API 312 Thread!

[Bauman]

Greg yea, it's a original Peter C. melcor #8

I use MillMax pins. Very nice.

I'll get the digikey partnumber to you when I get home.

cheers!
Fabio

 

[dukasound]

hi
Did you find all right value resistors for Gain Switch?
If you know MullMax part number for Newark or Farnell tell us.
On opamp pcb I saw a pair of two resistor in seies (R1 and R8).
You cant find right value?
Thanks in advance
Duka

 

[Category 5]

Part number for the Mil-Max receptacles at Digi Key is

ED5021-ND - Raised to make room for resistors underneath

They work great!

Shane

 

[fum]

I'm workin on some 312 type circuits, and after getting a keen answer to my algebraic questions in another thread
http://www.groupdiy.com/index.php?topic=1085

thought I'd post some resistor values I calculated for gain control in the circuit:

If you want a 3 dB scale, yielding a gain range of 22 dB to 66 dB, and you're using the resistor values in the schematic (20K, and 200 ohms) here's you're resistor values:

db resistor (ohms)
66 0
62 120
58 307
54 604
50 1075
46 1820
42 3001
38 4874
34 7842
30 12545
26 20000
22 31815


If thats too big a range, no problem, here's the same 12 position, only in 2dB increments

db resistor(ohms)
66 0
64 54
62 120
60 203
58 307
56 439
54 604
52 812
50 1075
48 1405
46 1820
44 2343


A true 22K rev log looks to give something like a 3.72 db per step ratio, and would look like ( second column is what the resistance value should be for this step, third column is the difference between the two, if you are building a stepped attenuator ( the sum of resistances equals each step value):



db resistor(ohms) ohm diff between steps
66 0
62 110 110
59 276 166
55 530 254
51 920 390
47 1519 599
44 2438 919
40 3849 1411
36 6014 2165
33 9336 3322
29 14434 5098
25 22257 7823


Hope this helps

ju

 

[Max]

API 312 4808 output - Who offers this output TX ?

 

[andre tchmil]

Hi, I have some questions:
where to connect the ground wire for the balanced output ? On the centertap of the output transformer ?

and where to add an output gain control ?

 

[rafafredd]

anyone knows what´s the ceramic caps used on the vintage 25*20? Are this just plain ceramics or COG/NPO types?

 

[Bauman]

Rafa,

ordinary ceramic discs... from the pics I got at least.

BTW got some Grayhill rotaries from Jay (thanks a lot man!),
the boards looks much cooler with them...


:guinness: :sam:
Fabio

 

[rafafredd]

Thanks, fabio!

 

[PRR]

> where to connect the ground wire for the balanced output?

Normally you do NOT ground the output. A floating output is much more useful than a Balanced output, because it can end up balanced or unbalanced just how you connect it.

The ground on the XLR will normally go to chassis in that case.

 

[andre tchmil]

ok. APi finished .
I used the simple schematic from the original 312.
and no rev log pot, just a "normal"22K , with the wiper connected to 1 side.
BUT, although I have lots of gain , the sound is dull.
:shock: :shock:

I used an Lundhall L1636 as input trafo
and original Api Group order output trafo.

 

[dukasound]

[quote author="andre tchmil"]ok. APi finished .
I used the simple schematic from the original 312.
and no rev log pot, just a simple 22K , with the wiper connected to 1 side.
BUT, altough I have lots of gain , the sound is dull.
:shock: :shock:

I used an Lundhall L1636 as input trafo
and original Api Group order output trafo.[/quote]

What opamp and what voltage you used???
Question for others:
What excatly voltage used API with 2520 and what voltage when is Melcor in use.
I heard very different answer in past.
Thanks
Duka

 

[jrmintz]

the sound is dull.

Check the cap in the feedback loop and the other caps.

 

[andre tchmil]

I checked nineties API 2520 and a more recent Millenia MM900.
Both are getting 18V.

Gonna check with a different cap.
I respond back.
thanks

 

[dukasound]

[quote author="andre tchmil"]I checked nineties API 2520 and a more recent Millenia MM900.
Both are getting 18V.

Gonna check with a different cap.
I respond back.
thanks[/quote]

Difference between 2520 and MM900 :?:
Where you find Millenia and what was the price.
Thanks
Duka

 

[andre tchmil]

Ah , Found it.
I studied Cjenricks input schemo and found my error in the grounding.
Stupid me and I can't say it enough : "WHAT A GREAT BOARD" this is.

Up to another project.
:guinness: :guinness: :guinness: :guinness: :sam: :sam: :sam:

 

[andre tchmil]

Duka, I got the MM990 from a guy called Pat M.
Ask around if you want to know him. :green:

I guess the MM's are slightly cleaner sounding.wish I knew all the sound characters for all the different brands.
Could be a good idea for a thread.

 

[dukasound]

[quote author="andre tchmil"]Duka, I got the MM990 from a guy called Pat M.
Ask around if you want to know him. :green:

I guess the MM's are slightly cleaner sounding.wish I knew all the sound characters for all the different brands.
Could be a good idea for a thread.[/quote]

Price?

 

[louder]

alo
i`m building some bauman`s boards(very,very nice ones)and since i`m in europe maybe i`ll go with sowter`s clones for input.
if any of you tried them,please let me know what you think.
best regards
pedro

 

[babyhead]

I am assembling a parts list for the 312 psu and was wondering what values for R1 R2 R10 and R11 should be. This probably leads to my next question...what transformer is suitable here? How beefy of a Digikey Amveco ie te62073-nd would work?

I am brazen with confidence after my SCA N72 success but know that I am way over my head...