Langevin 116B-Possible to DIY?

[C12VR]

Lately I have been really enjoying that Columbia Records 30th St. studio sound, which was reportedly created with Langevin preamps. Ostensibly, the classic 1950s period recordings were made using 116Bs or something similar, given that the 1961 Langevin catalog actually credits CBS' engineering department for the 116B's development. Given that originals are a PITA to service, maintain, adapt to modern I/O (massive, complex Cannon plug $100 for a single unit on Ebay), and sadly, prohibitively expensive, it follows that a DIY approach using modern I/O, layout optimized for noise rather than size, DC heaters, etc. could even improve on the original pre while economizing. One problem with recreating the circuit 1:1 is the fact that the transformers are seemingly unobtainable. The input was a high ratio, probably 1:15 or greater unit with "triple shielding." The output was wound for single-ended circuits, 16k:600 w/ tertiary feedback, capable of taking DC. Is there any suitable transformer that can be adapted to this purpose? Another issue is the grid caps for the 1620 tubes. Wat do?

 

[C12VR]

https://cinemag.biz/output/PDF/CM-S217D.pdfMaybe this, though expensive?

 

[emrr]

It's a lot like the 5116 and the GE and Collins 356A types. When I had some side by side with RCA BA-1A's, they were tonally very similar. 116's have treble boost EQ and the RCA's have some upper tilt in the transformers. Most of the sonic footprint in the way these things were used is the transformers, so if you need that, you need an original or something very similar from the same era of winding concepts. The Collins is more 'hi-fi linear' to the ear in comparison, but also softer and more period sounding than anything you'd make with new transformers.

The very long 30th Street threads don't have any clear answers in the documentation beyond when the various consoles changed out. The very earliest stuff could be RCA, given the broadcast side relationship with RCA equipment up to that point. There's some comments and pics with units having what look like stock rectangular ADC's. The 1961 catalog clue is as hot as any.

They make new grid caps. Tubes with higher input C might help steer towards older sound with newer transformers.

 

[C12VR]

Thanks for your input, truly a treasure trove of knowledge. On a somewhat unrelated note, what is your favorite tube mic pre that you have used? And do you know of any suitable OPTs for a 116B build?

 

[emrr]

I use Gates SA-70's and RCA BA-2's and BA-3's more than anything else. I no longer own Langevin 116/117/5116-B or Collins 356A's. I have Altec 428B/458A/459A finally coming on line soon. That Cinemag Peerless repro would work. No other obvious thing comes to mind in an off the shelf new part.

 

[C12VR]

I use Gates SA-70's and RCA BA-2's and BA-3's more than anything else. I no longer own Langevin 116/117/5116-B or Collins 356A's. I have Altec 428B/458A/459A finally coming on line soon. That Cinemag Peerless repro would work. No other obvious thing comes to mind in an off the shelf new part.

I notice the SA-70 has a very low feedback of 8db. Is there a way of calculating the feedback of this tertiary winding on the 116B? And why is it on the primary side in the schematic?

 

[gyraf]

Here's what I have on the subject - IIRC, we had a local company (DISA) doing something very similar around 1950

 

[C12VR]

Now that I think of it, I wonder how much of the sound is down to the use of triode-strapped pentodes vs the tertiary feedback. Maybe it is more economical and efficient to just go for a BA2C or Gates 5215. The Langevin 116 seems to be in the tradition of pentode V1 and pentode triode strapped for V2., so the Gates I mentioned, though it probably needs more DB feedback, is in the same province.

 

[C12VR]

EMRR, I read elsewhere that you said the BA2c was like a fender champ. This is not very encouraging information. How bad is the distortion compared to a 116 or 5116 type amplifier? It has an NFB loop, from what I can tell off the schematic.
EDIT: actually I can't see one

 

[dmp]

I built a BA2 (filter removed) and not sure how it is like a fender champ, lol
It's a pretty flat tube preamp with a nice sound, attributed to the iron. I've never listened to mine with different transformers though. The 1620 seems to be a good low noise preamp tube but they are going to get harder to get. You can use 6j7, especially in the #2 position.
The BA2 is a no feedback transformer coupled output with the 1620 triode strapped.

I used shielded wire to ceramic grid caps (easily available) and it works fine in a typical environment.

Your build options are to try available transformers or spend $3k+ for an original I think. Unless you get ridiculously lucky, the price of originals is mostly the iron.

I think the input side could use a 1:10 and there are very good vintage one's available at non-astronomical prices (i.e. LS-10)
I have a AM16 build - that was a PCB project here years ago. The fully balanced topology is a cool idea.

why is it on the primary side in the schematic?

I think it is just drawn that way, it isn't wound on the "primary side"
There isn't a primary side in the windings - the three windings are wound with each other typically. Without knowing the ratios, it's hard to say what the feedback level is. You may like it more without feedback.

The output could be any good 6v6 push-pull transformer (20-20k Hz) I think. Probably not a guitar amp transformer. Look at something like a LS-52.
Instead of using a tertiary winding for the feedback, you could experiment with feedback from the secondary and adjust R19/R20

 

[emrr]

EMRR, I read elsewhere that you said the BA2c was like a fender champ. This is not very encouraging information. How bad is the distortion compared to a 116 or 5116 type amplifier? It has an NFB loop, from what I can tell off the schematic.
EDIT: actually I can't see one

It's very encouraging, if you want a preamp to sound like tubes. You can almost square wave it and not hear distortion. I'd be happy with 16 channels of BA-2A most days; hell, they have a gain control unlike most period things. Distortion in 60's tube preamps with the usual 20-30dB NFB aren't far from transistor distortion in my book. SA-70 and RCA BC-2B preamps are in that weird 8-10dB NFB range that brings out edgier harmonics without damping them to invisibility, they are more aggressive sounding but still clip nicely.

The 30th St sound is undeniably that giant room, that talent, that distant mic technique, and those M49/U47/44-BX/etc. You could stick almost any quality period preamp circuit in there and it wouldn't change much if anything.

 

[dmp]

I built a BA2 (filter removed) and not sure how it is like a fender champ, lol
It's a pretty flat tube preamp with a nice sound, attributed to the iron. I've never listened to mine with different transformers though. The 1620 seems to be a good low noise preamp tube but they are going to get harder to get. You can use 6j7, especially in the #2 position.
The BA2 is a no feedback transformer coupled output with the 1620 triode strapped.

I used shielded wire to ceramic grid caps (easily available) and it works fine in a typical environment.

Your build options are to try available transformers or spend $3k+ for an original I think. Unless you get ridiculously lucky, the price of originals is mostly the iron.

I think the input side could use a 1:10 and there are very good vintage one's available at non-astronomical prices (i.e. LS-10)
I have a AM16 build - that was a PCB project here years ago. The fully balanced topology is a cool idea.


I think it is just drawn that way, it isn't wound on the "primary side"
There isn't a primary side in the windings - the three windings are wound with each other typically. Without knowing the ratios, it's hard to say what the feedback level is. You may like it more without feedback.

The output could be any good 6v6 push-pull transformer (20-20k Hz) I think. Probably not a guitar amp transformer. Look at something like a LS-52.
Instead of using a tertiary winding for the feedback, you could experiment with feedback from the secondary and adjust R19/R20

Edit - I was looking at the wrong schematic (117) the 116B is a transformer coupled 1620 - so similar output transformers as a BA2

 

[dmp]

Someone buy this and send it to CJ for a dissection

https://www.ebay.com/itm/124681611193?hash=item1d079a67b9:g:O0AAAOSwF3Fgd5RJ

 

[C12VR]

It's very encouraging, if you want a preamp to sound like tubes. You can almost square wave it and not hear distortion. I'd be happy with 16 channels of BA-2A most days; hell, they have a gain control unlike most period things. Distortion in 60's tube preamps with the usual 20-30dB NFB aren't far from transistor distortion in my book. SA-70 and RCA BC-2B preamps are in that weird 8-10dB NFB range that brings out edgier harmonics without damping them to invisibility, they are more aggressive sounding but still clip nicely.

The 30th St sound is undeniably that giant room, that talent, that distant mic technique, and those M49/U47/44-BX/etc. You could stick almost any quality period preamp circuit in there and it wouldn't change much if anything.

Ok, so we have differing values. I like the heavy NFB sound. I have a Newcomb tube preamp that has almost no NFB, and it's not for me. Good for some things, sure, but not something I could use as a utility instrument.
Regarding the 30th st. sound: Yes, that's partly true, but there is a unique sort of compressed brightness that I don't think comes solely from the room and talent. It's not merely the distortion quality that draws me to tube preamps in spite of the fact that they are a PITA compared to FET amps.

 

[C12VR]

@CJ Would you be willing to open this Langevin 313A up if I sent it to you?

 

[dmp]

There's an interesting clue on the tertiary feedback - with the feedback winding in parallel the gain is 40dB and with it in series the gain is 34dB (6dB more feedback). Wouldn't going from parallel to series double the feedback? Meaning the feedback is either 3dB (parallel) or 6dB (series)?

 

[C12VR]

wait where are you getting this info from?

 

[emrr]

I have a Newcomb tube preamp that has almost no NFB, and it's not for me. Good for some things, sure, but not something I could use as a utility instrument.

The Newcomb and the RCA are worlds apart. I wouldn't consider the Newcomb 'professional' equipment, and I don't consider tape machine electronics as preamps to be 'professional' grade equipment either. Altec 1566's and 1567's aren't 'professional' equipment. So....some more world view.

I'm using a U-67 into a BA-2A for vocals quite a bit, it's all very clean and present.

 

[C12VR]

The Newcomb and the RCA are worlds apart. I wouldn't consider the Newcomb 'professional' equipment, and I don't consider tape machine electronics as preamps to be 'professional' grade equipment either. Altec 1566's and 1567's aren't 'professional' equipment. So....some more world view.

I'm using a U-67 into a BA-2A for vocals quite a bit, it's all very clean and present.

What's the electrical difference that distinguishes the pro from the consumer gear? Is it just better frequency response and distortion?

 

[emrr]

Better transformers, better parts selection, better layout, better PSU isolation, etc. I wouldn't even call it consumer gear, just more PA/industrial is usually not on par.