The No.1 Website for Pro Audio
Anybody mod the Apex 480?
Old 4th March 2008
  #1
Anybody mod the Apex 480?

Hey fellow geeks, I've looked a lot at the mods for the Apex 460 and 435, just curious if anyone has modded the 480. I did searches on here, prodigy pro, and google and I can't find anybody saying anything about it. Looks like a nicer version of the 435, srt of like a FET version of the 460. Any opinions would be great, I'm thinking about doing a sort of U87 clone after I build my C-12 clone with a 460.
Old 25th May 2009
  #2
Gear Maniac
 
asplashofcitrus's Avatar
 

Bumping an old post, but I've had the Apex 480 for awhile and have not heard anything about it online other than the usual 460 tube, 205/210/215 etc. Anyone else want to chime in about the Apex 480? I may post some sound clips, and perhaps sell it because I want a Stellar Tube mic
Old 7th August 2009
  #3
Lives for gear
 
Insomniaclown's Avatar
 

Still nothing about this mic? I am looking to get rid of my Senn. e609 and putting the cash towards either a cheapy ribbon, or another condenser. There are no reviews online of this puppy either! How does it sound un modded?

I would expect the mods for this mic are replacing of the capacitors and removing an inner layer off of the grill. The grill mod seems to be common to apex mics. Maybe even a change in capsule if you wanted to really get into the nitty gritty.

I have a busted up apex 435, which I did love to death, and I plan on doing all 3 of the above mods to it. Maybe get a sick mic out of the deal. Maybe get a paperweight.
Old 28th August 2009
  #4
Gear Maniac
 
asplashofcitrus's Avatar
 

^ If you were talking about the Apex 480, I sorta had a thread about it earlier:

Apex 480 FET LDC Review-ish (Photos!)

and I was curious as to what mods I could perform with it as well...It's my first real multi-pattern condenser so I can't really compare it to anything, but I've tried other handheld mics like SM58, Sennheiser e865, and others and my voice sounds best with the Apex. I'm probably a middle/high tenor.

But anyone else with information on the Apex 480 needs to chime in!
Old 30th August 2009
  #5
Lives for gear
 
Michael_Joly's Avatar
 

From your pics the Apex 480 looks to be very similar to the CAD GXL-3000. FET / bipolar / transformer circuit.

The biggest couple of issues in the CAD GXL-3000, (I'm assuming this might apply to the 480) is the bias of the bipolar transistor is not ideal. The stock bias setting allow this stage to go into asymmetrical clipping before either the FET or transformer (which would result in a softer, more "tube like" distortion characteristic). At the very least, the bipolar stage should be evaluated for headroom capability relative to the FET and transformer and re-biased if (most likely) necessary.

The second issue with the 3000 (again, assuming this to be true of the 480) is the use of a K67-type capsule with its built-in HF peak followed by a flat-response circuit. The K67-type capsule was intended to be followed by a circuit that would attenuate the top end in a complimentary fashion to increase headroom, reduce sibilance and allow some control of the timbre balance.

In my opinion, a non-hyped-HF capsule like a K47 type would be a better choice for the circuit in this mic.
Old 4th July 2010
  #6
Gear Maniac
 
theBF's Avatar
 

This is an old thread, but this mic was on sale at my local store so I got one for $149 CAD. (We don't get those great American prices up here)

I haven't taken it apart yet to get the schematic written out but I did do some measurements on the audio. It looks pretty good for a cheap mic. If it had a nice 47 style capsule it would sound pretty good!

I have attached some graphs of performance. I inject -10dBu directly into the preamp FET. The distortion is actually lower than what I get with that level into my tube mics.

The preamp in this mic does exhibit a healthy hiss at the top end. I show the noise here un-smoothed because it gives a clearer view of what it sounds like.

I am going to see if I can find the source of the hiss.

The acoustic response shows the clear signature of the Chinese 32mm capsule. Makes the mic sound thin compared to the K47 based mics I have built.

I will post more news on this unit here as it unfolds.

BF
Attached Thumbnails
Anybody mod the Apex 480?-apex-480-elect.-resp-.jpg   Anybody mod the Apex 480?-apex-480-dist.-.jpg   Anybody mod the Apex 480?-apex-480-noise.jpg   Anybody mod the Apex 480?-apex-480-stock-response.jpg  
Old 4th July 2010
  #7
Gear Maniac
 
theBF's Avatar
 

APEX 480 Partial schematic

Ok So I took a look inside the APEX 480 and the good news is there is room for improvement.

This is just a partial schematic. It includes the preamp section only. I haven't traced through the rats nest that controls the polar patterns yet.
You can see it's a neat little circuit. The FET does the hi-impedance gain part for the capsule, but then a little emitter follower does the heavy lifting of driving the transformer. This also allows the insertion of a H.P. filter when you pass the signal through C5; a smaller value cap. This is also the reason the darn thing is so flat. The EF circuit can drive a cheap trafo and make it look good.

The 2SA1015 used in the emitter follower is listed as low noise and since it creates no voltage gain, I suspect the hiss I hear is all about the FET.

All the polarized caps are Tantulum! They could probably be improved by using Black gates.

FYI it looks like the capsule voltage is about 78Volts. Thats what I measure on the voltage tripler circuit on the other board.

By the way, my first impression of this mic was it sounded "tight" which is how I describe the Neumann solid state mics. I have been playing with tube mics for so long, I was surprised to hear this. Not sure how our ears can distinguish this solid state sound but it sure seems to be there.

Hope someone finds this useful.

BF
Attached Thumbnails
Anybody mod the Apex 480?-apex480-schematic.jpg  
Old 16th July 2010
  #8
Gear Maniac
 
theBF's Avatar
 

Some mods for the 480, (if anybody is interested)

Ok I did a little more (a lot more?) work on this thing and it's interesting. I am covering ground that Mike Joly has already done with the CAD 3000 with one difference. I have experimented with creating an internal EQ that compensates for the infernal high frequency response of the Chinese 32mm capsule. It's not a Neumann 67 by any means but it makes it a lot nicer and reduces FET noise in the process!

You can do the following things:

1. Change the capsule from 80 volts to 65 volts. This removes the "aluminum foil in your mouth sound" as my son calls it. :-)

2. Change the output tantalum caps to a good 100uF electrolytic and bypass it with a .1 uF of your choice.

3. Change the source bypass cap from 22uF Tantalum to 100uF electrolytic and bypass it as well if that's your style.

4. Replace both cheap mylar input caps with 1000pF Polystryrene. It's a tight fit. (distortion actually can be measured 10dB lower in the midrange after this one!!)

5. Change the bias resistor to the emitter follower to 390K ohms.

Then the final biggie: Change to a K47 type capsule if you have the dough.

-OR-

Bypass the biasing resistor with a small cap to create your own cheap 67 capsule EQ circuit.

820 pF will roll of the highs about 4 dB at 20KHz . (my preference)

1000pF rolls it off 6 dB at 20Khz. I would suggest mica or polystryene.

Schematics are attached. Send me a note if you have any questions.

Normal disclaimers ALL apply.

BF
Attached Thumbnails
Anybody mod the Apex 480?-apex-480-mods.jpg   Anybody mod the Apex 480?-apex-480-capsule-supply-original.jpg   Anybody mod the Apex 480?-apex-480-capsule-supply-mods.jpg  

Last edited by theBF; 16th July 2010 at 02:24 AM.. Reason: error
Old 16th July 2010
  #9
Gear Maniac
 
theBF's Avatar
 

APEX 480 acoustic response before after

Here is a rough acoustic response of the APEX 480 Stock and after the mods.
The other graph shows the effect the mods have on the internal preamp response.

That's it for me with this one.

BF
Attached Thumbnails
Anybody mod the Apex 480?-apex-acoustic-eq.jpg   Anybody mod the Apex 480?-apex-480-preamp-w_mods.jpg  
Old 16th July 2010
  #10
Lives for gear
 
Michael_Joly's Avatar
 

Quote:
Originally Posted by theBF View Post
...I am covering ground that Mike Joly has already done...
Thanks for the acknowledgement of my work.

Its worth repeating - the second stage transistor in these mics is often not biased correctly and results in asymmetrical hard clipping or harsh distortion / edgy sound and should be corrected.

Its interesting to note your use of the 2SK170 FET as an impedance converter - the low cost mics have adopted this part from Scott Dorsey's "plug and play, Shanghai Mike" article, but it is not the best device for the application in my opinion. Both Jim Williams and I favor faster FET types with more extended bandwidth and lower capacitive loading of the capsule to achieve better transient response than the 2SK170 can deliver.
Old 16th July 2010
  #11
Gear Maniac
 
theBF's Avatar
 

You are very welcome Mike.

I played around and found somewhere between 300K and 390K BIAS resistor gave me low distortion on the 2nd stage. Does that line up with your findings?

I didn't scope it like you did. I guess that would be the answer huh? :-)

BF
Old 20th July 2010
  #12
Lives for gear
 
Marik's Avatar
 

Quote:
Originally Posted by Michael_Joly View Post
Its interesting to note your use of the 2SK170 FET as an impedance converter - the low cost mics have adopted this part from Scott Dorsey's "plug and play, Shanghai Mike" article, but it is not the best device for the application in my opinion. Both Jim Williams and I favor faster FET types with more extended bandwidth and lower capacitive loading of the capsule to achieve better transient response than the 2SK170 can deliver.
Hi Michael,

I agree, besides other less than optimal schematic decisions, the Dorsey mod did not implement this device well.

On the other hand, this is already not the first time you are bashing the "poor" 2SK170. I'd be very interested to see any proof for it being "faster" (whatever it means), and how it has more extended bandwidth? Long ago I suggested you to look at its graphs for optimal bias conditions. Have you ever bothered?

Also, you keep repeating it over and over, but never bothered to explain how lower capacitive loading of the capsule achieves better transient response.

I'd really appreciate if finally, you whether provide any more or less meaningful data or explanation (which for some reason you just keep avoiding), or just stop bashing this FET.

Best, Mark Fouxman
Samar Audio & Microphone Design
Old 20th July 2010
  #13
Les
Lives for gear
 
Les's Avatar
 

There are significant tradeoffs between input voltage noise, input capacitance, and transconductance in a fet. Devices like 2sk170 of course have very low noise and high transconductance but with high input capacitance.

This just forms a divider with the capsule capacitance and attenuates the signal.

It has often been said that best results occur when the capsule capacitance and fet input capacitance are equal. I did an analysis of this for a source follower and found it to be true. So quite high input capacitance is often optimal by my analysis.

Words like "fast" and "transient response" mean nothing to me.

I think this mic does not use a source follower. It's a common source circuit with gain, and presumably Miller effect since its not cascoded.
I suspect the optimal point is still when input capacitance = capsule capacitance, but Miller capacitance must be included. I will analyze this.

Fully agree about the bias point of the emitter follower. It has a hard time driving a transformer at LF when the self inductance reactance poops out, severely limiting voltage swing on the negative half cycle.

Biasing well above Vcc/2 helps.
Old 22nd July 2010
  #14
Lives for gear
 
Marik's Avatar
 

Quote:
Originally Posted by Les View Post

So quite high input capacitance is often optimal by my analysis.
Well, this is exactly the point I was trying to make for quite a long time. Moreover, to connect the capacitance with a poor transient response IMO, is complete absurd.

For some un-explainable reason (or maybe just following his own agenda) Michael throws those things over and over again (including his notorious completely wrong classification of long-short ribbons, which he promised to fix long time ago, but alas...), every single time completely ignoring quests for explanation... Oh well...

Best, M
Old 27th July 2010
  #15
Gear Maniac
 
theBF's Avatar
 

OK I am going to stop after this.

I was not happy with the results of my last mods, even though there was an improvement in the APEX 480 after the mods were done. The sensitivity was way less than my other LDC mics and so I went looking.

I traced the aforementioned "Rats nest" for the polar pattern switch and I learned something very important.

The APEX 480 includes figure 8 pattern as a feature but it doesn't have enough capsule voltage to pull it off. What I mean is they only have 80 volts total. That means on the front capsule there was only 40 volts. (you need double on the back capsule to get figure 8). There goes the sensitivity. And when I reduced the voltage to 65, that made things even worse!!

So I decided I didn't need figure 8. Rewired the front to look like a Neumann FET 47. Big blocking cap and 65 volts on the capsule and voila! Sensitivity is way up and it SOUNDS WAY BETTER. I now only have card and omni, but I have other multi pattern mics for the fancy stuff.

I then re-thought some of my emitter follower decisions. Got about 3 dB more headroom out of it by decreasing the emitter resistor a littler and increasing the base bias resistor a little. When I tried for optimal biasing the current draw got too high and the phantom power voltage starts to sag. This thing really could use a little solid state voltage regulator... (stop me before I mod again!)

Then I took out most of the HF compensation, because it killed all the stuff above 10K to my ear. I added just a "little" eq like in the ELA m 251. 100pF just warms it up.

And... I did have a Peluso CEK89 laying around, so I put that in. It's a tighter spec 32mm capsule, but it needed a home.

So that's really it. I am done with this MOD and pretty happy with the mic now. In fact it sounds better now than my stock AT4040.

Still think the kicker would be a nice 47 capsule. Then it would rock.

BF
Attached Thumbnails
Anybody mod the Apex 480?-apex-480-mods-rev-2.jpg   Anybody mod the Apex 480?-apex-480-dc-board-rev-2.jpg  
Old 2nd October 2010
  #16
Gear Maniac
 
theBF's Avatar
 

I finally got in a CEK47 capsule for this mic. When I put it in it has 7 dB lift at 10KHZ! So after a little careful rolloff it looks pretty good and it sounds good too.

BF
Attached Thumbnails
Anybody mod the Apex 480?-cek47-acoustic.jpg  
Old 4th March 2011
  #17
Here for the gear
 

Quote:
Originally Posted by theBF View Post
Ok I did a little more (a lot more?) work on this thing and it's interesting. I am covering ground that Mike Joly has already done with the CAD 3000 with one difference. I have experimented with creating an internal EQ that compensates for the infernal high frequency response of the Chinese 32mm capsule. It's not a Neumann 67 by any means but it makes it a lot nicer and reduces FET noise in the process!

You can do the following things:

1. Change the capsule from 80 volts to 65 volts. This removes the "aluminum foil in your mouth sound" as my son calls it. :-)

2. Change the output tantalum caps to a good 100uF electrolytic and bypass it with a .1 uF of your choice.

3. Change the source bypass cap from 22uF Tantalum to 100uF electrolytic and bypass it as well if that's your style.

4. Replace both cheap mylar input caps with 1000pF Polystryrene. It's a tight fit. (distortion actually can be measured 10dB lower in the midrange after this one!!)

5. Change the bias resistor to the emitter follower to 390K ohms.

Then the final biggie: Change to a K47 type capsule if you have the dough.

-OR-

Bypass the biasing resistor with a small cap to create your own cheap 67 capsule EQ circuit.

820 pF will roll of the highs about 4 dB at 20KHz . (my preference)

1000pF rolls it off 6 dB at 20Khz. I would suggest mica or polystryene.

Schematics are attached. Send me a note if you have any questions.

Normal disclaimers ALL apply.

BF
My question is, how much do all these mods cost to do as far as parts?
Old 17th April 2011
  #18
Gear Maniac
 
theBF's Avatar
 

Sorry for the delay. I haven't been on for a while.

If you just change the electronic parts it doesn't cost much. Probably less than $20.

If the stock capsule is good then a little EQ cap makes it sound warmer.

A k47 capsule can be had for $100.

BF
Old 27th October 2013
  #19
Gear Head
 

Old thread, I know...

I'm interested in learning any updates on this mic mod that leave the figure 8 pattern intact.

I'm thinking this may be my next mic mod project. But, I really want to have the figure 8 pattern working. I figure I can do the electronic parts mod to bring the voltage up to the right level so the figure 8 will work and correct the biasing problem first. Then some time in the future replace the capsule with a K47 if I still feel the mic is too bright.

I do diffuse field recording and have a feeling the remaining brightness will be fine for me in that application.

Are there any updates on this?
Old 3rd December 2013
  #20
Gear Maniac
 
theBF's Avatar
 

I think that's the way to go.

When I learned how easy it was to raise the polarization voltage the multi pattern could stay.

Do not forget to change the caps on the DC board to handle over 100 volts where needed.

BF
Old 5th December 2013
  #21
Here for the gear
 

I bought a couple mod kits a few years back from you Brian. I only ever got one mic done though. It's been a while since I've done any recording but I was very happy with the first modded one. Taming that HF really helped.

Are you saying you've found a way to bump up the fig8 voltage and make it useable now? On my first mic I just cut the one trace and disabled the fig8, since I don't find myself using it too often anyway.

I've been more on the gear fixing/building lately rather than recording, but I may just go and mod that second mic over the holidays.
Old 25th June 2014
  #22
Here for the gear
Question for Brian Fox, did you mention somewhere the replacement zener value you settled on to recover the multi-pattern capability? I looked through the thread and on your page but couldn't find it

thanks

Quote:
Originally Posted by theBF View Post
I think that's the way to go.

When I learned how easy it was to raise the polarization voltage the multi pattern could stay.

Do not forget to change the caps on the DC board to handle over 100 volts where needed.

BF
Old 26th February 2017
  #23
Hm, simple alteration, good results

I have two of these CAD GXL3000s (APEX 480), one has been rebuilt with the "Linear 87" kit from Matt @ Microphone Parts, the other stock. (Apparently this particular 87 kit has been discontinued, not sure why.) The modded mic has the RK47 capsule in it and sounds great, as you would expect.

But lets talk about the other mic. I bought it on Craigslist for $30 and the capsule was damaged. I sent it back to CAD and they replaced the capsule for $30. (This was two years ago and I see that they have raised their repair charge to $50, BTW. CAD is a great customer service company, IMO, the repair was quick and the exchanges friendly.) So the mic is an older one, no tantalum caps onboard, electrolytics and polyester block caps, so probably pre 2010. However, in it's stock form coming back from CAD, it was thin sounding and rather anemic compared to my other mics. Basically the top end was not pleasant and pretty much sitting by itself in the sound spectrum with little bass and reduced mids. I never used it for anything and I figured I would rebuild it someday.

Brian Fox is a brilliant guy, no doubt, and so it was interesting to read his posts here regarding the 480 (GXL3000) mic. Reading what he wrote, I can easily see where, had I not done something different that solved my issues, I would be all over his suggestions. Well, except I want to keep the Figure 8 feature.

Alright, so here's what I did. I replaced the stock 2SA1015 transistor with a Toshiba version. (Here, if someone told me it was a stock Toshiba transistor to begin with, I wouldn't know. However, regardless of the brand of transistor that was in the stock mic, I bought the Toshiba version and replaced the original.) Then I changed C4 (4.7uf/50VDC) to a Nichichon Muse version cap. I also added the 100pf cap to the stock 180K resistor to knock back the highs a little bit (as Brian Fox suggested eventually.) This is all I did. And the mic was transformed into something I can use. The top end is pleasant, the mid and bass frequencies are now present. It's really not that bad a mic. I recorded the results before and after on my DAW running into a Great River NV-1 pre and the Manley ELOP limiter, btw, and you can clearly hear the difference between the two versions.

The Figure 8 sounds full, not frequency or volume starved, either.

Last edited by retsoor; 26th February 2017 at 03:44 AM.. Reason: spelling error?
Old 26th February 2017
  #24
Here for the gear
 

I am working on this mod for a gxl3000, I have another one stock that I am going to do the same thing eventually and have a matching pair. I based this on the info in this thread plus a bit off the Fox Audio website. I started out with just the capsule and transformer upgrade on one mic and that sounds pretty good. I had no intention of doing anything else with the circuit components but then I stumbled across this thread and decided to take it a bit further.
I could be wrong but I seem to recall the stock transistor being Toshiba when I looked into that awhile back. Did you notice any difference from the old one when you replaced it? Interested in why you replaced the C4 cap since that is not one that other people mention replacing? Anyway here is what I came up with:
Attached Thumbnails
Anybody mod the Apex 480?-gxl3000-schematic.jpg  
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Forum Jump
Forum Jump