an additional filter stage for the FET supply, but not the PNP side. Again, that might be OK for an electret capsule, which has high self-noise already (although in my experience it is not), but I would insert a copy of R3 between the zener and C4 (should that really be a tant?), and also select the zener for noise, I've found that about 1 in 20 12V zeners are outrageously noisy, like 10-20dB more than the average.