API 312 Thread!

shop deals on amazon
Advertise with us
Shop deals on ebay
GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
hey jeff, what's the idea behind the decoupling caps? I know they were on the original schemo, but...

I don't know where you'd put these on 3nity's boards, you could put them directly on the trafo pins, but that may not be the best place for durability.
 
mitsos said:
hey jeff, what's the idea behind the decoupling caps? I know they were on the original schemo, but...

I don't know where you'd put these on 3nity's boards, you could put them directly on the trafo pins, but that may not be the best place for durability.
Click to expand...
I would say on the pins of the 2622 as well. One can try without them. Results may vary.

I spoke with Avedis a few days ago. He had the great pleasure of speaking with Saul Walker at this past AES. They spoke a lot about the 2622. Word is that Saul used the caps to tame some HF ringing due to the 2622 not being such a great transformer, as compared to a Jensen. But hey, all of these little things are why they sound so unique and cool! I guess Saul was very pleased and happy that someone still cared enough to ask him about the 2622.

Cheers, Jeff
 
Guavatone (white market) was selling a 12P grayhill shorting. I think it is fixed end stop. Otherwise, either special order with digikey, etc or direct from grayhill.
 
hey guys,
i am building an Access 312 with Ed's trannies,
i saw Jeff's recommendations about linking pin 1&2 , and pin 3&4
i was looking at 3nity's board,
the ratio's jumpers doesn't seem to match correctly the tranny's pins,
pin 1 of the ratio jumper seems to go to pin 4 of the 2622,
Pin 2 jumper to pin 2 2622
pin 3 jumper to pin 3 2622
pin 4 jumper to pin 1
So i think i should put a jumper between ratio 1 and 3 on the board
and between ration 2 and 4 ,
does anybody who has allready done this can confirm ?
or Jeff ?
thanks for the help ,
Pacemaker
 
what revision the boards are?
revision 2?? PM for instructions or easy..dont matter if they dont match once the transformer is soldered in place just use jumpers...
 
pacemaker said:
hey guys,
i am building an Access 312 with Ed's trannies,
i saw Jeff's recommendations about linking pin 1&2 , and pin 3&4
i was looking at 3nity's board,
the ratio's jumpers doesn't seem to match correctly the tranny's pins,
pin 1 of the ratio jumper seems to go to pin 4 of the 2622,
Pin 2 jumper to pin 2 2622
pin 3 jumper to pin 3 2622
pin 4 jumper to pin 1
So i think i should put a jumper between ratio 1 and 3 on the board
and between ration 2 and 4 ,
does anybody who has allready done this can confirm ?
or Jeff ?
thanks for the help ,
Pacemaker
Click to expand...
Look at the schematic for the 2622 on the classicapi website.  the pin numbers and primary windings are not numbered the same.

http://www.classicapi.com/catalog/images/gallery/2622/2622-specs.pdf

jumping pins 1, 2 and then 3, 4 on the transformer will parallel your primaries.  I have done it, it works.
 
regularjohn said:
Look at the schematic for the 2622 on the classicapi website.  the pin numbers and primary windings are not numbered the same.

http://www.classicapi.com/catalog/images/gallery/2622/2622-specs.pdf

jumping pins 1, 2 and then 3, 4 on the transformer will parallel your primaries.  I have done it, it works.
Click to expand...

How/where have you soldered the 1000pf Caps?

do this caps need to be COG/NPO or any ceramic is fine?

thanks
 
jsteiger said:
The load R after the Zobel should be 150K.
Click to expand...

Why terminate the secondary with 150k?  The original 312's 2622 has no such termination.  There are a lot of mics out there designed for unloaded secondaries.
 
gridcurrent said:
jsteiger said:
The load R after the Zobel should be 150K.
Click to expand...

Why terminate the secondary with 150k?  The original 312's 2622 has no such termination.  There are a lot of mics out there designed for unloaded secondaries.
Click to expand...
Yes the load R is absolutely there. It is not on the schematic but it is on the boards. The R shown in the Zobel is not the same value as what was actually used on the boards either. The values and method I have shown is what was done on the input channels of my desk. Ed has verified that this was also on the 312 card he dissected when he designed his EA2622.

Jeff
 
jsteiger said:
gridcurrent said:
jsteiger said:
The load R after the Zobel should be 150K.
Click to expand...

Why terminate the secondary with 150k?  The original 312's 2622 has no such termination.  There are a lot of mics out there designed for unloaded secondaries.
Click to expand...
Yes the load R is absolutely there. It is not on the schematic but it is on the boards. The R shown in the Zobel is not the same value as what was actually used on the boards either. The values and method I have shown is what was done on the input channels of my desk. Ed has verified that this was also on the 312 card he dissected when he designed his EA2622.

Jeff
Click to expand...

I have in my hand an API model 312-5.  ABSOLUTELY no termination other than the Zobel network.
 
API quite apparently did many different things with their 312 cards. Ed has suggested the load R and like I said, it is on my input channels which BTW sound great and have original 2622's on them.  :)
 
I'm hoping someone can help me.  I have a 2 channel 312 I built a few years ago; it's been great but now it appears the gain / trim doesn't work on either channel.  I've tried to search, and found some info but it wasn't resolved. (plus gain hits on Again and AgainST!)  I get signal and it sounds fine, it's just low and doesn't change with the trim.  I'm fearing that my 2520's are dead and that all I'm hearing is the the boost from the transformers.  I'm using a JLM power supply and I used 12v relays; all of my voltages are fine.  I have jt-110k inputs and cinemage cm0q-2s outputs.  I know I can throw 5534's in there to test, I'm just curious if there's anything else I need to change (jumpers etc) or can I just pop them in?

Any other ideas of where to look would be GREATLY appreciated.
 
rbaker said:
I'm hoping someone can help me.  I have a 2 channel 312 I built a few years ago; it's been great but now it appears the gain / trim doesn't work on either channel.  I've tried to search, and found some info but it wasn't resolved. (plus gain hits on Again and AgainST!)  I get signal and it sounds fine, it's just low and doesn't change with the trim.  I'm fearing that my 2520's are dead and that all I'm hearing is the the boost from the transformers.  I'm using a JLM power supply and I used 12v relays; all of my voltages are fine.  I have jt-110k inputs and cinemage cm0q-2s outputs.  I know I can throw 5534's in there to test, I'm just curious if there's anything else I need to change (jumpers etc) or can I just pop them in?

Any other ideas of where to look would be GREATLY appreciated.
Click to expand...

V+/V- voltages at the opamps themselves are fine?  Seems strange that both channels would go out at the same time.  That points to the common link:  the power supply.
 
Yes, v+ and v- with the opamps out, just testing the pins gives me correct voltages---I'm sorry I should have included that.  Also now that I think back, it happened once before once, in a session...I switched out to a difference pre and then the next time I used it, it was fine.

If the opamps were bad, is this how they would respond?  (essentially if they we just not adding gain, but still passing audio perfectly)
 
Def check your DC.

what 312 board are you using?  how are your pots wired? One side of the pots needs to go to ground for it to work (usually through a e-lytic capacitor). Without this ground reference, the pot doesnt do anything.
 
I have gain.  One of the pots is completely toast (no continuity whatsoever between the two outside legs) and the other is just about dead.  If I wiggle the wires connecting it, It comes alive momentarily.

So....I haven't been around for a while.  Is anyone selling 22k rev log pots or am I better off going with switches?
 

Similar threads

frob
312 collected info, is this right?
Replies
1
Views
1K
soundguy
S
T
Calrec 1061 Filter Simulation - help needed.
Replies
7
Views
6K
TomWaterman
T

Latest posts

Back
Top