Started my poctop D49c build!!!

[achase4u]

Many thanks!

So, the T49 transformer is more made for the original tube as I understand it.  So I may just remove the filtering.  But you say its low pass filtering.  That means there will be more highs.  The problem with ht 5840 substitute is that it doesnt have as much lows, right?

I installed the tube.  My kester 44 doesn't want to be super shiny on the studs there, but I think it will work.

 

[ln76d]

T49 - let say it should be more linear in whole audio spectrum - so this is what you want
Sorry, my fault - i had in mind HPF not LPF. LPF is still in the circuit and you want to keep it.
It's a 600pF capacitor and doesn't affect so much usable audio frequency range but is more important for RF.
There's no any problem with 5840 - it doesn't fit exactly original specs and rest are stupid speculations from those which doesn't know what they talking about. First improvement for this tube is different cathode resistor.
Many people treat tubes like audiophiles do - everything is interchangable and some sound better some worse - it's a bullsh*t.
Every different tube works in different conditions and sometimes minor changes can save your tube before it will go to thrash.
Other thing is tube physical condition and keeping specs.
HPF is a "broadcast" filter which cut the low end at 40Hz - it sound even nice but is not so great in studio use.
Without it -  it will be still sound of m49 clone.  Not saying that clone would be similar to the original m49 anyway
If your kester is with the silver it wouldn't be shiny, if the turrets are silver plated  it also wouldn't be so shiny.
Try different temperature if you are using soldering station with regulation.
Anyway - you need little bit more practice with soldering (please do not take this negatively), clean the boards after work.
I would also make shorter tube leads and use some insulation tubing on some.

 

[achase4u]

T49 - let say it should be more linear in whole audio spectrum - so this is what you want
Sorry, my fault - i had in mind HPF not LPF. LPF is still in the circuit and you want to keep it.
It's a 600pF capacitor and doesn't affect so much usuble audio frquency range but is much important for RF.
There's no any problem with 5840 - it doesn't fit exactly original specs and rest are stupid speculations from those which doesn't know what they talking about. First improvement for this tube is different cathode resistor.
Many people treat tubes like audiophiles do - everything is interchangable and some sound better some worse - it's a bullsh*t.
Every different tube works in different conditions and sometimes minor changes can save your tube before it will go to thrash.
Other thing is tube physical condition and keeping specs.
HPF is a "broadcast" filter which cut the low end at 40Hz - it sound even nice but is not so great in studio use.
Without it -  it will be still sound of m49 clone.  Not saying that clone would be similar to the original m49 anyway
If your kester is with the silver it wouldn't be shiny, if the turrets are silver plated  it also wouldn't be so shiny.
Try different temperature if you are using soldering station with regulation.
Anyway - you need little bit more practice with soldering (please do not take this negatively), clean the boards after work.
I would also make shorter tube leads and use some insulation tubing on some.

Interesting.  However, did they make the original m49 so that it would be flat?  So changing to a 5840 then using the original transformer spec might cause some peaks or troughs?  Or does it not work that way?

My kester is good old fashioned leaded 60/40 solder.  The bottom of the board is nice and shiny on the joints.

I see the HPF will affect 40hz and under(if 40hz is the corner meaning 6db below point, then some frequency above is also attenuated).  This is interesting.  Did other Neumann mics use this HPF? Many records have been made this way, though more sub would be good for kick drums and bass etc...

The fabrication of the toroidal transformer mount is done.  Ah.  Deburring of the holes and everything.  I like metal work.

Yay!  Hopefully I can have the PSU done soon, and just work on the mic and then BAM!  Summer of m49...

 

[ln76d]

First M49 was virtually flat - there was no intended filtering.
If you achieve similar plate and cathode voltages there should be all fine.
There shouldn't be any peak. Oliver stated that with the 5840 there's low end drop comparing o the AC701k.
Another time he wrote that lower value of cathode capacitor is better for this tube.
Somtimes he mentioned about removing all filtering especially all feedback path.
Then he invented transformer with extended low and low mid.
All this doesn't add up!
This is what i wrote before. Keep voltage specs changing at least cathode resistor and all will be fine.
Here you can see how aproximated frequency responses were for M49C.
http://recordinghacks.com/pdf/neumann/M49-M50.pdf
You can always add HPF, you can even tune it to go lower, but this is another feedback path inside the circuit - which isn't needed.
One is enough
I'm not sure about U67 but U87 have also hpf, but it's tuned much more properly too keep better low end response - because it was typical studio use microphone. M49 had broadcast filters for broadcast use It was the biggest market in these times.
Think about switch S2 for cardioid only. You should like it.

From Klaus Heyne:
"All M49 models after 1957 had a “cardioid only” switch built in, to achieve a 4dB s/n improvement [as compared to setting the pattern] remotely, from the power supply. "

I found that on my mic builds, before i saw this text, that the best cardioid setting is with completely disconnected back diaphragm.
If you have no option for switch use 3pF capacitor instead 1nF.
This is also what i modified for your p67  - you have no connection by 1nF capacitor between two sides of the capsule.
It's a big improvement.

 

[micaddict]

Yep, U67 has the filter, too. Inside, S2 can be bridged or jumpered. Not to be confused with the  HPF on the body (200 Hz HPF).

I've never heard that the 5840 was anaemic in the lows, but ideally it may ask for a transformer with a different ratio? Wiser guys than I should be able to do the math.
Apart from ratio, size can play a part, too. Some say the big tranny in the first C12s goes a full octave lower than the later Haufe T14/1.
Anyway, no doubt Oliver had his reasons. But unfortunately, we can't ask him anymore.

And this brings me to another member who passed away recently. Kidvybes bought Dany's prototypes (thus in assembled state) of the M49b and the M269c. After that he had them fine tuned and among other things, the tubes were replaced for another type subminiature. Probably the 5703.  But we can't ask him anymore, either.

As for lows, it depends what you're after.  There's lows and there's deep lows.
If you'd want to capture the low note of a big pipe organ (16 Hz?) you  wouldn't want to use an LDC anyway. A true pressure microphone (omni SDC) would be needed.
Then there's the 20-40Hz range. Bass guitars used to be above that, but now often come with a low B (approx. 31 Hz). That said, if you miss the fundamental, you'll still hear the tone.
BTW, yes, a 40 HZ HPF will have audible consequences a little higher up, too. But as a matter of fact, the HPF in a U67 actually has a stated corner frequency of  30 Hz, not 40 Hz. But 40 Hz better represents the real world effect.

If you don't use instruments that go below 40 Hz, like vocals, acoustic guitars and many other instruments, you're often better off without the low end sensitivity. Full range mics are very sensitive to rumble. You can acyually see this when you look at the woofers of your speakers come play back time. You need great isolation to truly avoid that.

Then there's the usual lows as well as low mids. Let's say 40-400 Hz. This range is what actually in most cases gives that full and meaty sound. Think proximity effect etc. This sounds much more impressive than an SDC omni. But the latter goes lower.
If it's this kind of fullness and meat you're after, you should reconsider the -b version of the M49.

 

[micaddict]

From Klaus Heyne:
"All M49 models after 1957 had a “cardioid only” switch built in, to achieve a 4dB s/n improvement [as compared to setting the pattern] remotely, from the power supply. "

I found that on my mic builds, before i saw this text, that the best cardioid setting is with completely disconnected back diaphragm.

I fully agree.  Not just for signal-to-noise ratio, but it sounds different, too.

The question is, is it fully disconnected in the cardioid only position on the M49?
I think I remember this isn't the case. Lower noise, yes.
But please do fresh up my memory.

As a side note, I had a private conversation with Klaus yesterday and in my last reply I asked him to join us.
Haven't heard back on that one, yet.

 

[ln76d]

The question is, is it fully disconnected in the cardioid only position on the M49?

It's fully disconnected - same ways as in u47.

As a side note, I had a private conversation with Klaus yesterday and in my last reply I asked him to join us.
Haven't heard back on that one, yet.

I doubt that he would be interested (and maybe it is better that way).
He have his own forum, where he can control the flow of information, telling people what they can write and what not, and everything there for me looks like there's a god Klaus with his most sacred truth.
I noticed also that he don't like to talk about technical matters, most important is his holy hearing.
His forum for me is something like censored gearslutz, sometimes with some usefull informations and many stories and
theories. Personally don't know the guy

 

[micaddict]

I know the forum and I know what you mean.
The good news is that it does stay civil there.

Gearslutz is much less civil and is not owned by Klaus, but he does post there.
And not to promote his own stuff (although presence helps for anybody).
So why not here?

The other interesting bit is that he contacted me, rather than the other way round, to say he likes my posts.
I have to admit I was flattered in some way.
I have nothing to offer or teach him technically, so that can't be it.
And I don't deliberately promote his work, either.
So maybe it's just the mic bug we all share.
The same bug that has kept me here for over 1,000 posts.

Anyway, I woud give him a warm welcome. 

 

[Matt Nolan]

Gearslutz is much less civil and is not owned by Klaus, but he does post there.
And not to promote his own stuff (although presence helps for anybody).
So why not here?

Perhaps because at Gearslutz there is an audience which includes people who will buy his stuff. Here there is an audience of people who would rather build their own stuff.

 

[ln76d]

Don't get me wrong
I'm not against Mr Heyne here.
I can't say anything about his work, except that he is pricey
All personal opinions which i know are from people which probably will have a problem to change a bulb by itself - mostly end users. Probably I never would use his services anyway.
AND! I even don't mind advertising on forum. People need to earn, to make their work` well!
I'm not from those which everywhere looking for fraud and advertisment.
Other thing is that i don't like fooling people and any kind of ***** marketing!
Look for example for Jakob - he's a godfather of modern audio diy! Without his projects for diy i believe that there wouldn't be such evolution in diy which we have in last years! Also there wouldn't be few small companies which started or still are in buissnes with stolen Jakob projects
Did you ever noticed, that he's trying to make the business here?
Me not!
Everything need to be balanced.
I can agree with people like Klaus and i can disagree - but there need to be place for a dialog
Other thing is vintage stuff mythology, which is a fuel for salesman, servicman and other people which have profit from this.
It's some kind of fooling people - similar way to audiophile market and truly i would be happy if the forum wouldn't be affected this way. Some kind of that disease is with all the kits and many of its builders as i stated few times.
Some people will believe in the biggest bullsh*t when it's given respectively.
Want example?
There's a topic related to the PSU box - really nice looking box (great work)  - 7 pages, 94 likes - but!
It's still a box!
What the f**k is so intersting in the box?
Now look for many valuable topics from few  years - where is many great informations and place for debating but lack of interest.
They lie somewhere at the bottom of the sea of commercial topics.
It's sad.
These are only my personal feelings

Now lets back to the topic!

 

[micaddict]

Gearslutz is much less civil and is not owned by Klaus, but he does post there.
And not to promote his own stuff (although presence helps for anybody).
So why not here?

Perhaps because at Gearslutz there is an audience which includes people who will buy his stuff. Here there is an audience of people who would rather build their own stuff.

I hear you.
Still, we have guys like Tim Campbell (yes. he sells capsules) and even David Bock here.

I'll admit I'm an idealist.

 

[micaddict]

In76d wrote:

What the f**k is so intersting in the box?

LOL
I hear you, too,
But I can also understand those who might as well have the electronics housed in something nice.
Or classic looking even.

The cool thing IMO is the multitude of aspects to things like microphones.
That is richness.
There are designers, builders, modifiers, fine tuners, customizers, historians, collectors and even actual users like musicians and audio engineers.
And we can all contribute in some way.
And we can all learn from each other in some way.

Yes, this is a DIY forum.
I 'm no electronics wizzard, which is where I lack.
But I've seen very talented, electronic wizzards here who knew very little about the classic microphones.
And/or those who build microphones, but don't use microphones.
I believe there's something to gain for them, too .
Just some examples.

Right, back to the topic. 
Here's a quote from the late Oliver Archut, who BTW joined us, too, just before he passed.

Sound difference U47/M49, the U47 has a none polarised back plate in cardioid setting and the M49 don't, even if the switch inside the mic is set to cardiode only, the polarization is still active and most guys never read the manual pointing out that the polar switch need to sit and omni.
The theory of none voltage difference at cardiode setting sounds great but the reality is that 60V (backplate) vs. 60V (back-membrane) will still push against and repell, displacing the membrane and changing overall the sound pick up.
Even set at omni, there is still a capacitive leak via buffer resistors to ground to influence the sound.

 

[granger.frederic]

Gearslutz is much less civil and is not owned by Klaus, but he does post there.
And not to promote his own stuff (although presence helps for anybody).
So why not here?

Perhaps because at Gearslutz there is an audience which includes people who will buy his stuff. Here there is an audience of people who would rather build their own stuff.

I hear you.
Still, we have guys like Tim Campbell (yes. he sells capsules) and even David Bock here.

I'll admit I'm an idealist.

yes but i've never seen Tim tell someone what he has to do, think or hear ...unlike other mics gurus with 60 years old ears, if you see what i mean ...

 

[micaddict]

I do see what you mean.

 

[ln76d]

...unlike other mics gurus with 60 years old ears, if you see what i mean ...

I didn't want to point that out- but yes!
This is true as hell!
I always wonder if all these Klauses even bother to examine their hearing.
For example i believe that Mr Williams not - reading about his mods
Am making test once per year - right now everything is fine (even über-fine) but I am fully aware that it will change someday.

But I can also understand those who might as well have the electronics housed in something nice.
Or classic looking even.

I don't mind, i like also, using also old junk and don't like new designs especially, i appreciate good craft etc.
These boxes are nice and well designed.
My question is much more - what is so interesting in the box that there's 7 pages? At the end of the year, there proably will be over 50!
For me things like this are simple - good, nice looking - want to buy - buying, don't want to - not buiyng
It's only some example.

Right, back to the topic. 
Here's a quote from the late Oliver Archut, who BTW joined us, too, just before he passed.

Sound difference U47/M49, the U47 has a none polarised back plate in cardioid setting and the M49 don't, even if the switch inside the mic is set to cardiode only, the polarization is still active and most guys never read the manual pointing out that the polar switch need to sit and omni.
The theory of none voltage difference at cardiode setting sounds great but the reality is that 60V (backplate) vs. 60V (back-membrane) will still push against and repell, displacing the membrane and changing overall the sound pick up.
Even set at omni, there is still a capacitive leak via buffer resistors to ground to influence the sound.

I can agree this time with Oilver words
It's some kind of confirmation of what i said.
Other thing is that even with disconnected both sides and polarised back diaphragm - that difference is not so big.
Then  it will be like U48!
Huge difference is with capacitor between both sides.

 

[ln76d]

Ok then!
I've read Oliver words again!

As with many statements like this - some things need to be clarified - because few things aare too much simplified!
First - which M49? A,B,C? DEFGH - try to sing it as in sesame street
If A (in real world - without suffix) - yes this could be main difference if we assume that headbasket shape and mesh, transformer and hiller tube doesn't matter.
B or C - there's a lot of differences like:
-different capsule - ok - few u47 also had k47
-previously mentioned things
-first feedback - 8pF capacitor
-second feedback with HPF
-LPF
-even B and C have different cathode biasing
-temperature inside microphone body
And everything else!
So! This polarised back diaphragm, when using disconnected sides is totally nothing

 

[achase4u]

First M49 was virtually flat - there was no intended filtering.
If you achieve similar plate and cathode voltages there should be all fine.
There shouldn't be any peak. Oliver stated that with the 5840 there's low end drop comparing o the AC701k.
Another time he wrote that lower value of cathode capacitor is better for this tube.
Somtimes he mentioned about removing all filtering especially all feedback path.
Then he invented transformer with extended low and low mid.
All this doesn't add up!
This is what i wrote before. Keep voltage specs changing at least cathode resistor and all will be fine.
Here you can see how aproximated frequency responses were for M49C.
http://recordinghacks.com/pdf/neumann/M49-M50.pdf
You can always add HPF, you can even tune it to go lower, but this is another feedback path inside the circuit - which isn't needed.
One is enough
I'm not sure about U67 but U87 have also hpf, but it's tuned much more properly too keep better low end response - because it was typical studio use microphone. M49 had broadcast filters for broadcast use It was the biggest market in these times.
Think about switch S2 for cardioid only. You should like it.

From Klaus Heyne:
"All M49 models after 1957 had a “cardioid only” switch built in, to achieve a 4dB s/n improvement [as compared to setting the pattern] remotely, from the power supply. "

I found that on my mic builds, before i saw this text, that the best cardioid setting is with completely disconnected back diaphragm.
If you have no option for switch use 3pF capacitor instead 1nF.
This is also what i modified for your p67  - you have no connection by 1nF capacitor between two sides of the capsule.
It's a big improvement.

Very interesting.  I do understand that no matter what I do here, it won't really be an m49, though I am hoping to get into that territory, sort of reminiscent of the m49 heritage and will do something that none of my other mics really do.  I just like lots of flavors.

I can understand that if you keep everything else identical in the circuit and microphone, changing the tube will obviously cause a change somehow.  So it makes sense that if you swap out of the ac701k to the 5840, something will change. 

Was the original transformer designed to fit the ac701 to achieve a flat response?  If so, it would make sense for me to use a different transformer with the 5840.  These are all things that I don't know, though.

I think your way of doing things is similar, to change a few parts to keep voltage specs for the cathode and plate optimal for the 5840, and it should remain flat.  It's also more affordable than going from the $90 T49 transformer to the $290 dollar BV11r.  To get more low end, that seems like the least efficient way to go about it - but then again, maybe what it does isn't possible in other ways.

I don't know what Rigglers bodies will allow for a card only switch.  That is a bummer.  I wonder if it could be added to the polar pattern switch on the PSU somehow...

 

[ln76d]

You will get somehow m49 related microphone - it maybe 50%, 70% or 90%.
Left the 10% for original units
Don't get the kit builders paranoia in both ways - one believes that anything they build which looks similar would be same as original - the others will be drilling the topic to get their perfect clone.
Without orignal capsule, tube, headbasket or transformer - there will be some differnces. Some minor, some not.
Most important is to have microphone which you would like!
You can assume that your build would be identical to the time when you will get occasion to compare
Other thing - try to find pretty new m49 unit!
With the old one - the sonic possibilities are older to
Keep your mind open

I would not use any transformer which extend low end - this will affect whole audio spectrum. Transformer with the frequency drop will affect also but in much more pleasant way.
This is really not needed.
You want get closer - try vintage german resistors - carbon or wirewound - cathode and plate are most important.
Use MP capacitor at the output - i would use here 0,5uF - there shouldn't be any drop in low end response but overall it should sound better - and this is not the change which affect sonic character of microphone.
For B or C version extending low end is completely nonsense when you have HPF.  Without HPF there wouldn't be need to extend anything.
For switch - if the PCB system allows drill the bottom bell and mount little toggle switch - something like the U47 FET
You can't use the PSU pattern system to do that.

 

[micaddict]

I can agree this time with Oilver words
It's some kind of confirmation of what i said.
Other thing is that even with disconnected both sides and polarised back diaphragm - that difference is not so big.
Then  it will be like U48!
Huge difference is with capacitor between both sides.

...

Ok then!
I've read Oliver words again!

As with many statements like this - some things need to be clarified - because few things aare too much simplified!
First - which M49? A,B,C? DEFGH - try to sing it as in sesame street
If A (in real world - without suffix) - yes this could be main difference if we assume that headbasket shape and mesh, transformer and hiller tube doesn't matter.
B or C - there's a lot of differences like:
-different capsule - ok - few u47 also had k47
-previously mentioned things
-first feedback - 8pF capacitor
-second feedback with HPF
-LPF
-even B and C have different cathode biasing
-temperature inside microphone body
And everything else!
So! This polarised back diaphragm, when using disconnected sides is totally nothing

Yes, one could question if it is at all important.
But you said the best cardioid setting is with completely disconnected back diaphragm.
I basically found the same, but questioned if it's completely disconnected when the M49 is in cardioid only.
Do I understand you agree it isn't?
Not to nitpick, but since this is an M49 thread, it seems sort of relevant.
Plus I find these matters fascinating to begin with, of course. 

 

[ln76d]

Ok, i think i found the source of disinformation (which surprised me due to some facts which i don't want to share or even can't...)!
http://www.tab-funkenwerk.com/id89.html

Oliver had ideas to idealize his circuits.
If you will look into schematic for TLM conversion - here's something which remain m49 - something which keeps similarities between A and C version.
This is something similar to my idea for M49 related microphone.
It's really simplified. My first idea was really similar but i did several test - for example different cathode arragement.
Most important - is that without 8pF feedback and with 25uF - low end response will be  weak.
In this topology 100uF is the value which gives good point to start.
If we add to this permanently connected 1nF capacitor between the both sides of the capsules - low end would be even worse!
If Oliver used 5840 in this topology - we can add also different voltage specs at the plate and cathode...

Dear Oliver i would like to have you there!
R.I.P.