Jo Tech Service   Joar Falstad



New audio hardware.

Idea & solution by
Joar Falstad.   
Jo Tech Service 

Strong pass audio filter, with adjustable setting of minimum pass level.
This high speed, analogue system will strongly reduce  any audio signal below the preset minimum level , also inside a message .

Live /  real time   noise & hiss reduction / removal  /  cleaner /  filter  /  limiter  / blocker

No signal delay.  No change in pitch or tone balance .

Measured  audio
reduction outside pass level:   up to  100 x  or   20db
audio reduction outside pass level to come.
Strong pass audio filter test  :

Demo video , youtube

Test version.

Line input  0.3 -  0.75Vrms
Max signal 4Vrms
All versions have  galvanic insulated output, using a  signal transformer.

Read more   /   some video examples :
Real time analog audio   noise and hiss cleaner ,

Later version

One ch.  audio
background noise  cleaner.

A similar  stereo version is now in the making.

Service  &  Repairs


A Pilot 240B for test and repair,   just something to memorize.
This unik valve stereo amplifier is now back in action, after a long rest. 
One of the best amplifiers  in any class. 


The Beard   P35
most other  VALVE audio   amplifiers   have Direct Coupled audio signal inputs.

Note!      DC
audio signal inputs are not compatible with audio signal outputs found on modern preamplifiers or pc earphone output . 
 A DCvoltage pulse of several volts from a pc or modern preamplifier at Power ON, to this type of signal input can overload and damage the valve in the input stage

Convert to AC audio signal inputs .  Capacitors  is  a hint.

Note!  High Voltage inside the amplifier

elf oscillations in the amplifier.

Some input stage valves, mainly triodes, have internal positive feedback , this can be locally neutralized.
You'll get the best overall result by doing just that, before adding other oscillation cancelling parts in the input or feedback circuit.

Natural, non colored, high quality sound.
Even to day,  a good quality VALVE amplifier  has the best soun
d . 
High end 
amplifier  update
Sony  TA - 5650  Vfet pre & power amp

drifting bias fix.

Mosfet pre & power amp
 Great sound quality .  
 Hot inside, possible to fix.

Sony TA - 1120A
Solid state
pre & power amp 
 Great sound quality .


We are all most creative when we are "forced"  to find a solution .

Some older  ideas and solutions
, composed at our workshop.

Industrial Hardware.

-  analog multiplexer
Idea & solution by Joar Falstad

Industrial Analog Multiplexer
Detailled schematic examples
0 - 10V  /  4 - 20mA

Windows Program  +  industrial standard digital i/o hardware

Idea, design and programming by Joar Falstad

Advanced Public Address System   

Speakers  are included and arranged as group names. Latest USB-version has a capacity of more than 32000 patterns.

Manually speak to the addressed group.
play a prerecorded message, to the addressed group of speakers.     USB ver.
21 timecontrolled   fixed  announcements, will automatically Play a prerecorded message, to the addressed group of speakers.
Timecontrolled announcements,   w/separately file controlled speaker group addressing .
Sensor control will activate, log and play a prerecorded alarm message, to the addressed speaker groups.

Later version , USB

PC controlled. 
Detailled schematic examples.
ISA demo version download
First ver : ISA  Win95.  
Latest ver :  usb Win7
PC interface: Advantec USB 48ch DIO
Inputs and Outputs: Advantech PCLD-8761   24 ch. input / 24 ch. output .   Tested ok.


Windows Program   +  industrial standard  analog i / o hardware

Idea, design and programming by Joar Falstad

AD/DA Conversion and Data Acquisition made easy.
Easy setup. Easy to run and control.

Time and Masterfile controlled AD-DA conversion ,
Easy setup. Easy to run and control.
The Masterfile
is generated by the program itself , as a linear "Unit Value" function from a Time ref to the next "Unit Value" at the next Time ref.
There is no limit in number of Time ref's  from tne project start time to the final stop time.
PC clock is used to control the Time

First ver : ISA , Win95 .  Early demo version download
Next ver : PCI , Win98 . Plug & Play.
We are now working on a USB ver in Win7

Win 7  Program.     USB - DMX hardware

DMX  stage  lights control .

For your own and PC safety:   Use an insulated DMX USB interface . 

Program has separate  control of all spots .
Not designed for disco.

Stage & other  . 
How to connect  & more 

Free link to:  
Enttec  compatible  DMX    open source VB6  program download .  1ch. to 512 ch.
  Tested OK with :  Win XP + VB6 runtime files + VB6 installed on your computer

Free download:    DMX program
. Compatible with most DMX controllers.
Tested OK with :  Win XP  + downloadable   VB6 runtime files installed on your computer.

Enttec or compatible,  like Splabs DMX.
Insulated USB - DMX controller.    1 - 512 ch. 
Insulation USB to DMX output line connection  1.5KV
Internal 512 cannels memory w/repeat.
Works with most DMX programs.
Ask us

Ships alarm schematics and more


Vingtor, Stentofon

Old / obsolete intercom systems.  Replacements. Repairs.

Compact 32-2  /  VMP32-2
Old / obsolete intercom systems.  Replacements. Repairs
This system is still used on ships.

Power OFF when plugging / unplugging any board.
If done with power ON, most IC's  on the actual board
will blow
Some IC's are hard to find. 

Fixed repair prices , exclusive MVA / VAT   2017 / 2018 :

Examination of all boards in the VMP-32 exchange + message / mail to the customer  NOK1500.-

CPB / CPB-2 repair  NOK6500.-
SLB / SCB / PRB / RPB repair /  Each board   NOK3500.-
mark all SLB boards with a position number.

Station indoor, desk or wall, w/handset  :   VMP 619
Cable from station VMP 619 to old modular 4pole  wall socket , found on ships:  NOK150.-
Zenitel, AlphaCom,  ACM  

Later systems, often used on ships.  
Replacements. Repairs.
Manufactured also today . 
Compatible with Vingtor & Stentofon  wireing and stations.

Power OFF when plugging / unplugging any board inside the exchange.   
If done with power ON:   the actual board is damaged beyond any repair + possible damage to other boards!

Monacor Catalog  
We are one of several Monacor suppliers in Norway.

100Volt line. Pa speakers & amplifiers .
Monacor stage audio and DMX light equipment
Alarm systems ,  video , backup  , ip adressing, wireless and more.


Domain:     ( registered on 20-03-2001

contact:       Joar Falstad

phone:          +47  99718408



Company:     Jo Tech Service  Joar Falstad, Lykkmarka 53, 7081 Sjetnmarka, NORWAY


A big  company has now taken the  same domain name  . " jotech "
To protect our site  and  keep it seen on the internet , we'll  continue to add nice pictures , mostly from Norway.

 Norway , Trondheim

Morning view .
Norway, Lyngen alps  , Havnnes , Rotsund , Nordreisa

Norway, Ekne Falstadberget
Nostalgy from the 70's.  With Vital 15 feet

South Africa .  Cape Town

South Africa .  Cape Town

South Africa .  Cape Town

South Africa .  Cape Town

South Africa .  Cape Town

Norway , Malvik, the ghost tree

History . 
Windows95 , ISA controllers, homemade hardware ,  programming in Visual Basic 3