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Wohler B&B AM-2B Phase Scope Repair

When mixing there is a tool outside of your DAW to view the image of the stereo span. Here is the Wohler B&B “AM-2B” phase scope. It takes a stereo signal and transforms it to a visual representation of the pan stereo signal showing the spread of high and low frequencies. Essentially when you mix if it’s squashed it will look flat and when the tonality and stereo range is wide you will have a nice circular representation. This rack mount unit is super and has never let me down as long as its properly calibrated. (See rare attached manual for info). For this unit I replaced the power supply and also decided to replace the bridge rectifiers. I was able to source the exact power supply from the supplier Frost Magnetics in CA. They happened to have 2 original NOS on their inventory shelf. The units are not cheap but if you can get one for little and fix it’s so worth it. 🙂

Main Board Header
Old Power Supply
New Power Supply Top
New Power Supply Bottom
Inside Unit
Replaced Bridge Rectifiers
Main Board Back
AM-2B Service ManualDownload
AM-2B Tube Schematic D10-181GYDownload
AM-2B Tube Sheet D10-181GY_1988Download
D10Download

I was recently asked about this transformer shown above. I also have seen this model installed in some of these units. Please use the below photos for reference.

Eurorack-Modular for Guitarists and Beyond

For the longest time I’ve always been a traditional effect pedal fanatic for guitar, keyboard, bass and vocal rig setups. Recently I was intrigued by my friend Tada at BPNYC, explaining to me the flexibility, compact size and capabilities found in today’s modern eurorack-modular options. For a list all all boutique gear across the board including eurorack-modular please visit http://www.boutiquepedalnyc.us/ As a pedal board layout enthusiast, I was always faced with the problem of manufacturers custom sizing their brands of effects pedals. This always became challenging to find the correct layout for transport and live situations. For many years we have used standard 19″ racks in studios to stack our expanding collections of gear. The Eurorack format calls for modules of 128.5mm (slightly over 5″) height. Horizontal width is measured in “horizontal pitch”, where 1 HP = 5.08mm (exactly 0.2″). 3.5mm mono phone jacks are used for interconnection.

The physical specification is based on the Eurocard standard of:

  • 3U (133.4mm), where height “U” is measured in rack units, rounded for a lip.
  • 1HP (5.08mm), where width “HP” is measured in horizontal pitch units, rounded down. A card width is integer multiples of 1HP.

Eurorack modules may be further characterized by depth: shallow modules (2.5cm to 4cm[1]) can fit into “skiff” cases.

So through the past couple of years, musicians have been migrating away from laptops on stage using VST plugins to complex stompbox pedals in various shapes and sizes. Now that Eurorack-modular suppliers have grown and the new smaller standard has been adopted + quadrupled in complexity will we soon see musicians wearing their controls for live gigs into the expanse of this ever changing music technological period?

Below is a video clip of Tada from BPNYC demonstrating the possibilities of a eurorack-modular guitar rig setup. It was exciting to see the ranges and depths with just a few of the possible units that one can aquire to expand their musical inspiration. http://www.boutiquepedalnyc.us/eurorack-modular/

Erica Synths Plasma Drive

Special thanks to Tada at BPNYC for letting me demo Erica Synths Plasma Drive. Super cool pedal released early this year, it boosts audio signal to 3000V and transforms it into a series of continuous high-voltage discharges in a xenon-filled tube. You can check out more info here https://www.ericasynths.lv/news/plasma-drive/ Additionally you can get from my favorite distributor here http://www.boutiquepedalnyc.us/gamechanger-audio-erica-synths-plasma-drive/

Mesa Stereo Simul-Class 2: Ninety

Replacing my FET power amplifier that drives my “Studio Mains”. Upgraded the reserved 2U space in my rack with the Mesa Stereo Simul-Class 2: Ninety. I’ve choosen the second version of this Mesa because on the back of the unit you will see a selector switch for Instrument/Line & Lift/Ground. This allows me to easily integrate. Soon I will construct a custom foot-switch to change amp modes. Below you will find some inside unit photos and the manual.

Stereo Simul 2-90 ManualDownload
  • Mesa Ninety I
  • Mesa Ninety II

Casio SK-1 Bluetooth Mod

This is a very simple mod to make your Casio SK-1 even more functional. This add on allows you to transmit and receive audio from your phone or device to your SK-1. In this setup the board assembly I used fit in easily and came with a battery source. You will need to make a small cutout on the back and remove 2 back panel plastic mounts. I soldered wires to the momentary switch for on/off/pair control and mounted it to the side. Alternatively you can solder wires to the in & out of the Bluetooth module and attach them directly to the terminals of the SK-1 in/out jacks thus eliminating the hole in the back.

Carvin RX1200 Powered Mixer

This is a high power mixer with flexible routing. This unit had an issue where it would not power on. On the main power input board the relay failed and melted the power switch to the terminals and destroyed the relay and ceramic resistor. The fuse installed was rated too high and it never blew protecting the circuit.

This units design does not allow you to easily replace the fuse because it has high voltage inside. Use all precautions when opening! After opening the unit remove the control face. Then remove the power plug screws, 1/4″ input nuts, and board mounting screw from inside. To remove the board you would have to pull the board from the power switch lugs. In this case the damage was so bad I had to cut the bezel away from the power switch and the slide the board out. At that point I reworked the board to clean it up and ready for new installed parts.

Here is the schematic for the Power Input Board

16448D Schematic rx1200Download

Building a Test Rack Stack for Fixing Audio Equipment

Fixing electronic audio gear can be difficult without some good testing equipment. It is important to first consider what it is you wish to repair and which equipment is specifically needed to accomplish those tasks. On a basic level, you first want to start with a multi meter especially one that can measure capacitance, transistors and diodes. Then an oscilloscope can measure the shape of your signal. In this setup example I have a Frequency Generator, Audio Oscillator, Audio Power amplifier, Jitter Meter, Resistor Decade Box, Distortion Meter, Frequency Counter, Flutter Meter, Audio Oscilloscope, AC Variac, Variable DC Power Supply & AC Outlet connected to the AC Variac Output. 

Here are some of the manuals of the equipment in this setup.

Agilent 3325ADownload
ShibaSoku_AD725DDownload
Racal_1990Download
Matsushita_VP-7721Download
Leader_1851Download
Crown_XLSDownload

SAMSUNG CSC