Calrec PQ 1061

[Gus]

I am still looking at the schematic.

To build this with the microphone and line section the switches tommypiper is looking into for the 1081 should work fine with a 4pdt relay controlled by one of the wafers to handle the switching at input of the transformer

If we don't build it with the stock preamp what preamps would people want.

One that comes to mind for me is a modded 110 one with a cheap alpha 2p12T switch, yes it is an opamp design.

 

[cannikin]

Whats the word fellas?

 

[soundguy]

we should be building with the stock amp...

dave

 

[cannikin]

Trying to keep it alive...

this is going to best project if it gets off the ground. Love the calrecs!

 

[TomWaterman]

Hey!

Been real busy lately and kind of forgot about this....so BUMP!!!

Jus'wundering did you ever attempt to measure the MF inductor Buz?

I agree BTW about the mic amp if this ever gets off the ground I would like to build the original pre, surely the sound is in the input iron (2318).

When I get some time I'll look over this project and try and do a little more research etc.

Regarding the input and the gain switching - could it be done with a 2pole12 pos switch with a fine trim on the second amp stage? I haven't looked closely and have no schemo to hand at the mo. I like the idea of usng a relay to switch mic/line. Surely its cheaper to fire the relay from a dedicated Mic/Line switch rather than finding a spare pole on a rotary?

Anyway just thought I'd try and keep it alive
Cheers Tom

 

[TomWaterman]

Just thought I'd bump it again, for the sake of completeness I finally managed to post the layouts I did for the discrete gain block. This is for the TO-92 based version.

I know people are not up for using plugin modules but I figure its nice to have them here for the hell of it. If you guys spot errors in the layout then let me know, I'm no expert!!!

Here is the full layout as it stands - I wanted to add polygon fills for ground and a few spots like the original but never got around to figuring it out.

Here is the component overlay, I think the height could be reduced a fair bit by finding smaller caps for C2 and C3, Eagle's smallest caps are a little big.

The tracks from component side:

The track side (Mirrored):

And here's a little Photoshop montage so you can see the layout of original components and overlayed tracks compared to mine, almost the same I hope:

If I get some time this week I'll try and get my head around the schematic and the input switching etc....

The plugin module PCB above is a little over an inch and a half wide and about 1.2 inch high, a little too high to be mounted on top of a PCB on spacers in 1U I think. The pins should be the right size for the ones Buz mentioned earlier, 0.1" spacing.

Cheers Tom

 

[Gus]

Some thing to think about with the PCB layout.

Most good electros are radial so maybe you could add an extra pad for radial.

There are two main pinouts of to92 transistors EBC and ECB. Not a big deal it is easy to move the two legs to place the two styles in a board.

 

[cannikin]

Tom - you rock! Thanks for keeping it alive, Ok all you DIY gurus lets take it to the Next level so we can build this puppies. :grin:

 

[rafafredd]

Tom,

Would you post a photoshop montage of the main board?

 

[TomWaterman]

Hey Raf,

I would if I could but I don't think we have a scan of the mainboard just the plugin modules.....

By the looks of it, the original mainboard doesn't house that much as the filter caps etc appear to be mounted on smaller satellites as well.....

I think a complete re-layout is the way to go but if anyone scans the mainboard I'll be happy to photoshop it to show the component overlay as above.

-Tom

 

[TomWaterman]

OK I've been looking at the input stage right now, seems the transformer deals with the mic / line impedances so there would be no need to add a pad for the line input (I think that cropped up during discussions?).

One quick question, anyone know what the balancing capacitor is for? Its only active on the mic input and can be switched to either red or blue, +/-. Also what is AOT. I guess its like "Apply On Test" or something...do you think this cap is needed?

I'm also not getting the second line input and the fact the there are two red (+) connections for the first line input.

If you strip away the 2nd line in (unbalanced) and the extra red connection it seems relatively simple. [edit] the 4PDT relay at the input will work perfectly for mic/line selection.

I'm confused as to how the gain switch connects to line switch too....is there any way we could check that on the original? Where does connector 10 go?

Also the gain switch is a little odd, being that its not the standard 24 positions. An Elma would be overkill and I don't know of any freely available 17position switches.....

Do you guys think that the -10dB line level setting is needed? Would it be just fine with the gain set to 0 for line use. Buz or Cannikin how is it when you run a variety of line signals through it, do you find you need the attenuation or is plain gain enough?.....I guess a -10dB pad could be placed at the input if this is a problem.

If we could just go from 0 to 66dB on the gain switch it could be done with a 12 position switch at 6dB/step. There are grayhills quite cheap and readily available and the modular NSFs could be used for saving the most money, probably like $10 for a 2deck 12pole. The rest of the switches should be cheapish.

If we could find the value of pot needed to increase the fine trim to +/-3dB then we would have complete coverage of the full range and not much sacrifice. The final 3dB of gain here would net 69dB overall - enough for most I'm sure. I suppose +/-3dB on the pot would make it a value that doesn't exist though....

It seems the second stage doesn't change its gain until 40dB where it steps in to help out (am I wrong here??).

I would love to know how to calculate new gain resistor values so 6dB per step could be reached.

What do you think Dave, Gus, Buz??

Cheers Tom

 

[TomWaterman]

BUMP!!!

Any thoughts on that line gain?

-Tom

 

[cannikin]

Hey Tom;

I've had no problems with running line signals through it, I think would be fine with the gain set to 0.

Thanks again.

Your work on this is greatly appreciated!! :grin:

 

[soundguy]

[quote author="TomWaterman"]OK I've been looking at the input stage right now, seems the transformer deals with the mic / line impedances so there would be no need to add a pad for the line input (I think that cropped up during discussions?).[/quote]

this is the logic. these modules are very similar to 33114's and on occasion Ive had to pad the input transformer. We could probably do without a pad though.


[quote author="TomWaterman"]One quick question, anyone know what the balancing capacitor is for? Its only active on the mic input and can be switched to either red or blue, +/-. Also what is AOT. I guess its like "Apply On Test" or something...do you think this cap is needed?[/quote]

I completely dont get what this is doing at all.

[quote author="TomWaterman"]I'm also not getting the second line input and the fact the there are two red (+) connections for the first line input.

If you strip away the 2nd line in (unbalanced) and the extra red connection it seems relatively simple. [edit] the 4PDT relay at the input will work perfectly for mic/line selection.[/quote]

The second line input is probably something that was important to the BBC a long time ago. These modules were probably built for a spec the BBC wanted met in a console. No reason to keep that at all.


[quote author="TomWaterman"]Do you guys think that the -10dB line level setting is needed? Would it be just fine with the gain set to 0 for line use. Buz or Cannikin how is it when you run a variety of line signals through it, do you find you need the attenuation or is plain gain enough?.....I guess a -10dB pad could be placed at the input if this is a problem.[/quote]

this is a very nice design to have in a console but IMO really overkill for what we are trying to do. When connecting a line input to a 33114 I often find the selectable gain on the line input is often more confusing than more helpful. I would much prefer in most situations a switch for line input set to unity at +4dBu. A good compromise would be trying to use the mic trim pot on the line input but thats probably overkill.

[quote author="TomWaterman"]If we could just go from 0 to 66dB on the gain switch it could be done with a 12 position switch at 6dB/step. There are grayhills quite cheap and readily available and the modular NSFs could be used for saving the most money, probably like $10 for a 2deck 12pole. The rest of the switches should be cheapish. [/quote]

Fitting into a 12 position switch with a fine trim pot woudl be awesome and affordable.

thanks for putting in the time on this one!

dave

 

[TomWaterman]

Nice one Dave & Cannikin!

I was wondering about the BBC thing, I have a friend who's taking ages to help me with another thing but he was a BBC engineer who specced the desks when Calrec, Audix and Neve were building for the them.

I guess he would be as good a target as anyone for info....I'll be meeting with him for a beer at some point. If the beeb used the 1061 module in their desks he has probably repaired more then most.

We still really need to get some values for that MF inductor....

-Tom

 

[soundguy]

[quote author="TomWaterman"]Nice one Dave & Cannikin!

I was wondering about the BBC thing, I have a friend who's taking ages to help me with another thing but he was a BBC engineer who specced the desks when Calrec, Audix and Neve were building for the them.

I guess he would be as good a target as anyone for info....I'll be meeting with him for a beer at some point. If the beeb used the 1061 module in their desks he has probably repaired more then most.

We still really need to get some values for that MF inductor....

-Tom[/quote]


wow, for real??? That would seemingly be the biggest help for sure!

Maybe we are just better off just using an inductor that sowter has and building the eq around that. Whatever we build is gonna sound a little different anyway, right? What do you guys feel about that, is that just a ridiculous amount of additional design work to incorporate a new inductor instead of matching what is there? I would think so...

do you think that calrec might still support these? I wonder if we could email them and ask what that inductor value was...

dave

 

[TomWaterman]

Yep for real!

I was originally wondering if the sowter neve inductors could be used.....

what are the frequencies on the mid-range are they the same as the Neve 33114's...if so Geoff Tanner might be a good source of info. Good chance the 33114 inductor could be made to work.

I've not really studied the filters but are they not simple RCL networks buffered after each stage with a B205 amp?

Also I was wondering if we lost the low pass filter altogether, do you guys reckon we could just go straight into the B210 output amp and skip an active stage bringing it down to 7 in total?

Whats the Audix module thats similar...didn't peterpurpose have some of these at one point? I may as well ask this guy about all three.

Cheers Tom

 

[BuzAllen]

[quote author="TomWaterman"]

I'm confused as to how the gain switch connects to line switch too....is there any way we could check that on the original? Where does connector 10 go?

Also the gain switch is a little odd, being that its not the standard 24 positions. An Elma would be overkill and I don't know of any freely available 17position switches.....

I would love to know how to calculate new gain resistor values so 6dB per step could be reached.

What do you think Dave, Gus, Buz??

Cheers Tom[/quote]

Hey guys, glad to see this is still going on. Pin 10 on the edge connector on the module I have is a no-connection. I'm not sure what the intention was if if was installed in a console rather than the box I have. I have the gain equation figured out and written down but I am not at home and won't be much soon but when I am I'll post it along with measurements I made inside the box verifying the how the gain stages and xformer all interact to get the total gain. I have a complete schem for the thing (pre only)as well using a 12 pos switch for the gain with res values as well. I too was curious about the 'balancing' cap I think I remember checking it on the unit but forget the value.

Thanks for the gain stage PCB layouts Tom. I think I'll make some up when I get some DIY time someday.

Brian

 

[TomWaterman]

Great stuff Buz!!

I had a feeling edge connector 10 was something to do with the console.
Really cool you have figured out the gain equation. Can't wait to see what you have come up with....but no rush.

It seems the filters are in the feedback loop of the B205 buffer stages....not to sure about the EQ portion yet.

The MF inductor has five taps, sowter do a neve inductor T1280 with 5 taps but I've also no idea if the values are useable. They seem a little low (?).

I am also wondering about output iron as its not mentioned on the schem. The transformer that peterp had in a pic was numbered as 3955. Looks like a sowter. I'll try and find out a bit more and then email Sowter again.

Any idea what the iron is in your Averill box Buz?

Really glad to hear of your progress!

Cheers Tom

 

[BuzAllen]

[quote author="TomWaterman"]
Any idea what the iron is in your Averill box Buz?

Really glad to hear of your progress!

Cheers Tom[/quote]

The one in the averill box only had a # on it, something like a four digit number stamped on, nothing fancy, no manufacturer mark or anything. I'll peek again when I get back to it in a week or so.

Brian