DIY 1272 for Newbies? C'mon.

Hi folks,

I see 1073 clones mentioned, and 1290/1272 card resotration all the time in the forum, but has anyone ever taken a shot at a simple 1272 diy?

I only ask 'cause I'm so in love with my N72. Yes, I could build a couple more of the channels as kits from seventh circle, but diy-ing a couple seems like a great way to learn. I'm thinking I can simplify things greatly, building a dedicated (b+/-, 48v) power supply so nullifying the need for local regulation. Also, I wouldn't need phase. After that, it looks relatively simple...with the exception of sourcing the proper transformers. I'm not in a huge hurry though (doing lots of reading to get ready), so I can wait for some surplus transfos or until someone is selling a couple of i/o.

Basically, I'm just trying to do a bonehead version of the 1272, 'cause I just want the tone, no extras, and I want to understand it. Ireally don't think I'll ever need a jumper to "float the ground." Also, I pretty much want to take whatever schematics I can find, including Tim's and adapt them to this project. Please accept my apology if this is "bad show" in the world of DIY...I'm totally new to this. But, I don't see the issue (off the top of my head) if I'm not building for commercial purposes and have no intention of competing financially. Ever. Plus, I'm also operating under the assumption that if it's published on the internet, it's fair game. Again, maybe I'm wrong. I intend no disrespect to credited designers.

This might even be a great way to do an online version of an electronics tutorial, slowly walking our way through this over the course of a couple of months.

Any newbies into this? if we can get a crew together to tackle this, we might even be able to do the group buy for trannys...?

Thanks!

kelly

I did just find the DIY 1290 site. If anyone is interested, they've got a PCB pdf...

kb

Check out a schematic of the BA283 card, all versions. Dan Alexander has 183's for sale on his site as well as 283's. The N72 is the the same circuit, line make up gain amp, usually after summing on a Neve desk, the original never had a mic input or a gain switch on the front of the module (if it was even mounted on the surface of the desk,) it had a pot with a flat screwdriver slot cut in the shaft to set the gain of the sum. That's not to say you've got a bad idea. It's the same idea guys like D. Alexander and Brent Averill had when they had piles of 1272 modules around after cracking a console.

As regards what's on the internet, no it's not exactly public domain just because it's out there and you know where it is. There's some discretion advised, but you're probably not going to grab TimR's exact layout or gain structure solution to reproduce for $$$ so... I'm not sure how Great River approaches this because Neve is still very much in business has reissued the 1073 and the 1081 and probably to some degree expects recognition of the copyrights, which in the printed wortl last 50 years. It's both a copyright thing and an intellectual property thing. Which is not to say you shouldn't do what you've got cooking in your noodle.

I don't think you can diy a 1272 based pre-amp for much less than you can buy it from SCA. Check with the 1081 guys on BlackMarket, I never heard exactly how much they paid for iron but I'm pretty sure they got it all from Carhnill.

I've been thinking of doing some 1073's, which are more complicated by a mile than the simple 1272 circuit. The 1290 channel amp is a 1073 without the eq section, see Tekay's pcb and layout here:

http://www.vintagedesign.halmstad.net/diy_reseach_frames.htm

Go to DIYCorner, also check out Tommytones 1081 project while you're there. You'll see the original Neve 1290 uses two cards, look for Neve drawing # EN10041; there's one B189 and one B183/283. The 189 card has two of the same preamp circuits that are on the first half of the 183, I think it's called the B110 type amp IIRC. The 189 is fully stuffed, both halves. The 183 only has the voltage amp side stuffed, the circuit that outputs through the T03 transistor into the LO1166 xfrmr. Only one gain switch and one input transforer, the 10468. 1290 seems like the natural progression after building the 1272.

The 1073 up the ante more by adding an eq section and a line input transformer, the 31267. It's very close to the 1064, 1066, and the 1078. The 1080 seems to me to be the top of the heap for this itteration of channel amps, and then you off into wild new territory w/the 1081 which uses completely different topology, different card sets, a substantially different eq section. Those guys are paying some tall cash to put these together over on Black Market, but even, it's worth it if you've checked the price of the AMS Neve reissue.

ANYWAY!!! I've gone a little far afield from your original idea, which is good, but maybe a little redundant. I say go for the 1290, whether you build it out of used Neve cards you buy, or from TK's pcb, or from your own design. Be ambitious and do the 1073 or the 1066 since it doesn't have expensive dual concentric switches. OR do the 1290 and wire in an insert jack, like the Great River pre's; you can roll an eq later or you can insert your compressor, etc. That's just about what I was going to do bt eieto go the whole way and do a 1073 and maybe try to add a frequency roll of switch on the HF cut/boost pot. Check out Kev's GroupDIY/Project 1 page, he takes on all these questions/issues.

If you can organize a transformer buy I'm in as long as I don't have to pay VAT. I'm in on a tutorial of at least a 1290, but better a 1073.

rgrds,
Brad

hmm I'm also interested in a 1272 just purely for the tone. it wouldn't need to have any kind of gain, just +4 in, +4 out...

No gain, you mean like a fixed gain of (insert # dB)?

Interesting. In fact, what about a fixed gain of 60 dB, then wire a full fader? Just build two channels at a fixed pont in the 3rd gain stage (1290) and wire a full fader? That'd be ridiculous, but super simple right?

kelly

And thank a heap for the info, Brad! That's a ton of research just handed to me and I appreciate it!!!!!

kelly

i was thinking unity because i would stick it in line between my console and my computer to get rid of some of the "digital" sound of my recorders, but a fixed gain and a fader will work too.. what will the linearity be like though.. however i must admit that I don't know much about this pre since i've only recently thought about building one and haven't studied it.

:thumb:

I'm not exactly sure about linearity, except that we could probably find some distortion figures for different gain settings on the web?

I'll do some looking. Although honestly, I'm pretty sure I can live with the non-linearity, if I understand correctly that that's what the beauty of the neve sound is: quality distortion.

It's interesting...I don't understand that actually. Class A amplifiers are applied for their linearity, correct? It seems incosistant that I'd be complimenting the 12XX's distortion.

Maybe one of the more experienced can clarify...until then, i'll keep reading...

kelly

[quote author="Svart"]i was thinking unity...
:thumb:[/quote]

This would be fine too. It might even eliminate the third gain stage of the 1290?

I'm not going to be picky about it...my N72 is hands down my favorite piece and it's only got two gain stages...

kelly

What recommended to use just for a line amp stage like the api 325? The model #'s floating about is confusing! Basically, I'm aiming to make a range of amp modules to use on a passive summer - just plugin/out from a VERO rack mainframe...

Peesh :thumb:

[quote author="daArry"]What recommended to use just for a line amp stage like the api 325? The model #'s floating about is confusing! Basically, I'm aiming to make a range of amp modules to use on a passive summer - just plugin/out from a VERO rack mainframe...

Peesh :thumb:[/quote]

That's what a 1272 is. Many model numbers are here:

http://www.technicalaudio.com/nevejunk/nevejunk.html

Read the reason why this forum exists:

http://recording.org/users/kev/Project1.htm

It's a good read, Kev explains almost everything you might want to know up to the 1073.

[quote author="kelly"]No gain, you mean like a fixed gain of (insert # dB)?

Interesting. In fact, what about a fixed gain of 60 dB, then wire a full fader? Just build two channels at a fixed pont in the 3rd gain stage (1290) and wire a full fader? That'd be ridiculous, but super simple right? [/quote]

That's exactly what a 1272 module does without the additional gain stage of the 1290! To be more precise with the language there are two pre amps (what you're calling gain stages) and a voltage amp in a 1290, one preamp and a voltage amp in a 1272. There's a fixed gain pot (meaning it's a pot that's adjusted with a screwdriver that hides behind a plug in the face of the 1272 cassette) that controls the level of the B112 circuit, the first half of the BA283 card, there are fader connections on the pins out of the module, the B110 circuit is the second half of the BA283 card and the voltage amplifier. There is one gain stage and one amplifier, not two gain stages. The N72 works exactly as the the 1272 module but has a stepped gain switch inplace of a fixed gain pot, and a fader. Read Tim's scat, it's really simple. JLM's switch is different, it actually is a second pre amp AFAIK, so there is the first preamp on the 283, the JLM switch/card, and then the amplifier stage, it mimics the circuit of the 1290, the gain switch is IN BETWEEN the two pre amps, again, read the original 1290 schematic. 1290 you need two Neve cards, the BA283 and the B189, 1272 you just need the BA283. Which is to say you need those circuits. Read the original circuits, compare them to the N72 to see what Tim did to modify the circuit for 60dB of adjustable gain and what JLM did to make a 1290 out of a 1272.

I printed the 1272 manual last night so it's got to be in one of these websites somewhere. What you guys want is exactly what a 1272 is. Buy a BA183 or 283 card, wire in a pot, get two transformers, apply power and use it as a make up gain stage like it was originally used. There was a short thread about this a coupla days ago. Check it out:

http://www.groupdiy.com/index.php?topic=69&highlight=1272

This stuff is like Legos, you don't really have to fiddle with it too much you just have to understand how to wire the circuits together and the best hints towards that end are in the original Neve drawings. The sound comes from the transformers, not necessarily the amps driving the signal through the transformers. What you're liking is the St. Ives iron.

thanks for clearin that up! :thumb:

I built a 1272 as my second DIY project... it was a bit of a pain. I'm sure I could do it again fairly easily (and far better), but it wasn't what I'd call a straightforward DIY project.

I didn't do phase switching, nor local regulation, butthese things aren't really a big deal. For power supply I just bought a Power One +24V and built a +48V regulator. For transformers I've been pretty happy with the Sowters in mine...sounds a little different than the St.Ives, but still has the right overall character.

I built mine with a 3 pole 12 position gain switch/pad, but if I were to do it again I'd want to be able to pad the input and control the two stage gains, as well as the fader seperately. Just to have fun with overdriving a stage or two...these amps distort in a really cool way, it's not just the iron. I think that being single ended helps the distortion characteristics.

Cheers,

Kris

Wow...thanks for all the info.

I'm kind of into getting the cards, but I like the idea of studying the schematics and digging into it. I've got enough gear to record what I do, I would just love to understand electronics and build a great pre at the same time.

For some reason, I'm still hot on the idea of a 1272 with a switch between unity and, like, 50 db of gain, with a full fader. The thing is, I'm not so sure that adding the adjustable gain is a huge issue...just a stepped attenuator and a resistor network, right? I thought it might be easier, because you wouldn't have to integrate a swithc between the votage and pre, amplifiers. I dunno. I'm getting way ahead of my self...:grin:

Hey, if someone has a second, what's difference between the two amplifiers? One is a preamp and the other a voltage amp?

That's throwing me way off of what little I already know. Crap, back to the books!

Thanks again, everybody, for chiming in right now.

[quote author="bradzatitagain"]
It's a good read, Kev explains almost everything you might want to know up to the 1073. [/quote]

thanks

Although many things are not linked from the front page , as I am trying to get the google hits down to the second page, many of the Group DIY pages are in fact still there.

This will not go on for ever and eventually some things will move across to the DIY Factory and the RO Group DIY pages will be deleted.

Projects 1, 2 3 and 4
yes there is a 3 and 4 that never got released as time ran out at the old place and triggered a rethink.

It all takes time and to some degree I am still paying for the very quick and large expansion of Tech Talk and Group DIY ....
then the amazingly quick death of Tech Talk.
:shock:

There is enough Neve BA283 info out there so chase down as many links and cross-links as you can find and it will all fall into place. My favourite beginner project with a BA283 is the addition of the JLM switch kit. I also think that once you have a couple of higher gain Neve units then a few basic 1272 for loud sources like drums is fine and will save you a little money and perhaps space ... more per box.

[quote author="thearnicasync"]Wow...thanks for all the info.

I'm kind of into getting the cards, but I like the idea of studying the schematics and digging into it. I've got enough gear to record what I do, I would just love to understand electronics and build a great pre at the same time.

Hey, if someone has a second, what's difference between the two amplifiers? One is a preamp and the other a voltage amp?

That's throwing me way off of what little I already know. Crap, back to the books!

Thanks again, everybody, for chiming in right now.[/quote]

Oy!!!

http://www.technicalaudio.com/pdf/neve/0283-allvers.pdf

Compare these to the schemos you got with Tim's N72. The circuit on the left of this drawing is the preamp, the one to the right is the voltage amp, NPN, DC volts travel through the primary of the output transformer, check out specs of 2N3055.


Adjustable gain, as you have on the N72:
[quote author="tekay"] To build a proper pre out of a 1272 you'll need a 3x12 switch to make it work like the 1290 but without the 50-80dB gain settings. also need to add a 1k5 in serie with a 100uF cap for the rear stage gain boosting.
_________________
----------------------------------
Thomas "Tekay" Kristiansson
Halmstad
Sweden [/quote]

You've already got a fader on the N72, so it seems like all you'd need to do is peg the pre at 50 and use Tims schemo to wire your fader. It stands to reason that whatever resistors are in series with the gain switch at whatever decibel level you want the preamp to be fixed at would be your hard wired resistors between your input the the pin you knick it off, U in Tim's schematic also? But to be certain check out the 1272 schematic:

http://www.jlmaudio.com/Schematic.htm

1290:

http://www.technicalaudio.com/pdf/neve/1290-EN10041.pdf

[quote author="kelly"] For some reason, I'm still hot on the idea of a 1272 with a switch between unity and, like, 50 db of gain, with a full fader. [/quote]

So was Sir Rupert Neve, apparently.

[quote author="kelly"]The thing is, I'm not so sure that adding the adjustable gain is a huge issue...just a stepped attenuator and a resistor network, right? I thought it might be easier, because you wouldn't have to integrate a swithc between the votage and pre, amplifiers. I dunno. I'm getting way ahead of my self[/quote]

Are you sure you're not actually behind yourself? To dispel the confusion, you already got what you've described w/your N72. If you adjust your gain switch to 50db w/Tim's bassackwards fader fully counterclockwise and then turn the fader fully clockwise do you still pass signal? I'd think that you shouldn't. The original Neve 1272 circuit will allow you to do exactly what you are describing if in fact you don't already have it w/the N72. There's absolutely nothing to figure out. The original circuit also allows you to adjust the gain before the fader. Read the original Neve specifications of the 1272 to determine what the full rated gain is before the fader pin outs. In other words RTFM.

Ciao!

Interesting you mention drums, Kev, 'cause that's exactly what I want - pres that are simple and application specific.

Basically, I've got an n72, that I can adjust for quiet stuff, now it would be nice to get that sound on kick AND snare. And bass. Ahhh...the dream.

Thanks for the BA283 nod, I'll start searching.

Again, thanks...

kelly

Brad, you rule so much!!

THANKS.

kelly

Ive been reading the recent rash of neve threads with a little frustration, for the new guys to this, try to think out of the box a little bit, it will make the process a lot easier for you when deciding what you need for a project.

1073, 1272, 1290, et al. were just package descroptions used by a big company to keep things in order. there is no reason for anyone here to be looking at neve the way neve looked at neve. Like many of the 70's console companies, neve was the most erector set of them all, meaning they spec'd a few different kinds of transformers, a few different types of amps, etc, and used them every where in a console. All you need to do is familiarize yourself with the erector set neve elements and you can build your own thing to do whatever you need it to do. If you are DIY'ing, there's no reason to spec to neve unless you are building a neve console.

1272's were used for makeup gain on a passive mix buss in a neve console. The impedance of the mix buss is the commonly accepted mic input impedance. Neve used transformer isolation everywhere. Conveniently, where the package designed to amplify the mix buss to reference level was designed to do just that, it also works if you plug a mic into, as its the right impedance and can supply sufficient usable gain. The transformers and amplifiers used to make a 1272 didnt need a wide gain control as a summing amplifer, it was set gain with a fine trim adjustment. Of course, if you were to use the same parts as a mic pre, like in the 1073, you can integrate pads and feedback loop gain boost to give you a level of control that is more appropriate for a microphone. This is basically all that was done with the seventh circle kits and everyone elses kit. The parts were put together with the control element to make it more convenient to use with a microphone.

Just look at this stuff in terms of block elements and forget the neve numbers or what it was supposed to do in a neve console, that info is ultimately irrelevant to you as a builder. If you want to build a mic pre that has two gain stages, you can follow the idea of the 1272 with a 283 surrounded by transformers and add the switching you feel best suits your needs. If you want a mic pre that has three gain stages you can follow the block of the 1290 and you can make a pre with 4 stages if you really wanted Im sure. A 1272 with two stages can supply as much usable gain as the api 312s that everyone here builds along with countless other pres that top off around 55dB or so. Dont pidgeon hole yourself into following what neve did, they took their stuff and built the circuits out of the building blocks that best fit the needs of the console they were putting together, since you are not in a position to have to answer to the needs of a console, free yourself to build something for yourself which will address the needs of what you need. I cant see any good reason to build a mic pre from an amp that has a feedback loop that is easily manipulated and NOT put a gain control on there especially if you are building it to USE it making a recording. Its not very hard to do and its certainly a lot easier to do once you just look at these things as little blocks that can fit together to form a usable thing for you and not get intimidated by trying to adhere to some standard that some old english company set forth to address their own problems.

dave

[quote author="soundguy"]Ive been reading the recent rash of neve threads with a little frustration, for the new guys to this, try to think out of the box a little bit,

Just look at this stuff in terms of block elements and forget the neve numbers or what it was supposed to do in a neve console, that info is ultimately irrelevant to you as a builder.
dave[/quote]

Dave, I've started a few of these threads. I agree with your suggestion to color outside of the lines, but I don't completely agree w/your suggestion to discard the console data that shows how to wire these things up. If a person doesn't understand the B110 or B112 circuit in themselves, there's no help in discarding the Neve drawings, part number, boards and the various circuits, that info is the only way to learn about it if someone is also teaching themselves electronics at the same time. A bunch of these recent questions have been posted to clarify details of a modified circuit either diy'd here and archived on the web, or the JLM circuit or Tim's circuit. I don't believe there's anyway to understand those mods, from a beginners point of view, without knowing what the original circuit had been in Neveland.

The story I've read is that the 1272 mic pre stuff came about because Averill, Alexander and other console dismantlers had big piles of 1272's left over after selling off the channel amps. If it were a pig instead of a desk, these guys are basically using everything but tail and the squeel. So instead of trying to hawk them for less money than they'd like, they turn them into pre's. It at least appears easy so everybody wants to do it. Fair enough. But, now four years later, there's so much data out there on this excercise that no one would really have to ask a single question here, they'd just need to search, download and read. A perfect knucklehead like myself could buy Tim's kits, assemble according to instructions, test the circuit as suggested and still not know how the hell it works. I could make it without even knowig what a trasistor does. THAT'S A BIG PART OF SCA'S PRODUCT. People who record themselves and know not much electronically can have fantastic pre's at a rock bottom price all for learning how to solder.

If somebody wants an easy answer to question they'll have a shot and maybe get one, follow the advice and still not know what the hell just went on. 48 hours ago I wasn't sure what the difference between a 183 and 283 was. I wanted to know so I found out. But if people aren't even willing to click on the links somebody sends them and read what's there, it starts to put a little Gus S. in me. If somebody says, You can't do it any cheaper than the SCA kit, and the advice is ignored, well then why bother?

That is presuming this is real life and not college where you can pay somebody to do your homework for you. I think it's fortunate to have people here who are willing to answer questions and slice big chunks of research time off any endeavor. It's good fortune, it's good luck, it ought to be treated that way. I mean you don't ask the dealer at a poker table to hand you four kings, you know what I mean?

RANT OFF!

rgrds,
Brad