thekid777

Langevin AM16 input and output pads...
« on: October 18, 2012, 08:25:44 PM »
Hi, I read a lot of things but can't figure what would be best to have pads on the input and output of my AM16s
I read I would need a "T" pad, but then read other thing which say a "H" pad is needed to keep it balanced...
All I know is the AM16 want to see 600 ohms all the time at the inputs and outputs to perform correctly
Any help please?!!
Best regards


CJ

Re: Langevin AM16 input and output pads...
« Reply #1 on: October 19, 2012, 04:19:38 PM »
those guys have a pretty low gain already,

unless you are on the kick drum or a 200 watt marshall with a u67 in front,

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

thekid777

Re: Langevin AM16 input and output pads...
« Reply #2 on: October 19, 2012, 04:30:44 PM »
50dB is not that bad!
I would like to have color options at the input and fine gain for the output to get it right in my daw...

CJ

Re: Langevin AM16 input and output pads...
« Reply #3 on: October 19, 2012, 09:00:40 PM »
hmm, the manual does say 45 db, i wonder how the input is strapped for that reading,

mine sounds more like 40 db,

here is an H and T pad Calculator

Bournes makes a 15 dollar variable T pad,

http://www.nu9n.com/tpad-calculator.html
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

EmRR

Re: Langevin AM16 input and output pads...
« Reply #4 on: October 19, 2012, 10:30:03 PM »
U pad and T pad.

This has been covered in other posts a bunch, use the search function for millions of opinions.   

AM16 can be strapped for 3 different input impedances, and at least 2 different output.  The manual can be found online if you don't have it.  At 600 out strapping it likes an output load between 600-1K, higher and it has a large treble boost from ringing.   
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

thekid777

Re: Langevin AM16 input and output pads...
« Reply #5 on: October 19, 2012, 11:57:02 PM »
Thanks guys!
For Doug: You mean U pad at the input and T pad at the output?
Using these would make input and output unbalanced or I'm missing something?
Preamplifiers are already wired at 600 input and ouput.
Thanks
« Last Edit: October 22, 2012, 10:37:52 AM by thekid777 »

PRR

Re: Langevin AM16 input and output pads...
« Reply #6 on: October 20, 2012, 01:12:15 AM »
> make input and output unbalanced

It's transformer FLOATED. Not intrinsically "balanced".

Unless you need incredible precision, a simple pot is fine.

At the input, if leads are just a few inches, a 1K pot is fine.

Considering the OUTput level, and modern gear impedances, I'd use 620 ohm 1/2W fixed and a 10K pot across that to trim the delivered level.

thekid777

Re: Langevin AM16 input and output pads...
« Reply #7 on: October 22, 2012, 10:35:39 AM »
Thanks!
What are the resistors values needed to have a 2Kohm input and output impedance matching the AM16 input?
Sorry for my ignorance!
« Last Edit: October 27, 2012, 07:45:49 AM by thekid777 »

thekid777

Re: Langevin AM16 input and output pads...
« Reply #8 on: October 22, 2012, 10:41:53 AM »
Considering the OUTput level, and modern gear impedances, I'd use 620 ohm 1/2W fixed and a 10K pot across that to trim the delivered level.

Thanks Mr, the 620ohm fixed resistor help to avoid the problem Doug described?
"At 600 out strapping it likes an output load between 600-1K, higher and it has a large treble boost from ringing."

mikeyB

Re: Langevin AM16 input and output pads...
« Reply #9 on: October 23, 2012, 08:15:14 PM »
Hi CJ - trawlled the bourns website but couldn't find the T pad - do you have any part numbers?

As always - thanks in advance!
making better music!


CJ

Re: Langevin AM16 input and output pads...
« Reply #10 on: October 23, 2012, 10:32:21 PM »
i saw one on the Drip website, but now i can't finbd it  :-X

email Drip, i bet they will know,

cj
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Re: Langevin AM16 input and output pads...
« Reply #11 on: October 25, 2012, 06:55:38 AM »
ok, too much permafrost,  :o  or was it the bubble hash?  :o :o

must have been the permafrosted And the bubble hash, i wish the feds would raid these places, costing me a fortune,  :o 8)  try this, take a small piece of black hashish, heat it up in the palm of your hand until you can mash it flat, roll it out just like a pie crust only smaller, then sprinkle in some good indica and roll it up like a burrito, then sprinkle some stativa on the outside to aid combustion, and you have the perfect hybrid steamroller load, ....what was the question?  why did i catch a cold?   :P

here is the Correct answer, my apologies to you and Drip who is wondering what the h you are asking about,  :D

BTW, has anybody done bidness with this place?

i was thinking about the API parts kit since i have a few raw boards to stuff,

30 bucks is pretty DIY unfriendly, but i love the conductive plastic Alps pots in the LA2a, if you have never used conductive plastic, you are in for a treat, smooth as silk, and they actually track a log curve a lot better than AB or CTS or whatever.
 bet this guy was once a forum member or still is,

that blue color that Bournes uses is a winner, kind of like Fluke yellow, only different, i wanna buy it just because it looks so nice, but then, it gets burried behind the panel so wtf, over?  :P

don't look to the left of that website unless you want your visa maxed out, too much good stuff in one place,



cj

http://classicapi.com/catalog/index.php?cPath=48
« Last Edit: October 25, 2012, 07:34:09 AM by CJ »
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

thekid777

Re: Langevin AM16 input and output pads...
« Reply #12 on: October 27, 2012, 06:11:31 AM »
What would be the resistors values needed to have a 2Kohm input and output impedance matching the AM16 input?
It's to run a U47 int the padded AM16
Thanks for your help


Bump :)
« Last Edit: October 27, 2012, 08:38:32 AM by thekid777 »

hoodun

Re: Langevin AM16 input and output pads...
« Reply #13 on: January 25, 2015, 06:41:12 PM »
> make input and output unbalanced

Considering the OUTput level, and modern gear impedances, I'd use 620 ohm 1/2W fixed and a 10K pot across that to trim the delivered level.

I'm confused by this. So the correct way to wire this would be to  1 620 ohm resistor to the output and a 10k log pot from wiper to one of the pins going across to adjust from 620 - 9380?  Is this equal to or better than a 600ohm stepped attenuator? Makes sense to me with modern gear but others say they get too much treble with a 10k.

Rob Flinn

Re: Langevin AM16 input and output pads...
« Reply #14 on: January 25, 2015, 07:31:43 PM »
I used this output attenuator that Winston O'Boogie drew for me with my AM16. I used the right hand one with the 301R resistors, eems to work fine.

If you short pins K & H it puts it into high power output mode (+24dBm as opposed to +18dBm), but that also doubles the harmonic distortion & unsurprisingly doubles current draw from the PSU, therefore making the AM16 run hotter.  In the manual it says to keep them ventilated.
regards Rob

hoodun

Re: Langevin AM16 input and output pads...
« Reply #15 on: January 26, 2015, 10:34:46 PM »
What would be the resistors values needed to have a 2Kohm input and output impedance matching the AM16 input?
It's to run a U47 int the padded AM16
Thanks for your help


Bump :)

I do not think this is possible with a transformer wired to 50 150 and 600 ohms.  If Im understanding your question correctly.

hoodun

Re: Langevin AM16 input and output pads...
« Reply #16 on: January 26, 2015, 10:41:16 PM »
I used this output attenuator that Winston O'Boogie drew for me with my AM16. I used the right hand one with the 301R resistors, eems to work fine.

If you short pins K & H it puts it into high power output mode (+24dBm as opposed to +18dBm), but that also doubles the harmonic distortion & unsurprisingly doubles current draw from the PSU, therefore making the AM16 run hotter.  In the manual it says to keep them ventilated.

This is how I wired my in the past (left side unbalanced). I also used a stereo log pot.

I think the right would be the same as putting a 620ohm between pins 2 and 3.  I am trying it this way with a 10k log pot to match the modern equipments imp. If the math is right this will give me between approx 585 to 600 in adjustment.

I also have a Mallory T Pad 600ohms (someone is selling a bunch on ebay right now). I may use this if I can get it to fit. Probably not though (its too wide).

The input pad is where I get confused. JLM has a variable pad with a 1k log and a resistor...  I know its simple but Im having brain fatigue from reading so many posts.

Also, has anyone added a pot to R1 to adjust gain? Is a 250ohm pot too much?
« Last Edit: January 26, 2015, 11:28:36 PM by hoodun »

Biasrocks

Re: Langevin AM16 input and output pads...
« Reply #17 on: January 29, 2015, 01:43:39 PM »
A fixed, switchable 20db 'U' pad is your best bet.

'Usually you see a switch which adds a 620 ohm in series to each
balanced input wire and a 169 ohm that shorts between the two.
This will give a 20 db pad. '

It's the best match and is recommended as the most transparent option.

There's a discussion here

http://groupdiy.com/index.php?topic=139.0

Mark
« Last Edit: January 29, 2015, 01:50:11 PM by Biasrocks »
http://SharktankPro.com

"I'd rather use an SPX90 than a UA plugin....." Joe Barresi

Biasrocks

Re: Langevin AM16 input and output pads...
« Reply #18 on: January 29, 2015, 01:45:04 PM »
Rob, is that 47R resistors on the other side of the pot? Is this how you wired yours or did you omit them?

I used this output attenuator that Winston O'Boogie drew for me with my AM16. I used the right hand one with the 301R resistors, eems to work fine.

Mark
http://SharktankPro.com

"I'd rather use an SPX90 than a UA plugin....." Joe Barresi

Rob Flinn

Re: Langevin AM16 input and output pads...
« Reply #19 on: January 29, 2015, 02:22:01 PM »
Rob, is that 47R resistors on the other side of the pot? Is this how you wired yours or did you omit them?

I used this output attenuator that Winston O'Boogie drew for me with my AM16. I used the right hand one with the 301R resistors, seems to work fine.

Mark

I think I left them out, but it was a looong time ago now.
regards Rob


 

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