Calrec PQ 1061

[gang of elk]

i've been looking for BFR41/81 and not much out there.

so far have found only one cross ref for BFR41, ECG297, type: T-NPN, Si, AF PO, Dr, Pd 0.75 W @ $1.81 each

BFR81T05 cross refs to ECG383, type:  T-PNP, Si, AF Driver $2.30 each

(http://www.moyerelectronics.com)

anybody have better luck?

EDIT: also,  2N930 cross refs to ECG123A, type: T-NPN, Si, AF/RF Amp
 $1.47 each

 

[TomWaterman]

Hey all good stuff guys!

I'm about to get cracking on finishing the gain block layout.....

I'm totally with you guys about splitting it at the insert stage.

One eurocard per stage. The only problem is that bloody mid-range inductor.....what caps are in there? are they Philips? I expect Wimas would be just fine or not?

Whats cool is that the pre only could be balanced out with a TX and the eq only board could be balanced with TX in and out. A great way to get some iron flava. Simple stages as well. A 8ch mixer with these would be rocking......perfect for tracking drums!

JLM PSU is a good call, I've been meaning to get a bunch of these from Joe for all my projects....

As far as the transistors go I found these links:

http://www.advancedsemiconductor.com/transistors/MISC_TRANSISTOR/BFR41.shtml
http://www.advancedsemiconductor.com/transistors/MISC_TRANSISTOR/BFR81.shtml

I found BC212s, 2N930 at Farnell as well as the more common BC182LB.

Thanks for the links Brian - I'll check those pins out. I hope it keeps raining out there.........:thumb:

Tom

 

[Bauman]

I have a couple of JT-13k7A (1:5, 150:3.8k) input transformers, was thinking about them as starting point for this project then switch to Sowter later, do you think it could work ok?

 

[BuzAllen]

I found something on those transistors. Apparently these guys must have some old stock or something. Kind of pricey for a to92 package device though.

http://www.cricklewoodelectronics.co.uk/Cricklewood/customer/home.php?cat=185&page=8&xid=69a4717577fbb6795469c8f28f0e1941

For the pre section the inline signal path caps c3 and c6 are tantalums, c2 and c5 are aluminum electro's, marked BP(M)CE Japan. Not sure what manufacturer these are but there definately no the originals. c1 and c4 are some type of axial cap, silver in color. I'd guess films, Ive seen some like this before. The filter caps for the EQ's are not marked for manufacturer but are the same 'style' appearance-wise as the ones on the gain stage pictures (silver ones).


I was going over the schematic and using the Averill unit to follow it and I am now thinking that there is a difference between the two as far as the gain switching/input section is concerned. The Averill unit is marked as a 1061 on the front, though the board is marked 1161 as gyraf pointed out. And the schematic is 1061. The wafer #'s and purposes on the primary i/p and gain switch don't line up with the schematic as far as I can tell and there are some other variants as well as far as routing the input.

This being said I think just going with the schematic was a good idea. Since we are talking about making the pre and EQ separately, should we include the extra stuff for a line input on the pre, or just set it up as a mic pre only using the 10 or so gain posistions and eliminating the 5/6 line gain settings, this would have the advantage of using simpler parts, a 2 pole 12 pos. switch. Or do we want to go just as the schematic is. If that is the case then it looks like we would also need a line switch as can be seen where it is labled on the left of the schematic as pin 10. Although I am not entirely sure what that switch accomplishes, if it exists, simply because when in one of the 'line' positions the gain resistors are disconnected from the series. Anyone on this? Did that make any sense at all?

Any thoughts on mic input section with respect to these ramblings (or not)?? Mic only, lic/line leaving the line in for the EQ?

Brian

 

[cannikin]

My vote: mic pre only, Line in for the EQ.

 

[soundguy]

well, I think we should set it up so it works with a 150/600 primary input transformer and then design the input around that part. That would be my suggestion.

dave

 

[BuzAllen]

Does anyone know anything about the tx in question (mic in). It would seem to have to be a low ratio since there is not a pad preceding it. If not I'll do some testing tommorow.

So lets get an idea from everyone what we want in the pre section.


+48 (with led?)
polarity?
150/600 Ohm switch?
Pad (if neceasry, might not be)?
Gain switch
Trim


So lets get a consensus on these things, particuarily the gain switch. Go for the same -70 to +10 sensitivity, 16pos or a 12 pos with greater steps (roughly 6db) or less range (-60 to 0) and same +/- 5db steps?

Can anyone give some input on the 'balancing' capacitor labeled for 'adjust on test (AOT)' on the tx's primaries mic taps. tx's are my weakest link in this stuff.

EDIT: also lets talk about what might go on the PCB vs. point to point. In some ways a pad, 48, polarity (if the DPDT kind pre tx), and 150/600 type switches are more simple just to do point to point upstream of the PCB leaving only the 2 gain stages and various resistors/caps on the PCB with connector for i/o, pwr and gain switch. would make a really simple PCB, could do two pre's on one fairly small PCB, or keep them single? Makes just about any type toggle work rather than having to get a switch with a specific mounting pattern. potentially keeps it cheaper. thoughts?


Brian

 

[JustinS]

I'm a fan of having all of the necessary bits on the main pre pcb i.e. polarity, pad, gain etc. I did notice that there isn't a pad on the schematic, I know on some Helios pres they used a Lustraphone transformer that was 150 / 600, and they switched to 600 to act as a pad...

I don't think that having necesarry controls on the main pcb will increase the complexity of the PCB significantly & people can always front panel mount their pots etc and wire them to the PCB for layout flexibility. Also another thought, if the initial gain switch is to be simplified (which I think is a great idea) we should think about changing the value of the fine gain control +/- 2.5dB is a little small +/- 10dB is probably a better ballpark... Thoughts??

Justin

 

[BuzAllen]

Good point regarding the switches, one could easily do as you say and still mount them off PCB if desired.

I agree about the trim, in use the +/- 2.5 thing is never enough, I'll turn it up then realize I really need another click on the switch. But people who are more particular about exact levels might appreciate it.

It looks as though the way it is implemented is just a 5db attenuator with the +2.5 figured into one of the gain stages so at center it's '0'. It could easily just be an individual preference by adjusting the values of the att. network post the first gain stage (looks like changing r9 would have that effect). With the same gain setting resistors on the switch and the trim at +/- 5 you'd end up with something like +2.5, -7.5 relative to the overall gain of the circuit.

Brian

 

[soundguy]

I have never used any mic input transformer at any ratio that did not need a pad in front of a drum kit or a loud guitar amp regardless of what mic was being used. Food for thought. I didnt see any wiring for the sensitivity switch on the schem, my guess is that there is a pad built into the switch, that is certainly how neve 33114's were wired and this seems to be largely inspired by that amp. At any rate, if we go with lorlins on a board, chances are we'll need a seperate switch for the transformer tap and a pad before it.

As for switching, Id personally like to keep as much as possible on a pcb and go with relay switching.

dave

 

[BuzAllen]

I checked and Justin is correct about the 600 Ohm tap working as the pad, it's just like the schematic, 600 kicks in at -25sense. I checked on the unit and there is no additional resistive padding prior to the tx. it is mic in straight to the tx. So that being the case we could have both the 150/600 switch and a resistive pad as Dave said. Could be a way to generate different sounds, use either the 600 Ohm tap as a pad or leave it at 150 and use the resistive pad? could also thow the 600 Ohm tap in line and use high gain, lots of options.

How does this sound for the circuit?:

48V Toggle
Pad (Resistive pre xformer) Toggle
Polarity Toggle
150/600 Toggle

12 Posistion Gain switch (-70 to -10 sensitivity)
Trim Pot

Does anyone have interest in doing the Main PCB's. Tom? Anyone? If not I could maybe take care of it though my time is running out in a few days for this stuff.

Or is there any hurry at all since we don't have a price/timeframe on the tx's.?

I'll re-draw a schematic with the current layout we are looking at after some feed back comes in from the above questions. I see this is a 'popular' thread from the index so some people are reading it. Anyone else want to jump in with input who's considering building this thing?



Brian

 

[soundguy]

are you guys planning on doing PCB's for a pre only? Seems like you might be able to build it point to point... Might be most efficient to wait until we get an idea about the inductors and then do the whole board set together for the pre and eq.

dave

 

[BuzAllen]

I not sure there is a plan yet. I agree with the point to point. As I had mentioned, it was my original goal when I first looked for these schematics. The ideas for the 2 PCB, 1 pre, 1 eq, appeared and then I though maybe that was a good direction because some might want a pre, some an EQ, some both and PCB's might make it more frendly for some. I dunno. Outside of maybe 7 or 8 of us there hasn't seemed to be many speaking up with interest. If that's the case, maybe start with the small board gain stage PCB and point to point a pre with those and the surrounding components then use the same gain stage since we have it to work through the EQ?? If it turns into a viable project then there it is, if not then we got some easy to build pre's.

I was thinking along the lines that if were going to make this thing might as well take it the direction that would be the most useful/affordable/easy to construct for others.

Brian

 

[soundguy]

who was looking into the iron? perhaps after there is clear direction on which way to go with the transformers/inductors then there migth be more interest in having someone lay out boards. It doesnt seem to be worth doing a preamp only board if there are plans to do the whole thing.

dave

 

[JustinS]

I was thinking that the pre / eq would end up modular (at least someone sugested that)... i.e a pre board (w' input & output iron) & an optional insert point for the eq board. So those that want EQ can have & those that don't won't . I'm probably all for having it all on one main PCB, that might limit enclosure styles (is that a drama??), but hey... maybe just a layout for the amp card for the moment is the way to go... we could then experiment with different eq options point to point & make up the pre point to point as well. I'm not quite sure why there doesn't seem to be more interest in these. They sound amazing, and the EQ is fantastic - more flexible than a 1073... cheaper to build than an 550 or 1081. Maybe all the potentially interested people are deep into $$ 1081 style...

Justin.

 

[cannikin]

For what its worth, I'm planning and prefer building the whole thing - Pre/EQ. I think 2 boards would make in easier in some ways. But I have a feeling once this gets off the ground others will jump on it, especially if there are boards for it.

Since I'm completely new and won't be much help with design - its up to you guys.

 

[TomWaterman]

I'm still tidying up the layout for the gain block and I need to sleep now!!

I'll post it up some time this week....at this stage - I'm not sure we have a supply of all the transistors and that elusive MF inductor is a real problem.....

I'm not sure I have the time or skill to take on a full board layout for the whole module but in the mean time maybe the gain bloack will allow peeps to point-point the pre stage and see if it blows up, sounds glorious etc

I'm in touch with Sowter concerning the iron. Inductor is not theirs but I have shot an email off to Brent Averill to see if they know anything about it.....not sure where else to look for info..ideas?

Sowter can remake the 3553 input tx and now know the correct colours for the leads..... I'm waiting for them to get back to me concerning price.....I expect a group order is the only way to get them cheap and up until now people are staying quiet.....I guess many are watching this thread though.

I still think a board for each section would be best, I like the features for the mic pre that Brian has suggested.....12position switch with trim really cuts down on expensive switches etc and it sounds flexible.

I know I'm up for having a stab at the full module.....

I still wonder if one of the Sowter Neve inductors will work?

Also - I assume this module is fairgame for self building as its not even in production(repro) by Calrec, unlike the AMS1081?

Cheers for now
-Tom

 

[JustinS]

Hmmm, someone could try to work out the inductance values from the frequencies / cap & resistor values... maybe I'll try that tonight.

Justin.

 

[BuzAllen]

I just took the inductor out of its magnetic casing. If anyone can suggest measurement methods other than an inductance meter (don't have one) I'd be happy to do some tests. If not I'll be in LA a lot working over the next days/weeks maybe I could stop by a couple shops and measure it.

I suppose I could put it in a filter circuit and measure the respose at different generated frequecies or run an FFT to get an idea. Maybe there is a simpler way?

Also I'm headed out of town shortly for a while so if anyone involved would like me to gather any other info out of the unit or measure anything I can get at let me know.

Brian

 

[cannikin]

Hi Guys;

So whats the plan? I hope this project doesn't die on the vine, I've been using my Brent Averill Calrec all week and wish I had (at least) 4 more of them. :shock:

Just trying to keep it alive.