Mastering Stereo Insert Switcher with Flip Construction Information

[mediatechnology]

KA Electronics/Rockmore-Labs introduces the Stereo Insert Switcher designed by Markus Samper aka majestic12.

This is the construction and application thread for the Stereo Insert Switcher.

Mastering Stereo Insert Switcher PC Board: https://ka-electronics.com/shop/index.p ... rch=insert

Features

Full bypass with fully-balanced hot/cold switching. Fully passive.
Two Inserts with Flip.
Backbone signal flows through the connections on the left to the right.
Insert connections are on a 25 pin D in a modified Tascam format.
AES Tascam-format DB-25 breakout cables from Hosa (AES-803T), Mogami (GOLD AES TD DB25 XLR-03), Planet Waves and others may be used. (To use AES cables with the Insert Switcher the male and female XLR breakout connectors need to be reversed.)
Normal signal flow is Left/Right In > Insert 1 > Insert 2 > Left/Right Out.
Flipped signal flow is Left/Right In > Insert 2 > Insert 1 > Left/Right Out.
Cascadable using additional boards in series for more backbone inserts.
Configurable as an three Input Selector using the backbone and return inputs.
Sealed low signal current relays.
Socketed relays are user-replaceable.
No logic required: Uses sustained/latching SPST push button or toggle switches.
LED outputs. (Current-limited to 10 mA; 24V/2K21Ω.)
Isolated audio, relay and chassis grounds.
Series-parallel coil connections reduce power consumption and heat.
Relay coils are 12V, control supply is 24V.
Can be powered from low-cost 24V switching supplies.

Mechanical and Power Specifications

Board Size: 3.8" x 2.75"
Mounting holes: M3 0.125" diameter on a 3.5" x 2.45" pattern.
Assembled Board Size: Height: 0.7"; Depth with DB-25 Connector 4.0" overall, 3.8" depth behind panel.
Power Requirements: Coil current using Omron G5V-2-H1-DC12 relays, 14 relays and 3 LEDs on, 120 mA typical 2.82 W. Low sensitivity relays are not recommended as they consume 7.7 W under similar conditions.

Bill of Materials

Update 4/27/23. Added Phoenix connectors and relay sockets to the Mouser Project Manager BOM: https://www.mouser.com/ProjectManager/P ... e32774ab41

The insert switcher can be built as a two insert switcher with flip, an insert switcher without flip a single insert/bypass or two independent insert/bypass..
The bill-of-materials is for a two insert with flip.

The Mouser BOM cannot be edited.
To edit, load it into the shopping cart.
Remove the number of relays as needed.

A fully-configured switcher uses 14 relays.
Without flip 8 relays are required.
A single insert uses only 4 relays.
For XLR I/O or hardwired applications do not install the 25 pin D connector and wire directly to the board.

A Mouser bill-of-materials with 14 Omron relays is here: https://www.mouser.com/ProjectManager/P ... 446ab230fc


Stereo Mastering Insert Switcher PC Board, Fully Balanced, Passive, Two Insert with Flip.

Schematic


Mastering Insert Switcher Schematic, Audio Flow, Sheet 1

Larger Image: https://www.proaudiodesignforum.com/ima ... heet_1.png


Mastering Insert Switcher Schematic, Relay Coil Wiring, Sheet 2

Larger Image: https://www.proaudiodesignforum.com/ima ... heet_2.png

V1.2 Board


Mastering Insert Switcher Schematic, Relay Coil Wiring, Sheet 3

Larger Image: https://www.proaudiodesignforum.com/ima ... heet_3.png

A note about relays

The relay coil requirements are 12V.
The control supply is 24V: A series/parallel connection is used to reduce current.

The Mouser BOM specifies Omron G5V-2-H1-DC12 "H1" high-sensitivity relays.
With all relays engaged the 24V supply current is about 135 mA.

Panasonic DS2Y relays are polarity sensitive.
On boards before V1.2:
Do not use Panasonic relays unless you intend to reverse the control supply, diode and LED polarity.
Omron, Fujitsu, Takamisawa etc. do not have a coil polarity requirement.

On V1.2 boards Panasonic DS2Y relays may be used.

Two Inserts with Flip


Stereo Mastering Insert Switcher PC Board Stuffing Diagram.

DB-25 Insert Connector Pinout


Stereo Mastering Insert Switcher PC Board, Tascam DB-25F Breakout Cable Pinout

You can get breakout cables here:

The insert switcher uses a female DB-25.
Planet Waves provides breakout cables which are also DB-25F.
To use the breakout cables male-to-male snakes are available in various lengths from 5-25 feet.

Female DB25F to Stripped Ends: http://www.amazon.com/Planet-Waves-PW-C ... B001PGXIUM
Male DB25M to DB25M 5' Snake: http://www.amazon.com/Planet-Waves-Modu ... B001G7J2EG

Relay and LED Connections


Stereo Mastering Insert Switcher PC Board, Relay Control and LED Connector Pinout

Other Configurations

To eliminate the Flip function do not install six relays.

The normally-closed contacts of the flip relays are jumpered (shown in pink).
The relays that are used are RE3, 6, 9, 10, 11, 12, 13 and 14.
The relays that are not used are RE1, 2, 4, 5, 7, 8.

Two Inserts without Flip


Stereo Mastering Insert Switcher PC Board Stuffing Diagram without Flip.

Single Insert or Full Bypass

The normally-closed contacts of the Insert 2 and flip relays are jumpered.
Install relays at RE3, 6, 10, 13.
The relays that are not used are RE1, 2, 4, 5, 7, 8, 9, 11, 12, 14.

Split Backbone. Two Independent Full Bypass.

I/O points are at the flip relays.


Stereo Mastering Insert Switcher PC Board Stuffing Diagram for Split Backbone. Useful for Two Independent Full bypass.

Larger version: https://www.ka-electronics.com/images/j ... _Large.jpg

[mediatechnology]

This is the Insert Switcher V1.2 silkscreen showing polarity reversal of the +24, SWT Gnd and diodes to allow the use of Panasonic relays.

[mediatechnology]

Just learned that Panasonic has changed the status of the DS2Y relay series to "not recommended for new designs" in anticipation of their eventual discontinuation.

Omron and Fujitsu/Takamisawa relays can be used.

The following are the high coil sensitivity 12.5 mA/150 mW versions:

Fujitsu RY-12W-K (Mouser 817-RY-12W-K). https://www.mouser.com/ProductDetail/817-RY-12W-K
Data sheet: https://www.mouser.com/datasheet/2/164/ry-914629.pdf

Omron G5V-2-H1-DC12 (Mouser 653-G5V-2-H1-DC12). https://www.mouser.com/ProductDetail/653-G5V-2-H1-DC12
Data sheet: https://www.mouser.com/datasheet/2/307/ ... 536510.pdf

I'll leave the Mouser BOM as-is to use Panasonic relays while they're still available.

[mediatechnology]

Mastering Stereo Insert Switcher Test Connector

I don't sell many assembled and tested Insert Switchers because they're an easy build and most people buy unpopulated boards. But, when I do build them, testing with an Ohmmeter requires a lot of concentration to check every possible path.

Fortunately I found a simple and easy way to check them to catch any missed solder connections or a bad relay. Neither has actually occurred - but I test them anyway after assembly.

What I came up with is a connector with 100Ω resistors from Hot and Cold on Insert 1 and 200Ω resistors on Insert 2. The resistors are installed on both the sends and returns. For testing the backbone input path a 300Ω resistor is installed on the backbone output.







Connecting an Ohmmeter to the Hot and Cold backbone inputs allows the resistors in the send path to be read through all the contacts.

When the Inserts are Off the backbone input reads the 300Ω output termination. (This checks the entire NC contact path.)
Engaging Insert 2 reads 200Ω.
Engaging Insert 1 reads 100Ω.
Engaging Flip, with both Inserts 1 and 2 On, switches the reading from 100Ω to 200Ω. (Showing that Insert 2 is first in line.)

By moving the 300Ω resistors to the backbone input and the Ohmmeter to the backbone out the returns can be checked.

When the Inserts are Off the backbone output reads the 300Ω input termination.
Engaging Insert 1 reads 100Ω.
Engaging Insert 2 reads 200Ω.
Engaging Flip, with both Inserts 1 and 2 On, switches the reading from 200Ω to 100Ω. (Showing that Insert 1 is last in line.)

Using this method the test time drops from 10-15 minutes and a lot of brain cycles to about 2 minutes. At the cost of a used re-purposed DB-25M and about 10 resistors its worth it. For someone building several insert switchers you might want to make one of these up. Better to find the unsoldered or bent pin or a bad relay before assembling several boards into the case.

[bobkatz]

Hi Wayne and all! I have a "special" application for this board.

I have a pair of Classic Western Electric 111C transformers. I want to create a box that uses these transformers for color. It will have a bypassable series input resistor, a rheostat (two terminals of a pot) from 0 to 2 kohms. And if possible, a switchable 600 ohm termination.

OK, here's my plan:

For the series resistance, it's easy, put the pot on insert #1. Put the transformers on insert #2.

For the switchable load resistance, I wonder if I can modify the flip function. Disable the flip function and use the flip function to put a 600 ohm resistor across the output of the transformer. Do not insert the first flip relay (RY1). Jumper the NC contacts on the board for the first flip relay. Do not insert the second flip relay (RY2) and jumper its NC contacts.

Now for the termination resistor. I wonder if I can adapt the third flip relay to terminate the transformers with an optional 600 ohm resistor. I'm thinking out loud here: Cut the trace from pin 8 of RY4 leading back towards RY1. Cut the trace from pin 9 of RY4 leading back towards RY1. Connect pin 4 of of RY4 to OUT +. Connect pin 13 of RY4 to Out -. Put 600 ohm resistor across pin 8 and 9 of RY4.

Repeat for right channel.

[mediatechnology]

Hey Bob thanks for dropping in!
I'll have to wrap my head around the board mods.

Are you sure its possible to actually get color out of a "big iron" 111?
There was a recent post at DIYAudio about that and the level of power it would take to saturate it, if at all, required IIRC a bridged 75W power amp to get enough drive voltage.
I need to find the 111 distortion plots showing it could handle ridiculous levels of signal without color.
You might want to look for a softer target.

I'll see if I can find that link at DIYAudio.

[mediatechnology]

Its a long thread: https://www.diyaudio.com/community/thre ... bu.385849/

[bobkatz]

Hey Bob thanks for dropping in!
I'll have to wrap my head around the board mods.

Are you sure its possible to actually get color out of a "big iron" 111?

Nice to be here, Wayne. Hope you are well. Excellent point. Thanks for the link from DIY audio. I am looking for subtle color, but depends on how subtle we're talking about. To be honest, I haven't tested the 111 yet with this series resistor approach. Here is the spec on a Jensen transformer that's got less headroom than the 111, with different source resistances: Jensen JT-11-11SSP-7MPC
Data sheet at https://www.jensen-transformers.com/wp- ... p-7mpc.pdf

Before I commit to the 111 I will have to test this circuit! I don't think the DIY thread even considered using a build out resistor. That could be the trick to make a silk purse into a sow's ear.

My mastering system's peak level is +18 dBu, quite conservative for this transformer. Worst case scenario I can replace them with a cheap model and keep the rest of the circuit. It'll be less labor for me to use a cheap transformer instead of designing a high headroom, high gain feed amp and then an output attenuator from the transformer.

And public thanks to Bill Whitlock for advice on making a transformer do "color".

[bobkatz]

BTW, the termination resistor idea is meant to linearize the transformer so I might be able to get away without the switchable termination since I'm looking for color.

[bobkatz]

Regarding the board mod to adapt the flip to being the termination resistor. I might have to give it up because with the relay coils being in series, it looks like RY4 and RY8, which I want to keep, are involved in that series/parallel arrangement. It looks like I would have to do a lot of whacking and slashing to power just RY4 and RY8... the schematic for the series/parallel coils is starting to give me a headache.