Langevin AM-16 Racking

jensenmann · Apr 25, 2007

Hi there

Finally I made it to get my AM16s racked. Here´s some pictures with how it turned out:

If you want to take a closer look check this:
http://www.twin-x.com/groupdiy/displayimage.php?album=12&pos=9

This thingy has definitely the highest packing density of all the stuff I ever made.
Big thanks to MikoKensington who needed new tires and sold me the complete "kit" with modules, PSU and case. All the clean wiring you can see was Mikos work, all the crap was added by me :grin:

I hope to soon find some time to check this Preamp and compare it to my other stuff.

:guinness:[/url]

dissonantstring · Apr 25, 2007

good golly!:shock:
awesome work jens! :thumb:
i really can't believe that you made that fit into a 1U!
amazingly patient and neat work!
-grant

idylldon · Apr 25, 2007

Very nice work! I have four of these to rack and have a couple of questions:

1.) What's the "hi gain" setup?
2.) What did you use for the output pad?

Cheers,
:sam: :sam:
Don

guavatone · Apr 25, 2007

tight like a Tiger (Toight!)

mattmoogus · Apr 26, 2007

[quote author="idylldon"]Very nice work! I have four of these to rack and have a couple of questions:

1.) What's the "hi gain" setup?
2.) What did you use for the output pad?

Cheers,
:sam: :sam:
Don[/quote]

Hey Sam, the high gain switch is something Joe (JLM Audio) figured out that gives an extra 5db of gain. It also sounds quite different in this mode, so its quite a useful thing to have.
Re the pad, its on the input not the output and allows you to bring the AM16s back to unity gain. The reason that you dont want to pad the output of this kind of fixed gain pre is that you reduce its headroom as you turn the pad down. A lot of people dont seem to get this concept...

Jens, you might find you need to use shielded cable for the hi gain switch wire as we found using unshielded wire here sometimes made the circuit unstable. Also, rememeber AM16s need to be loaded to 600ohms to be flat, so there should be 680R across pins 2&3 of the output XLRs. I dont remember if we put them on before we sent the rack over...

Enjoy them - theyre great mic pres to have in yr arsenal!

M@

guavatone · Apr 26, 2007

Yeah, those Gain switches are handy, 6dB boost I think. I used a relay to switch the Gain, it puts a cap into the AM16 Circuit. And variable pad with the pot before the AM16 is the way to go.

jensenmann · Apr 26, 2007

M@, thanks for the info.
I really forgot about the 600Ohm thing, though I read that some time ago.

The high power switch simply shorts a resistor which is limiting the current of the outputstage. Looking forward to extensive comparisons, but time is a little short now. I have to hurry to a rehearsal with a new drummer for my band. He´s a guy I wanted to play with since a looong time. Hope he likes our songs...
:guinness: :guinness: :guinness:

dukasound · Apr 26, 2007

Nice Jens :thumb:

JLM Audio · Apr 26, 2007

This thingy has definitely the highest packing density of all the stuff I ever made.
Big thanks to MikoKensington who needed new tires and sold me the complete "kit" with modules, PSU and case. All the clean wiring you can see was Mikos work, all the crap was added by me

:grin:

From memory most of the clean wiring was done by Matt at JLM.

Yeah, those Gain switches are handy, 6dB boost I think. I used a relay to switch the Gain, it puts a cap into the AM16 Circuit. And variable pad with the pot before the AM16 is the way to go.

The High Gain switch if done right gives 10dB extra gain making 55dB total gain. The 2 wires to the AM16 from the high gain switch don't need to be shielded just twisted tightly.

M@, thanks for the info.
I really forgot about the 600Ohm thing, though I read that some time ago.

Yes must have a 600ohm output load to keep the frequency response flat on the AM16. Use a 680R resistor between pin 2 and pin 3 on the output XLR if running into modern 10k loads works perfect.

The high power switch simply shorts a resistor which is limiting the current of the outputstage.

I would recommend wiring the AM16 in High power mode permanently so you have +24dBM out and doing the DC trim in this mode. In low power mode the maximum output drops to +18dBM. We use the High Gain switch on the JLM AM16 rack for 55dB high gain mode not high power mode.

Jens send me an email and I will show you how to get the high gain going.

emrr · Apr 27, 2007

you guys spill the beans on the gain boost mode!

mattmoogus · Apr 27, 2007

JLM Audio said:
The High Gain switch if done right gives 10dB extra gain making 55dB total gain. The 2 wires to the AM16 from the high gain switch don't need to be shielded just twisted tightly.

Click to expand...

Shows how much I know! :roll:

:grin:

M@

jensenmann · Apr 27, 2007

Joe, thanks for your offer, but the high gain switch is working perfect.
I did the DC trim when I recieved the modules. First I checked all the static voltages (in HiPower mode) then adjustet symmetry.
:guinness:

Edit: after having reread your post, Joe, I thought to understand that there is possibly a difference between high power and high gain mode?
Ok, I´ll drop you a mail

Jonkan · Apr 27, 2007

thats a very nice racking. Im impressed!
/J

Biasrocks · Jan 6, 2010

JLM Audio said:
The High Gain switch if done right gives 10dB extra gain making 55dB total gain. The 2 wires to the AM16 from the high gain switch don't need to be shielded just twisted tightly.

Jens send me an email and I will show you how to get the high gain going.

Does anyone have this information?

I'm in the process of racking up my pair of AM-16's and it would be a nice addition to have this boost mod.

Anyone know???

Mark

guavatone · Jan 6, 2010

foo pa was here

Biasrocks · Jan 6, 2010

Cool, thank you very much for the info Charlie.

Mark

jensenmann · Jan 7, 2010

Joe supplied me with this info, too. But he told me not to spread it.

JLM Audio · Jan 7, 2010

jensenmann said:
Joe supplied me with this info, too. But he told me not to spread it.

Yes I give a heap of this type of mod info freely to any DIY guys with instructions not to put it up on the web or hand it on just because we have had some of our mods used or turned into commercial products by other companies. So putting up a cut and paste of my email on the web without asking my permission instead of just saying to contact me for the info is a bit annoying.

Biasrocks · Jan 7, 2010

I completely understand and will honor your wishes.

I'm sure Charlie was just trying to be helpful, I certainly appreciate the information.

Thank you.

Mark

guavatone · Jan 7, 2010

Very Sorry Joe. I thought quoting was the proper thing to do.

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