DIY 1272 for Newbies? C'mon.

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hey brad-

I just reread my post, it sounds kinda snotty and I think I read that way a bit online, my new yorker personality doesnt translate well at all online. What irks me is the symantics of this and Ive said this before elsewhere. People talk about turning a 1272 into a mic pre, as if its not a mic pre in the first place.

you have a 10468 steup transformer on the input on a 1272.

you have a 10468 stepup transformer on a 1073 and a 1290 which are "mic pres".

You've got a 283 amplifier board which we'll assumed is stuff A-V on the 1272 which is not a mic pre.

Youve got a 283 amplifier board in a 1073 and a 1290 which are mic pre's.

Youve got a LO1166 output transformer in a 1272 which is not a mic pre.

You've got a LO1166 output transformer in a 1073 and a 1290 which is a mic pre.

Kids, whats the difference outside of the symantics by which you are calling it? Thats my only point.

The first couple of steps on the 1073 switch are attenuation and then I think 2 clicks of boost? The third stage in a 1073 is out of the circuit until whatever, 50 dB or something? Then its engaged. So at gains you use normally, or at least in gains I use normally recording %80 of the things on a rock record, there is no difference in use or sound between what you have in a 1272, 1290 or 1073 in regards to the amplifier.

My point in not stressing about following the neve model completely is based on the fact that you could, for instance, hook of a 10468 into a 283AV into a LO1166. Place a 20dB pad in front of the 10468. Wire the fader between the stages as a full fader to 0dB. Use a cheap switch to boost either the front amp, the rear amp or both simultaneously on a dual band switch, all three will sound different, I suggest boosting both together, but thats my taste, experiment. If you wire it like that, youve just saved yourself having to buy a very expensive elma switch and a lot of time wiring a complicated switch. You wont find those notes in the neve docs. If you study the neve docs, the stuff was made SOOOOO well, it tends to be overkill in a lot of cases and lotsa stuff was just too damn confusing for me when I was starting out, so I simplified like I just explained, and it makes the same sound coming out of the speaker, works like all the other gear I have so I know the flow and is fully fabulous. So when I say disregard the neve model, Im suggesting that you can take the circuit and come up with an easier and more affordable way to implement it, thats all.

when you look at a neve console, there arent a lot of different circuits and parts, its very few building blocks put together to make a very cool thing. Just take those same building blocks and make your own cool thing. You dont need the complicated 1073 elma switch if you are just starting, there are way easier ways to do it. when you look at these things like building blocks instead of "1272" or "1073" its sometimes easier to understand it. Thats at least what it took to get it in my thick head.

trying to be helpful only-

dave
 
This is my simple version:

http://www.groupdiy.com/index.php?topic=2818&start=0

Maybe of some interest to you that wants a easy to do NEVE type preamp.
 
I'm watching this with interest as I have a 1272/BA283 board ready to go (courtesy of lsfsound) but I have yet to decide on xfrmrs depending on what is easily available here and have to decide whether to do JLM's "hotrod" mod on the gain switching or just opt for the JLM 1073 switch module.

Kev, if you have any comments with your knowledge of what may be available locally I'd love to hear them. I know I can get Lundahls but I don't know that they have a xfmr which will sit well on the output.

:cool:
 
Brad:

I'll reiterate that I really, really want to understand how the pre works, and set myself up with a couple more channels at the same time. No, this is not financially the best decision. I mean, why build another power supply when there's one in my SCA chassis?

In some ways, it's a dumb idea in the big scheme of things.

But...I want to calculate voltages. I want to understand how AC and DC relate in this circuit. I really want to understand impedence. I read about inductance last night...very insteresting. Next up is capacitive reactance, then...

Again, thanks to everybody. I do the searches, but I'm still piecing it together.

kelly
 
As you've already discovered, building this stuff doesn't necessarily lead to any kind of deep understanding of circuit behavior. Before you go spending a bunch of money on transformers and rotary switches and whatnot, I suggest you find an easy to use SPICE simulator and spend some time with it. Try to find one with a generous component library, but don't worry if it doesn't have models of BC184s or 2SK389s or whatever. Start with the most basic single transistor common emitter amplifier, not the BA283. Model it using whatever general purpose NPN transistors you have available. Simulate it every which way, but be systematic about it. See what happens if you double the value of the collector resistor, or halve it, or make it ten times as big. Same with the emitter resistor, the power supply voltage, the bypass capacitors, etc., etc. When you've got a handle on a simple single transistor circuit, see what you can make out of two or three.

Troubleshooting is another great way to get your head around transistor concepts. See if you can find some simple transistor puzzles used to train techs to spot circuit problems. Once you understand how various transistors need to be biased, you can spot faulty components pretty easily. You'll also have a better idea of what DC conditions need to be present for the circuit to pass an AC signal.

A thorough understanding of capacitors, inductors, filters, and impedance means understanding complex numbers and some ideas from calculus, sooner or later. I think anybody that can read can learn this stuff, so don't let it put you off. Get the student manual for A of E and do some problems, it'll help.
 
Thanks a lot Tim!

Funny, getting through the Stan Gibilisco Teach Yourself Electronics gets a little crazy. I forgot Trig...:grin:

kelly
 
[quote author="HiString"]Kev, if you have any comments with your knowledge of what may be available locally I'd love to hear them. I know I can get Lundahls but I don't know that they have a xfmr which will sit well on the output.[/quote]

Lundahls .... :sad:
Rick, I think, in Sydney ... it's all bad

Trust me,
stay tunnned as a Friend of Group DIY will have a solution very soon.

it's all good again.
 
[quote author="thearnicasync"] But...I want to calculate voltages. I want to understand how AC and DC relate in this circuit. [/quote]

get a simulator ... I use CM2000 ...
as Tim said,
perhaps start with a more simple circuit and work your way into the Neve unit.
It has some interesting features about it.

Simulate a circuit and then make it and verify the predicted results ... move on to the next bit and let things get more complicated.
 
hey Kev, I'm using CM2k also, do they update libraries or do i HAVE to build all my macros from scratch?? i haven't been able to use very many of the parts in the libraries so i keep having to create my own. i have NO idea how to do so for spice simulations!

any good websites or other media with tips/lessons/tricks?
 
A couple of user groups out there but generally I think CM2k is now out of service .. so to speak.

That NZ one looks like a good option but is still an unknown item.

In the mean time,
what units do you want for the library ??
this is Schematic of PCB we are talking about ?
 
both the footprint libraries for traxmaker and part libraries for circuitmaker. i've had to make a lot of IRF's dual FETs and thing like TVS's and weird stuff like dual LEDs.

their naming conventions for pcb footprints is killing me too! things like RC18 for a chip SMD device, but what size? 1206?2512? ahhh!

ok enough ranting, gotta try to get this done before going home!
 
[quote author="thearnicasync"]Thanks a lot Tim!

Funny, getting through the Stan Gibilisco Teach Yourself Electronics gets a little crazy. I forgot Trig...:grin:

kelly[/quote]

Well for f%^ks sake, I guess you're going to have to rewind the tape a little farther then...

I don't wanna hear anymore excuses, man, I have a masters in English w/ emphasis on Narrative Theory. I haven't electrocuted myself yet fixing 45 year old Ampex power supplies, neither have I experienced any delitorious effects from doing MATH. Perhaps if you lightly sand the surface of your brain you'll open up the fibers a little to enhance absorption.
 
Soundguy,

Thanks for the explanations...........it is the first time I have grasped how the 1272/BA283 and other Neve #'s were related. :thumb:

Kev,

I have spoken to Rick in Sydney and while the Lundahl LL1538 or LL1538XL will sit OK on the input they don't have a suitable substitute for the output. So far, I know of only two output options......the Neve LO1166 or Sowter's 8751. If you have any other ideas OR know of anyone in Aust., stocking Sowters please let me know. Also any specifics on the gain switching.

Schematic required: if anyone can email a copy of the SCA 1272 schemo, it would be greatly appreciated as I can't access it on the website.........just send me a PM and I'll let you know my email addy.

ChrisO :cool:
 
[quote author="bradzatitagain"][quote author="thearnicasync"]Thanks a lot Tim!

Funny, getting through the Stan Gibilisco Teach Yourself Electronics gets a little crazy. I forgot Trig...:grin:

kelly[/quote]

Well for f%^ks sake, I guess you're going to have to rewind the tape a little farther then...

I don't wanna hear anymore excuses, man, I have a masters in English w/ emphasis on Narrative Theory. I haven't electrocuted myself yet fixing 45 year old Ampex power supplies, neither have I experienced any delitorious effects from doing MATH. Perhaps if you lightly sand the surface of your brain you'll open up the fibers a little to enhance absorption.[/quote]

No kidding. Psyched, I got the Art of Electronics book today...it's so much more fun than the other stuff I've been digging through. Page sixty and they're already doing transistors...

Yes!

kelly
 
[quote author="HiString"]Soundguy,

Thanks for the explanations...........it is the first time I have grasped how the 1272/BA283 and other Neve #'s were related. :thumb:

Kev,

I have spoken to Rick in Sydney and while the Lundahl LL1538 or LL1538XL will sit OK on the input they don't have a suitable substitute for the output. So far, I know of only two output options......the Neve LO1166 or Sowter's 8751. If you have any other ideas OR know of anyone in Aust., stocking Sowters please let me know. Also any specifics on the gain switching.

Schematic required: if anyone can email a copy of the SCA 1272 schemo, it would be greatly appreciated as I can't access it on the website.........just send me a PM and I'll let you know my email addy.

ChrisO :cool:[/quote]

Chris, just get Joe's circuit, (no offense Tim R.) shows how with a cheap switch, like Tim's, and also how with the JLM Switch that adds the extra B112 circuit, that's the best way IMHMFO. E-mail Tim for his SCA circuit he'll probably just give it to you, since he's got at least page 1 of 4 of his instructions on his site for download. 1 SCA power supply will run 8 SCA circuits. And since Tim's been following along w/us here maybe he can reveal some "ancient guarded secrets"... Joe's scat shows a 5.6k resistor between pins P and L if you want 5dB steps from the gain switch, a 5k log pot if you want a fader from -90db to 0db, a 5k log pot and a 5k6 resistor if you want a fader from -5db to 0db. There you go. Thank Joe.

This isn't that hard, you guys, the mystery was wrung out of this like a worn out old dishtowel a few years ago, just do the legwork on the www you'll find at least three established and succesful ways of getting this done. Why not just buy xfrmrs from Carnhill? Do you have to pay VAT in Australia? I mean if it's the difference between $50 a channel and you've only got two channels sell something on eBone (grandma's silverware?) JLM says the Lundahl at the input sucks, the Sowter should be hooked up backwards or it sucks (maybe Sowther has fixed this since JLM published his waveforms on the www,) the OEP super-sucks and the best cheaper (little bit) input alternative is the St Ives L31267 line input hooked up backwards. But it's my impression that you don't get the 1200 ohm input impedance option that way. I've got chopped Oktava ML52 (which is one reason why I'm building these 1073s anyway, Neve iron as a gift another) that would love the 1200 ohm input. I think the transformer savings really only starts to add up when you're build 16 or 24 or 32 of these things as amps for a custom mixer or something. @ 2 channels, just buy the best xfrmrs and spring for the Carnhill knockoffs (and YES they ARE knockoffs despite Carnhills' marketing claims, even though AMS Neve hasn't bothered to push the point in a British courtroom, just like they probably leave Kleet, Tim and Great River alone too, I dunno. Tim Ryan or the Great River people or anybody else that sells modified 1272 knockoffs could answer that, and while I'm slightly curious about it, it might be a delicate coversation best had off-forum, I dunno. I'm pretty sure the 1272 as Neve produced it is not yet in the public domain, US or Europe or otherwise. Anybody that's making a pre from scratch is probably violating copyright protections. You know Disney will roam around the US sueing and closing down preschool daycare centers, for chrissakes, because they have bad paintings of Minnie and Mickey, Pluto, Goofy and Donald Duck on the wall, for which they did not ask permission, so who knows what AMS Neve does. They'd probably start swatting people when products begin encroaching upon their own marketshare, which doesn't seem likely, no offense, of course, to Tim Ryan or Joe Mallone or Great River or Mercenary or anybody else. I know for a fact Coco Chanel could have care less about knock-offs being sold out of the back of trucks in the alleys of Paris; Christian Dior had a different attitude. Tim? Joe? Fletcher? Sir Rupert?)

Buy the best you can and then do two more later with some other xfrmrs and A/B them. It's a pretty shakey proposition to ask for end-user opinion here with something so subjective as transformer influenced audio output. What can you say, "fat?" Whatever w/the sound when the BA283 alone w/out an additional B112 starts clipping, that's in the same realm as personal sexual preferences, as far as I'm concerned.

Just run your phantom to the center tap on the input like Joe Malone does.

All above IMHGDO, YMMV, TANSTAAFL, etc., ad nauseum, ad bacculum.

cheer me up before I have to do it myself,
Brad
 
[quote author="HiString"] ... If you have any other ideas OR know of anyone in Aust. ... [/quote]

well ... :green:

JLM 1:4 Input transformer $40AUD + GST or $30USD.

and

New JLM output transformer like 2503 ratio 1:1:1:1 (4 x 75ohm)
JLM%20Output%20transformer.jpg


:shock:

yes this is the API styled unit BUT very soon it will get a GAP and will be ready to be used in the Neve circuit.
...
and will fit into 1RU.

Joe is a very clever fellow.

Sit tight and all will become clear. :thumb:
 
Kev,

Thanks for that info. I thought Joe had an input trannie but I couldn't re-find it on his site. I may have to contact him and get some advice on the switching options (his "hotrod" mod or the JLM 1272-1073 module) and also see if he has an ETA on the output trannie............I really want to get this pre finished to give my ribbon a fair chance in a project we have coming up.

ChrisO :cool:
 
[quote author="Peter Knight"]Que?[/quote]

:roll:
you gonna have to just work it out
somethings I just can't say in an open forum like this

Jakob's projects are great
The early days of Group DIY and I drove a couple of the Gyraf favourites as hard as I could but alas I don't have my own.
Many of then call for a Lundahl trafo and when I looked on the site for an Australian distributer and got a quote ...

well ... :sad:

then came the G9 with the OEP/Lundalh with the combined footprint for the first time.
As you know I did complete a couple of G9's and there are out on perminant loan and doing a fine job
but alas ... still no G1176
I did recieve a gift of a Lundalh and it will find it's way into my G1176 when I have time.
thank you to the sender. :thumb:
 

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