bump!

i wonder how many have been spoken for....

Approximately 70 have been spoken for. I created a page of info that I've rounded up over [[url=http://[/URL]="http://web.qx.net/j…"]here.[/]="http://web.qx.net/j…"]here.[/] It's by no means complete and the web page is kinda hackish but I slammed that together in about 10-15 minutes. I wanna straighten it out some but for now it's fine.

Fallout (Jay) and I have discussed the project some. We need to work on the board layout and PS. My personal preference is to have the front panel controls mounted to the pre-amp circuit board. That can be a bit of a pain though. We'll have to see how things go.

The PS that I'm thinking about does +/- 15 volts via 7815/1915 regulators. That should give us an amp a side with should supply the pre's with more than enough juice as they consume 65ma at +30dBm output. I was thinking about using a LM317 for getting the +48 phantom supply and also doing a 7812 for a "control" supply for relays and LED's and such. That might be a bit excessive though.

When I get a chance I'l build up a PS. Of course Kev's got a new PS under development that might be perfect for this and just about any other DIY opamp project.

Peace,

James

I have question. Are the module type opamps that much different from a good IC OPA2604 etc? The NE5332 can often sound very good to this day. IIRC it is a mid to late 1970s design.

Has anyone used the API transformers with an opamp circuit?

Gus is that you? The NJ guy? It's gotta be, not many other Gus' i know on these forums! :D We met at that class in New Brunswick a few years back and spoke a bit on Aron's stompbox page.. Dunno if you remember me.. LOL. Drop me a PM when ya get a chance...

-Jay

Yes Jay its me. What was that a win98 or nt class??? I am still working at the same place also same email I gave you as well . I have been building/modding microphone circuits. I even have a nice little metal lathe now as well as a toy taig lathe.

Great to run into you again Gus.. Yeah it was a WinNT class if memory serves me right. I lost your email address but for some reason i remember it as YOURNAME@yahoo.com? Is that right? If not drop me a PM.. Catch you later..

-Jay

You may want to consider + and - 18vdc for your supply. (they can go as high as 20vdc) You can get the full 65db of gain with that. At 15 I think it is only 60db. They can actually run down at 12vdc but the only crank like 50db or so.

I run my originals at 15.5vdc(thats what I had laying around) and they sound really good, but you may want the extra gain.

Joe

Originally posted by gus:
Are the module type opamps that much different from a good IC OPA2604 etc? The NE5332 can often sound very good to this day.

Yes these things can be considered to be different to a normal IC as we know it.
There are made of discrete components and often potted, for secrecy AND for temperature stabilization.
For us DIY'ers it can make for a potentialy simple high high quality Mic-pre. Most of the hard work is inside the pot.
All we potentialy need to do is chose the larger components and assemble and provide power.

Hopefully High Quality parts will equate to Great sound.

stand back ... Shameless plug

JLM Audio
http://www.jlmaudio.com
look for the JLM990 Discrete IC

Some schematics to drule over
http://www.jlmaudio.com/JLM990%20Mic%20Pre.pdf
http://www.jlmaudio.com/JLM990%20Mic%20Pre%20Single%20Rail.pdf

Two options here.
Dual rail at 34 volts
Single rail at 60 volts

:eek:

That should keep the BIG voltage boys happy.

JRE, the gain shouldn't be related to the rail voltage, surely? -Headroom, yes, but gain, no.

Also, a halving of the rail voltage would reasonably be expected to equate to a halving of the maximum level, therefore a 6dB reduction. -I really don't see how the difference between 18V and 20V could possibly be 5dB... one-point-something perhaps, but not five... -and running at 12V compared to 20V resulting in a fifteen dB drop? ...??? That should be a 5dB drop I would have thought...

Unless I'm on completely the wrong track with what you meant, those numbers can't possibly be anywhere near correct, surely?

Keith

I’m interested…where do I sign up? Also, what about the input tranny (Mfg? – Jensen?) and the 2520? Can’t we get them cheaper in quantities too?

Originally posted by Kev:
[QUOTE]stand back ... Shameless plug

JLM Audio
http://www.jlmaudio.com
look for the JLM990 Discrete IC

Some schematics to drule over
http://www.jlmaudio.com/JLM990%20Mic%20Pre.pdf
http://www.jlmaudio.com/JLM990%20Mic%20Pre%20Single%20Rail.pdf

Two options here.
Dual rail at 34 volts
Single rail at 60 volts

:eek:

That should keep the BIG voltage boys happy.

The ad says:"Coming Soon JLM990 IC and PCB & Kit". Do you know how soon and how much?. Also, can this be used in place of the 990 on the Jensen schematics and at +/-24V? (is there a spec sheet?)

I’m interested…where do I sign up? Also, what about the input tranny (Mfg? – Jensen?) and the 2520? Can’t we get them cheaper in quantities too?

Fallout is taking names of people that want output trannies. We've been talking about it. I've actually got the extra cash to front the whole run of a 100. We're pretty close to having that 100 accounted for. I'm still holding out for a few days in case we have more interest that way I'll just buy more transformers.

As for input tranformers we're looking at using the Lundahl 1538XL. They are $57 a pop from K and K audio. I've got all the information I know of gathered at my [[url=http://[/URL]="http://web.qx.net/j…"]site.[/]="http://web.qx.net/j…"]site.[/] Take a look around there and get some ideas. 8 channels of these guys are gonna run you between $1200 and $1400 depending on how fancy you get.

Peace,

James

The input transformer can be an API 2622 (pretty much impossible to find, but is the original part for these suckers). The Jensen JT-110 was used in some API consoles. The Lundahl 1538XL works as well, and I believe that is used in one version of the Old School Audio API style preamp. Also, for an even cleaner sound you could go with a Lundahl 1636 (amorphous core). I will likely build 2 with the 1538XL, and 2 with the 1636 (I like flavours).

The circuit is super simple, and should reward good parts choices. I will likely stick with Forssell gain blocks, but would consider going for a grittier type block on the 1538XL based channels. Anyone know where to get original API 2520's?

Anyone else notice that the output transformer is located in the feedback loop of the op-amp? Neat...I suppose that cancels out some of the distortion introduced on the primary side of the transformer.

Regarding the voltage issue, I think +/- 15V is more than enough for these guys, there is not much to be gained in terms of headroom from a 4-6 more volts in the supply.

Cheers,

Kris

Originally posted by Flatpicker:
[QUOTE]The ad says:"Coming Soon JLM990 IC and PCB & Kit". Do you know how soon and how much?. Also, can this be used in place of the 990 on the Jensen schematics and at +/-24V? (is there a spec sheet?)

Yes it does say coming soon.

The op-amp has been available for a while. Not front page news .. so you had to know about it to order it. I do have one but just haven't had time to do any work with it.

Coming soon is more about some applictions than it is about the JLM990 itself.

Can this be used in a +/- 24 volt circuit ?

I believe so BUT I have not done it so please check with Joe for more details.

I needed something to go along side my AM16 in a 1U rack, and now this! What's approx price/availability on the JLM thingamajig?
I know it's been around here for a while, but sometimes things just need a jump start to get going, ya know what I mean?

Nice job James, and I love your chassis punches! Fallout, you are the man for handling this size order!

The SPA690 from Inward Connections (they guys that made the Vac Rac stuff a few years back) also fit the 2520 footprint but can run on +/-24 volts. You can reach them through [url="((deadlink))[/url] .

Inward Connections also sells custom I/O transformers made for them by Riechenbach, and they have a four channel kit you can purchase and build yourself. Good stuff.

Peace,

Joel

Originally posted by cjenrick:

Nice job James, and I love your chassis punches! Fallout, you are the man for handling this size order!

No, James is the MAN! I'm just helping organize it..

-Jay

P.S. You're the man too.. Your T4B rocks! Now i just gotta get around to building the LA2A to use it in! lol....

I think I tackled the OpAmp thingy awhile back. I s'pose that's in another thread. Anyway...The choices that I know about are:

Hardy JH-990
Millennia Media MM99
Forssell Technologies JFET-990
Avedis' 1122
Joe Malone's JLM-990
API 2520
Jensen 990

I believe that's about it. I'm sure there are others out there. Alot of those are obviously 990 variants. The 990, although pin compatible with the 2520, isn't a 2520. Each one of those opamps is gonna have a slightly different sound and interact with the surrounding circuitry a bit differently. Has anyone compared these different opamps? Perhaps I need to go out and take a look at these various offerings and pull their specs into a table.

Anyway....For the purposes of creating an API 312 clone I would think that first up would be genuine 2520 opamps and second would probably be the 1122 opamps. I wouldn't know exactly though because I've never used them.

So there's some stuff to marinate on. Have fun!

Peace,

James

Well, I just put my name on the list for two of them. I've been wanting to do this for a long time but never got around to getting started. Thanks for all the help and info, guys!

Just a thought:

Current api 2520's are apparently surface-mount built now instead of larger, handwired components. I don't know if they really sound all that different, but I'm assuming that Avedis' 1122 is hand-wired like the originals. Perhaps these should be considered a 'first choice' for an accurate 312 clone??

Also, don't forget to add the SPA690 from Inward Connections to the list of options. It doesn't appear that anybody has noticed my above post, or a previous post about it a few days ago. If you are not checking out Steve Firlotte's stuff (trannies, opamps, etc...) you are missing out. He is extremely cool, makes great components, and is a likely friend to the DIYer. He has been very helpful and gracious to me, and I definitely like to promote businessmen like him.

:D

Joel

Looks like the 312 project is moving ahead!

I just realized something, your gonna place a 2,000 dollar order! You might need a little money up front, eh?

Do any of you guys have the schematic(well obviously), if there's one available online could you point me to it?

Thanks!

Do any of you guys have the schematic(well obviously), if there's one available online could you point me to it?

I've gathered alot of pertinent information at my [[url=http://[/URL]="http://web.qx.net/j…"]site.[/]="http://web.qx.net/j…"]site.[/] Most of the info comes from Dan Alexanders site. Dan has tons of data sheets on just about everything. I just consolidated the pieces related to the 312 project. I'm gonna do some more diggin' on opamps and see what I can come up with.

For budgeting I think a safe margin is gonna be about $150 a channel with between $100 and $200 for the case depending on how elaborate you get. That pushes the cost of an 8-channel preamp into the $1300-$1400 range. That's probably a conservative number but shields you from some gotchas that might pop up along the way.

Peace,

James

So anyone here loading the output of the 2520 with 600 ohms?? Thinking about a 600/600 TX for output... I'll give it a try anyway.

Can anyone tell me what the differences are between this (API) preamp and the Neve 1272 variants?

Are there a set of DIY steps, parts list, etc. for this project and if so where can I find the info?

I too would be interested in ordering some of the bulk order transformers ... at least to set aside for this project sometime in the future (in case all the details aren't yet available to begin sooner).

Thanks,
Steve

Originally posted by Steve Ginn:
Can anyone tell me what the differences are between this (API) preamp and the Neve 1272 variants?

Are there a set of DIY steps, parts list, etc. for this project and if so where can I find the info?

Back track to page one of this thread and have a read. Most of your initial questions will be answered.
James has a web site with most of what you need as background to this.
http://web.qx.net/jgreenlee/

Group DIY has Project 1 which refers to Neve 1272

Stay tuned here and to Group DIY and I'm sure all you future questions will be answered.

Here is an interesting email I got this morning:

Regarding 2520 type op. amps: If you can get the source impedance
up a little (higher turns ratio IP trannie) then I would tend to
go for a JFet front end op amp rather than a BJT. There are a couple
out there - Millennia, Forssell (sp?)Technologies. Fred Forssell
has the schematic on his website for the first rev. that he designed
for Millennia if you wanted to build your own. I just think JFets
sound nicer and would gladly overlook the potential for a little
extra noise if my source Z wasn't optimum. I've been tinkering around
myself with a design that uses the same Toshiba 2SK170/2SJ74 family
but is a folded-cascode design (essentially a single gain stage device)with
active loading. It's starting to sound VERY promising.
If you felt like fooling around with a JFet design then let me know.
Those Toshiba low noise devices are sometimes hard to get in small
quantities but I have tons of them and can spot you a few.

If you really need to go with a BJT type device then why not 'roll
your own' with that as well? That way you can mix and match, dial
it in with your choice of passive and actives, operating points etc.

I know, quit moding before you even get started. Build the original first...
but I thought you'al might be interested...

originally posted by Kev:
Back track to page one of this thread and have a read. Most of your initial questions will be answered.

Hi Kev,

I read that and the other info posted at the other sites as well. I guess I should have been more specific. What I meant was what was the differences between the API and Neve preamps in terms of sound characteristics, not technical specs. I know they are both renowned and have incredible followings, but I just wondered what the differences were and why someone might prefer one over the other. Except for the hard to get parts, the API looks very easy to build.

thanks,
Steve

What I meant was what was the differences between the API and Neve preamps in terms of sound characteristics, not technical specs.

Neve's are typically thought of as "thick" sounding. "Warm" "Thick" "Big" "Juicy" Those are the adjectives that you'll typically find associated with Neve preamps. It's my opinion that the Seventh Circle Audio 1272 kit is an excellent place to start with DIY. Of course I also think that the API 312 is a great place to start some harder edge DIY.

Now...The API sound. API's are typically thought of as "punchy." "Punchy" "Snappy" "Big" "Juicy"

As you can see...Where Neve's are thought of as more "warm" API's are thought of as more "punchy." The API sound is mainly a characteristic of the 2520 opamp and the API transformers. Changing these components will yeild a different sound. Check the Old School Audio website for the differences made by just the input transformer.

The Neve sound is more developed by the overall circuit design. It's a much more complex circuit and as such it's sound can be altered in many different ways. That's probably one of the reasons that the various Neve clones sound slightly different from each other.

Peace,

James

Originally posted by Steve Ginn:
...What I meant was what was the differences between the API and Neve preamps in terms of sound characteristics, not technical specs...

You can hear for yourself here at: Silonex Inc.

Anyone have a printed circuit board layout of the original API board (or an improved version)?

Originally posted by James Greenlee:
Neve's are typically thought of as "thick" sounding. "Warm" "Thick" "Big" "Juicy" Those are the adjectives that you'll typically find associated with Neve preamps. It's my opinion that the Seventh Circle Audio 1272 kit is an excellent place to start with DIY. Of course I also think that the API 312 is a great place to start some harder edge DIY.

Now...The API sound. API's are typically thought of as "punchy." "Punchy" "Snappy" "Big" "Juicy"

[/QB]

Hi James,

thanks for the reply ...

from the way you describe these it sounds like it would be helpful to have both in the studio.

Would you characterize the Neve as being best for things like Vocals, Acoustic Guitar, Strings, etc. and the API best for things like Brass, Sax, Electric Guitar and maybe edgey synths?

The reason I ask is that I am a wind player (sax & windsynth) and most of my recording will be either my saxes or my synths; but on occasion vocals, acoustic guitar and keys. Also, will my selection of mics match up better with one or the other mic pre? I use an AKG-C414, a couple of Neumann's, an MD-421 and a Shure Beta 98.

Finally, it is my understanding that the 1272 (or SCA N72) is single gain stage whereas the 1073 that some of the others here are building, is dual stage (I may be misunderstanding/misquoting here). What is the effect or significance between these two and do they have different sound qualities?

Thanks,
Steve

I'm working on a flat version, no potted opamp. It'll have option for the input Lundahl TX and some other one on board. Considering to leave the output TX out of the board, not sure yet. Also not sure if it'll be single layer (nice for DIY) or 2 layers (nice for shielding and a tight opamp layout)... just thinking about it... :confused: :confused: :confused: :confused:

Steve, you pretty much have the concept of API vs Neve down.

Most studio's have both. Electric guitars, and drums and horns are killer through API. Vocals and accoustics are killer through Neve's. You will always find exceptions to the above guidlines.

I find the API's are somewhat more articulate than Neves. They seem prety fast resonding and have a tight bottom end. A Snare really cracks through an API.

The Neves are smoother, richer but give up a little of the tightness and punch.

THe site listed above with sound clips is pretty good. CHeck it out.

Joe E

I wanna branch off and discuss components real quick. There are notes on the API 312 schematic to replace C4 and C5 with "polystyrene" caps. I'm in the process of digging through the Panasonic website and the Digikey website (I looked at Newark but they don't seem to carry the Panasonic caps. At least you can't find them by manufacturer part number.) to put together a shopping list for the API312 project.

For the electrolytics I picked the closest values of Panasonic FC series caps that Digikey had. Now I'm a little thrown off by the polystyrene caps. I can find polypropylene and polyester but no polystyrene. So what to use? Should I use tantalums instead?

Some other things to think about would be the facilities everyone would like to see. Alot of 312 type pre's have Gain, Pad, Polarity, Phantom and Mic/Line. I'm thinking about bailing the Mic/Line switch. The pad might be useful as the minimum gain is 25 db. (unless your transformer ratio is different) Polarity I don't really need as I can flip that easily in my DAW. Phantom will be needed.

What's everyone's take on what they want? Do we make the kitchen sink version with all the luxuries? Or do we make a streamlined version with just what we all need?

Peace,

James

re: polystyrene

i don't think panasonic makes any (not sure). i ended up using the xicon axial polystyrene caps from mouser, and they worked well for me. pg.433 in the catalog, under plastic film caps.

ed

Originally posted by James Greenlee:

What's everyone's take on what they want? Do we make the kitchen sink version with all the luxuries? Or do we make a streamlined version with just what we all need?

I'd have to say phantom power is must, phase switch would be nice, everything else doesnt matter... My 2 cents....

-Jay

The newer more affordable API rack still lists for like $500 and doesn't fit in a 19" rack. $500 buys one helluva nice box and power supply to house and juice your pres. A friend of mine is gung-ho on the idea of a modular rack. I just don't see it as being a good economic choice. OSA has some nice rack choices as well including a 11 slot, 19" rack. I'm all for keeping it in it's own enclosure.

Just so everyone knows I put up a modified parts list with Mouser part numbers for the mic pre. It also has some opamp and transformer options listed. You can scope it out [[url=http://[/URL]="http://web.qx.net/j…"]here.[/]="http://web.qx.net/j…"]here.[/]

Peace,

James

What are the power requirements of the API? Does anyone know of a power supply that could supply +24V for a set of 1073/1272 cards and a set of API cards in a single box? It would be nice to have 4 Neve's and 4 API's in a 2U rack space unit, but the power supply is probably the biggest factor right?

Steve

P.S. As for the API, instead of a hi/low switch, is there any way to configure it with a Neutrik combo connector with automatic selection?