Ela M251 wet tantalum?

[tonycamp]

can anyone tell me what was used in the original? After a search, I can't seem to find any capacitance value or voltage rating, only that it's a wet tantalum...

thanx for any info
T

 

[ln76d]

There were used different values - 1uF/150V and 3.2uF/70V (schematics shows mostly 150V) like in C28 and also 1.6uF/125V.
Only brand  i know is ERO and model EBF.  There could be used other brands also.
Cathode tantal capacitor was also ERO.
Resistors Beyschlag and ceramic caps Ingelen.
Ceramic tube socket (and also probably  connectors) - Hirschmann

Here you have something similar:
http://www.ebay.de/itm/4pcs-NOS-ERO-ROE-ETS-B-3-3uF-75V-MILITARY-GRADE-Axial-TANTALUM-Caps-for-AUDIO-/171732773449?hash=item27fc122a49:m:mohGq5YoqD1-Z4JBH7v2PnA

 

[Delta Sigma]

Found these caps 300V 3uF Tantalums.  Little more comfortable of a voltage rating.

Were there really 70V caps in original 251s? That could provide some comfort as I have some 125V wet tantalums I'm planning on A-B-ing with the polypropylene from Mouser (their polyester from Dany's BOM has gone obselete).

 

[Matt55]

I used these in my 251 clone. Sounds so lovely. I believe Jess Jackson also used that one too

http://www.ebay.co.uk/itm/191130283180?_trksid=p2050601.m570.l5999&_trkparms=gh1g%3DI191130283180.N36.S2.R1.TR1

My clone has the TC12 capsule, 1950s GE from Bowie and the AMI transformer. I didn't take a reading of voltage at the cap but clearly it gets nowhere near 120v. I purchased 4 caps from the link above they measured 3.48, 3.55, 3.55, 3.63 I used one 3.55 and put the other in a seperate bag for when I come to build the stereo partner.

Thanks, Matt

 

[ln76d]

Were there really 70V caps in original 251s?

Yes, as in C28. At the plate you will get 60V? 62V max? Current is around 1mA?
Remember that it was in 50's.

I found that there also were used siemens caps at the output.

 

[gary o]

I have 3 C28A's from early 60s came from BBC they all have 3.2 uf  70V in them, only one capacitor seems ok, I have a homemade point to point built Elam M 251... I borrowed a original Haufe T14/1 tran & the working capacitor, Im using Tim Camble capsule, mic sounds very nice but is not my favorite mic, I dont hear the 3D effect people talk of..... I compared the sound of C28a cap to modern polprop 3.3uf large cap, sounds same to my ears, dont know if vintage cap is up to spec but def doesnt sound worse.

 

[micaddict]

I have a homemade point to point built Elam M 251... I borrowed a original Haufe T14/1 tran & the working capacitor, Im using Tim Camble capsule, mic sounds very nice but is not my favorite mic, I dont hear the 3D effect people talk of.....

Although it willremain a mystery why some old ones with the Haufe do have the "3D effect", I would try Marik's  tranny in that point to point build.
Samar CT12.
BV8 size, mind. 

 

[Matt Nolan]

You often see quite low voltage caps in this position in older mics. For one, the older PSUs take a while to reach full B+, so the capacitor doesn't have to track that quickly. Also, in the C28, the transformer primary is referenced to B+, not to ground, and the leads are swapped to preserve polarity. This is a smart move. The heater takes a while to warm up and warm the cathode into emissivity, so the tube doesn't conduct for a while. The B+ can often come up faster than that, so the anode can be sat there at B+, output cap charging away through the anode resistor - if the other end of the trafo is at ground. With the other end of the trafo at B+ also, the capacitor has nothing to worry about while the tube is not yet conducting.

The 251 is not wired like this though. More room in there than inside a C28, so less need for a lower voltage (and hence physically smaller) output capacitor.

 

[OPR]

I think of the 3d effect can be thought of in a different ways, for example I hear this as an "effect" with smaller core transformers and even some capacitors, as the frequency ranges compress and saturate at different rates it seems to give the effect of divisions which appear as foreground and back ground in an exaggerated processed way. The other way 3d can be thought of is as ultra transparent and realistic with little audible artifacts caused by electronic components... well that's how I see it  so I guess it depends on which type of 3d your after  I'm sure other could describe it in another way

 

[gary o]

I have often read about this 3D effect with C12 Ela mics, a lot of myths seem to grow around unobtainable gear wondered if there was anything in it, maybe its too subtle for my ears..... my quest is to build my ultimate mic tho I dont know what that is yet haha, the 3 D would be interesting. I have read how special & un re creatable the C12 Ela capsule is, as I say I dont have original & my thoughts are  in most cases the capsule is 90% of the mics over all sound, my capsule is the Tim cambel, I would guess the 3D sound would come from the clever capsule . I read good reports & yes I think it sounds nice but as a vocal mic I have better sounding mics all down to my favorite capsule sounds best in just about every circuit I have tried. I read the C12 Elas have never really been favored for vocals over the years, the great Joe Meek had one & 2 U47s but only ever used the 47 for vocals....... sorry Im rambling on a bit , getting back to the main point the wet tantalum if there is 3D or any magic dust in its wettness & we cant get hold of correct values to play with could we parallell higher value down to 3.2uf for extra magic sound could worth a try 

 

[ln76d]

I agree with smaller core transformers, i used for example really small beyrdynamics in some microphones and these sound incredibly good.
With T14/1 there's another story - many people believe that the magic 3D effect is only in the old versions not from current production.
I had to measure ratio of three different T14/1 but i forgot about that. I will make it soon

For most of the magics in vintage microphones in many cases  responsible is the price!

Many myths over the years was proclaimed by people which were selling these type of gear or servicing it or manufacturing replacement parts.

I agree that old microphones have their mojo, mostly due to the imperfection of technology.
Thicker diaphragms, transformers, resistors, tubes or even selenium rectifiers. Those are the parts which creates all noises, harmonics, nonlinearities, non linear frequency response, weaker sensitivity, voltage swing etc.
Today most of the microphones is boosted in every way like everything in digital era but our ears mostly prefer all these imperfections

There's a place between zero and one for all these imperfections

From my experience, the higher output capacitor value - worse overall sound.
I prefer other places in the circuit to correct low end response.
I didn't found any capacitor which would sound better than MP.
In most cases polypropylene sounds worse than even polyester at the output.
If you want "effect" close to 3D, don't use MKP before transformer!
Carbon composite resistors aren't good replacement for German made carbon or wirewound resistors!
Carbon comps are good for guitar amplifiers

 

[JessJackson]

3d effect is very apparent.

Ive encountered it many times with rented vintage C12's and less occasionally Elam's. Never fully achieved it in my builds.

Think it must be to do with phasing and comb filtering on some level. Maybe full passive PSU, no regulators? maybe wire wound and carbon composite resistors? maybe tubular ceramic caps? play a part?

If you closed your eyes you would think you were using a stereo mic on a stereo bus.

If your in LA, there is one c12 from i believe FX rentals which has a red ring around the bottom of the head basket which i used to rent, this mic has this 3d sound. as long as it hasn't been modified in the past couple years, definitely worth renting to see whats going on.

 

[ding]

In case no one has read thru the D-ELAM 251 thread...

75V is the steady-state voltage seen across the bypass capacitor. When you first turn the thing on, especially with  a solid state PSU, the B+ will come up before the heater warms up - i.e. before the tube starts to conduct and so the plate voltage will be at full B+. Possibly more as, without the tube conducting yet, there is less current draw and so the B+ will be higher than the steady-state value. This may not be for long enough to blow an under-rated capacitor straight away, but it may well shorten its life.

There are mic designs where the output transformer is wired in opposite phase and between the plate and B+, rather than between the plate and ground. I don't know for sure the prime intent of this, but it could be to avoid this start-up problem and allow a physically smaller capacitor. You see it in the C28, for example.

Also this...

Good point, David Bock. I have been unable to find any wet tantalums over 125V in the 3.3uF range, and they are very expensive. Do you think it's really worth it sound-wise, and is it dangerous to use a cap of 125V? And wouldn't it be dangerous for the transformer if the wet tantalum goes caput? I read that they short when they fail.

I've never seen the wet tant in a 251 short out (I have seen loss of capacitance), though I've seen plenty of tants short out in ATR124 decks taking down the whole machine (smoke optional).
I have also seen original T14/1 xfmrs go open. That wire is mighty fine.
IF your new build mic does not copy the exact footprint of the 251, you should have more room for other cap options. Then you can listen and decide for yourself. But in a vintage 251, space is at a premium so the original cap is a must, unless you are willing to crack the plexiglass body, as some repairs guys are willing to do. FYI there is no electrolytic that will fit in that space that sounds good so don't bother.
Yes you can use a 125v cap, though it's safer with higher tolerances. The occasion of reaching 125v across the cap occurs at power up, when the B+ is there but the tube hasn't fully heated. Reaching full B+ once the tube is heated will likely not happen during normal use, unless you stick it in a kick drum.
I have found NOS went tants (of the value you need for this mic), even recently, so I know they are out there

 

[gary o]

Im very interested in the 3D effect are there recordings of this anywhere ? Is it just the Ela m25X or do C12 do it too....is it thought to come from capsule, transformer our wet tantalum head basket grill components or combinations of these things ...... will it be ore heard on drums rather than vocals.....bigs thanks 

 

[TLRT]

What type of cap was used in the original C12?(I know the value was 0,5uf) Btw the green soviet K42Y's are not bad at all however they are not true PIO caps. Anyway I like them in my builds.

 

[tonzauber]

in both my original C12 a large metal can  0,5uf Siemens Cap is used.

 

[tonzauber]

and from the other side (it's hard to fully read when it is installed)

 

[ln76d]

What type of cap was used in the original C12?(I know the value was 0,5uf) Btw the green soviet K42Y's are not bad at all however they are not true PIO caps. Anyway I like them in my builds.

It's 0.5uF MP - Siemens but the same you can find under ITT brand.

 

[ln76d]

tonzauber - do you want exchange trafo for original T14/1?

 

[tonzauber]

Nope because then my original SM204/23 wouldnt be an original SM204/23 anymore