1290 1073 Line-in - please vote w/ your preference.

Well I got a bit of extra time on my hands and have been thinking about the best way to implement a line-in (using a 31267 I/P transformer) on my EZ1290's. I have a few things in mind, and would love to get your feedback.

A:
Add a 1X12 rotary and a mic/line switch next to the existing 3X12. The 1X12 handles switching of the line input's 7 gain positions, the 3x12 handles switching of the mic input, and the mic/line switch selects between the two. Pros: no gain positions lost. Cons: Added cost of a 1X12 Grayhill, mic/line switch, more holes to drill

B:
Lose the upper 3 gain positions of the 3X12 (65, 70, 75dB), and add 3 line input positions below the 20dB gain position. Out of the 7 line in positions of an original 1073 I would probably pick the lowest, middle and highest. Pros: simple, cheap, effective Cons: preamp max gain reduced from 75 to 60dB, coarse 15dB gain steps for line in.

C:
Both A and B are compromises. Ideally I would want to use a 3X24 PCB mount rotary, but I don't know of anyone who makes one. If there is such a beast it will be pricey I'm sure. Is there an Elma or Grayhill I need to know about?

If you have no clue what circuit I'm talking about, please see original here:
http://www.technicalaudio.com/neve/neve_pdf/1073-EH10023.pdf

EZ1290 here (Page 10):
http://www.musiciansgig.com/ez1290/assembly.pdf

Thanks for your input!!

M.

what about a 20 dB pad infront of the mic transformer??

I like the concept of B, but I would make the line in -5,0,+5dB.

jo

Martin, nice to see this.

Please not B. I would not build it. With ribbon mics everywhere these days I need to go all the way up to max gain on acoustic instrument sources.

Also, very important -- what is the point of building a 1290 if you aren't going to take advantage of the original Neve three-stage amp gain?!! I can get a two-stage 1272 to go up to 60 dB - so this makes the 1290 (under option B) superfluous.

(For purists, yes I know a 1272 is a slight compromise pushed up to 60dB gain, but I have built it and it works just fine in the real world. The point is that a 1290 has really creamy gain up through those levels taking advantage of a third amp stage and you're throwing this away by not wiring it to go the last 15dB of gain.)

I would go for C if it becomes possible, like the original. Yes it will cost.

Therefore A is also good. We're going to have to buy a 31267 transformer anyway, so the investment impediment is already established for the faint of heart.

I've learned from experience, if you can build it right the first time, do it. Just do it. It's always worth it in the end. Otherwise don't even start. Build something else.

BTW, what is the utility you have in mind? Add EQ with your circuit? Various line amp needs, like passive mixers, etc?

Martin, Electroswitch makes(or did make) a 24 position multideck
vertical PC switch. It was the E5 series, but i never priced them.

http://www.electro-nc.com/rotaryus/e5.pdf


If not a 24 pos. switch, then I'd say option A. If you were making one board and the builder had the option to implement it or not, it works out for all.
The added cost of a mic/line switch, a single deck greyhill,
and some other misc. parts(31267 aside) isn't really that much.

Looking at the new 1073dpa block diagram it looks like are not using a input transformer for the line input.

The block diagram shows something like a operationa amplifier stage, but it could be also just a pad, really don't know.

Anyone has a 1073dpa and would be so kind to investigate a bit ???

About the rotary swtich, take a look at Joe Malone website, in his 1290 he uses a nice PCB switch that I suppose is a 3x24.

I don't recall who make it, but the are absolutely cheap.
Anyone remember who make them ?

Thanks for the feedback guys!! I think I like option A as well. It makes the EZ1290 boards completely upgradeable from their bare form yet will not significantly increase cost/labor. In this configuration, building "just" a 1290/1073 pre will be as simple as it's always been. Adding a line-in 31267 will be very straightforward affair.

The next logical step will be to add the EQ section, perhaps a summing bus w/ faders so you could add some Neve sweetness during mix. I'll contact Bluzzi shortly and see where he's at with the EQ project.

Take Care,

M.

PS. Neeno, I'm not sure which block diagram you're referring to? Do you have a link?

The next "Langley" mic amp product has a Grayhill 1x12 rotary switch on it so we will soon be stocking these (as well as the 3 x 12)....

[it is basically the "Langley" mic amp upgrade that we sell for the consoles with a balanced output stage, DI input, rumble filter, switchable impedance and balanced right through for low noise..... in a 500 series format.... that will probably be available as a kit of parts for self-build... the prototype is being tracked at the moment.... if anyone is in the northwest of the UK that has a lunchbox they can beta test it for us....].

Colin
www.audiomaintenance.com

So basically to have a line input you need and extra input transformer for line signals, plus the 1x12 switch and a simple DPDT switch?
thats it?

Hi.

Did this project ever get underway?

I'm wanting to add line in to my EZ1290 but was originally thinking of just buying the VTB9046 line tx and switching between it and the mic tx using a DPDT switch. Am I right in thinking that it would not work too well? I note that the 9046/9045 have different secondary impendances also.

I would rather have tx mic and line inputs than use a DI for line in.

waiting for 8*A

solderspongebob said:

Did this project ever get underway?

Click to expand...

It did - after much beating around the bush on my part and repeated prodding from members I might add!!  ;D Proto boards are on their way to me. Here's what I decided to do: a completely separate board for line-in only. Why?
1a) I am building a 16ch line mixer (with an all Neve frontend, passive summing with 1272 makeup)
1b) anyone else frustrated with DAW mixing? (pls post responses on Gearslutz.com, not here)
2) this makes it easy to add a (trim) fader to an otherwise balanced mixer. I am using P&G 3000 series
3) My signal flow is always as follows: mic - mic pre - A/D, D/A - mixer - speakers&masterlink. IMHO it is just more convenient to separate line-in from mic pre and have the line-ins grouped together.
4) it's a small PCB - basically BA183 + switch - and less expensive than the EZ1290. passive components are cheap/negligible. Yes, you will have to buy an extra LO1166(VTB9049), but they are cheap at 17GBP. Even if you added line-in to the EZ1290, you're buying extra switches and L31267.

I hope these will be useful to some!!

m.

I am building a 16ch line mixer (with an all Neve frontend, passive summing with 1272 makeup)

Click to expand...

Sounds tantalising - Bet your mixer weighs a ton when all that iron's in there  but sounds big and lush nonetheless.

I'm gonna go with Igor's universal preamp board and add DI to my EZ1290's; drawback is there is now too much to fit in the 1U case so I've ordered a 2U case (mind you, they're on offer at Canford at only £29 + vat at the moment!)

Thanks for the fantastic EZ1290 project madriaanse 

Thx for the link Kamel!! Are those switches good enough for high quality audio?

Best,

M.

EDIT: for some reason Kamel's post disappeared, but here's the link: http://www.commutatori-palazzo.it/inglese/commutatori/en_5VCS.htm

Thanks Soldersponge! I'm excited to kick off the project!!

M.

sorry i did a mistake with he edit function

i know Pallazzo for the 1x24 positions, and they are good and not too expansive, but it seems that the 4x24 position PCB version is BBM, but you can aske mr Pallazzo, he is a gentle guy, to know about shorting switch

is 2n2 at the line input transformer, Polystyrene  or ?

Kambo,


Here's a picture of the input transformer from a 1272 (which shows a 180pf cap and 5.6K resistor)

The cap in this picture is not polystyrene (or at least not like any polystyrene that I've seen).



I think any type of film cap would work.

thank you Skylar...

i have a question re bom at
http://www.groupdiy.com/index.php?topic=22828.msg270585#msg270585

there are some  Polystyrene  caps, c9, c10,c11 etc but on digikey list they are ceramic caps... i guess they are ok to use there...

i have founded Polystyrene caps, but they are 160V rated.. from farnell.. i suppose they are ok to use too, they are more expensive tho.

edit link : http://tr.farnell.com/lcr-components/fsc-160v-100pf-2-5/capacitor-100pf-160v/dp/9520015

The BA283s had polystyrene caps for C2, C3, C5, C9, C10, C11, C16 (original schematic designations).
The 1290EZ uses the same designations I believe, but you may want to double-check.

If you want to stay true to the original, you can use polystyrene caps in those places.

Here are Mouser part numbers for these caps in polystyrene flavor:
C2 220pf — 23PS122
C3 4700pf — 23PS247
C5 330pf — 23PS133
C9 100pf — 23PS110
C10 1500pf — 23PS215
C11 680pf — 23PS168
C16 1000pf — 23PS210


Now, how much (if at all) this will alter the sound is debatable I'm sure.
I wouldn't know because I have not tried both ways yet.
I have been using Tim's N72 pres (Seventh Circle) and love the sound (it uses ceramics in these spots).

I'm about to finish a 4-channel BA283-based pre with polystyrenes.
Surely these pres will sound different, but that will probably be attributable to differences in iron used more than anything.

These polystyrenes are cheaper than those ceramics...might as well use poly in my opinion.

EDIT: or better yet, try BOTH types and see what you get.

thank you Skylar. mouser list is great alternative for the caps...
i guess i will try different caps and see....
i will soon have 8+2 boards to fill for my passive summing

EDIT : what other transformer options we have for this project... i am getting some carnhill transformers for ins and out,
but i like to try other options too

EDIT 2: which caps in are in the audio path on this BA283 based line in module; that will effect the audio most....

EDIT 3: i see that madriaanse using all 5% carbon resistors. how about PRP 1%metal film resistors... do you think its worth trying them or, difference would be debatable....