ruffrecords

Re: Another Neve 1272 summing mixer.
« Reply #40 on: May 22, 2016, 04:17:52 PM »
That will work fine. The two DPDT relays have replaced the 4PDT switch.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #41 on: May 22, 2016, 06:19:09 PM »
Again Ian thank you. And i just want to reitirate how much i appreciate you guiding me through this.  I hope others can use it later as a guide for their own ventures.
There certainly is a good deal of info online regarding different bypass schemes. It is almost overwhelming but nevertheless interesting.
If there's a harder way to do this, I haven't found it yet.

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #42 on: May 27, 2016, 02:57:47 PM »
It's coming together (albeit slowly) and in the meantime I read/research/read.
Okay, so I have two 47k bus resistors per channel for 8 channels.  I am using the JLM hybrid opamp:

 http://www.jlmaudio.com/JLM%20Hybrid%20Opamp%20circuit.pdf

to drive the pans, faders, and auxes.
All 8 channels L and R will attach to the L and R bus.
All 8 channels aux outs will attach to the aux bus.
I am vacillating between using vero board or terminal tags (or a copper bus bar) for my left and  right buses that will tie into the L and R vtb 9046s and then onto the L and R Ez ln-72s.
I believe I need a star ground but no 0v bus bar because it is virtual earth?
The aux bus will feed the aux send and return driver amps as well as an aux master fader and I am not sure how to implement this fader.  I would imagine I need to have the aux master fader at the end of the aux send driver?
How do I (and do I need to)  determine the auxes impedance?
I will need an unbalanced to balanced driver for the aux sends and returns will need a balanced to balanced driver?
I think a bit of trial and error will be in order.
I'd love some suggestions on the L and R and Aux busses and how to actually physically implement them (i.e. vero board, bus bar, etc..) .  I've been looking online and it seems all manners are used but with such a low channel count I am not sure how best to implement it. 
Kind of the million dollar question, I know.


This is a lot of work (and will continue to be) and not cheap and even though it's a time consuming it is also rewarding.  I found some really awesome neve console docs the other day (75 pages) unlike anything ive seen yet (including dan alexander, orphan, klett, tanner,) and i felt like the digital version of indiana jones. It's the path not the destination kind of bs blah blah blah.  
Onward.
And as always I am grateful.
« Last Edit: May 28, 2016, 12:18:11 AM by Rocinante »
If there's a harder way to do this, I haven't found it yet.

ruffrecords

Re: Another Neve 1272 summing mixer.
« Reply #43 on: May 28, 2016, 06:45:10 AM »
Some time ago a did a passive mixer for a client. I designed some small PCBs. Each PCB held the channel gain pot , pan pot and bus feed resistors. I just tracked the connections to each pus to a pad on the PCB which I set to have quite a large diameter. The pots were right angle PCB mounting so when you fitted the pot to the PCB and then the PCB to the panel, all the boards were parallel to each other.  I then simply ran a copper wire through all the bus holes and soldered each one to make the buses. I have a sketch of the idea somewhere; I will see if I can find it. You can get 10 small PCBs  made at Seeedstudio for about $10 plus shipping so it is not expensive. Or you could do the same thing with small squares of vero board.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #44 on: May 28, 2016, 12:01:47 PM »
Thanks Ian that was generally what I was thinking and a layout would be very very appreciated.  Being able to possibly use headers or terminal blocks seems great for troubleshooting and repair especially trying to trace backwards and having a 'hub' to do so seems smart. I haven't tried Seedstudio yet but those are really great prices.
I still have parts on their way here (so far I've imported from 6 countries for this project and including Great Britain it'll be 7) but should be able to get a good start for two channels at least.
Cheers
If there's a harder way to do this, I haven't found it yet.

Re: Another Neve 1272 summing mixer.
« Reply #45 on: June 02, 2016, 09:31:20 AM »
this is indeed a great thread idea.

Is the summing of your channels going unbalanced into the input TX of the 1272 output?

Which master 2 track output was used in the 8024 or 8028?? ? was it not a BA438 BA440 LO1173 as per the attachment?

Which console used the 1272 as the master bus?

Michael

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #46 on: June 02, 2016, 12:08:38 PM »
Many of Neve's consoles  including the 8028 used 1081 channel amplifiers which were made up of ba338 and ba340s.  The 8028 could be fitted with 1073's with the 1272's as line amps and in the busses.  That was their intended purpose. 
Many consoles from the 8038 to the bcm-10 used a variant of the ba438 and ba440 (which includes the ba338, ba340-which are nearly identical earlier versions) and (ba638, ba640 which were better spec'd IC based later versions and considered improved by the BBC because of their faster slew rate.)
The 33415 modules are everywhere and lasted a while.
The 8038, 8068 (which ive had the pleasure of using several times) 8014, 8034, 8024, 8026, and 8036 all had ba340's or ba440's in them including 1272's
Yes the summing mixer is balanced throughout.
Little JLM Hybrid Op Amp pcb's arrived yesterday and are sitting on the bench waiting to be populated.
« Last Edit: June 02, 2016, 12:46:09 PM by Rocinante »
If there's a harder way to do this, I haven't found it yet.

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #47 on: June 02, 2016, 12:31:30 PM »
Could someone tell me the Eagle library component name for the Edac or Cinch 15/30 card holders that are commonly used for 500 series backplanes? 
I got the molex kk 15/30 pin but i need the holes for the amphenol 15/30 pin card holders.  I've decided to maybe use a backplane i guess as it'll be better laid out that way and will make wiring less cluttered.  Not so surprisungly my channel layouts were instinctively laid out the same dimensions as 500 series .
« Last Edit: June 02, 2016, 12:42:18 PM by Rocinante »
If there's a harder way to do this, I haven't found it yet.

Re: Another Neve 1272 summing mixer.
« Reply #48 on: June 02, 2016, 01:08:55 PM »
Hey,

i found that neve 8024 console pdf book too. Amazing.

3 Questions.

1) So, was this Neve board summing balanced signals to the BA438 440? With the  LO1173 tx being the last TX in line with the master 2 track?

2) If so, how? Did each balanced line come form the channel eq post ba283 and output tx and summed with resistors on each hot and cold +/- of each channel tx?

3) where on the this schematic does the output get summed to the bus?

I thought the signals were mixed unbalanced......???

Michael

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #49 on: June 02, 2016, 02:39:03 PM »
Oops I thought you were reffering to the summing mixer.
Yes that PDF is awesome. 75 pages of Neve, Neve, Neve.

As far as balanced Neve consoles; this quote from Geoff Tanner:

"The audio path generally went from the channel routing unit, to the mix bus via a mix resistor (usually 15Kohm), from the mix bus to the transformer (that lived inside the mix bus amp) and the t'other side of the transformer was taken back to the B- coppery bus and hence back to the send amplifiers in the routing unit who were connected to the main B+ and B- power busses.

The use of the chunky copper or aluminium power busses meant that the impedance from any channel, be it on the far left or far right of the console, was kept very low so that the circular path of send amp - mix bus - mix amp transformer - send amp was consistant throughout the console.

The 51 series was the first Neve console to use quasi-balanced mixing with vastly improved noise and crosstalk figures.

Up to the 8078, all Neve console inputs and outputs were transformer balanced and isolated. Later consoles could be fitted with transformers either as stock or as an option, depending on the console type and spec."

Should clear everything up.

If there's a harder way to do this, I haven't found it yet.


Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #50 on: June 07, 2016, 01:41:38 PM »
I've been tweaking on Eagle and developing a backplane while trying to get ideas online for a  master section/utility board.  I've come across a few threads but nothing substantial.  At any rate I am fairly sure I am going to use a backplane  but before I send this off to the fab house could someone please take a look?
What i really like is the backplane kind of nicely sums my left and right bus as well as provides an aux bus that I will connect to via a header.  I have also put in an additional aux out/bus just in case .  A question I am wondering is how should I split the aux bus into L and R to feed the send drivers?




Now I know I can ignore (I should probably delete it?) the 0V out on the backplane.  I read Ian's grounding 101.  The Backplane LR bus out then feeds the EA-10468 (wired in reverse) and then the EZLN 72's. 
From the EZLN72's the L and R will go to the 1166 output transformers then to a 'master section/utility board' that will split the LR + and - to feed the VU meters, Monitor out, Master Insert IO,  and aux bus send and return.
Below is a block diagram of the master section utility PCB.






The pcb I am designing doesn't look much different.
Any ideas?
The aux bus I am weary about.  I also need to figure out fader value for the aux master fader.   I am using JLM regurgitator for the send and return.
I am still unsure how I will drive the monitors but I have options including JLM regurgitator or DOA's or the Ba340's.
« Last Edit: June 07, 2016, 09:22:33 PM by Rocinante »
If there's a harder way to do this, I haven't found it yet.

ruffrecords

Re: Another Neve 1272 summing mixer.
« Reply #51 on: June 08, 2016, 03:40:47 AM »
Hey,

i found that neve 8024 console pdf book too. Amazing.


Michael

I have not heard of this. Can you post a link?

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: Another Neve 1272 summing mixer.
« Reply #52 on: June 08, 2016, 03:45:02 AM »
Your backplane looks very similar to the one I designed for the EZTubeMixer project. It looks OK to me. The on;y thing you need to be sure of is the power tracks (if any) are meaty enough.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #53 on: June 08, 2016, 11:33:57 AM »
Ian
I can't recall where i found the Neve PDF but it goes over most attachment maximum file sizes (at 27 mb which seems ridiculous) so I haven't been able to attach it to the forum.  I emailed it to you.
If there's a harder way to do this, I haven't found it yet.

ruffrecords

Re: Another Neve 1272 summing mixer.
« Reply #54 on: June 08, 2016, 01:39:11 PM »
Ian
I can't recall where i found the Neve PDF but it goes over most attachment maximum file sizes (at 27 mb which seems ridiculous) so I haven't been able to attach it to the forum.  I emailed it to you.

Many hanks, received and filed away!

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

API

Re: Another Neve 1272 summing mixer.
« Reply #55 on: June 27, 2016, 02:17:51 PM »
Would love to get a copy of the 8024 manual as well, can you possibly send it to me as well?

Then i need to correct you on the summing amps, most of the early 80-series consoles did use the 1272 as a summing amp.
There were a few models that used the 3415 line amp but not the BCM-10 and 8014 (and most others) which used the 1272.
Both are very good though but sounds slightly different from eachother.

Either way, great project that you are working on!
It will be much harder than you will like to admit though, i know since i have gone through something similar with my Neve desk restoration, lol!
One thing that i thought bout was that your input amp uses the API 2520 opamp and then you use the 1272 in the summing.
I guess that you realize that they uses different powersuplies?
Just something to think about when calculating power ratings for your supplies.

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #56 on: June 28, 2016, 11:43:43 AM »
API,
Just PM your email and I will happily send you the docs.

You are correct regarding the series that used the 1272's and 3415's  and I forgot where I said what when.  I am not trying to directly copy any one console series but more use the various amps they used and that gave the magnificent results they achieved and hope I get just a smidgen of same vibe.  I have some b338's and b340's I built.  I might make a mic pre out of them.   I might get them to work in this summing mixer.  It's honestly also academic and a challenge.
Now as far as the 2520 op amps I am using strictly JLM Hybrid DOA's and APP 992's which both like to operate at 24v.  I m also using Omron G5v-2h-24 for the relays which keeps the whole thing currently only needing a dual rail (and in some cases single rail) 24v PSU. 
I currently have a 24v x 2 50va antec toroidal I have been holding onto for this along with several psu's that should be fine (expecially since IIRC Martin used a 30va on his 8 channel ez1290).
Right now I am waiting for the backplane pcb's to arrive and then it's to begin to wire the whole kaboodle together.  Right now I have my utility distribution pcb on veroboard but I might get a pcb made for that too.  And yeah it's a challenge.  Hardest project yet.  Lot's of stuff to keep in mind.  I'm probably over my head but at this point I've read so much regarding mixer design I am pretty certain that with  help from this forum  I can eventully figure out whatever comes up.  Well I hope so anyway.  The backplane pcbis going to provide several solutions for me and it sure beats wiring everything.  At the moment the master section is mostly on paper but will soon begin getting put together too.
Oh and here is a few progress pics.  The psu will be external.


If there's a harder way to do this, I haven't found it yet.

ln76d

Re: Another Neve 1272 summing mixer.
« Reply #57 on: June 28, 2016, 05:58:19 PM »
Here are two manuals from neve - pretty good lecture:
http://lcweb2.loc.gov/master/mbrs/recording_preservation/manuals/

Also many other nice documents, catalogs etc.

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #58 on: June 28, 2016, 11:56:01 PM »
In76d thats quite the collection, thank you.
If there's a harder way to do this, I haven't found it yet.

Rocinante

Re: Another Neve 1272 summing mixer.
« Reply #59 on: June 29, 2016, 12:47:16 AM »
And thats the same misc pdf i have so thanks as gain for the link. Lots of great neve info in there.
I might just do what Teekay had suggested and use the ba226 (with his modifications) for the send bus amp. Id have to design and have another pcb made....
I also have a few Helios 22113s i made awhile back....
If there's a harder way to do this, I haven't found it yet.