Calrec PQ 1061

[peterc]

PeterC - did you ever wind that inductor?

I wound 2, then dropped one..... The formers are very brittle, & it is broken.

I have not put it into a cct tho, I was hoping to get onto the PCB design myself & then try the inductor. Unfortunately that is not possible for the forseeable future.

I'll send the inductor to the person who builds a prototype though.

Regards
Peter

 

[TomWaterman]

BUMP!

Just spent some time going back over this project.

Bummer about breaking one of the inductors Peter. Lets hope we can get to a prototype soon-ish to try out the other one. Thanks for offering the other anyway.

I've got loads to post (thoughts n'stuff) but I'd like to sort a few things out first.

I am working on this again (PCBs n'all)...

Anyway, I'll start with the first thing that has cropped up in my mind.

The transistors for the amplifier stages. Buz - you mentioned you had built some of the amps - what transistors did you use for TR3 / TR4 (the output pair)?

They are supposed to be BFR41/81 but I can't find them anywhere reliable so I've been thinking about possible substitutions. The remaining bits (TR1 & 2) can be gotten from Farnell very easily.

Is there any kind of transistor substitution guide online? Somewhere you can enter parameters and a search will create a list of subs??

The info I have found on the BFR41/81 pair is:

Part Number = BFR41
Description = Si NPN Lo-Pwr Bipolar Junction Transistor
Manufacturer = Various
V(BR)CEO (V) = 50
V(BR)CBO (V) = 60
I(C) Abs.(A) Collector Current = 1.0
Absolute Max. Power Diss. (W) = 800m
I(CBO) Max. (A) = 100n
h(FE) Min. Static Current Gain = 150
@I(C) (A) (Test Condition) = 500m
@V(CE) (V) (Test Condition) = 10
f(T) Min. (Hz) Transition Freq = 150M
C(obo) (Max) (F) = 6.5p
Package = TO-92
Military = N

Part Number = BFR81
Description = Si PNP Lo-Pwr Bipolar Junction Transistor
Manufacturer = Various
V(BR)CEO (V) = 50
V(BR)CBO (V) = 60
I(C) Abs.(A) Collector Current = 1.0
Absolute Max. Power Diss. (W) = 800m
I(CBO) Max. (A) = 100n
h(FE) Min. Static Current Gain = 25
@I(C) (A) (Test Condition) = 1.0
@V(CE) (V) (Test Condition) = 10
f(T) Min. (Hz) Transition Freq = 150M
C(obo) (Max) (F) = 6.5p
Package = TO-92
Military = N

I've spent maybe an hour searching to no avail. Any idea on some good subs for the output...modern devices that will be easily obtainable for the forseeable future?

Thats it for now
Cheers Tom

 

[cannikin]

Yeah!! :grin:

 

[gyraf]

Any idea on some good subs for the output

BD139/140? That TO-126-housed pair seems to work pretty well for just about any type of A/B output stage:

http://home.planet.nl/~midde639/specs/BD135_137_139.PDF

Or possibly the TO-92-housed BC327/337 pair:

http://www.semiconductors.philips.com/acrobat/datasheets/BC807_BC807W_BC327_5.pdf

Jakob E.

 

[TomWaterman]

Thanks a lot Jakob, I'll read through the datasheets. Was already thinking about the 139/140 pair, thats the Melcor P/P pair innit?

I'm a little ignorant to discrete design (need to learn more) so do you think these can be dropped in without too much trouble, maybe just a change of R8/R9??

What kind of parameters am I looking for with regard to the original BF41/81 pair, hFE, Power Diss, VCEO, VCBO?

Thanks for any help
-Tom

 

[gyraf]

They are BFR41/BFR81, not BF41/81:

http://www.datasheetarchive.com/semiconductors/specsheet.php?specsheet=451883

http://www.datasheetarchive.com/semiconductors/specsheet.php?specsheet=451930

Jakob E.

 

[TomWaterman]

Yeah thanks I knew that - just a typo!

The datasheet archive material is the stuff I have copied above....

-Tom

 

[cannikin]

Hey Tom

just curious.. are you working just the Pre-amp or Pre+EQ?

I wish I could help you more with this I really want to build these :?

 

[TomWaterman]

Hi David

Well I'm trying to do both, but I'm starting with the preamp. I have actually made a little site for the whole project (with the aim to turn it into a complete DIY thing when I get my head around it all - which is tough as I'm clueless really!).

Basically, the site has all of the info I've collected already plus my new schematic for the mic-pre section and PCBs to follow. I have written a load of thoughts on there.

My direction after reading everyones thoughts in this thread is as follows:

Split the design in half, a eurocard for the preamp with iron on-board and a eurocard for the EQ. I'm still getting my head around the EQ but should hopefully be removing the filters, going for 6 freqs on each of the three main bands (cheaper available switches) and adding a full output fader on the EQ.

The idea is that the pre can be built separately or linked to the EQ and have the last EQ amplifier stage drive the output transformer (when the EQ is engaged) or just build the EQ on its own and add off-board iron for a standalone EQ. Kind of like DanKs EQ2NV etc. I've still got plenty to chat about here before this really goes anywhere.

Eurocard will fit in 3U racks for 8 channel packs, the whole shebang could be linked inside a single 1U rack.

I'll PM you the site location so you can check it over for me if you like before I put a link up here for everyone....

Tom

 

[kvintus]

What happened to this project? Now I can't even find the schematics anymore. The link to Gyraf doesn't work...

/Anders

 

[cannikin]

Its still on....

Just be patient ... your gonna be happy!

 

[kvintus]

:grin:

Good to hear. Could you email me the schematics since I can't seem to find them anywhere right now. There was a couple of things I wanted to check before I go to sleep.

EDIT: Nevermind. I found it!


/Anders

 

[TomWaterman]

Yeah, its been on hold recently due the holidays and some other work, but I just lost my only source of income so I will have some time on my hands the next week or two until I find more employment.

I have to update my new schematics and then I'll finish the PCB. I need to get some dimensions from Sowter and want to ask them if there is a way for them to make the 3553 input tx in a can that could pcb mount into 1U. What are you guys thinking - you planning the project as well Anders? It would be a shame if a bunch of us were working on the samething without knowing.

Did you two see my redesign thread for the micpre? I'd appreciate all the input I can get.
I'm determined to complete this project but things are slow going at the mo.

Tom

 

[kvintus]

[quote author="TomWaterman"]you planning the project as well Anders? [/quote]

Yes, lots of things to do but I'll get to this one some day too... I'm mostly interested in building the EQ section so I haven't payed much attention to the micpre section yet. I built the amplifier on breadboard a couple of months ago and it behaved well IIRC.

Do we have a source for the inductor yet?

/Anders

 

[TomWaterman]

Glad to hear the amp went well, what did you use for output transistors? I'm going to build one with BD139/140 soon...

If your looking at the EQ - we may as well pool our resources together. It would be a waste of time for me to work on it, only to have you do it better!

As for the inductor - you can roll your own and use PeterC's values or use the Sowter Neve inductors as I calculated in another thread. The curves are different but I think pretty useable. Another option is a custom Sowter/Cinemag with any values you want to form your own freq points and curves. I have started laying out a PCB for Wima/Sowter Neve inductor but want to make a few changes to the schematic and arrangement.

So how far have you got with it? After looking at it, think I'll need to change the first B202 to non-inverting and then remove the filters. I think its cool, but have not spent much time looking at the switching around the filters and eq in/out, the schematic is a little weird in that respect for me as I'm trying to split the module in half at the insert point. Have you got your head around that?

Tom

 

[TomWaterman]

Bump...

-T

 

[kvintus]

Glad to hear the amp went well, what did you use for output transistors? I'm going to build one with BD139/140 soon...

I used a standard BD pair. Could well have been 139/140 IIRC.

If your looking at the EQ - we may as well pool our resources together. It would be a waste of time for me to work on it, only to have you do it better!

I don't know if I can do it better, but I'm willing to help.

As for the inductor - you can roll your own and use PeterC's values or use the Sowter Neve inductors as I calculated in another thread. The curves are different but I think pretty useable. Another option is a custom Sowter/Cinemag with any values you want to form your own freq points and curves. I have started laying out a PCB for Wima/Sowter Neve inductor but want to make a few changes to the schematic and arrangement.

I can't find PeterC's values anywhere. Can you point me in the right direction? I was thinking about rolling my own.

So how far have you got with it?

I don't want to disappoint you, but at the moment I'm just staring at the schematics and trying to sort out all the ideas in my head. I'm quite far from starting to actually build something. At this point I'm not even sure if I want to make a clone or if I'm going to design something that is just inspired by this circuit. Probably I will build something quite close to the original first.


/Anders

 

[TomWaterman]

OK cool, well I'm glad your not too far with it in a way as it would defeat the time I've put in so far!!! :wink:

Peters values here
Peters inductor here

Have you seen my redesign schematic? I'd be interested to know your thoughts as I'm about ready to have a go at the preamp section. I will be ordering some input txs from Sowter asap (within the next few weeks) and hopefully some pcbs soon after that.

I have to draw out my new EQ schematic and will need some time to get my head around it but essentially I'm trying to make this a project for everyone, cheap-ish switches (lorlins except for gain switch), ready-made pcbs and the option to do pre, eq or both together. Its a clone but not a totally direct copy part for part.

I hope it works! Plans for next week are to layout a switch pcb for panel mount toggles, gain switch and output fader, along with the main mic pre board. I must also breadboard my 48v regulator to see if that works properly...I've got three amplifier layouts for TO-126 output pair, new radial caps and wima polys, they are double sided and have ground planes on both sides. I'll pick one eventually.

What would you like to see in the re-make?
Cheers Tom

 

[kvintus]

Peters values here

Cool! Very close to my calculations. Apperantly I did something right...

Have you seen my redesign schematic? I'd be interested to know your thoughts as I'm about ready to have a go at the preamp section. I will be ordering some input txs from Sowter asap (within the next few weeks) and hopefully some pcbs soon after that.

I've seen it but I haven't had the time to really study it. But as far as I'm concerned it looks good. Go for it!

I'm trying to make this a project for everyone, cheap-ish switches (lorlins except for gain switch)

Good idea, except that the mid frequency switch has to be something else than lorlin also, right? Or perhaps you could skip a couple of frequencies and make it lorlin compatible.

What would you like to see in the re-make?

Looking good so far. I don't have much to add, except that I tend to like compact units, so I would really like to fit it behind a small front panel, something like 4 x 8 cm. That's for the EQ section only.

Keep up the good work! I'll quit my current dayjob the 10th february so after that I'll have some more time to think about this I hope.

/Anders

 

[TomWaterman]

Yeah I'm planning on 6 positions only for the mid-band, off and 5 diff. freqs, I've calculated some combinations based on Neve 1073 spacing and the Sowter Neve inductor.

Funny you mention compact spacings as I'm laying out the pre and eq on eurocards that will fit vertically in a 3U rack....the preamp will fit fine but the EQ is a bit of a squeeze as lorlins are too big. I'm not planning on pcb mounting the eq switches and pots so one could use small Elmas to save space....

By the way did you really mean 4x8cm?? thats freakin' tiny!
-Tom