Results 1 to 7 of 7

Thread: weird solid state amp with interstage transformer

  1. #1
    Junior Member
    Join Date
    Nov 2018
    Posts
    7
    Thumbs Up/Down
    Received: 0/0
    Given: 4/0
    Rep Power
    0

    weird solid state amp with interstage transformer

    I got this nearly 40lbs chunk of metal on my table that appears to be some kind of 400W amp. Looks like a Bell Labs creation circa 1970 and described on this page. Does anyone have a schematic for this thing? The one on the page linked above became "404".

    0 Not allowed! Not allowed!

  2. #2
    Supporting Member
    Join Date
    Aug 2017
    Location
    Portland, OR
    Posts
    721
    Thumbs Up/Down
    Received: 255/1
    Given: 106/2
    Rep Power
    3
    Was it made by Bell Labs or is it a bell ringer (or bell tower) amplifier? Google tells me that Verdin is a bell, carillion, and organ company. Seems many of their amplifiers were made by McIntosh.

    0 Not allowed! Not allowed!

  3. #3
    Junior Member
    Join Date
    Nov 2018
    Posts
    7
    Thumbs Up/Down
    Received: 0/0
    Given: 4/0
    Rep Power
    0
    Your question prompted further sleuthing and I believe you're right. It appears to be a clock tower amp made by Bell Electronics (now possibly Abell Electronics) not Bell Labs. The wiring is very tidy; the conduits are appropriately twisted and the layout is nice and tight. This indicates the designer understood parasitics. I'd like to get it hooked up to hear what it sounds like. Other strange things about this amp beside the interstage tranny are its 4 pin power input and 1V max signal input. It shows 70V on its panel which could either be its rails or its swing. I might be looking at a class A amp. Anyone else have a clue about this thing?

    0 Not allowed! Not allowed!
    Last edited by Dulles; 11-09-2019 at 07:02 PM. Reason: spelling

  4. #4
    Stray Cap DrGonz78's Avatar
    Join Date
    Oct 2011
    Location
    Scottsdale, AZ
    Posts
    2,145
    Blog Entries
    1
    Thumbs Up/Down
    Received: 349/5
    Given: 239/0
    Rep Power
    11
    Isn't 70v the output used for outdoor speakers or something?

    1 Not allowed! Not allowed!

  5. #5
    Supporting Member
    Join Date
    Aug 2017
    Location
    Portland, OR
    Posts
    721
    Thumbs Up/Down
    Received: 255/1
    Given: 106/2
    Rep Power
    3
    Quote Originally Posted by DrGonz78 View Post
    Isn't 70v the output used for outdoor speakers or something?
    https://www.belden.com/blog/broadcas...peaker-systems

    3 Not allowed! Not allowed!

  6. #6
    Junior Member
    Join Date
    Nov 2018
    Posts
    7
    Thumbs Up/Down
    Received: 0/0
    Given: 4/0
    Rep Power
    0
    Very illuminating, thanks. So is the interstage transformer in the unit a global audio line transformer output that eliminates the need for a speaker to have its own transformer or just the 70V interface that allows the speaker with transformer to connect to it?

    0 Not allowed! Not allowed!

  7. #7
    Supporting Member
    Join Date
    Mar 2018
    Location
    Germany
    Posts
    2,382
    Thumbs Up/Down
    Received: 1,808/1
    Given: 1,033/2
    Rep Power
    5
    Quote Originally Posted by Dulles View Post
    I got this nearly 40lbs chunk of metal on my table that appears to be some kind of 400W amp. Looks like a Bell Labs creation circa 1970 and described on this page. Does anyone have a schematic for this thing? The one on the page linked above became "404".
    The link in the other forum doesn't open.
    Are you sure that it's an interstage transformer and not an OT? What's its size, can we see pictures? Where is it connected?
    A 70V line only makes sense for power distribution - not for signal level. Typically the amp has a step-up OT and each speaker a step-down transformer.

    https://en.wikipedia.org/wiki/Consta...speaker_system

    1 Not allowed! Not allowed!
    Last edited by Helmholtz; 11-09-2019 at 09:58 PM.
    - Own Opinions Only -

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Interstage transformer
    By mozz in forum Theory & Design
    Replies: 4
    Last Post: 11-19-2017, 04:20 AM
  2. interstage transformer
    By uneumann in forum Theory & Design
    Replies: 16
    Last Post: 03-10-2014, 07:48 PM
  3. Epiphone EA-50T Interstage Transformer
    By Ted in forum Vintage Amps
    Replies: 5
    Last Post: 03-20-2013, 08:57 PM
  4. Power transformer for solid-state amp?
    By TheEHMan in forum Maintenance, Troubleshooting & Repair
    Replies: 5
    Last Post: 08-03-2012, 06:48 PM
  5. Interstage transformer primary question
    By Groover in forum Theory & Design
    Replies: 2
    Last Post: 03-04-2009, 06:17 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •