Lundahl LL2911 in ribbon mics, thanks to Kevin Carter

[tommypiper]

Special thanks to Kevin Carter for helping me with a few projects, including a Lundahl for my ribbon mic which totally opened up the sound. And for his generous, selfless help with a 1272 project of mine. (On Kevin's bench, AdrianH and I measured my 1272 prototype with a whopping 84 dB of gain - more on this in a future post). Lundahl don't advertise that they make a transformer for ribbon mics, but in fact they do, the LL2911.

The idea started when Scott Dorsey and others were saying they had good luck with this transformer in their RCA mics, improving signal to noise. Scott has been recommending it for the 77DX series. Dan Haug put one in his 74b and was very helpful with info. I've heard they also work in a 44. So I got in touch with Kevin (he's Lundahl's sole distributor in the US) and he helped me out.

The Lundahl definitely reduced the low end hum and improved the response in my Jr. Velocity, which needed a transformer anyway. The Lundahl is probably a good candidate for upgrading any ribbon mic, including the Oktavas and DIYs. The transformers come encased in mu metal and I've been impressed with the sound and noise reduction. Call Kevin at K&K Audio and he'll fill you in.

I'm also planning to try Lundahls in a Neve down the road and would like to hear from others who have tried them in a 1272 or other Neve. (Kevin has some ideas about replacements for the 10468.)

I want to give a public thanks to Kevin for all his help and mentoring in recent months, not only to me but to others in his area. He has many projects, a lovely BC-2B mic preamp kit and an original mic pre and other designs and is very modest about discussing or posting online, but is in fact a huge DIY enthusiast and supporter. Cheers to Kevin. For those who don't know him, he is a gem to our community.

 

[Plexibreath]

He was very helpful when I bought 2 Lundahls for my ongoing API 312 project. I'll soon contact him about other variations for this project.
Kelley

 

[CJ]

He has some neat DIY projects at his site as well.
:sam:

 

[adrianh]

Wait till June 18 to contact www.kandkaudio.com
He is on vacation.
Yes Kevin is very helpfull.

 

[Marik]

Tommy,

Yep, Kevin is one of the greatest guys, and cheers to Kevin!!! I made mic pre based on his phono stage one, and it is one on the most musical pres money can buy. And yes, all his help is invalubale.

Concerning LL2911... I have been using this one for a few years in all my DIY ribbon mics with excellent results. Some cautions for using it in Oktava ML52, though. This mic uses two very narrow ribbons and their impedance is about 1.3 Ohm. When you connect it to 1:37 LL2911, you get about 1780 Ohm, so input impedance of the pre should be adjusted accordingly. If you drive long cables, the impedance that high might not be a good thing. You can also connect the trafo as 1:18, but you loose gain and the output impedance is still high at ~420 Ohm. Generally, ribbons for their best operation need a load at leat 5-10 times higher than 'normal' condencers, and it is a good idea to keep the ribbon impedance as low as it is possible to avoid all the above, and its HF loading.

 

[Winston OBoogie]

...

 

[bradzatitagain]

[quote author="Marik"]Tommy,

Yep, Kevin is one of the greatest guys, and cheers to Kevin!!! I made mic pre based on his phono stage one, and it is one on the most musical pres money can buy. And yes, all his help is invalubale.

Concerning LL2911... I have been using this one for a few years in all my DIY ribbon mics with excellent results. Some cautions for using it in Oktava ML52, though. This mic uses two very narrow ribbons and their impedance is about 1.3 Ohm. When you connect it to 1:37 LL2911, you get about 1780 Ohm, so input impedance of the pre should be adjusted accordingly. If you drive long cables, the impedance that high might not be a good thing. You can also connect the trafo as 1:18, but you loose gain and the output impedance is still high at ~420 Ohm. Generally, ribbons for their best operation need a load at leat 5-10 times higher than 'normal' condencers, and it is a good idea to keep the ribbon impedance as low as it is possible to avoid all the above, and its HF loading.[/quote]


Marik, have you had any luck w/any other xfrmr in particular in the ML52? I've got a couple I've been ignoring for about a year.

rgrds,
Brad

 

[Marik]

Besides LL2911 I also used Cinemag 1:28. They are very different sounding, though. I prefer to keep both of them, depending on the sound I am after. I have not had chance to try it in ML52, though. I don't have a problem with loading, as my pre load is variable. Once I spent way too much time trying to mod Oktava and after I exhausted all the possibilities, finally sold it, as I just did not like it. Besides, I have about 15 ribbon mics, I think.
The stock trafo in ML52 is not good, IMO. Replace it with either trafo, and it's already gonna be better. Another big problem is it's grill, it needs to be completely rebuilt. Take it off and try to record without it, and you will see what I mean. The stock ribbon itself is thick. Might benefit from replacement, as well. But here ones again we are back to impedance mismatch. Also, another problem could arise--increased noise.
IMO, this mic is more of a problem than its worth.

 

[bradzatitagain]

It looks like the grill could be opened up, the flats on the sides of the cage could have slots machined into them easily; then perhaps remove the screen and reinstall the silk alone. Did one just now will try an a/b; perhaps just a lighter guage or more open screen in front of the silk.

'S'funny cuz some guys rave about this mic, they compare it to the RCA DX77. Most reports seem to peg it as instrumental, especially electric guitar, which I have yet to try. I wrote both Jensen and Lundahl, will measure the voltages through the transformers to try to determine turns, and if it's rated to load at 1500/nominal 300 or 1000/nominal 200 then there's a start for figuring the output impedance. The ribbons seem awfully fortified.

I don't mind fiddling w/them, I got them for $160 each new. I'll post back if anything good comes of it, wish me luck!

 

[Marik]

[quote author="bradzatitagain"]It looks like the grill could be opened up, the flats on the sides of the cage could have slots machined into them easily; then perhaps remove the screen and reinstall the silk alone. Did one just now will try an a/b; perhaps just a lighter guage or more open screen in front of the silk.[/quote]

The slots would not do anything, as the problem is in resonances of the grill itself. Much more of help would be whether cutting front and rear braces, or at least dampening the grill.

[quote author="bradzatitagain"]'S'funny cuz some guys rave about this mic, they compare it to the RCA DX77. [/quote]

Yeah, whatever... Some compare MXL2001 to U87....

[quote author="bradzatitagain"]... will measure the voltages through the transformers to try to determine turns, and if it's rated to load at 1500/nominal 300 or 1000/nominal 200 then there's a start for figuring the output impedance. [/quote]

I am not sure if I am following you here.

 

[bovox]

I know for sure that on Kev´s 1272 page, we have a comment on
trying Lundahl as a substitute. I´ve build the 1272 with the LL1527
in 1:2 mode and it works with pleasure. It´s a more open upper
responce and a whole new character ( read different /not better)
than with the original.
But with this high broadband Tx you have to make sure its the
right output transistor ( Motorola) otherwise you get spikes
( as told in anotherthread.)
The recommended load with 1527 is 3-4 kohms, then you get an
input prim imp. around 1 kohm. I´ve used the "cheap" way
and placed a 5 kohm log pot + 180 ohms to ground just after
the Tx and get a variable gain from 10 to 40 dB.
Cheers Bo

 

[bradzatitagain]

[quote author="bovox"]I know for sure that on Kev´s 1272 page, we have a comment on
trying Lundahl as a substitute. I´ve build the 1272 with the LL1527
in 1:2 mode and it works with pleasure. It´s a more open upper
responce and a whole new character ( read different /not better)
than with the original.
But with this high broadband Tx you have to make sure its the
right output transistor ( Motorola) otherwise you get spikes
( as told in anotherthread.)
The recommended load with 1527 is 3-4 kohms, then you get an
input prim imp. around 1 kohm. I´ve used the "cheap" way
and placed a 5 kohm log pot + 180 ohms to ground just after
the Tx and get a variable gain from 10 to 40 dB.
Cheers Bo[/quote]

I think we got way lost here....

I was musing on an Okatva ribbon mic, model MK52; I think we crossed wires somehow and ended up in a Neve 1272? Advice duly noted nevertheless!

[quote author="Marik"]I am not sure if I am following you here.[/quote]
Long day, just meant to say I'll measure the transformer for turns.

[quote author="Marik"]The slots would not do anything, as the problem is in resonances of the grill itself. Much more of help would be whether cutting front and rear braces, or at least dampening the grill.[/quote]
This is definitely your expertise, Marik, I defer. I wouldn't know the first thing about redesigning a grill. I could take a closer look at a few others, this one at least appears similar to the Altec birdccages, a larger and completely different shape. Is your thinking to remove all the narrow grill bars, front and back, leaving the sides as is? maybe a little surgery on the top, leave two in the middle on top to protect the inner grill, slice a few slots in the wide side pieces to open it up for M/S. A few coats of heavy enamel paint on what's left might damp it fairly well, reinstall mesh and silk as is.

Don't get me wrong, I'm not trying to convince you to like the mic, but I could imagine re-welcoming it here, even if it ends up as more of an amp'd guitar effect than an accurate mic. I know when you simply speak into the mic it sounds like your head is in a 5 gallon plastic bucket. (Maybe that's what a "classic" ribbon mic is supposed to sound like!) My guess is nobody would want to sing into it as is.

 

[mig27]

On a side note:

I also wanted to order an LL2911 to upgrade my Oktava ML52.
But Per from Lundahl Sweden just got back to me saying they're out of stock and will only run another small production batch if there's enough interest. :sad:

He also mentioned this:
"But the MC input LL1678 is not too far from the LL2911."

Has anyone had some hands on-experience with this LL1678?

Cheers,


Michael

 

[bradzatitagain]

Data sheet shows a source impedance of 50ohm, a tad higher than the mics 1.3 ohm transducer, it can be termminated for 10ohm/10k at 1:32 but then you'll have a big output impedance, not what you'd want if you were going to use it for M/S and need to split the output. DCR of 1678 is 4.5 primary 375 ohm secondary. DCR of 2911 primary is 0.2 secondary 59ohm. It seems kind of far off.

Cinemag has a replacement for the RCA44 they may have others similar, and Wes Dooley has to buy transformers from somebody. Beyers 1:19 is the one used in some of their old ribbons I think, a Beyer 1:15 might do something favorable. I think I'll drop AEA a note and see how they chew on this particular piece of fat.

 

[Michael_Joly]

There are full details of my extensive work on the ML-52-02 over on rec.audio.pro

Use Google Groups and search "oktava joly ml 52"

The first search result is a summary, the second search result is a long thread with a lot of knowledgable contributors. It documents my ML-52 investigations over a period of several weeks. The full thread is worth reading if you want to see how layer by layer we analyed the ML-52 and tried successive fixes.

I analyzed the frequency at which the grille resonates, tried 3 different damping techniques, cut out the fins and replaced them with stainless steel wire mesh - all failed to totally eliminate grille problems. I finally rolled a new grille from bronze window screen.

With the Lundhal installed, new grill, heavier ribbon output wires and metal windblast/HF boost shields removed the mic is now clear and open sounding - quite versatile.

There's a pic at the bottom of post #36 in this HomeRecording.com thread:
http://www.homerecording.com/bbs/showthread.php?t=131639&page=2

Sorry for the ugly links, can't figure out HTML on this board

 

[Flatpicker]

Hi, Michael. Good to see you here.

[quote author="Michael_Joly"]Sorry for the ugly links, can't figure out HTML on this board[/quote]
Don't worry - most of us can't either...

 

[Bear]

Anyone gotten their hands on the Nady ribbon mic? Worth modding?

Bear

 

[synthetic]

I checked it out at AES. It sounded very smooth on my voice, as much as one can judge at a trade show. It was bigger than I expected. I've been having the same thought about getting one and modding it.

 

[wilebee]

??? Would this LL2911 fit into an rca sk46 its about 2/3 the size of a 74b what are the overall dimetions of the transformer ? Wil

Wilebee

 

[Marik]

[quote author="wilebee"]??? Would this LL2911 fit into an rca sk46 its about 2/3 the size of a 74b what are the overall dimetions of the transformer ? Wil

Wilebee[/quote]

You can find LL2911 specs here:

http://www.lundahl.se/pdfs/datash/2911.pdf

[quote author="mig27"]



He also mentioned this:
"But the MC input LL1678 is not too far from the LL2911."

[/quote]

Actually, it looks very interesting. If you put all primaries in parallel, you get 1.12 Ohm DCR primary, which looks like a perfect match for ML52. With secondary in series you get 1:32, so imp. ratio is 1.12 Ohm: 1.14K, but in parallel it is 1:16, so the output impedance is around 280 Ohm, which is very close to what we need. The problem is that with smaller ratios the sensitivity goes down.