Results 1 to 8 of 8
Like Tree2Likes
  • 1 Post By g1
  • 1 Post By darkfenriz

Thread: Randall RG75 G3

  1. #1
    Supporting Member
    Join Date
    Dec 2009
    Location
    UK
    Posts
    2,891

    Randall RG75 G3

    Has anyone got the schematic for this amp? - this is the one with the 12AT7 in the power amp. The schematic is one of those that got lost a few years back.

  2. #2
    g1
    g1 is offline
    don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    8,852
    J M Fahey likes this.
    Certified Dotard

  3. #3
    Supporting Member
    Join Date
    Dec 2009
    Location
    UK
    Posts
    2,891
    I'd already looked at that one, but didn't notice the power amp was over two pages first time round. How dumb is that? Thanks for the reply. Interesting filter section feeding the tube (IC3/IC4) with the simulated inductors. Funnily, the owner of the amp complains that it sounds like a filter or wah is engaged all the time. I guess it is.

  4. #4
    Old Timer
    Join Date
    Dec 2007
    Location
    Poland
    Posts
    1,500
    I think that this is the same as in L5 Lab Series amp. But in the amp there was a pot to adjust the filtered signal (or disable it).

    Mark

  5. #5
    Senior Member
    Join Date
    Jun 2007
    Posts
    598
    Quote Originally Posted by MarkusBass View Post
    I think that this is the same as in L5 Lab Series amp. But in the amp there was a pot to adjust the filtered signal (or disable it).
    Randall's filter simulates the response of an amp with high output impedance driving a speaker load: Basically upper high frequencies are boosted, and low frequencies at somewhat narrow band.
    Lab Series "Multifilter" was a comb filter that mimicked "cone nodes" of loudspeakers: The uneven frequency response the driver starts to introduce near its response's high frequency limit.
    So no, not the same function.

    I wonder... Has anyone else noticed that these newer "OEM:ed" Randall preamp designs are cloned from Fender's SS amps? Fender has been relying and following that preamp architecture for over 30 years.
    Last edited by teemuk; 06-13-2017 at 03:56 PM.

  6. #6
    Member
    Join Date
    Apr 2015
    Posts
    59
    Quote Originally Posted by teemuk View Post
    Randall's filter simulates the response of an amp with high output impedance driving a speaker load: Basically upper high frequencies are boosted, and low frequencies at somewhat narrow band.
    Lab Series "Multifilter" was a comb filter that mimicked "cone nodes" of loudspeakers: The uneven frequency response the driver starts to introduce near its response's high frequency limit.
    So no, not the same function.

    I wonder... Has anyone else noticed that these newer "OEM:ed" Randall preamp designs are cloned from Fender's SS amps? Fender has been relying and following that preamp architecture for over 30 years.
    Ha ha, exactly.

    Not only it looks copied circuitry (with some changes to switching channels and they forgot to redraw one crucial resistor in fender's input bootstaping stage), but also drawn in a similar style, which would suggest redrawing without understanding. Checked side-by-side with Fender Stage schematic, which is very typical for Fender solid state circuitry past decades.
    g1 likes this.

  7. #7
    Old Timer
    Join Date
    Dec 2007
    Location
    Poland
    Posts
    1,500
    Quote Originally Posted by darkfenriz View Post
    Checked side-by-side with Fender Stage schematic, which is very typical for Fender solid state circuitry past decades.
    I'm not able to find the filter that we are talking about on the Fender Stage schematic. Can you post a schematic of the amp with this filter?

    Mark

  8. #8
    Member
    Join Date
    Apr 2015
    Posts
    59
    Mark,

    Fender and Randall preamps are similar - that's what I mocked on.
    I believe that you're talking about the filter in the power amp section that I honestly didn't look at.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Randall RG75 G3 Combo amp
    By andywragg in forum Maintenance, Troubleshooting & Repair
    Replies: 18
    Last Post: 06-30-2016, 06:36 PM
  2. Randall RG75 G3 Plus
    By diydidi in forum Schematic Requests
    Replies: 4
    Last Post: 03-21-2016, 02:33 PM
  3. Randall RG100 G3 plus
    By suhogruz in forum Schematic Requests
    Replies: 0
    Last Post: 11-30-2013, 06:57 AM
  4. Randall RG75 Schematics-PT specs
    By Robert M. Martinelli in forum Schematic Requests
    Replies: 7
    Last Post: 01-19-2011, 02:52 PM
  5. Randall RG200 G3 Low power
    By reflection77ca2000@yahoo.ca in forum Maintenance, Troubleshooting & Repair
    Replies: 9
    Last Post: 10-15-2009, 11:18 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
  •