How many are missing out on patched channels on Deluxe Reverb?

Discussion in 'Ampage Area' started by Gretschmen65, Nov 23, 2020.

  1. Gretschmen65

    Gretschmen65 Country Gent

    May 20, 2016
    QLD Australia
    For those who have had the enjoyment of patching the channels on the Tweed Bassman and other Tweed amps where this option is available, they know how full and rich the tone can be.

    Sadly the Blackface amps can't be patched i.e. plug into the #1 input of channel one and then patch out of the #2 input for channel 1 to input #1 of channel 2. Now you can adjust the level of each channel to get a beautiful richer sound out of your amp.

    You can't do this on the Deluxe Reverb or Twin because the vibrato channel has one extra stage of amplification
    causing the two channels to be 180 degrees out of phase with each other and causing cancellation of fundamental and other important harmonics.

    You can however run both channels with the use of an A/B/Y footswitch as long as the footswitch has the facility to invert the phase of one output (either A or B).

    Here is one very good reason not to mess with the original design by "clipping" the bright cap on the vibrato channel IMO.

    If you clip the bright cap you will certainly darken the Vibrato channel. It will still not be exactly the same as the normal Channel but it will be closer. In doing this you loose some of the advantage of playing both channels in parallel.

    With the A/B/Y switch I use, one channel has an isolation transformer in the signal chain. It is by reversing the direction of current through the primary of this transformer that the switch achieves the necessary 180 degree change of phase to allow the two channels to operate together in phase.

    Now, here is the best part for your tone. with the inductance introduced at the input to one channel and the capacitive differences of components between the two channels the channels will not be in perfect phase - let's say 5 degrees out. When signals are a bit out of phase they are also leading or lagging the other channel in time.
    This time difference can add a beautiful richness, not available with one channel and now you can mix a dry Normal channel signal with a wet Vibrato channel to your liking.

    With the slight lag associated with the phase difference of the channels you actually get what I hear to be more like a Twin bass thump.

    I no longer use the DR without jumping channels.
     
    sgarnett likes this.
  2. El Marin

    El Marin Gretschie

    176
    Oct 4, 2018
    Madrid, Spain, EU
    I am sure there must be some other method of jumping channels.

    I have that mod done in my Twin Reverb, and the tremolo is nor dark by any means. I also can use tremolo and reverb on both channels and Normal Channel has a Bassman tone stack. A complete different animal
     
    lathoto likes this.
  3. Gretschmen65

    Gretschmen65 Country Gent

    May 20, 2016
    QLD Australia
    Yes, a completely different animal. It's not a blackface Twin Reverb. :)
     
  4. El Marin

    El Marin Gretschie

    176
    Oct 4, 2018
    Madrid, Spain, EU
    Well, not anymore. But it still has the Vibrato channel untouched
     
  5. smuc

    smuc Electromatic

    4
    Nov 22, 2020
    Austria
    I modded my DRRI to have the Reverb on the normal channel which also made it possible to bridge the channels. To my ears, not really worth it as the channels were sounding almost identical due to the bright cap mod I did earlier. Changing the speaker though, as well as the NFB selector (65/68)? Well, that was a whole different story. :cool:
     
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