Anyone got the new Stellar CM5 yet?
#61
6th January 2012
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Quote:
Originally Posted by jackinthebox View Post
i see. more like the original C12 circuit. thanks for the info.

you seem very well informed in all things Stellar.
...actually, the Chinese tube mics in general...they've been a passion of mine for years...it's quite impressive how far they have come over the past decade...I've tried many (sE, ADK, MXL, Karma, Advanced Audio, M-Audio, Avantone, iSK, CAD, Apex, Nady, Cascade, Stellar, Studio Projects, Mojave, etc) but kept only a few (more like a dozen or so)...the tube mics originating from this one particular factory (a branch of China's oldest) are IMHO, exceptional...but I'm not alone in that sentiment...many of the current crop of pricier "boutique brands" are also depending upon this factory to supply them with various components, from capsules to bodies, etc...but you already know this, I'm sure...

...and one of my favorite activities is bringing some of my favorite "keeper" tube mics to other local (slut) studios, where we can shoot them out among a broad range of microphones including some very highly regarded ones...makes for some very interesting and equally enlightening sessions...
#62
6th January 2012
Old 6th January 2012
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Quote:
Originally Posted by jackinthebox View Post
Do you think the buyer covering the shipping charges to try out a loan mic is reasonable?
Absolutely, but here's a twist for you. How about they cover shipping costs to them, and if they decide to BUY the mic and keep it, you discount for 1/2 of shipping costs. That would let me know you're serious about getting mics into my hands to check out.
#63
6th January 2012
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The C12 circuit is a plate follower circuit that uses one of the triodes to amplify the signal. The most modern tube mics uses both triodes as a cathode follower circuit. The second triode is used as an impedance converter to lower the impedance. This means you can effectively use a lower ratio transformer. I prefer the Plate follower circuit because the tube and transformer are driven harder and become part of the signature sound of the microphone. It is good to see that the CM5 is a plate follower circuit.

This is also true with Fet mics. The U87, Oktava 219/319 and many other classic Fet mics use a single Fet driving a transformer. Most of the newer mic designs utilize a PNP transistor to drive the transformer. This second stage of amplification also lowers the impedance and reacts similar to the cathode follower tube mic circuit.

Another configuration that is in some of the old Groove Tube / Sterling mics, most of the new pencil tube mics and the M149 Neumann mic uses a Fet followed by sub-mini tube that acts as the impedance converter. The addition of the tube in the circuit IMO does not give the mics the classic sound and action of a tube microphone. When I mod the GT/Sterling mics and pencil tube mics, I remove the Fet and reconfigure the circuit to have a single triode driving the transformer.

The CM6 uses a pentode tube that is strapped as a single triode and is a plate follower circuit. Pentodes have a very nice Hi- Fi sound. The U67 is the classic pentode microphone

Jackinthebox, it is nice to see all of the stacked film capacitors in your mics. This makes a big difference in the sound of the mic. What is the second large film used for in the circuit? They look like 1uf or 2.2uf. Can you post a pic of the other side of the mic? ..........Pleeease .....












Jim Jacobsen
JJ Audio


.
#64
6th January 2012
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Jim - have you ever examined an MXL Genesis with an eye on modification? If so, what did you do? When pushing the tube it's very rich, but it is a bit spitty (and of course has a noise floor). Any thoughts?
#65
6th January 2012
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Jackinthebox, it is nice to see all of the stacked film capacitors in your mics. This makes a big difference in the sound of the mic. What is the second large film used for in the circuit? They look like 1uf or 2.2uf. Can you post a pic of the other side of the mic? ..........Pleeease .....

here you go. They are both 2.2uf but they different rated resistors along side each one. They appear to both be ouput transformer coupling caps but i can't work out if they are in parralel or what.
It's not actually my design, i have been trying to get hold of the tech who introduced me to this mic but to no avail so far. i would be interested to hear your thoughts on the circuit and any areas that could be improved.

I believe it is a single triode design and it performs well. The components all appear to be of a high quality and the dual bobbin 4:1 transformer matches well with the tube. The 7 in cable seems to be the weak link but my replacement Gotham GAC-7 improves things drastically i that department.
I have been told it is possible to soften the K67 type capsule with a parallel cap over C5 - alongside the blue cap on the tube side of the circuit board. I haven't tried this yet as i don't think it is necessary really but i will experiment with it at some point. As far as i know the mic doesn't have a negative feedback circuit as it should for a true 67 circuit but the circuit doesn't seem to be too bright and peaky without it. I'm looking out for a small full range driver to make an echoic test chamber to some accurate frequency response measurements. I have tested with sweeps on fuzzmeasure using my ATCSCM50As but it's not the most accurate test rig. I could really do with someone in London with an audio precision rig to run a couple of quick tests for me!





#66
6th January 2012
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Quote:
Originally Posted by drBill View Post
Absolutely, but here's a twist for you. How about they cover shipping costs to them, and if they decide to BUY the mic and keep it, you discount for 1/2 of shipping costs. That would let me know you're serious about getting mics into my hands to check out.
An interesting idea. It would certainly be possible to do that sort of thing within the UK but overseas might get a little prohibitive cost wise.

Everyone who has tried one so thinks they are great value for money so i would hope there wouldn't be too many returns.
#67
6th January 2012
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Quote:
Originally Posted by changeng View Post
Jim - have you ever examined an MXL Genesis with an eye on modification? If so, what did you do? When pushing the tube it's very rich, but it is a bit spitty (and of course has a noise floor). Any thoughts?

Changeng,

The MXL Genesis uses the 12at7 tube. I am not sure of the circuit that is in this mic, however all circuits can be improved with better capacitors all around. Being transformerless, the coupling capacitors need to be the very best. Filtering and capacitor value can be used to "tune" the microphone's top end.











Jim Jacobsen
JJ Audio
#68
6th January 2012
Old 6th January 2012
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Quote:
Originally Posted by kidvybes View Post
...actually, the Chinese tube mics in general...they've been a passion of mine for years...it's quite impressive how far they have come over the past decade...I've tried many (sE, ADK, MXL, Karma, Advanced Audio, M-Audio, Avantone, iSK, CAD, Apex, Nady, Cascade, Stellar, Studio Projects, Mojave, etc) but kept only a few (more like a dozen or so)...the tube mics originating from this one particular factory (a branch of China's oldest) are IMHO, exceptional...but I'm not alone in that sentiment...many of the current crop of pricier "boutique brands" are also depending upon this factory to supply them with various components, from capsules to bodies, etc...but you already know this, I'm sure...

...and one of my favorite activities is bringing some of my favorite "keeper" tube mics to other local (slut) studios, where we can shoot them out among a broad range of microphones including some very highly regarded ones...makes for some very interesting and equally enlightening sessions...
They really are getting better all the time. I think they have learnt from the modders and are now really getting the idea that if you put a few bucks more into the components people will pay the extra happily if the product stands up against the big guys. It's mainly that the wage cost is so low over there that we are able to get things to market for a fraction of the price they would cost to manufacture in the US or Europe. It always surprises people when the cost doubles when you put say a Tim Campbell capsule in!
#69
6th January 2012
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Quote:
Originally Posted by jackinthebox View Post
They really are getting better all the time. I think they have learnt from the modders and are now really getting the idea that if you put a few bucks more into the components people will pay the extra happily if the product stands up against the big guys. It's mainly that the wage cost is so low over there that we are able to get things to market for a fraction of the price they would cost to manufacture in the US or Europe. It always surprises people when the cost doubles when you put say a Tim Campbell capsule in!
...true...and there are some highly-regarded pricey "boutique" mics out there with very similar origins...
#70
7th January 2012
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The 2.2uf Epcos cap looks like it is the last stage of filtering/ decoupling on the B+ voltage and the 160v capacitor is the transformer coupling capacitor. Both of these capacitors are MKT / polyester capacitors. They are the same as the Seimans.

The 100uf looks like it is the cathode bypass and it has a small film bypass capacitor to add back some highs into the mic.

The tube is the Russian 6c31b-p and was used in the early Lomo 19a19 mic.

The ceramic cap (C5) should be replaced with a Polystyrene, Silver Mica, or polypropylene.










Jim Jacobsen
JJ Audio
#71
7th January 2012
Old 7th January 2012
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[QUOTE=Haz-Mat-Strat;7409287]The 2.2uf Epcos cap looks like it is the last stage of filtering/ decoupling on the B+ voltage and the 160v capacitor is the transformer coupling capacitor. Both of these capacitors are MKT / polyester capacitors. They are the same as the Seimans.

The 100uf looks like it is the cathode bypass and it has a small film bypass capacitor to add back some highs into the mic.

The tube is the Russian 6c31b-p and was used in the early Lomo 19a19 mic.

The ceramic cap (C5) should be replaced with a Polystyrene, Silver Mica, or polypropylene.

I thought that ceramic cap looked like a bit of a weak link. Would you recommend replacing it with something of the same value?
It say 102 2kv on it. I guess that's 1000pico farad. I have had trouble finding a 2kv Mica cap anywhere.

How about this sort of thing?

http://uk.farnell.com/evox-rifa/phe4...mmp/dp/1678922

This looks interesting too but 2000pF.

http://www.ebay.co.uk/itm/DUBILIER-M...item1c226852fc

It looks as though the rest of the circuit is pretty decent though.

A better transformer would probably help.

I have been researching the LOMO19a19 with a view to converting the OM7 to as close as possible to a replica but i haven't been able to find any info on the transformer yet. I know it used a CK12 edge terminated capsule. The lundahl 1587 could be a possibility. Obviously the headbasket on th 19a19 was quite different to any other tube mic i've come across but they do sound lovely. I found this circuit which could be a good starting point.
An OM19 perhaps!?

#72
7th January 2012
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To properly trace the circuit you will need to take out the wire on the tube and draw out the circuit. According to Rodabod's schematic that you posted, the transformer is directly coupled with a 1uf capacitor to ground. Check your mic for this configuration. Check all of the voltages.

You do not need a 2kv cap on C5. 160v will work. 1000 to 1500pf will give you a good sound. I like polystyrene.

Polystyrene Capacitor 160V 1000pF | eBay

Talk to Oliver at Tab Funkenwerk about a transformer.






Jim Jacobsen
JJ Audio




.
#73
7th January 2012
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i wonder why they used such a high voltage cap?

TAB recommended their T8 but the tube is pretty obscure so i need to try one and see how it works.
#74
9th January 2012
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[QUOTE=Haz-Mat-Strat;7409746]To properly trace the circuit you will need to take out the wire on the tube and draw out the circuit. According to Rodabod's schematic that you posted, the transformer is directly coupled with a 1uf capacitor to ground. Check your mic for this configuration. Check all of the voltages.

I have since discovered that the 6C31b-p needs 6.3v for the heater and 100v for the anode so Rodabods 19A19 circuit seems slightly odd. There is also no coupling cap between the tube and transformer.

Rodabod, if you are around I would love to hear your thoughts.
#75
9th January 2012
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just wanted to say that I'm pleased about how open and cooperative everyone is being here! mic modding is a business, and sharing ideas seems counterproductive, yet I personally have increased my faith in all of the modders participating here as a result of seeing this information sharing.

modders and of course end users who are sharing info as well.

really good to see.

I mod my own mics for my own uses and learn from this stuff too, but I don't do the quality of work that the pro modders do (nor do I take my mods to such extremes by any means... just capacitor value changes for the most part with occasional component quality upgrades where I feel I'll get the most bang for my buck).

really great thread... one that is turning into a modding thread rather than just a cm-5 information thread.
#76
9th January 2012
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My CM5 should be coming any day now,can't wait to use it! I've heard that its VERY close to the TF 251(more so than the c-12).
#77
9th January 2012
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Quote:
Originally Posted by Illmo View Post
I've heard that its VERY close to the TF 251(more so than the c-12).
Really? Vintage? Reissue? Care to elaborate?
#78
9th January 2012
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Quote:
Originally Posted by drBill View Post
Really? Vintage? Reissue? Care to elaborate?
hahah you crack me up Bill :-D

but anyway, I think the cm-5 is definitely going to be a nice mic based on everything I've ready of it's design.

Just for fun (and because I'm like MR. low budget...) I'm sort of trying to build my own cm-5 at home right now.... figured it was a fun project that couldn't go wrong since imho ANY mod to an apex 460 is an improvement.


When I'm done I'll have a cm-5 and my old 460 self-modded mic design which uses the stock capsule with a HF filter capacitor and some other similar mods (which makes the cm-5 much more modded than my own 460 design aside from mine having a crazy head basket shape). will be fun to compare the two afterwards, not that I'll have any way of knowing that my knockoff cm-5 sounds like a real cm-5, as it were, but based on what I see/read of the circuit/capsule/tube it should be pretty close.

fun stuff.

I'm more inclined toward the cm-5 described sound than the cm-6 which from clips I've heard is very clean and clear but just a little too bright for my typical uses.
#79
10th January 2012
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Quote:
Originally Posted by dkelley View Post
hahah you crack me up Bill :-D
Why? I'd like to know what he's heard. I still haven't heard any clips of this mic. And I concur with your thoughts below. Hopefully it will be much less bright than the 6. If so, I might check it out. But I'd still like to know about the comparisons to a Tele 51.

Quote:
Originally Posted by dkelley View Post
I'm more inclined toward the cm-5 described sound than the cm-6 which from clips I've heard is very clean and clear but just a little too bright for my typical uses.
#80
10th January 2012
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Quote:
Originally Posted by drBill View Post
Why? I'd like to know what he's heard. I still haven't heard any clips of this mic. And I concur with your thoughts below. Hopefully it will be much less bright than the 6. If so, I might check it out. But I'd still like to know about the comparisons to a Tele 51.
You can hear a clip here:

Hundreds$ to Thousands$ Female Mic Shootout
#81
10th January 2012
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dkelley wrote:
Quote:
just wanted to say that I'm pleased about how open and cooperative everyone is being here! mic modding is a business, and sharing ideas seems counterproductive, yet I personally have increased my faith in all of the modders participating here as a result of seeing this information sharing.
Exactly. This way the love, passion, enthusiasm, faith, overall quality and GAS will only grow. Both mic buyers and modders will benefit. Win, win situation. And in the end the best modders will likely benefit the most. This not only holds for mic modding BTW and IME in many disciplines and crafts the best are often the least afraid to share.



Henk
#82
10th January 2012
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Quote:
Originally Posted by dkelley View Post

Just for fun (and because I'm like MR. low budget...) I'm sort of trying to build my own cm-5 at home right now.... figured it was a fun project that couldn't go wrong since imho ANY mod to an apex 460 is an improvement.


When I'm done I'll have a cm-5 and my old 460 self-modded mic design which uses the stock capsule with a HF filter capacitor and some other similar mods (which makes the cm-5 much more modded than my own 460 design aside from mine having a crazy head basket shape). will be fun to compare the two afterwards, not that I'll have any way of knowing that my knockoff cm-5 sounds like a real cm-5, as it were, but based on what I see/read of the circuit/capsule/tube it should be pretty close.

fun stuff.

I'm more inclined toward the cm-5 described sound than the cm-6 which from clips I've heard is very clean and clear but just a little too bright for my typical uses.

Most dfinitely Fun Stuff!

Are you going to keep the existing circuit or rewire the tube to change it to a plate follower?

There are many choices for the coupling capacitor that will smooth out the high end of the mic. Polypropylene is the best when you have the size constraints of the 460 body tube. Axon, Multicap, Mundorf all sound very nice in these circuits and they will fit.

Paper in Oil metal box capacitors sound "nice and vintage" however you must remove the transformer can and be creative in mounting the capacitor to the body rails.

The nice thing about rolling your own mic mods is that you can do things at your own pace and you can improve components as the budget allows.

Now you have available parts that did not exist 10 years ago. Transformers, capsules, and a wide variety of parts and suppliers that cater to the microphone industry. The quality of these parts have improved greatly over the years and now some of the newer "stock" mics have better components (mostly capsules) and have dialed back the bright, bright, bright sound that was the classic cheep mic sound.


You might consider one of the CK12 type capsules and remove the filtering. That will get you closer to that Vintage sound.

Dont forget the power supply.









Jim Jacobsedn
JJ Audio







.
#83
10th January 2012
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Quote:
Originally Posted by Haz-Mat-Strat View Post
You might consider one of the CK12 type capsules and remove the filtering. That will get you closer to that Vintage sound.
thanks jim, yea I'm good with all of it (I do a lot of diy work and circuit design/building) but I still have to figure out where to source one of those edge terminated capsules from.

I don't actually use credit cards which makes life difficult in this way. I need to be able to cod or send money and ensure delivery or something like that.
#84
10th January 2012
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There was a groupbuy here:
http://www.groupdiy.com/index.php?topic=45458.0

I was just in time and got the last one.
Perhaps there'll be a second.
Hey, we could even do it here.

Not modding circuits myself, mind. But I'll be experimenting some with different capsules.


Henk
#85
10th January 2012
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These are a good choice for an inexpensive CK12 style capsule. Also ADK CK12 capsules sound very nice. Also the TC12 by Tim Campbell is outstanding.



I know some are out of the general "low budget."






.




Jim Jacobsen
JJ Audio
#86
10th January 2012
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any very cheap mxl or similar mics that have one of these cv-12 type capsules in them? every cheapo I've come across (that is actually a legit LDC) uses the 67 style. cuz I could buy one with the cv-12 type cap and swap it with the 67 in my 460 to get the 460 sounding right and the other mic would become a standard chinese bright ldc (unless I put a HF filter on the other mic at this point).

edit: wow, that group buy made the capsules something like $28.50 each, right? I'm trying to figure it out from the thread. amazingly cheap for something so cool.
#87
10th January 2012
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Quote:
Originally Posted by dkelley View Post
I still have to figure out where to source one of those edge terminated capsules from.
...I also like the 6-micron C12 capsule used by Dave Thomas, Stellar and quite a few more costly brands...you can get them from Advanced Audio here:
Advanced Audio Microphones

...as to that group buy thread, Ningbo Shengke/TongXin who supply that capsule (same as the microphoneparts.com version), are not very accommodating these days in terms of selling their capsules in bulk to anyone other than mic manufacturers...that same vendor (WGT) was on eBay selling them a while back (for about $30) and once the factory found out, those auctions were terminated...

http://www.nbmic.com/products.asp?id=102
#88
10th January 2012
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Yes, as a matter of fact, the thread in the groupbuy link started about the RK-12 and the question was if the WGT is the same.
HTML Code:
http://www.wgt1979.com/en/productsd.php?pid=66


Henk
#89
10th January 2012
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P.S. Excuse the poor linking on my part. Nothing seems to work lately.


Henk
#90
10th January 2012
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Quote:
Originally Posted by legato View Post
P.S. Excuse the poor linking on my part. Nothing seems to work lately.


Henk
I just said that to my wife last night in bed...
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