Author Topic: Input tran ratio for Federal AM864/U limiter?.  (Read 5445 times)

gary o

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Input tran ratio for Federal AM864/U limiter?.
« on: February 28, 2005, 08:04:30 PM »
Hiya anyone no what the ratio of the input transformer is for a Federal AM864/U limiter.
I made a DIY AM864 with a 1:4 input tran,but could that be too high?

Thanks people.....Gary O.


tubemonkey35

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Input tran ratio for Federal AM864/U limiter?.
« Reply #1 on: February 28, 2005, 09:29:25 PM »
Let me look at the shcemos for it; I have two of these units.

tubemonkey35

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Input tran ratio for Federal AM864/U limiter?.
« Reply #2 on: February 28, 2005, 09:37:19 PM »
Looks like I'll have to take lid off of one and look the trany itself. I'll do it tonight or in the A.M.

gary o

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Input tran ratio for Federal AM864/U limiter?.
« Reply #3 on: February 28, 2005, 10:01:59 PM »
Hey thanks! no rush

Gary O.

rafafredd

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Input tran ratio for Federal AM864/U limiter?.
« Reply #4 on: March 01, 2005, 06:59:38 AM »
On the schematic I have, it´s listed as 600:10k input and 10k:600 output. So, itá a 1:4 and 4:1 !

gary o

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Input tran ratio for Federal AM864/U limiter?.
« Reply #5 on: March 01, 2005, 06:30:28 PM »
Hiya Rafa I might be wrong but I dont think thats how it works Sowter for instance have various input trans that are 600 to 10K that are 1:7 also 1+1 to 10 aswell as the 1:4 ratios.

Cheers..... Gary O.

Rob Flinn

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Input tran ratio for Federal AM864/U limiter?.
« Reply #6 on: March 01, 2005, 07:08:01 PM »
Gary

I think Rafa is on the right track here.  The impedance ratio is the square of the turns ratio.  So if you  had a 600:10K  then the square roots of these to numbers would be 24.5:100, which is 1:4 (rounded up a bit)
regards Rob

Capital letters.  The difference between helping your uncle Jack off his horse, & helping your uncle jack off his horse ........

gary o

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Input tran ratio for Federal AM864/U limiter?.
« Reply #7 on: March 01, 2005, 10:46:43 PM »
I stand corrected cheers.. sorry Rafa, I just had another look at the Sowter site too.
When I spoke to Brian S about the trans I might need for my various mic pre & limiter projects when it comes to the input tran he says the ratio doesnt matter too much depends how much level I want, im talkin 1:4 ,1:7,1:10 is that all in the same ballpark?, I use his top quality 9045 1+1:10 usually does sound better than the cheaper ones.

Cheers guys ....Gary O.

rafafredd

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Input tran ratio for Federal AM864/U limiter?.
« Reply #8 on: March 02, 2005, 08:55:31 AM »
If I would mess with this, I would use a 1:2 2k4:10k at the input for as a higher input impedance and a lower signal on the grid, and maybe a 6:1 at the output, to load the plates more gently, and have a lower level output. I think a 4:1 at the output would give too much level for normal line level use.

tubemonkey35

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Input tran ratio for Federal AM864/U limiter?.
« Reply #9 on: March 02, 2005, 10:58:12 AM »
Should I still take the cover off and check?

P.S. I have a resistor on the back wired across the output to tame it going back into my console.

I also send signal to it via a fader so I can control the input gain better.


gary o

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Input tran ratio for Federal AM864/U limiter?.
« Reply #10 on: March 03, 2005, 06:38:20 AM »
Dont worry about taking the cover off then Tubemonkey the guys have pointed out the ratio for me but thanks for that.

For the output im using my BA6As output transformer 3.65 ct 1 8K 600R with a home made 3 pos daven T attenuator something like 10:1 step down, the output levels are nice for me like this, I did try a Sowter 8650 which is 9:1 worked well but not as nice sound as the BA OP tran.

It just seems strange that the AM864 it will only work with a 500R daul ladder attenuator & not with the 500K daul ladder.

rafafredd

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Input tran ratio for Federal AM864/U limiter?.
« Reply #11 on: March 03, 2005, 08:09:38 AM »
Yes, the attenuator thing you are experiencing at the input is very strange....

skrasms

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Input tran ratio for Federal AM864/U limiter?.
« Reply #12 on: June 28, 2005, 09:03:53 PM »
In a circuit like this how do the input and output actually get wired to an XLR? I'm wondering how much it would matter if I got input/output transformers that were only center tapped on one side (hoping they'll be easier to find).

Has anyone found any transformers still in production that work here? Mouser has some cheapies ($2 and bad specs) that meet the output requirements, but after a couple days of searching I haven't found anything to match the real requirements and actually cover the audible frequency range.

CJ

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Input tran ratio for Federal AM864/U limiter?.
« Reply #13 on: June 28, 2005, 11:17:45 PM »
ebay
If I can't fix it, I can fix it so nobody else can!
Frank's- www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar- http://tdsl.duncanamps.com/schematics.php

rafafredd

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Input tran ratio for Federal AM864/U limiter?.
« Reply #14 on: June 29, 2005, 03:19:12 AM »
Man, there are many many transformeres that would work from the major audio transformer companies...

Sowter, Lundahl, Jensen, Cinemag, and at the input, even OEP...

If you can´t find the right model, just contact Brian at Sowter or Per at Lundahl. Both guys are great people!!!  :thumb:

skrasms

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Input tran ratio for Federal AM864/U limiter?.
« Reply #15 on: June 29, 2005, 09:17:01 AM »
I went through the Cinemag, Sowter, and Jensen sites and couldn't find anything that had a center tap on both sides. That's why I asked how the input and output actually wire to XLR's, to see if I could get by with something simpler. How do the input and output get wired?


 

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