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[rjd2]

hey folks, i figured it would be a good current-and future-resource if we kept all the info about the mods in one thread. that way no one has to wade thru 150+ pages to find something, we can all pow-wow w/ info, and that thread can be for things strictly group buy related.

attached is a photo(from the other thread) on a proposed placement for the tranny. as there are no pics im aware of on its placement, that seems to be something we'll all need. my plan was to just heatshrink the exposed pins after soldering, and maybe wrap w/ electrical tape, or leave as is. this placement is VERY snug; no play at all. it also required bending the ends of the rail part of the body. maybe someone has a better placement?



im gonna have a few wiring questions, but i'll start with this one:
should i assume the build notes mean that the INNERMOST pins of the tranny should be jumpered, and the OUTERMOST pins be the actual solder points? im not used to reading these kinds of schems, so the diagram notes are unfamiliar. thanks.

[compasspnt]

Good idea...wading through that other thread is a pain now.

For the record, here is the Mod website:

http://www.compasspointstudios.com/bulldog/bulldog-tnc_upgra des.html

[MI]

Terry,

Make this into a sticky?

MI

[Mike JM]

I have one quick question I've been unable to find a suitable answer to searching.

It seems I'm a bit late to the party. All the ACM1200 mic group buys ended months ago. So for someone looking to get in now on the TAB/Compass trafo/PCB mods, what are my best options?

As I understand it, the ACM1200 is fundamentally an SYT1200, while an Apex 460 is an SYT1100.

Apex 460's are abundant, as are Nady 1150's. Will either of these be a perfect substitute? I know the mod PCB's offer pad and low cut switches, and so does the ACM1200 body. I think the Apex/Nady mic bodies lack these switches.

Also, would the PSU's be equivalent, and are different PSU mods needed to get different mod types working? ie. Doesn't a c12 circuit require different currents from a u47?.

Thanks.

[rodabod]

You should be fine with a Nady/Apex model. They may omit the switches, but the loss isn't massive. The PSUs should be the same for the respective models which have multi-pattern control.

[Future_One]

I'm going to be modding an Apex 460 with the T47 circuit and xformer.  

As mentioned above, the Apex 460 doesn't have a pad or filter.  Could anyone shed any light on bypassing these switches when installing the new pc board.

Thanks.

[Mike JM]

rodabod wrote on Sun, 23 August 2009 15:17

You should be fine with a Nady/Apex model. They may omit the switches, but the loss isn't massive. The PSUs should be the same for the respective models which have multi-pattern control.

Thanks. I looked it up and neither the original C12 nor the original U47 seemed to have pads or low cuts either, so perhaps jumpering those out would only make for a more authentic reproduction.  

Future_One wrote on Sun, 23 August 2009 15:34

I'm going to be modding an Apex 460 with the T47 circuit and xformer.   As mentioned above, the Apex 460 doesn't have a pad or filter.  Could anyone shed any light on bypassing these switches when installing the new pc board.

+1 and also for the c12 board please.

[rodabod]

Future_One wrote on Sun, 23 August 2009 21:34

Could anyone shed any light on bypassing these switches when installing the new pc board.

Don't wire anything to the low-cut switchso that it is left open. Wire the pad switch closed by shorting the PCB pads with a jumper wire.

(Edited due to schematic change).

[rodabod]

Mike JM wrote on Sun, 23 August 2009 21:42

+1 and also for the c12 board please.

Strangely, the switch is shown as being wired differently on the '12 schematic. On it, the 6dB patch switch should be wired closed in order to switch the pad out.

[rodabod]

rodabod wrote on Sun, 23 August 2009 21:51

Future_One wrote on Sun, 23 August 2009 21:34   Could anyone shed any light on bypassing these switches when installing the new pc board. Just don't connect either switch to the board; ie. leave the switches open.

Hold on a second, Oliver, the '47-inspired schematic's pad switch shorts out the cathode bypass resistor and the cathode resistor. Since it's a cathode-bias design, is this not going to push the bias to ground? The other schematics' pad switches make more sense at first look, unless I'm just getting tired.

Roddy


EDIT: Schematic changed, wrong version had been uploaded...be sure you use the new one.

[Mike JM]

I have one more question for the designers or anyone at all that knows these schematics well.

To what extent are these circuits accurate, and to what extent have they been modified so that they can all fit the same PCB kit layout? I imagine significant liberties must have been taken with the true signal paths to get to the point where a 3-in-1 was possible.

In that case, which would you say is most faithful, and what changes, specifically, have been made with each? I have read that the C12 design is a direct recreation of the AKG C12 as Oliver is known for modding them. I just compared schematics and to my eyes I think that one is at least identical to what he does. The only difference is I think we can omit the acm1200 resistor A if we don't have a pad.

http://recforums.prosoundweb.com/index.php/fa/9331/0/20536/
   http://www.compasspointstudios.com/bulldog/page1/files/page1 -1010-full.jpg

Sorry to ask so many questions and I don't mean to put you on the spot, but when I read things like:

Quote:

It should be absolutely understood that these microphones, when finished, will not sound exactly like any certain vintage microphone. But they will sound very, very good, and will be reminiscent of the sonic style evoked by the mic each is “based upon.” We are employing that related type of design in each of the circuits.

I find it either means one of two things. Either the designer is just warning overzealous customers to not expect the impossible (ie. changing a circuit will not give you a $10k vintage mic or improve a mediocre capsule), or the design being offered bears little actual resemblance to the one it is supposed to represent.

For example, recordinghacks describes the u47 here as "based on a simplified 47-inspired electronics circuit." http://recordinghacks.com/microphones/TnC-Audio/ACM-1200

Thanks again.

[rjd2]

hey mike, just a guess here, but i would assume that the mods are intended to improve the "weakest links" of the mics designs/parts.

im pretty sure the goal here was to provide something high on the cost/benefit ratio. not enter into a race of "faithful reproductions of 10k vintage rare mics for $200".

plus, most of the folks here are working music people, not semantics people, so it might be best to just chalk it up to "inspired by", and jump right in.

[Oliver Archut]

Hello Roddy,

seems like that all of us that worked on the mod, seemed not to catch it, so I contacted the guy who drew these for correction.

Faithful reproduction?

I think it was made clear that "NONE OF THESE MODS" will give you an identical mic with reference to the classics.
The idea was to come up with several different varieties of general flavors attributed to a 47, 49 and a C12.

Best regards,

[Mike JM]

rjd2 wrote on Sun, 23 August 2009 18:10

hey mike, just a guess here, but i would assume that the mods are intended to improve the "weakest links" of the mics designs/parts. im pretty sure the goal here was to provide something high on the cost/benefit ratio. not enter into a race of "faithful reproductions of 10k vintage rare mics for $200". plus, most of the folks here are working music people, not semantics people, so it might be best to just chalk it up to "inspired by", and jump right in.

Absolutely, and I wasn't trying to argue semantics or offend anyone. I was just investigating and thinking out loud a bit - trying to get a more accurate impression of what the designs specifically/schematically were or weren't.

I think I'm going to do 2 of the C12 types with CT12 caps, Tab transformers, and Apex 460 bodies. They should make exceptional overheads and piano/acoustic mics. Then I think for U47 I will go with the IOaudio MK7, which I think is a better representation of the actual U47 schematic, which is what I personally want.

[compasspnt]

OK, I think the problem with the "47 inspired" schematic was my mistake...looks like I uploaded the wrong file, a previos draft version.

Thanks for catching that.

The right one (I think it is, please check me Roddy and Oliver!) is attached here, and also has now been uploaded to the website in place of the other one.

Regards!