R/E/P Community

R/E/P => R/E/P Archives => Klaus Heyne's Mic Lab => Topic started by: Steve Hudson on January 10, 2008, 11:04:49 AM

Title: M269 vs. M269c
Post by: Steve Hudson on January 10, 2008, 11:04:49 AM

I picked up an M269 this week and am in love with it. I've read Klaus' post saying that with the cathode bias mod (making it an M269c) the mids open up a bit but the mic retains the same timbre. Is the difference in tone subtle or is it worth having Sennheiser make the upgrade?

Title: Re: M269 vs. M269c
Post by: Klaus Heyne on January 10, 2008, 02:29:28 PM

Quote:

with the cathode bias mod (making it an M269c) the mids open up a bit but the mic retains the same timbre.

Yet another senior moment (or, more likely, a result of being the sleep-deprived father of a six-year-old): I cannot recall any such statement.

The main difference in M269 will be the noise floor improvement with the 'c' version, about 2-4 dB.
Timbre differences between fixed and self bias are rather small in AC 701 -equipped mics.

Another way to put it: I see no sonic disadvantages converting to 'c'.

Title: Re: M269 vs. M269c
Post by: Steve Hudson on January 10, 2008, 03:16:23 PM

Klaus, here is your post on the Neumann message board from 2004 (link included):

http://neumann.com/forums/view.php?site=neumann&bn=neuma nn_archive&key=1081415839

"M269 conversion to M269c is not complicated.
The M269 mic will not sound better as a 'c', but it will have a slightly lower noise floor, and its mid range response will be a bit more slender and transparent, due to different cathode tube biasing.
This, again, is not in itself a sound improvement, but a different interpretation of timbre.
Kind regards, Klaus Heyne"

What I am curious about is the degree to which the midrange becomes "a bit more slender and transparent" with the "c" mod, and I take it that your opinion is that is a very subtle change in tone.

Title: Re: M269 vs. M269c
Post by: Klaus Heyne on January 10, 2008, 05:16:25 PM

Yes, very subtle and hardly noticeable, unless you can hear two similar mics with their different biasing side by side. The non-'c' will be a tad more cottony in the mids. Thicker may be another word, less resolved yet another.

Again, this is a very slight sonic difference.

Title: Re: M269 vs. M269c
Post by: Steve Hudson on January 10, 2008, 05:30:29 PM

Thanks. Mine was one of the last M269s made without the "c" mod (Feb 1965) and since I'm quite happy so far with the sound of the mic I think I'll keep it stock for now.

On a slightly different tangent, do you know why Neumann designated the omni and figure 8 patterns on this mic with the letter "F" instead of the standard graphic of each polar pattern?

Title: Re: M269 vs. M269c
Post by: Klaus Heyne on January 11, 2008, 03:58:50 AM

The 'F' stands for "Fernumschaltung" (remote pattern control). If your pattern control switch is on one of the two 'F' either side of center postion (carioid) the pattern of the mic can be remotely switched from omni to carioid to eight, and anything in between, via the continuosly adjustable pattern knob on the power supply. (It does nto matter which of the two 'F' positions you choose-they both do exactly the same.)

When the switch is on cardioid, the pattern control of your power supply is bypassed, and an extra 4dB of s/n for the mic is gained.

This is the cleverest pattern choice system ever invented:it retains the best s/n in the most prevalent pattern (card.) Yet it also makes it easy to quickly dial in any incremental pattern from omni to eight, when needed.

Title: Re: M269 vs. M269c
Post by: Steve Hudson on January 11, 2008, 11:37:23 AM

Thanks. I knew the "F" setting corresponded to remote pattern changing from the PSU (and I agree that it's a very well-implemented scheme) but was curious what the "F" stood for.

Title: Re: M269 vs. M269c
Post by: Steve Hudson on June 18, 2008, 05:23:00 PM

My M269 just came back from Sennheiser and was given a clean bill of health (the mic required no work; the Korby PSU was the cause of some noise) and they confirmed that it already has the "c" mod. Best ebay find ever.

Title: Re: M269 vs. M269c
Post by: J.J. Blair on June 19, 2008, 02:13:24 AM

Steve Hudson wrote on Wed, 18 June 2008 14:23

the Korby PSU was the cause of some noise

Can you be more specific? I've heard that it may have to do with the method of heating the tube, and was wondering if this is on that list.

Title: Re: M269 vs. M269c
Post by: Steve Hudson on June 19, 2008, 11:00:07 AM

The Korby PSU's filament voltage was set on 2.8 volts instead of the required 4 volts and the plate voltage had been turned down to the minimum 85 volts instead of 120 V. The output tranny was set at 50 Ohms instead of 200. He made these adjustments and the mic sounded great. I was afraid that the AC701 had gone bad but Mr. Sattler said it checks out fine. Do these voltages drift over time? If so, what's a good service interval to have PSU voltages checked?

Title: Re: M269 vs. M269c
Post by: J.J. Blair on June 19, 2008, 01:54:37 PM

Steve, thanks for the info. Was this a Korby serviced mic? Or did he jut make the PSU?

Title: Re: M269 vs. M269c
Post by: Steve Hudson on June 19, 2008, 02:19:17 PM

I don't know if Korby ever saw this mic. An LA gear dealer listed the mic with a Blue shock mount and the Korby PSU with a ridiculously low "Buy It Now" price so I took the gamble as it was not an "as is" sale.

Title: Re: M269 vs. M269c
Post by: J.J. Blair on June 19, 2008, 02:36:55 PM

Yeah, they are nice indeed. I have a M367 here right now. It's my understanding that it's the same mic with a different connector.

I had the opposite problem though, as the voltage was 160V, and the headroom just went to shit as a result. When I fixed that, the sound got so much better. I'm going to replace the PSU with one of Oli's though, to protect the tube. Have you measured the voltage when you power up the mic, to see if the Korby ramps the voltage or just goes full on? The PSU I have here jolts it, which is the main reason I'm making the change. I just spent a the same amount a pair of AC701s that we used to spend on a single VF14.

Title: Re: M269 vs. M269c
Post by: Steve Hudson on June 19, 2008, 02:46:41 PM

Hmm, if the Korby doesn't ramp I might pick up one of Oliver's PSUs just to protect the tube (are they stock items or special order?). I can't rely on my super-secret source of affordable (and guaranteed) AC701s having stock when I need a replacement. BTW, do Neumann NKM supplies ramp up the voltage? I have one for my KM54c.

Title: Re: M269 vs. M269c
Post by: Barry Hufker on June 19, 2008, 04:11:11 PM

While trying to take nothing away from Oliver, Scott Hampton of Hamptone makes fine power supplies which ramp up. You can find Scott quickly with a search on the web. I have several and like them very much.

Title: Re: M269 vs. M269c
Post by: Fruition Music on June 26, 2008, 05:20:09 PM

Steve Hudson wrote on Thu, 19 June 2008 11:00

Do these voltages drift over time? If so, what's a good service interval to have PSU voltages checked?

I adust my voltage in my N52a about once a year, I've been told dial it to 3.95v by Klaus. (measured at the tube, not the p.s.! K.H.)

I've also been looking for a replacement PSU for my other N52 used with my KM254...does anyone rebuild N52s? Worried about the stablytes in it going bad.

Title: Re: M269 vs. M269c
Post by: seedyunderbelly.com on June 27, 2008, 07:56:17 AM

Barry Hufker wrote on Thu, 19 June 2008 15:11

Hi Barry,

Yes Scotts work is Top notch imo

I have dealt with him for 15 years he is a genious rock. Solid and as thorough as they come often not to his advantage. I would Highly reccomend Scott's supplies-

The address is:

WWW.hamptone.com

His Jfet pre is unique and good also.

I have opened his mics/pres and the work is beautiful.

j