API 312 Thread!

[Greg]

[quote author="BackHand"]So you compaired you're DIY 3124 against the original API 3124 and you're DIY did not sound the same?[/quote]Correct
[quote author="BackHand"]Do you have the same OP Amps as in the original?[/quote]
The opamp that I was using was actually an older 2520 than what was in the 3124. I also compared it to the Melcor 1731, so that one will definitely sounds different.

[quote author="BackHand"]In what whay whas this DIY version diffirent in sound from the original?[/quote]Let me first say that the 3124 is really not the same thing as an original 312. It uses a different 2520 and a different input transformer. So I wouldn't say that the 3124 is an original 312, nor would I expect it to sound like one. Even my DIY version will have a different sound than an original 312 since I'm using a different input transformer. But regarding the 3124 and my DIY 312, the DIY 312 sounded a little more rich in the mids, but wasn't as bright at the top. That's the main difference.

 

[dukasound]

Hi
Yestarday I finished soldering two 1731 and two 2520 R1. Melcors works but both 2520 not. 2N3053 and 2N4036 were very hot and I quick disconnect. Probably I made mistake on both. I use BC550C, BC560C and 2N3053 and 2N4036. Here is layout. If you can help me.

Thanks
Duka

 

[asm]

on the 312 PSU, what are R1 and R2? they are labled "???" and on the screenprint it looks like a lytic cap with a jumper :?

any ideas?
thanks.

 

[pmroz]

asm
from this thread, previous page (26):

Quote:
- what are the values for R1 / R2 on the PSU ?

Bauman wrote

22R / 5W, totally optional. Just use a jumper if you want.

 

[asm]

oops, brain is fried.

thanks!! :green: :thumb:

 

[BackHand]

[quote author="Greg"][quote author="BackHand"]So you compaired you're DIY 3124 against the original API 3124 and you're DIY did not sound the same?[/quote]Correct
[quote author="BackHand"]Do you have the same OP Amps as in the original?[/quote]
The opamp that I was using was actually an older 2520 than what was in the 3124. I also compared it to the Melcor 1731, so that one will definitely sounds different.

[quote author="BackHand"]In what whay whas this DIY version diffirent in sound from the original?[/quote]Let me first say that the 3124 is really not the same thing as an original 312. It uses a different 2520 and a different input transformer. So I wouldn't say that the 3124 is an original 312, nor would I expect it to sound like one. Even my DIY version will have a different sound than an original 312 since I'm using a different input transformer. But regarding the 3124 and my DIY 312, the DIY 312 sounded a little more rich in the mids, but wasn't as bright at the top. That's the main difference.[/quote]

Thanks Greg, great reply :razz: !
Just one more thing...the DIY 3124 do you think it would sound like the original (today's version) with sowter and Melcor 1731?.. :grin: :?:

 

[pmroz]

Just one more thing...the DIY 3124 do you think it would sound like the original (today's version) with sowter and Melcor 1731?..

When you say 'original (today's version)' , it's kind of a gray area...
Fabio's boards are based on an 'original' design from around 1975-80? or so. Nowadays the 'original' made by the company has different parts than the old 'original' opamps. Most of the current 'original' parts are SMD (surface mount).
BTW the Melcor DOA is an entirely different circuit than either 'original'.
There are discussions about these things in the threads, by people smarter than me...

 

[Bauman]

When you say 'original (today's version)' , it's kind of a gray area...
Fabio's boards are based on an 'original' design from around 1975-80?

Yes, very very grey to me actually. Maybe Peter P. can shed some light on this matter...

Pedro?!

:guinness:

 

[dukasound]

Fabio, please watch my post about 2520.
Thanks
Duka

 

[balluda]

Hi, I only get sound from my Instrument jack no Mic or Line,what could be wrong(a million things I guess) I´m using Fabio´s PCB and 1731 with Sowter in . I get no V when I measure between the + & - where the 1731 should be,shouldn´t I get that ? /greetz Balluda

 

[Neeno]

How is your input tx connected ?
Remeber that you have choose the input impedance, soldering your primaries in series/parallel (you can choose from 150ohm or 600ohm input imp.)

Your HIz input is working because the HIz signal is directly connected to the opamp, bypassing the input tx, that's used only for the mic/line input.

Hope this helps...

Neeeeeeeeeeeeeeno

 

[drpat]

...

 

[Greg]

[quote author="BackHand"]Thanks Greg, great reply :razz: !
Just one more thing...the DIY 3124 do you think it would sound like the original (today's version) with sowter and Melcor 1731?.. :grin: :?:[/quote]

I don't know really since I've never heard the sowter. I'd speculate if you want to get a DIY 312 to sound like the 3124, I'd use a Jensen input transformer, Profile 4804 output transformer, and a modern 2520. If you put a Melcor in there, it will definitely sound different. From my experience, it'll be a little softer and smoother mids, but not as punchy. I have two channels and one uses a 2520 and the other a Melcor; everything else is the same. And they sound different.

 

[louder]

alo
well,i have a new api 3124+,and fabio`s clones with melcor.
they ain`t night and day,but 3124+ it`s cleaner and does not pushes any frequency forward.
the clone with melcor,does something to the upper mids,that i would describe like gritty,seems to compress the sound.well,it`s almost as guitar amps with and without tube rectifier.when you push them hard,the sound seems to compress(with tube rect).
the other day just for fun i did some voice over,with a u89,very soft,and you could not tell one from the other,but when you start to put some presure on your vocals,then you get what i told you about.
well,the clones have cinemag 75101 input,and sowter output.
hope i could help you all but it is hard for me to put in words the sound you hear,even more in a language not mine.
note:just try the clone with a mic with low output(441-sm7-m500)on egt,very loud and you`ll see what i mean.
best regards
pedro

 

[Greg]

louder:
Have you tried your clones with a 2520?

 

[louder]

alo greg
not yet.
just too lazy to finish them.
maybe i`ll stick one 2520 from 3124+ in the clone and then i`ll tell ya.
best regards
pedro

 

[northsiderap]

Here's my .02

Eight channels - I added Some Jensen 115s to line amps, sticking to the original API schemos. The Jensen 115s are bolted onto the board through the little hole that one of the tie-wraps holding the output xformer cable was in. A little 'Z' shaped piece of metal holds the xformer off of the board, making room for other components and allowing access to the xformer wiring.

Thinking about making a summing bus also, so it'd be a DIY 3128m??? What topology would be best for a summing bus here? Anyone know what API uses? I have a pair of Melcor AMLs or MAP DAs I could use. Or should I make channels 7&8 the Melcors and use the API 325s for summing amps? I also have a nifty DC class-A design for a 6+db line amp with 6k input Z and 600 output Z. I could use my own amp module here maybe.

It'd be nice to find some 4 or 5 band passive EQs for the summing bus that I could drill or snap into my current design.

I have some old Fairchild LDRs, I could put those in the loop somewheres too I think. Maybe I'll add a giant lever on the side of it to make it look like a slot machine while I'm at it. Then I'll add a cowboy hat. :wink: :guinness:

Sounds good. Seems like gain is a little low for some reason, but nice and clean. My phantom bus is wired, but I haven't installed the phantom switches. The pad and phase are in though.

The case is an old 386 computer case. I made top/bottom/rear panels out of an old VCR case. If you see one headed for the trash somewhere nab it! These make kick-butt DIY cases. I'm guessing they're already shielded pretty well too. Instead of keeping it, send it to me. Seriously. I'm not joking here people. Send it.

 

[Greg]

Nice work !!! 8 channels of API in a computer case... nice style indeed !!!

 

[mhartung]

Thinking about making a summing bus also, so it'd be a DIY 3128m??? What topology would be best for a summing bus here? Anyone know what API uses?

Funny you should ask. I have been mixing a record for the last few days on an old API console and I did some investigating of the summing and have found that it apperas that there are summing resistors on input channels (47K ohm for the left and 47K ohm for the right-post pan pot) that feed a buss pcb that runs the length of the console (28 inputs), which in turn is sent to a card labeled ST ACA which is THE summing amp for all the channels. This card is in the back of the console and has a 2520 and an output tranny each for left and right. I didn't have time to dig into where the signal goes from here but I imagine that it gets sent to the master fader on the console.

HOpe this helps

mike

 

[northsiderap]

How about the pan pots? Anyone know if they are dual ganged, single ganged, passive? I'd like to get as close to the original API sound as I can. These things are already running at a noise level of about -127db, which is astonishingly close to the factory specs when they were released...