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lotech · 4th September 2011

I picked up a used Apex 435 and was planning on modding the heck out of it--I've used and enjoyed the tlm103 and c414 as drum overheads but can't part with the $$ to add either of those mics to my mic cabinet now. I figured a tricked-out apex would probably do the trick for a fraction of the cash.

While I have one now, I plan on getting another to make a pair.

I set up the stock 435 directly over the kit with the capsule as close to my blue baby bottle (early all latvian model) as possible. I was shocked when the 435 sounded better to my ears in that application. I can put up some audio files, but it had a very nice capture of the cymbals and actually had better low-end extension than the BB, capturing a lot more of the depth of the kick and floor tom. Overall, a lot better OH mic than the BB.

While I'm almost taken aback by how good it sounds stock, I plan continuing. the RK-47 from microphoneparts.com seems to be a good compromise of price vs. performance and should bring some refinement to the mic.

I have not been able to find a schematic for the mic, and haven't figured it out myself. Apex says the mic uses the same electronics as their 430, but the 430 uses a transformer output and the schematic is completely different from the 435.

Therefore I have a few questions.

1. other modders have reported excellent results in bass response by changing C3 and C4 to 1uf audio grade caps (I've ordered some audiocap thetas) and repacing c15, 16 and 17 with polystyrene caps at stock values to help midrange definition. is there any sense changing the other caps in the mic? they are for the most part extremely crude looking tantalum caps, some very crude ceramics on the power side of the board and a couple of cheap-looking metal film caps. Recommendations?

2. transistors: both Jim Williams and Michael Joly advocate using the hitachi family of PNP transistors (2sa1083/4/5). Stock transistors are 2n5401s. the hitachi transistors have far better specs than the 5401s and this change makes sense. what else might need to be changed for the 1083/4/5 to work in the circuit?

3. fet: again, the siliconix J305 is recommended. The K170 is stock, and I gather that it has a pretty good reputation in "audiophile" circles, with some saying the J305 is not a meaningful upgrade. Mssrs. Williams and Joly disagree. I do not have a scope and re-biasing the fet is probably far beyond me. Thoughts?

4. Resistors. The parts cost is fairly minimal to upgrade the resistors to good metal film resistors, but it in preparing, it would seem that the resistors are all 5 or 6 band coded and either 2% or .1% resistors. This seems wrong to me. is it possible?

I can post pics if that would be helpful.

Thanks,

Derek

4th September 2011	#9
lotech Gear interested Joined: Jan 2011 Location: Canada Posts: 25	435 project I picked up a used Apex 435 and was planning on modding the heck out of it--I've used and enjoyed the tlm103 and c414 as drum overheads but can't part with the $$ to add either of those mics to my mic cabinet now. I figured a tricked-out apex would probably do the trick for a fraction of the cash. While I have one now, I plan on getting another to make a pair. I set up the stock 435 directly over the kit with the capsule as close to my blue baby bottle (early all latvian model) as possible. I was shocked when the 435 sounded better to my ears in that application. I can put up some audio files, but it had a very nice capture of the cymbals and actually had better low-end extension than the BB, capturing a lot more of the depth of the kick and floor tom. Overall, a lot better OH mic than the BB. While I'm almost taken aback by how good it sounds stock, I plan continuing. the RK-47 from microphoneparts.com seems to be a good compromise of price vs. performance and should bring some refinement to the mic. I have not been able to find a schematic for the mic, and haven't figured it out myself. Apex says the mic uses the same electronics as their 430, but the 430 uses a transformer output and the schematic is completely different from the 435. Therefore I have a few questions. 1. other modders have reported excellent results in bass response by changing C3 and C4 to 1uf audio grade caps (I've ordered some audiocap thetas) and repacing c15, 16 and 17 with polystyrene caps at stock values to help midrange definition. is there any sense changing the other caps in the mic? they are for the most part extremely crude looking tantalum caps, some very crude ceramics on the power side of the board and a couple of cheap-looking metal film caps. Recommendations? 2. transistors: both Jim Williams and Michael Joly advocate using the hitachi family of PNP transistors (2sa1083/4/5). Stock transistors are 2n5401s. the hitachi transistors have far better specs than the 5401s and this change makes sense. what else might need to be changed for the 1083/4/5 to work in the circuit? 3. fet: again, the siliconix J305 is recommended. The K170 is stock, and I gather that it has a pretty good reputation in "audiophile" circles, with some saying the J305 is not a meaningful upgrade. Mssrs. Williams and Joly disagree. I do not have a scope and re-biasing the fet is probably far beyond me. Thoughts? 4. Resistors. The parts cost is fairly minimal to upgrade the resistors to good metal film resistors, but it in preparing, it would seem that the resistors are all 5 or 6 band coded and either 2% or .1% resistors. This seems wrong to me. is it possible? I can post pics if that would be helpful. Thanks, Derek __________________ www.mildgouda.com http://soundcloud.com/derekvandusen/wired