Neve 1073 using Lorlin and Pots?

[Spencerleehorton]

Hi Guys,

I'm in the process of making some original Neve BA283, BA284, B205, B211, BA182 pcbs to put together several pre amps and wondered if i could use a combination of a Lorlin 12 way switch pot for frequency selection and a 10K/47k pot for the gain rather than the expensive dual concentric pots?
I already have some 3 gang Russian made pots for making up the gain control and these work fine when using a mesh screen over the connections but only have 11 clicks on them, so i'll loose a position a the top.
I only want to have these for Mic so i can save a little on loosing the line txf.
I have also had some really good results using some Sowter txf as input txf but will be getting the carnhill for output txf.
Im also trying to keep 2 units into 1U as these will be replacing my 6 x SSL 9K unit as i don't use it.
below is a low res of where i'm at with the pcbs.

regards

Spence.

 

[Spencerleehorton]

Am thinking about putting 4 units into 2 x 1U or 2U but possibly having just the BA283/284 with a link cable to the other 1U for the EQ section in 1U, just kicking around ideas at the moment, its either that or going 500 series as i could have another 8 channels of this giving me 10 channels of Neve as well as my 8 x API-312 and 8 x SSL9k.
if there is way i could scale down the EQ section would be great to try and get all 8 into a 2U!?

Spence.

 

[Spencerleehorton]

Hi,
realistically on a first little measure up its looking like i can possibly get 8 units in a 2U but only if i loose the EQ and HPF.
will have 48v, Polarity and Pad.
hopefully the output txf's will all fit in there and the input txf's should as long as the 2U unit is nice and long.
have also put the power in there and the input output will be on multicore to cut down in drilling and space.
going to cut down the pcbs and do away with the pci slot bit and just have pads there.
will look into doing the EQ section in another 2U and see about a possible way to link the units.

Spence.

 

[pvision]

Go 3U?

Plenty of racks & styles out there. You can get eight 50.6mm plug-in modules across a rack, with a bit spare, or do a 500-Series style board with an edge connector

You'll get 8 channels on a db25 connector

I was looking at these after Ian Thompson-Bell mentioned them

http://www.conrad-electronic.co.uk/ce/en/product/525367/Slide-in-cassette-Slide-in-cassette-Front-plate-Aluminium-natural-anodisedcover-sheet-Perforated-aluminium?ref=list

Nick Froome

 

[Spencerleehorton]

Im really liking the idea of doing a 500 series and these look perfect!
The 51x rack chassis works out at about £250 with shipping, I don't think I need that at the moment so I can build a psu and make a rack chassis to hold them in for the moment.

regards

Spence.

 

[Spencerleehorton]

Hi,

I have looked at the dims of these boxes and they are pretty tight, 166mm deep and 50.6mm width by 128mm high.
not sure if i'll get everything in but i'm sure gonna try!!! thinking i'll probably get the bigger version and if all else fails i can use it for just one, if all is good then maybe put two inside!
My first attempt at laying out i think i can get;
Input Gain switch, Presence gain/frequency select, Hi Gain/frequency select, Low Gain/frequency select, 48v and Polarity switch. Might possibly get another switch in there, could be for HPF 3 way selection 80hz, 0ff, 160hz, and just use some decent caps on the switch and do away with the original HPF.
Price wise its looking like about £100 for all 4 cases, £180 for output TXF and about another £120 or so for the other components. £400 for 8 x Neve preamps!

 

[pvision]

You can get two depths of the 3U cases. They do a 6U as well…

The case has a cutout at the rear for a standard DIN multiway connector or you could cut the rear panel for Neutrik XLRs, etc

Working out dimensions from the diagrams isn't easy, but it seems you lose a bit of width in the case when compared to the front panel - so if the panel is 50.6, there's about a 1 mm lip plus the thickness of the side panels to consider

The advantage of the 50.6 module is that eight fit in a rack. They don't fit exactly - the rack size is normally 84TE (or 84HP) where one TE/HP is 5.08mm wide. So the module in question is 10TE

So you can fit eight 10TE modules plus a 4TE panel 20.32mm wide. That 20.32 would be ideal for a power switch, LEDs, etc

A couple of links

http://www.conrad-electronic.co.uk/ce/en/product/534000/Schroff-24563-191-BGT-EuropacPRO?ref=list
http://uk.farnell.com/schroff/24563-192/subrack-3u-235mm-84hp/dp/1455796
http://uk.farnell.com/fischer-elektronik/bgt-384-180/3-u-subracks/dp/1858338
http://www.produktinfo.conrad.com/datenblaetter/525000-549999/525367-da-01-ml-Einschubkassette_10TE_de_en_fr.pdf
http://www.fischerelektronik.de/web_fischer/en_GB/cases/N08.4/Profiles%20for%20insert%20modules%20and%20part%20front%20panels/PR/GP%20190/index.xhtml

This is my understanding of the system. Hopefully others with more knowledge will correct my errors…

Nick Froome

 

[Spencerleehorton]

ok, thats great, i suppose the next question is if i'm going to build 8 of these, what psu should i build?
i'm allowing 122mA for each module so i want 24v 1A.
figured out the gain switch, couldn't get my head around how the resistors were mounted but all connected to gnd, then realised there was a bit of wire that connected them all, easy peezy!!
16 resistors on each switched pot x 8, bit of work to do!!!
have measured up lorlins and 10k/50k pots and will fit in the enclosure along with the bypass switch, 3 band EQ, 48v and polarity switch.
all pcbs should be able to fit nicely in the 220mm long enclosures along with the input and output txf's.
i'll stick with my idea of multicore cables for XLR output/input.
this is shaping up to be a tasty project now!!!

regards

Spence.

 

[pvision]

How about this:

24 Volt regulator TO-220 case
http://uk.farnell.com/on-semiconductor/mc7824ctg/ic-v-reg-24v-7824-to-220-3/dp/9666257

Heat sink
http://uk.farnell.com/fischer-elektronik/sk-145-37-5-sts-220/heat-sink-to-220-etc-12-c-w/dp/4621414

If you need 48 Volts as well as 24 V… I don't know about transformers. Do the grounds of the 48V and 24V need to be isolated? I don't know the circuit

Nick Froome

 

[Spencerleehorton]

Yes, I got plenty 7824 and heat sinks, there is a little circuit that I can use from the ssl9k Psu which I can mod with a trim control for 48v and 24v. I've already built this Psu for my other Neve 1290.
I'm gonna knock up a couple of boards for the BA283 and BA284 and start putting together the gain switch and putting together the pcb.
I have txf which I can use for Input and output to get them all working and getting the sizes right so everything will fit inside the cases.
I have emailed Conrad but not heard anything back yet about the bigger 220mm cases?
Regards

Spence.

 

[Spencerleehorton]

Getting there now!!!

 

[Spencerleehorton]

Bit more progress.

 

[Spencerleehorton]

Little bit further!

 

[Spencerleehorton]

Few more

 

[Spencerleehorton]

This is what I've ended up with for the Psu.

 

[shabtek]

so pretty, brings tear to ones eye.  long live DIY

 

[Spencerleehorton]

Transistors have turned up, I thought I had read that neve selected the ones that were over 600 hfe, my ones come out at around 440, 430, 420,  410. So I will try and use some others for pre sections which have over 600 hfe.
On the input pcb BA284 for the transistors it would seem only T1, T2, T4, T5, T7, T8 need to be 600hfe or above?

Regards

Spence.

 

[pvision]

Are you "stacking" two 24 V supplies on top of each other to get the 48 Volts?

I was trying to work out the logic of having two rectifiers but a little (24 volt?) light went on in my head and I realised that the two 100 uF capacitors DC isolate the two halves of the psu

I feel as though I am learning!

Though after a second look I am even more confused...

Nick Froome

 

[Spencerleehorton]

Hi pvision,

i am learning to and certainly don't profess to know what is going on with getting to the 48v exactly but its a type of voltage doubler.
As far as i'm aware with it both rectifiers get 24v ac then the top is coupled with another 24v feed.
it works, so for the moment i'll wait until a light goes on in my head!!!

Spence.

 

[Spencerleehorton]

Meanwhile I've gone though 100 Bc184c and only managed to get 12 at about 560hfe!

Will see what next batch brings!!! Hopefully over 600hfe.

Spence.