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General Discussions => The Lab => Topic started by: audiox on June 01, 2015, 06:05:49 PM

Title: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on June 01, 2015, 06:05:49 PM
Long time no see. But here we go again.

Studer 169 Mic Preamplifier & EQ section in a single 500 series module. See the drawing attached.

Fully discrete signal path available. The mic pre is discrete just like the original, but the EQ and the output stages allow IC or discrete op-amps. Swapping between the types is easy, no circuit modification required.

There are pads for wiring miniature toggle switches which provide the following options:

- high pass filter
- phantom power on/off
- input attenuator
- phase invert
- selectable LO and HI filter frequencies

There is also free space in the middle of the PCB for output transformer experimenting.

The board is single sided with large pads making it suitable also for the home etchers.

DOCUMENTS:

Schematic diagram
https://drive.google.com/file/d/0B_XBYPfmG8pVcXRLUk5qT2t5SU0/view?usp=sharing

Layout with component designations
https://drive.google.com/file/d/0B_XBYPfmG8pVMHJ0QmhKZkEzU1k/view?usp=sharing

Layout with components values
https://drive.google.com/file/d/0B_XBYPfmG8pVbXh5RDluTFdWUkU/view?usp=sharing

Copper mirror (for home etchers):
https://drive.google.com/file/d/0B_XBYPfmG8pVNnRhRHItZnozU0U/view?usp=sharing

Front panel:
https://drive.google.com/file/d/0B_XBYPfmG8pVLWE2b0s2bmpJR1k/view?usp=sharing


Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ)
Post by: weiss on June 01, 2015, 07:57:30 PM
Great idea! Is it also possible to enable HPF?
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ)
Post by: audiox on June 02, 2015, 04:44:32 PM
Great idea! Is it also possible to enable HPF?

Yes, there are connection points for a high-pass filter switch. I just forgot it from the list.

Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ)
Post by: audiox on June 04, 2015, 06:55:04 AM

Schematic published. Other documents will follow...

https://drive.google.com/file/d/0B_XBYPfmG8pVcXRLUk5qT2t5SU0/view?usp=sharing

Note. Options not shown for clarity. I will draw separate wiring diagrams for the numerous options.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ)
Post by: SoundOfRolf on June 05, 2015, 04:09:50 AM
Absolutely fabulous!!!

This is just the thing I was looking for.

Great work!

-T

Ps. Just ordered panels and pcb's for the eq. :) Well no harm done. There's always need for just a good eq.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ)
Post by: KDE on June 08, 2015, 04:09:05 PM
you should throw a line switch on it  H-Pad on the input of the pre
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ)
Post by: audiox on June 10, 2015, 06:45:16 AM
you should throw a line switch on it  H-Pad on the input of the pre

There are pads for wiring miniature toggle switches which provide the following options:
- high pass filter
- phantom power on/off
- input attenuator
- phase invert
- selectable LO and HI filter frequencies
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on June 13, 2015, 11:47:59 AM
Layout drawings & copper mirror for home etchers published. See the first post.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Rocinante on June 13, 2015, 12:59:53 PM
Awesome.  Very awesome.  Thank you.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Jano1954 on June 14, 2015, 09:01:04 AM
Thanx Audiox for the nice schematics.
I am planning to build at least 2 of these modules during my summerleave.
I want to use the modules with the DOA's you use.
I am fairly new to this board and I am looking for a description of these DOA.s
I suppose you did publish them in the past, but I can't find it.
Either I am looking the wrong way or it is not there anymore.
Can you put me into the right direction or supply  with the schematics and pcb drawings for these DOA's?
Thank you so much
Jan
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on June 17, 2015, 02:01:04 AM
I am fairly new to this board and I am looking for a description of these DOA.s
I suppose you did publish them in the past, but I can't find it.

The Neumann OA10 could be one alternative:
http://groupdiy.com/index.php?topic=34105.0
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on June 17, 2015, 02:52:03 AM
Any plans on ready made PCBs for those of us who can't etch? :)
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: peterc on June 17, 2015, 06:35:22 AM
Very nice project....

Peter
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Niketouille on June 17, 2015, 08:33:24 AM
Hi,
Do you have any front panel template or drawings ?
Regards
G.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on June 21, 2015, 06:20:09 AM
Do you have any front panel template or drawings ?

I will prepare the mechanical drawings when I have time. Possibly next week but can't promise.

Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on June 28, 2015, 09:49:43 AM
Do you have any front panel template or drawings ?

https://drive.google.com/file/d/0B_XBYPfmG8pVLWE2b0s2bmpJR1k/view?usp=sharing


Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on June 30, 2015, 02:29:47 AM
Hello!

Questions, questions, questions  :)

You don't happen to have gerber files?
I'm planning to order some PCBs from dirtypcb or itead.
I asked Gustav, but he doesn't seem to do these?

You said in the EQ thread that:
- resistors 1% metal film
- 100n power decoupling caps, ceramic multilayer 50V or higher R=5mm
- pF range capacitors, ceramic, any voltage R=5mm
- nF range capacitors, polyester, any voltage R=5mm
- 10u electrolytics, 25V or higher R=2.5mm
- 100u electrolytics, any voltage R=2.5mm

Is it the same here? Any brand recommendations?

There are 5 different NE5534 at Mouser. Could anyone help me to pick the right one?

Is there room for option switches? Between the pots right?
I'd like to have the panel ordered with holes for the switches.

The pots come from AML right?
P1=2k2 rev. log OM-01-014 - 16mm - 1 gang
P2 = 2x 22K LIN center detent (order code OM-01-023)
P3, P5 = 2x 10K LIN center detent (order code OM-01-005)
P4 = 2x 100K REV LOG (order code OM-01-059)

And THANK YOU for this project!

-Tony



Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on July 07, 2015, 06:45:53 AM
You said in the EQ thread that:
- resistors 1% metal film
- 100n power decoupling caps, ceramic multilayer 50V or higher R=5mm
- pF range capacitors, ceramic, any voltage R=5mm
- nF range capacitors, polyester, any voltage R=5mm
- 10u electrolytics, 25V or higher R=2.5mm
- 100u electrolytics, any voltage R=2.5mm
Is it the same here?
Yes.

There are 5 different NE5534 at Mouser. Could anyone help me to pick the right one?
Any of them will be fine. The -A version has guaranteed (lower) noise specs.

Is there room for option switches? Between the pots right?
Sub miniature toggle switches should fit. But may require some redesign of the front panel texts.

The pots come from AML right?
P1=2k2 rev. log OM-01-014 - 16mm - 1 gang
P2 = 2x 22K LIN center detent (order code OM-01-023)
P3, P5 = 2x 10K LIN center detent (order code OM-01-005)
P4 = 2x 100K REV LOG (order code OM-01-059)
Yes, originally designed for the 16mm Omeg potentiometers.

Other potentiometers: pin spacing 5mm, row spacing 7.5mm or 10mm.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on July 09, 2015, 09:35:36 AM
I found some very affordable pots, but the 2k2 and 22k pots are hard to find. Could I use 2k and 20k pots instead or 5k and 50k with a resistor in parallel?
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on July 10, 2015, 04:52:04 AM
I found some very affordable pots, but the 2k2 and 22k pots are hard to find. Could I use 2k and 20k pots instead or 5k and 50k with a resistor in parallel?
The value of the 2.2k revlog is non-critical. The 22k lin can be replaced with a 20k lin as well (affects the max boost/cut approximately 0.5dB).

If using other potentiometer types, please note that the dimension from the first row of pins to the front panel should be 4.8mm or less.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: iprovlek on July 10, 2015, 07:50:27 AM
GREAT PROJECT Audiox...

You nail every time.....

Thanks......

 ;D
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: iprovlek on July 10, 2015, 07:58:02 AM
What is value of L1!?

Can I use 10ohms in place of L1!?

Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on July 22, 2015, 05:46:20 AM
What is value of L1!?
Practically any ferrite bead should be fine.

Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on November 10, 2015, 11:01:56 AM
Hi!

I've finally got a board etched and am filling it. Audiox, did you have some smart idea how to utilize those extra pads for switches?  Or just wire off board? Mostly interested in phantom, pad, polarity and maybe hpf.

-Tony
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: 2Low on November 11, 2015, 01:08:32 PM
Any plans on ready made PCBs for those of us who can't etch? :)


Great project !

Any news about PCBs ??
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on November 12, 2015, 07:47:59 AM
Yes PCB's would rock!

I etched one and built it. It's not pretty but it's working. I would rather take a factory made PCB though.

I thought I made some heavy mistakes or built a radio as there was some strange noise and it started oscillating like crazy on higher gain or frequency gain settings. Turned out to be the Lindell 510 rack. Moved to a slot further away from the PSU and voila works as expected. Low noise, huge gain. Need to do that pad. I wired a switch for the phantom and added a red LED with 10k resistor.
Should the LED be connected to ground or chassis? Or is the only down side connecting to ground the pop that it gives when turing on? (chassis so far away......) :)

Thanks for the project! I'll do at least one more....waiting for some brave to have some PCB's manufactured.

-Tony
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on November 12, 2015, 07:54:24 AM
BTW checked DirtyPCB and pcbway prices. From 50 to 88(immersion gold) dollars for 10 pcs.
Not bad. Needs them gerbersssss.

-Tony
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: zayance on November 12, 2015, 12:07:37 PM
Hi There,

What equivalent for BC239 do you guys use?
Or maybe someone have some spares?

Thanks in advance

Best,


T.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on November 12, 2015, 02:25:17 PM

What equivalent for BC239 do you guys use?



I used BC239 :)

Try www.uraltone.com (http://www.uraltone.com)
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: iprovlek on November 12, 2015, 02:48:55 PM
I try BC550c and BC109C!

With this two I get more Bass!BC239 has less bass than BC550 and BC109!

This preamp is amazing!I use him on everything!Planning to do 12 channels of this!

It would be great to use PAD,HIPASS FILTER,+48V,LINE,PHASE and differnete freq on high and low freq!
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: zayance on November 12, 2015, 05:48:35 PM
Good to know.

RS has tiny toggle switches that take very little space on frontpanel.
ref:ZL36S0101
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ)
Post by: SoundOfRolf on November 26, 2015, 08:55:47 AM

Note. Options not shown for clarity. I will draw separate wiring diagrams for the numerous options.

It would be nice to see these and compare to what I did.

BTW there seems to be some DC offset (~50mA. The 169 EQ's I built have 100mA). How to trim it or should I put some output caps or just never mind it?

 ;)
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: 2Low on January 18, 2016, 03:14:08 PM
Any plans on ready made PCBs for those of us who can't etch? :)

Bump

Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on January 19, 2016, 04:05:26 AM
Here's my babies

Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on January 19, 2016, 04:12:19 AM
I'd like to share my front panel if somebody would have any use for it.
I wouldn't recommend to use it as is as it has really small clearance for the text as you can see in the photo above.

It's not fully my writing. I used a panel from the EQ thread and modified it with help from Frank who also produced the panels.
Thanks for that.

I'll try to attach it here as linking to outside services tend to stop working with time.
Just change the extension to .fpd
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Vac11 on April 14, 2016, 07:36:53 AM
Hi all,

can I use for mids  (frequency and gain) concentric pot with these parameters?

2x 100K rev log (for frequency sweep), 1x 10K linear witch center tap (for +- gain)

When I add a 10K resistor parallel on 1. and 3. lug on the 10K gang, everything could be Ok...  Or not?

Thanks

M.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on April 18, 2016, 09:31:04 AM
can I use for mids  (frequency and gain) concentric pot with these parameters?
2x 100K rev log (for frequency sweep), 1x 10K linear witch center tap (for +- gain)

The P5 value is not critical. A single 10 kohm potentiometer should be fine.

Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Spino on April 19, 2016, 04:14:00 PM
cool project indeed! is it supposed to be mounted on an L-bracket?
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Vac11 on April 20, 2016, 01:19:29 AM
Mounting on the L-bracket is possible to... Here is another possible solution:

https://drive.google.com/file/d/0B_XBYPfmG8pVMjVkMDYzNTEtYzdhMS00ZDlkLWJjNWMtZGZjMGFiODAzYTNl/view?ddrp=1&hl=en#
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Jano1954 on April 20, 2016, 04:11:41 PM
Can you tell me who sells the knobs you are using Sound of Rolf?

What is the make, modelnumber, partnumber and where to order?
Thnx
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: SoundOfRolf on April 21, 2016, 01:04:23 AM
@jano

They were the cheapest knobs I could find on Ebay...   :D

http://m.ebay.com/itm/181561933265?ul_ref=http%3A%2F%2Frover.ebay.com%2Frover%2F0%2Fe11401.m2368.l3160%2F7%3Feuid%3D25056d828cc44ccdb2c4473aefeea2e8%26loc%3Dhttp%253A%252F%252Fwww.ebay.com%252Fitm%252F181561933265%253F_trksid%253Dp11400.c100368.m3767%2526_trkparms%253Daid%25253D333008%252526algo%25253DRIC.MBE%252526ao%25253D1%252526asc%25253D20150120121922%252526meid%25253D267015fadae64a16a06d4485fd6bac5e%252526pid%25253D100368%252526rk%25253D1%252526rkt%25253D8%252526sd%25253D271669025083%26srcrot%3De11401.m2368.l3160%26rvr_id%3D0&_trkparms=aid=333008&algo=RIC.MBE&ao=1&asc=20150120121922&meid=267015fadae64a16a06d4485fd6bac5e&pid=100368&rk=1&rkt=8&sd=271669025083&_trksid=p11400.c100368.m3767&_mwBanner=1 (http://m.ebay.com/itm/181561933265?ul_ref=http%3A%2F%2Frover.ebay.com%2Frover%2F0%2Fe11401.m2368.l3160%2F7%3Feuid%3D25056d828cc44ccdb2c4473aefeea2e8%26loc%3Dhttp%253A%252F%252Fwww.ebay.com%252Fitm%252F181561933265%253F_trksid%253Dp11400.c100368.m3767%2526_trkparms%253Daid%25253D333008%252526algo%25253DRIC.MBE%252526ao%25253D1%252526asc%25253D20150120121922%252526meid%25253D267015fadae64a16a06d4485fd6bac5e%252526pid%25253D100368%252526rk%25253D1%252526rkt%25253D8%252526sd%25253D271669025083%26srcrot%3De11401.m2368.l3160%26rvr_id%3D0&_trkparms=aid=333008&algo=RIC.MBE&ao=1&asc=20150120121922&meid=267015fadae64a16a06d4485fd6bac5e&pid=100368&rk=1&rkt=8&sd=271669025083&_trksid=p11400.c100368.m3767&_mwBanner=1)
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Jano1954 on April 21, 2016, 03:28:41 AM
Thnx
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Spino on April 22, 2016, 04:45:51 AM
What is value of L1!?

Can I use 10ohms in place of L1!?

if L1 on audiox's schematics is the same as L1 in studer's schematics then the 169 had these:

Quote
yes, original L where Philips p/n 62.01.0115. they can be changed with TDK p/n B82114-R-A4.
in italy, they can be found at Distrelec with code 350214.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Vac11 on April 27, 2016, 09:36:29 AM
Hi,

I´d like to add a "EQ In/out" switch in this circuit... In attachement is scheme... I want to use preamp separately without EQ "affecting".
Are my thougs proper? Make it sense?

Thanks

M.

Edit: Schematic modified...
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: audiox on May 05, 2016, 01:53:13 PM
I´d like to add a "EQ In/out" switch in this circuit... In attachement is scheme... I want to use preamp separately without EQ "affecting". Are my thougs proper? Make it sense?

No, it doesn't work. In your drawing the EQ (U2) output will short the mic pre output signal.

The additional switch should select between the mic pre output and the EQ output signals.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Vac11 on May 07, 2016, 07:10:10 AM
Thank you very much... I modified schematic. I hope it is right now.

M.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Vac11 on June 06, 2016, 05:10:53 AM
Hello,
I have some news about my construction of this chanellstrip ...

1) No smoke when first time turn on.
2) Preamp works great - a ton of gain.
3) On the doas sockets is proper voltage +-16V.
4) The device is powered with about 0.04A with all DOAs in sockets.
5) Device works great with NE5534 and also with my DOAs (SGA-SOA1).
6) The preamp, mids and bass are working properly and sounds realy great to my ears.

I have troubles with HIghs. They dont work correctly. When I turn the HIghs pot to the O (center) position or to the CW end I get some radio high frequency oscilation, distortion and small loss in gain... When I turn this pot CCW (to -15dB) oscilation is gone and preamp and Bass and Mids on EQ works correct.

I try swap L1 ferrite for another... Without any changes. I used this ferrite:
http://www.ebay.com/itm/10pcs-50pcs-Inductor-beads-3-5-9-0-8-AXIAL-FERRITE-beads-3-5x9x0-8-/351711605313?var=&hash=item51e3a53241:m:mURskzUy_RH4zptyIE6It5Q
and
http://www.gme.cz/bl01rn1a1d2b-p140-018

I desoldered and after then measured R21, R22, R23 and R24, R25 (correct values) and I reheated C16, C17, C18 in filter... Without any changes...

I double check HIghs potentiometer wiring - everything is OK. I measured potentiometer value. It is OK (2x10K lin).

Please can you help me and guide in the right direction? Can it cause a bad choice of ferrite L1? Any advice would be very helpful...

Thanks Audiox for this amazing project!

Best

Milan


Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: zayance on September 05, 2016, 06:51:52 AM
Hi Audiox,

Wondering what was the idea of the HPF option empty space on PCB, i guess building a simple CR filter there but just to confirm.

Thanks.


T
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on June 28, 2017, 04:28:52 AM
Reviving this thread for a couple of questions.

For those that have built one of these, would an H-Pad or a T-Pad be more optimal in this circuit? I am currently building the PCBs I have laying around and and the first one I built with an H-Pad, but I would like to get more attenuation, but I don't know exactly what resistance values to use for source and destination with the calculators that are available online. Since the pad will be when used in conjunction line level output devices, I used 600ohm for the source and 200 for the destination as I am using a NTM4 transformer on these builds. I used the values given, but I am getting around 15dB instead of the desired 30dB or something close to unity. I can follow along with formulas, but I get lost trying to figure which values are what I need to use.

The other thing is the HPF. I guessed and used 100nF in the spot that says HPF, but I don't hear anything happen when I make the connection between the adjacent OPT pads. I didn't think anything else was required to make this work. I might have the wrong capacitor value for this circuit.

Other than that, I've managed to cram all the features in one 500 series unit. Selectable frequencies for Low and High, Pad, Polarity, EQ In/Out, and +48. The mic preamp is quiet and sounds really good as does the EQ section. I'll show what I did to make it all fit after I figure out the Pad and HPF.

Thanks!

Paul

EDIT: EQ Bypass scheme doesn't quite work right as described or as I had previous drawn. See below
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on June 29, 2017, 12:04:55 AM
It's all been figured out!

I wound up doing all the options on this guy:

EQ In/Out
HPF
Mic/Line
Selectable HF/LF
Polarity
Phantom

I tried to attach the .fpd file that I am using, for some reason that file extension is not allowed. I thought I was able to do that in the past. Hmmm... I can email it on request. It's a modified version of the one that was posted earlier on this thread

The EQ In/Out selector placement is the trickiest one. I had to trim the center facing legs of the MF select and HF gain and then file down the edges of a tiny SPDT switch and wedge in between the pots. I still need to add a little super glue to it to hold it to the board, but once the pots are soldered in around it the switch doesn't move. The holes to attach the panel to the PCB or to an L-bracket have been left. The hole to the left of the +48V switch is for a phantom LED indicator.

Right now I have one circuit fully working, but I still have to install it into the front panel. That will have to wait as I leave town this weekend. My goal was to just get the board working before I left. Then I have 5 more to do when I get back.

I'll send pics when I get back. In the meantime, I would happy to answer any questions if someone is building one and would like to add some of the extra options.

It's a shame these boards aren't readily available.

Thanks!

Paul

EDIT: EQ Bypass scheme doesn't quite work right as described or as I had previous drawn. See below.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on July 12, 2017, 04:00:12 PM
Wanted to share my front panel design file that I'm using. It's a modified version of the layout posted earlier on this thread. The ones I actually have have errors on them because I'm an idiot. This file has been corrected. Just change the extension to .fpd.

I'll post all the info tonight on how to implement hopefully just in case there are still some people out there holding on to boards and are waiting to start on this project.

Thanks!

Paul
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: 2Low on July 12, 2017, 04:28:07 PM
yes yes , boards please !!!
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on July 13, 2017, 01:23:14 AM
Okay, here we go...

For the EQ In/Out switch, I followed the provided schematic earlier in this post and came up with this. The VERY first thing I would recommend is removing the Link at the top of DOA 2. If you forget to do this then test the switch, in the bypass position you will generate painful, squealing feedback at weaponized levels. So do this first. Seriously.

To avoid a bunch of cutting traces and cut down on the number of jumpers being used, I moved C15 to the two solder points above R34 that are not connected to anything. You will have to cut the trace that connects those two points. Positive side connects to R34 as shown and the negative goes to the pole of the SPDT for EQ bypass. I ran this wire through the unused DOA socket hole to connect directly to the capacitor.

The connection for the Bypass position of the switch depends on how you want the HPF to function. If connected to position 1, the HPF will still function when the EQ is bypassed. In Position 2, the HPF is bypassed with the EQ. Buyer's choice.

For the EQ In position of the SPDT, I connected it to the unused output connection of U2 (pin 6) since I'm using DOA and these points are tied together on the board.

The Link that is directly under the DOA 1 outline needs to be removed otherwise the HPF will be bypassed all the time.

For the HPF capacitor I wound up using a 1uF. Seems to roll off around 80Hz. Some might prefer 820nF to get just the HP frequency a little higher.

The HF and LF selection modification was taken from the 169 EQ page:

https://groupdiy.com/index.php?topic=36522.240

I thought about using some different frequencies, but I haven't bothered trying to calculate those values, so I went the lazy route and used other people's work.

The Pad is -30dB which is unity gain for this circuit. I used an H-Pad with the following values:
                           -Input (primary/secondary) - 390R, Bridge - 6.65R, Output (primary/secondary) - 82R-
This should be right at -30dB @1kHz.

The +48V indicator LED positive leg connects to the On position of the phantom power switch with a 2k4 resistor as the LED used is 20mA. There is a solder pad directly below R17 on the side towards the gain potentiometer which connects to the ground plane. I used this for the negative led of the LED.

Frank was kind enough to make me L-Brackets for this project, but that in addition to the faceplate allows only the minimum length of bushing on the pots to be exposed to fasten a nut to it. I had to flip some of the nuts over or use different ones to accommodate where the threads actually ended on the bushing. That might not make sense, but it will become very apparent if you decide to use an L-Bracket.

5mm spacers seem to be the correct length for attaching this board to an L-bracket.

All of the switches I used (except for the first one I built) are sub miniature C&K, which are very expensive for DPDT in this size. You can use the slightly larger miniature ones which will save you money, but the labels on the faceplate will get covered up by the mounting nuts and depending on which pots you use, the bottom corners of the switches will need to be sanded to fit. The holes drilled on the faceplate are to accommodate sub miniature toggles with bushings up to 5.20mm.

EDIT: EQ Bypass scheme doesn't quite work right as described or as I had previous drawn. See below.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on July 13, 2017, 01:38:01 AM
The EQ In/Out switch used were Grayhill SPDT's as they were the smallest ones I could find that would fit between P3 and P4. Even then, the inside terminal connections of P3 and P4 (I used the Omeg pots as specified) have to be trimmed to make enough room. To avoid destroying your pots like I did, trim the as much material as you can with some quality small side cutters and then make any final adjustments with a Dremel or similar tool. I tried to just do it all with the Dremel and ruined the connection points on the side I was trimming. I had to replace nearly all of the those pots. Solder leads onto the SPDT before installing it between P3 and P4. It will lay on the PCB. I applied some super glue to switch and adhered it to the board. I put the faceplate on and then used a small screw driver to push is as forward into the EQ in/Out hole on the faceplate as it would go and then let the glue set.

http://www.mouser.com/ProductDetail/Grayhill/34DWMSP12B4M7RT/?qs=sGAEpiMZZMvudeGI7i40XH5ikTL9b%2fLMCL3Hg40qXYo%3d

EDIT: EQ Bypass scheme doesn't quite work right as described or as I had previous drawn. See below.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on July 13, 2017, 01:45:46 AM
Here's a pic of the finished board. I'm just waiting on knobs and these are done. I do have a pile of OA10's to build to put in the 6 units I built. There are lots of off board connections so it gets a little challenging to keep it neat.

So there you go. It can be done, but does require some patience and paying attention.

Thanks a million to audiox for this project.

Thanks!

Paul
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on July 29, 2017, 01:27:16 AM
And finally finished.
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: dedaman on October 15, 2018, 04:07:33 AM
The Neumann OA10 could be one alternative:
http://groupdiy.com/index.php?topic=34105.0

Do you think the DOA be replaced by a NE5532 ? Wouldn't be an easier build?  Do you think it will sound too differently?
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: iprovlek on October 15, 2018, 09:46:59 AM
Potato Cakes strips looks great....
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on May 05, 2019, 02:31:29 PM
I dug these out to put them to use when I realized my initial EQ bypass scheme is not actually correct. It can create a low end popping sound when switching in/out. I'm trying to find a better way to do this within the parameters of the 500 series panels I have, but haven't found a way yet. The way I posted above will bypass the EQ as I confirmed it will pretty much work, but I don't believe things are being loaded properly. I'll keep poking around and when I find something I'll post it here.

Thanks!

Paul

EDIT: EQ Bypass scheme doesn't quite work right as described or as I had previous drawn. See Below
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on November 05, 2019, 12:52:10 AM
So it was pointed out to me that the EQ Bypass scheme doesn't quite work right as described or as I had previous drawn. And it can't be done simply by breaking the connection at C15 and jumping into R32 as the impedance isn't matched correctly at that point and there is a drop in gain. To do this correctly would require another op amp scheme to go directly from the preamp to a balanced output with the proper gain and impedance at the output stage. So I've abandoned needing to use an EQ bypass as the center detents for the frequency gain is near spot on, at least for me.

However, I do have one small thing that I have been unable solve. All but one of the six modules I've built have something slightly off when I sweep the mid frequencies while boosting the mid band. On the unit that is fully working, I can see the frequency selected being boosted with proportional bandwidth and that consistent when sweeping the full range. For the other 5 modules, when I sweep to the middle of the range (approximately 800-3k) the bandwidth is widened and is about 4 dB less gain than the working unit, but at the ends of the frequency range the EQ behaves exactly as is expected. The difference in how it sounds is more dramatic than how it looks on an analyzer. Gain, level, HF and LF all seem to be matched.

I've done the swapping of op amps replacing the pots in the mid band and have been making comparisons between the fully operation and slightly less operational units. Aside from a missing connection or a misplaced part which has yet to be seen, the only thing that remotely makes any sense is that there is some sort of phase cancellation going on in those specified ranges, but I wouldn't know where. The Mid section of the schematic is isolated from everything else, and there aren't many things to check, so I've been going around in circles hoping to find something new. It did occur to me that the unit that seems to have a fully working mid band could be the faulty one, but that would only make sense if the natural characteristic for this circuit is that the bandwidth widens and lessens in gain in the mid section. I've attached the portion of the schematic that has the gain, EQ, and output sections. As is, they all are working fine and I could put them back together and not think about the slight differences, but when doing listening tests the mid band seem more useful with the consistent gain and bandwidth as the fully working one does and I would like all of them to function accordingly. I could certainly use some fresh ideas where to do testing.

Thanks!

Paul
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: manulaudic on June 10, 2020, 08:35:40 AM
Hi, maybe someone can help me figure out what i've done wrong with this.
I've finished my units and everything works except the HPF.
I have soldered 100nf as well and wired the spdt switch so that lug 1 and 2 connect to the holes on the PCB.

I checked with the schematic but as that part of the design isn't drawn up, i'm not quite sure if i have it connected properly.

If someone can help me out would be great !
Manu
Title: Re: DIY 500 series STUDER 169 Recording Channel (Mic Pre + EQ) Documents Published!
Post by: Potato Cakes on June 30, 2020, 02:44:03 AM
I posted about this here:

https://groupdiy.com/index.php?topic=59616.msg840872#msg840872

I had to remove the jumper below DOA 1 to get HPF to work.

Thanks!

Paul