Topic: Schoeps KC5 and CMC-5 or CMC6

[dream]

Are there any experiences which Schoeps amplifier works better with a KC5 active cable, CMC5 or CMC6?
I have both amplifiers and the mentioned cable. The cable is unbalanced and may be it operates better with
one of the amplifiers concerning interferences etc. Many thanks for some info.

[stevetoney]

Others have explained to me that the voltage delivered by both preamp bodies is 48V to the active cables...IOW Schoeps capsules need 48V to operate.  Since the CMC6 can operate with a lower supply voltage, the CMC6 must include internal components to transform the voltage to 48V, whereas the CMC5 needs 48V supplied to it.  Otherwise, I've been told that both preamp bodies are the same in terms of the functions that they provide to the sound, amplification, etc. 

Logically, if 48V is being supplied from both models through the KC5 cable, it stands to reason that there would be no difference in performance of the active cables.

Having said this, I'm not an expert.  I'm just extrapolating the information I've been told to make a logical conclusion.  But my logic might be all wrong.

EDIT:  Please read DSatz's response below for corrections to this post that I made earlier today...particularly with respect to my statements about 48V being supplied to the microphone capsule...which Mr. Satz corrects me to state that it's actually 60V.

[DSatz]

dream, the amplifier that Schoeps normally recommends nowadays for all phantom-powered operation is the CMC 6--, because it can be used either with standard 48-Volt or standard 12-Volt phantom powering (with twice the power efficiency at 12 Volts--very interesting for people who run their equipment on batteries), and because CMC 6-- amplifiers made in the past several years have better immunity to extreme radio-frequency interference, while the same level of protection wasn't added to the other, older amplifier models.

If I were buying new amplifiers today, there is no question which one I would buy. It's not that the old ones were slouches--I can remember only two RFI problems in 30+ years of using them--but the number of devices that radiate energy at radio frequencies has increased enormously in the past decade, the wavelengths being used are shorter than were commonly in use when the series was designed in the early/mid 1970s, and nowadays your vocalist may very well have a Blackberry in her pocket while she's standing six inches from your microphone.

Apart from that, however, the performance of a CMC 5-- or CMC 6-- with active accessories such as a "Colette" cable is precisely equivalent; neither model is better than, worse than, or different from the other at using them.

--tonedeaf, just to explain some details, since you seem interested in these things (bless your heart): The voltage delivered by any Schoeps CMC amplifier to the microphone capsule (whether or not an active accessory is used, such as a Colette cable), is 60 Volts rather than 48. This gives higher sensitivity and a better signal-to-noise ratio. All amplifiers of the Colette series contain DC converters to derive the polarization voltage from the incoming powering. This includes the CMC 5--, which is designed for 48-Volt phantom powering only. Since its current draw is about 4 mA, the voltage drop across the specified supply resistors is almost 14 Volts, leaving the microphone to receive only about 34 Volts anyway. The same applies to the CMC 6-- when it is powered at 48 Volts rather than 12 Volts.

Prior to 1974 Schoeps made the CMT series of microphones, in which the powering was just as you describe: The 12-Volt models used DC converters to create 60 Volts for capsule polarization, while the 48-Volt models used the input voltage more or less directly to polarize the capsules. But that limited the 48-Volt models to a very low supply current (< 1 mA) so that the voltage drop across the supply resistors wouldn't be excessive. That current limit, in turn, somewhat limited the maximum SPL that the microphone amplifier could keep up with. In addition, the capsules for the 48-Volt versions had to be trimmed a little differently to compensate for the lower polarization voltage, with the result that the capsules weren't fully interchangeable between the 12-Volt and 48-Volt mikes.

The higher-current, transformerless design of the CMC 5-- amplifier allowed the maximum SPL of the microphone to increase to ca. 130 dB, and allowed users to use any Colette capsule and/or accessory on any CMC amplifier regardless of voltage. The CMC 6-- amplifier was introduced many years later, but its 48-Volt mode works the same way as the CMC 5-- in that the incoming voltage is still stepped up to 60 for polarizing the capsule.

--best regards

[stevetoney]

The reason I was somewhat sensitized to the voltage difference between the CMC5 and CMC6 is that I recently obtained a preamp that was designated as an Oade m148.  An m148 supplies 48V phantom power.  However, upon receiving the preamp, it wouldn't power my microphones.  Hmmm.  Doing a bit of diagnosics, I discovered that the preamp was only putting out about 18.5V.  I opened it up and discovered that the preamp was actually an m118, which is basically the same preamp but only providing 18V phantom power.  As I think I had mentioned to you sometime ago, my CMC5's are somewhat skitzy, so I decided to go ahead and buy a pair of CMC6's...which now I'm very pleased with particularly since, as you mentioned above, with the lower voltage input, the runtime from the batteries at the lower voltage is FANTASTIC!

Anyway, thanks for the feedback, but thought I'd explain just a bit about why I was somewhat partially informed about some of the differences (at least from the end-user perspective) between the two products.

[dream]

Many thanks for the answers. I distilled that I can use either CMC body for equivalent results. The CMC5 body
is (was) a Strässer 24V version which was serviced and adjusted to CMC5 specs by Andreas Grosser, it was my entry into the Schoeps range. The CMC6 I bought only a few weeks later. I use these Schops with Grace Design m201A/D, m101 and Lunatec V3 and I'm delighted with the results. Usually I don't think about which body I use with my capsules. With the KC5 I thought there maybe a difference. And frankly I hoped Mr. Satz would answer and I thank him also for all the other valuable info he is giving out here concerning microphones - what a great source of clear written info coming from deep knowledge. Usually I lurk here, because my focus is composing and producing and 'only' use my mobile equipment for sampling purposes. Otherwise my microphone needs are for recording voices.
I hope I wasn't too talkative, going slowly back into lurking mode ...

[DSatz]

tonedeaf, a CMC 3-- (for 12-Volt phantom powering) and a CMC 5-- (for 48-Volt phantom powering), for any given date of manufacture after the earliest production batches in 1973/74, are precisely the same amplifier and are built on the same printed circuit board, with only two solder bridges closed for the 12-Volt version which are left open for the 48-Volt version. So, if you ever know for certain that you will want to use your CMC 5-- amplifiers with 15-Volt (i.e. 12-Volt) phantom powering for some length of time, you might consider converting your CMC 5-- amplifiers to the CMC 3-- setting. Since you also indicated that you've had some kind of problem with them ("skizzy" ?), I would recommend sending them back to the factory for checkout, and to let them rebridge the amplifiers for 12-Volt operation.

There they would also replace the ID ring on the amplifiers so that their model identification will match what is inside. This is important because Murphy's Law frikkin' GUARANTEES that otherwise, you or someone else WILL (not "may" or "might") some day plug them into 48-Volt phantom powering. This won't harm the microphones but it might harm the power supply, since a CMC 3-- connected to 48 Volts tries to draw around 11 mA. About five years ago when this happened to me, an otherwise very nice portable preamp/converter went "poof" (yes, it was audible) and put out a tiny column of white smoke which hovered for a minute next to the preamp, and there was the "uh-oh" smell of a fried printed circuit card in the preamp/converter. The damage was expensive to repair; fortunately, it occurred on my test bench rather than just before a concert recording.

Just FYI I had the reverse of this same conversion done at the factory--I bought my first Colette-series microphones as CMC 3-- (12-Volt) microphones because that worked better with the battery-operated Nagra IV-S recorder that I was using at the time. Then after I switched to digital recording, I had the amplifiers converted at the factory to 48 Volts (and checked out at the same time, since by then they were 15 to 20 years old). The factory put new ID rings on them, and now they are real CMC 5--s. However, since I got hold of a pair of CMC 6--s with the RFI improvements, those are what I always use first.

--best regards

[DSatz]

dream, hello, and many thanks for the kind words. Yes, a Colette cable will work equally well with a CMC 5-- or a CMC 6-- (or a CMC 3-- or CMC 4--, or even the "private" 24-Volt versions which Schoeps has built for the ORF and for Strässer--the latter being sometimes called the "CM 90").

However, I'd recommend (and Schoeps recommends) that any stereo pair be made with the same type of amplifier for both microphones, because both the output impedance and the frequency and phase response at the lowest audio frequencies is often a little different between any two of the different versions--and in several respects our hearing is more sensitive to inter-channel differences in sound than to anything which affects both channels of a stereo recording the same way at the same time.

--best regards

[dream]

However, I'd recommend (and Schoeps recommends) that any stereo pair be made with the same type of amplifier for both microphones, because both the output impedance and the frequency and phase response at the lowest audio frequencies is often a little different between any two of the different versions--and in several respects our hearing is more sensitive to inter-channel differences in sound than to anything which affects both channels of a stereo recording the same way at the same time.

I had no plans to use CMC5 and CMC6 for stereo applications and of course I think about getting another CMC6 one day ...
right now a Neumann RSM-191 is my stereo sampling mic and the Schoeps mics are used for single channels only.
Many thanks anyway for the hint.

[pyiteac]

DSatz,

I love your posts about all types of Scheops stuff.  My brother now has a pair of M221's and what he has done with those is special.  I really enjoy the tone of the vintage Ak 701 Telefunken Scheops 221's.

Now to my question as it kind of relates to the CMC5/CMC6 discussion.  I currently use a VMS02ib as my pre/capsule power supply.  My question is what does the VMS02ib line up more like in sub 50hz production.  The CMC5 with a 30hz roll off or the CMC6 with the 20 hz roll off.

I'm thinking it has the 30 hz roll from my experiences but an expert opinion would be valued.  Thanks for your time and your expertise. 

[DSatz]

pyiteac, according to the catalog from back then, the low-cut filter in the VMS 02 IB starts at 30 Hz but has a steep slope (18 dB/octave) below that. That's different from either a CMC 5-- (30 Hz filter but only a 6 dB/octave rolloff) or a CMC 6-- (20 Hz filter, 12 dB/octave).

--best regards, and thanks for the kind words