Langevin AM16 input and output pads...

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thekid777

Well-known member
Joined
Aug 1, 2009
Messages
455
Location
France
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
 
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...
 
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
 
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. 
 
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
 
> 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.
 
Thanks!
What are the resistors values needed to have a 2Kohm input and output impedance matching the AM16 input?
Sorry for my ignorance!
 
PRR said:
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."
 
Hi CJ - trawlled the bourns website but couldn't find the T pad - do you have any part numbers?

As always - thanks in advance!
 
ok, too much permafrost,  :eek:  or was it the bubble hash?  :eek: :eek:

must have been the permafrosted And the bubble hash, i wish the feds would raid these places, costing me a fortune,  :eek: 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
 
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 :)
 
PRR said:
> 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.
 
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.
 

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thekid777 said:
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.
 
Rob Flinn said:
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?
 
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
 
Rob, is that 47R resistors on the other side of the pot? Is this how you wired yours or did you omit them?

Rob Flinn said:
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
 
Biasrocks said:
Rob, is that 47R resistors on the other side of the pot? Is this how you wired yours or did you omit them?

Rob Flinn said:
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.
 
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