Source fo "Feed Through" Capacitors for U67 - Help

[Whoops]

Hello,
I need a source for the Feed Through Capacitors as used in the Neumann U67.
In the U67 schematic that's C12, C13, C14, C15, C16, those are 2000pf or 2200pf.

Anyone knows a source for these kind of capacitors?

I found a source in ebay for feed through caps from Bulgaria but those are much bigger than the ones used in the U67,
but I can't find any other source for these kind of caps. Farnell and Mouser don't seem to stock also this type.

Here are 2 photos of the caps I'm referring to,
in the vintage U67 those are grey and in the Reissue U67 mic they're blue:

 

[ccaudle]

Various capacitor manufacturers make feed-through parts. You will probably have to measure some existing parts to get the right size. Vishay make some, although that package style is becoming much less common.
C12 and C13 are on the signal lines. I did not see any notes in the schematic I found about dielectric in the original design, but I would avoid X5R and X7R on signal lines. Those are the most common ceramic capacitor formulations, but the capacitance varies with voltage, so can add distortion. I don't know how noticeable that will be at microphone levels, so might be OK if you can't avoid it. C0G would be the preferred formulation for signal lines if you can find it in 2000pf feed-through.

Is this for repairing an existing mic, building a new mic but using an existing PCB layout, or from scratch? If starting from scratch it might be easier to find a different form factor. There are feed-through caps in surface mount packages that may be easier to source.

 

[Whoops]

its a new build but with a pcb made with the same form factor of the original U67, so surface mount is a no go.

I'm looking for the same form factor as the photo I shown, thank you

 

[RuudNL]

Something like this?

KER. DOORVOERC 1800 pF – Van Dijken Elektronica

www.vandijkenelektronica.nl

 

[moamps]

https://www.rf-microwave.com/en/nbp/nmp/feed-through-capacitor/cp-s08/

 

[gyraf]

Durchführung

 

[Whoops]

Something like this?

KER. DOORVOERC 1800 pF – Van Dijken Elektronica

www.vandijkenelektronica.nl

Hi Ruud,
Thank you friend, that’s exactly it, unfortunately it seems they only have the 1000pf and 1800pf values

 

[Whoops]

https://www.rf-microwave.com/en/nbp/nmp/feed-through-capacitor/cp-s08/

thank you much, it seems a good source gonna try to order from them

 

[Moby]

Hi Ruud,
Thank you friend, that’s exactly it, unfortunately it seems they only have the 1000pf and 1800pf values

Those bastards are with high tollerance. 1.8nf instead 2nf will do the job. Trust me the problem is that I can't see the voltage rating

 

[ccaudle]

unfortunately it seems they only have the 1000pf and 1800pf values

Those are just to filter RF interference entering the microphone. The exact values are not critical.

 

[MidnightArrakis]

I was going to mention that this style of feed-thru capacitor is commonly used within "RF" equipment and since I have worked with several different types of commercial and military-related "RF" companies designing their PCBs, if you can send me a detailed mechanical drawing of the part you need, I just might be able to come up with a feed-thru cap of what you are looking for.

As far as the voltage rating goes, since condenser microphone use "Phantom" voltage of 48VDC, I would guess that the voltage rating of the caps are either 50V or 63V. Does that make sense?

/

 

[ubxf]

I don't think a U67 likes phantom power it's a tube mic.

 

[Gus]

Two of the caps should be matched very closely for the signal outputs for good CMRR at RF frequencies.

Also as posted in this thread check what material is used as the dielectric

 

[ccaudle]

I don't think a U67 likes phantom power it's a tube mic.

Indeed, the two caps on the signal lines should have very low voltage across them, but one of the caps is on a power supply feed and shows 210V on the schematics I saw. You would want a cap rated near 300V on that pin.

 

[Whoops]

Yes, Gus and ccaudle are correct, thanks

MidnightArrakis, the U67 is a Tube based microphone, B+ voltage is around 210V in this mic. So the cap that’s in this line should be rated higher than that.
The other 4 caps can be rated at a much lower voltage

thank you all

 

[mad.ax]

The M269C (basically a U67 with an AC701) schemo says 2000pF/500V~ for C12->C16

Axel

 

[mad.ax]

Same thing for M267, M269 (non C), and M367. All show 2000pF/500V~.

Axel

 

[Whoops]

Same thing for M267, M269 (non C), and M367. All show 2000pF/500V~.

Axel

The 500V rating is not needed for the caps.
In the U67 on C14 that sits on the B+ line (aprox. 210V) will need an higher voltage, 300V or 400V will be enough for that cap.

All the other ones C12, C13, C15, C16 can be much lower voltage caps.

If in those schematics Neumann stated all at 500v, it's because as a company they buy parts in Bulk, big quantities, so it's easier and cheaper for them just to buy the same cap for all positions instead of buying smaller quantities of 2 caps with different voltage ratings.

 

[Whoops]

I ended up buying the 2200pf Feed Through Capacitors from Ebay.
All were located in Bulgaria but from 2 different sellers.
I'm very happy with the service and the parts.



For the 400V capacitor I bought these ones:

2200pF 400V ± 20% Feedthru Feed Through Ceramic Capacitor KTP-1AB N70 (5 pcs)​

2200pF 400V ± 20% Feedthru Feed Through Ceramic Capacitor KTP-1AB N70 (5 pcs) | eBay

2200pF (2.2nF) 400V ± 20% Feedthru Feed Through Ceramic Capacitor KTP-1AB N70. It is unused and in perfect condition. Important information.

www.ebay.co.uk

And for lower voltage ones (smaller) I bought 2 types, one made in Germany and the other many in Russia, both are 200V:

2200 pF 2.2 nF 200 V LOT OF 10 GERMAN CERAMIC FEEDTHROUGH CAPACITORS​

2200 pF 2.2 nF 200 V LOT OF 10 GERMAN CERAMIC FEEDTHROUGH CAPACITORS | eBay

A bout Item: 2 200 pF/200 V, high quality, ceramic, feedthrough capacitors. Capacity: 2 200 pF± 10%. The condenser consists of a ceramic tube coated with a inner and outer electrode, which is within the output, which connects the power source and load.

www.ebay.co.uk

2200 pF 2.2 nF 200 V LOT OF 10 RUSSIAN CERAMIC FEEDTHROUGH CAPACITORS​

2200 pF 2.2 nF 200 V LOT OF 10 RUSSIAN CERAMIC FEEDTHROUGH CAPACITORS | eBay

A bout Item: 2200 pF 200 V, high quality, ceramic, feedthrough capacitors. Capacity: 2 200 pF ± 10%. These capacitors are produced and sold without nuts. The condenser consists of a ceramic tube coated with a inner and outer electrode, which is within the output, which connects the power source...

www.ebay.co.uk

 

[mrbutterskin]

If anyone in the US is looking for a source for these, Surplus sales of nebraska has a large variety:

Axial Wire Feedthrus - Solder In

Feedthru filters, solder mount feedthrus

www.surplussales.com

I got the ones labeled

(FRI) FT2404-152

1500 pF, 350v