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Magic Six and the Blues Jr Tonestack

Discussion in 'Glowing Bottle Tube Amp Forum' started by PBO Blues, Dec 7, 2017 at 11:08 AM.

  1. PBO Blues

    PBO Blues Tele-Meister

    Age:
    63
    293
    Jan 15, 2016
    Chatham County, NC
    I read with great interest this old piece on the "basis" for the magic six settings in classic Fender amps:

    http://www.singlecoil.com/docs/magic-six.pdf

    Yes, I know every speaker is different. Yes, I know every room is different. Yes, I know about component tolerance variations. Yes, I know I should just twiddle the knobs and use my ears. Yes, yes, yes.

    But I am led to wonder how my stock 2015 Lacquered Tweed Blues Jr's tonestack differs from "classic" Fender gear. Or if it does at all. An academic exercise, if you will. How does the Jr's architecture compare to the architecture of the BFs and SFs and venerable tweeds of the past? And based on that, how does the logic of the magic six apply, or not?

    Or does the EL84 vs. 6L6 engine make it all apples and oranges?

    And while I'm asking potentially stupid questions, what, exactly, makes a Blues Jr bluesy?

    Thanks for your patience and assistance in my giving a few more whacks to a probably long-deceased equine.

    Mike
     
    Last edited: Dec 8, 2017 at 8:30 AM

  2. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    First of all, I don't believe in these settings at all. This assumes every guitar and speaker in every amp is the same and that all players are the same. This is just one guy putting his opinions into a cool-looking pdf.

    Second of all, unless you get up to the bigger Fenders, there is no mid control, so this doesn't make sense to me there either.

    The tone stack itself is pretty standard Fender. Very similar to everything since the 5F6a bassman.

    The only thing that makes a Blues Junior bluesy is the name and the marketing :D
     

  3. PBO Blues

    PBO Blues Tele-Meister

    Age:
    63
    293
    Jan 15, 2016
    Chatham County, NC
    Fair enough. Not sure I buy in completely, either, but it's a somewhat reasoned starting point that led me to think about any practical architectural differences in the Jr. The approach seemed a good reference mechanism.

    The Jr does. Unless you mean that the Jr's is not really a mid control. If that's true, why?

    This is what I'm looking for. Thanks!

    I suspected as much.
     
    Last edited: Dec 7, 2017 at 2:46 PM

  4. corliss1

    corliss1 Tele-Afflicted Gold Supporter

    Sep 13, 2008
    Lansing, MI
    I just meant that about half the vintage blackface/silverface Fenders don't have a mid control, which is what that article was based off of.
     
    PBO Blues likes this.

  5. Axis29

    Axis29 Poster Extraordinaire Ad Free Member

    Jan 2, 2007
    Virginia, USA
    Actually, those lower sized, vintage Fenders do have a mid control, it's just a fixed resistor instead of an adjustable one, via pot. I've hear dit postulated that if you set the mids control on 6, you supposedly are approximating the same value as the fixed resistor Fenders. Not sure how true that really is, but I read it on the Interwebs, so it must be true. :lol:

    The tweed architecture is different than the later brown and blackface preamp architecture. It is not just about cap and resistor values, but where the gain stages are in relation to the tone and volume controls.

    In the classic 5f6-a Bassman preamp, it goes: input > gain > volume > gain > EQ > PI

    In the Blues Jr preamp, it travels the same path: input > gain > volume > gain > EQ > PI

    The ab763 Bandmaster's preamp is different: input > gain > EQ > volume > gain > PI (this is the arrangement that appears with the 6g7 amps too)

    Does a Blues Jr sound like a tweed Bassman? Nope, not at all. But, it is more tweed-like in architecture. The values are different, tubes are different, iron, speakers, etc. Plus, there are added things like the Master Volume, Fat switch, etc. I can honestly say, I've never heard any of the Blues series that actually sounded like a tweed amp, accept maybe the 410 DeVilles. They can get kinda close. But, they all have a certain upper mid frequency thing going on that's different.

    Do they sound like a brown/black/silverface amp? I think even less... because of that upper mid thing. They sound like a modern Fender to me.
     
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  6. clintj

    clintj Friend of Leo's

    Apr 4, 2015
    Idaho
    At least with the typical AB763 amps, the mids are a lot higher than 6. The Mids pot is a 10k-A, so at 5 it'd be about 1.5 to 3.0k, depending on taper. The fixed resistor is often a 6.8k, which would be up around 8 or so on the pot.
     
    Axis29 likes this.

  7. MMARSH

    MMARSH Tele-Meister

    358
    Jun 21, 2015
    CA
    One of the things about the Jr's mid control is that even if you dial it all the way down, it is still in the circuit. Turn all the tone knobs fully counter-clockwise and you still get sound from the amp. This is because the mids are still coming through. That means (to my ears) muddy tone. Easy fix: http://billmaudio.com/wp/?page_id=58 now, all tone knobs down, nothing comes through and you have more control of the mids in your tone and cleans up the low-mids mud.
     
    LiteAsh and PBO Blues like this.

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