About ISDN & IP Sessions

Information you need to know about ISDN sessions

ISDN Studio Plymouth, Devon

At our ISDN Studio Plymouth we have facilities supporting all codec options with the option for self-operation, or with an engineer taking care of all levels from the control room. We can establish audio/video Source Connect, SKYPE and phone patch links with multiple directors/contributors located elsewhere

What is ISDN?

Simply put, ISDN is an enhanced phone line which allows the transmission of audio at up to 128k, or much higher when using IP (see below).

Our ISDN line and specialist equipment at our ISDN studio Plymouth enables us to connect to similarly equipped studios, broadcasters, advertising agencies, actors and voice-over artists the world over from our ISDN Studio Plymouth.

Why use ISDN / IP?

In a word… convenience! It enables the receiving studio to record at their end in real time and have the files instantaneously. The voice quality between the artist and the remote studio director is also far better than over a phone patch link or SKYPE.

Uses for an ISDN connection

  • Record a commercial voiceover locally without having to travel.
  • Promoting a book or record? – Make a live studio quality insert to almost any radio station, or even lots of stations one after another.
  • Direct a session from anywhere in the world when you can’t get to the studio in person.
  • Add a well known voice to your advert or TV programme – Many famous voices have ISDN at home, we can hook up directly with them.
  • Play a mix to your record company, then adjust it in real time if they suggest changes.

What is the quality of ISDN audio?

128k at 48k sample rate using MPEG Layer 2 (MPEG 2) is the best quality you can get from ISDN and the noise floor is low enough for most professional uses. Most of our voice-over sessions will connect this way. It uses the full bandwidth available to make a single mono signal as good as possible.

What if I want higher quality?

Then there are 2 options.  At our ISDN studio Plymouth, the systems we use to encode and decode audio to send / receive audio will also transmit over IP via a broadband connection.

You may use Source Connect ‘Now’ via a web browser which will connect up to 256K.  (log on details at the bottom of this page)

ISDN Studio PlymouthAlternatively you can use Audio TX. Again, this is now pretty common in many studios and is slowly replacing older hardware. Technically using this system it is possible to transmit at uncompressed 48k, although this can be (and usually is) problematic if there is heavy broadband usage in the area at either end.

From out ISDN studio Plymouth we have found that we can comfortably transmit at 320k, which is significantly better than over ISDN and noticeably better. In fact you would be pretty hard pushed to notice any difference between this and an uncompressed bitrate and so recommend this where possible.

There are no additional phone call fees for transmission over IP.

Failing this, and/or for the best possible quality, we can also record the session locally (whilst still maintaining an ISDN/IP Link for high quality monitoring and reference recording purposes to you) and then send you the files via FTP immediately after the session.  With the recent advancements in high speed broadband and file transfer websites, this now makes it possible to forward the uncompressed recorded files within a matter of minutes which makes sense for any serious project and is strongly recommended.

  • ISDN (128k) 11% 11%
  • IP (320k) 28% 28%
  • Uncompressed (1152k) 100% 100%

Connecting to our studios with ISDN / IP

  • ISDN number +44 (0)1752 569018
  • Landline Number +44 (0)1752 562670
  • IP (via Audio TX) – connects using the remote studio’s current IP address. Go to http://whatismyipaddress.com to determine this and let us know
  • IP (Source Connect Now) – ONLY via Chrome browser. Go to: https://now.source-elements.com/#!/guest
    User name: aprilmedia
    Passphrase: We will provide you with a passphrase to access the session



At our ISDN studio Plymouth, we can print last minute script changes for the VO talent. We also can provide a laptop in the voiceover suites, or a video feed from our control room monitors to display scripts or other media as required.


Take a look at our FAQ page for technical information on ISDN/IP sessions