Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups darrenriley.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

5CE5 Build

Discussion in 'Shock Brother's DIY Amps' started by Mat, Nov 27, 2017.

  1. Mat

    Mat Tele-Meister

    282
    Oct 14, 2003
    Australia
    No not a typo!

    Having been dudded on a tweed pro that I bought paid for and haven’t received I figured I’d let karma do its’ business on the seller and I’d build one for myself.

    The concept is essentially a 5E5 with an octal and 12AY7 pre-amp channel in a TV front cabinet. Planning to wire the octal channel up for 6SL7’s as I have a few and I understand that sonically they’re close to a 6SC7 which are getting hard to get.

    Still tossing re switchable NFB.

    Any thoughts / advice much appreciated.
     
    CoyotesGator likes this.

  2. jsnwhite619

    jsnwhite619 Tele-Afflicted Ad Free Member

    Sep 10, 2013
    Georgia
    Are you building the cabinet yourself? If you're doing a tv front, I'll be following! ;-)
     

  3. Mat

    Mat Tele-Meister

    282
    Oct 14, 2003
    Australia
    No, I decided to get one built by the Speaker Factory up in Brisbane once the chassis is complete (and I sell some gear!).
     
    jsnwhite619 likes this.

  4. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Note that the 5E5 Pro is much different from the 5E5A Pro.....so....which one are you going to build with that octal preamp channel? (;^) The 5E5 is somewhat like the 5C5 in the preamp...except for the method of Biasing the input stage....but differs in the PI while both amps are cathode biased outputs. The 5E5 and the 5E5A both have cathodyne PI, but the 5E5A is fixed biased and has a much more complex preamp than the earlier Pros.
    If one had the chassis to do it, having the simpler tone stack on the octal preamp channel and the more complex tone stack in the 12A-7 channel makes for a very versatile amp, ime. I would suggest cathode Biasing for both preamps instead of using the grid leak bias on the octal. Run the cathodyne PI and have switched cathode/fixed Biasing. There ya go...a 5C/E/E-A Pro. Best of three worlds. But......since you have decided on a vintage style cab and chassis, that rules out that versatility.
     

  5. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    I would think the 6SL7 is harder to get as it is more versatile with the split cathodes. Just doodled a bit. Could do a fixed bias or a switch for it, a few ways to do it out there.

    [​IMG]
     

  6. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    That 6SL7 channel is like a 5E5A, is it not? It is not like a 5E5 Pro at all. The 12AX7 channel looks more like the 5E5...which is a big 5E3 Deluxe.
     

  7. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    Wally, I was taking the points in your post and running with it. It is easy enough to Do a 5E5 with a 6SL7 in one channel and a 12AX7 in the other. Heck, I even drew that up without any switches. You know how hard that was?
     

  8. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    Well my amp is not too far off from what you're talking about I guess. I have what I call a hot-rodded 5c5.

    It has a cathode biased 6l6gc power section with a bigger PT to get closer to 28-30 watts.
    It has a larger 5e5a/bandmaster/super OT.
    It has two channels, both running a 6SL7.
    One channel is chathode biased and one channel is grid leak biased.
    It uses a paraphase phase inverter.

    It has more power than a standard 5c5 or 5e5, but it's more compressed and squishy than a 5e5A because of the cathode biased power tubes and the paraphase phase inverter.

    It's also in a custom made flip-top tweed cabinet with a reconed 60's p15n. IMG_2640.JPG IMG_2641.JPG IMG_2645.JPG IMG_2646.JPG
     
    Teleka, milocj, Wally and 2 others like this.

  9. Mat

    Mat Tele-Meister

    282
    Oct 14, 2003
    Australia
    Wow, some great thoughts and examples here.

    Essentially I have a 5D5 chassis so I was planning a 5E5 platform with one octal channel from a 5C5 with grid leak biasing replacing one of the 9 pin inputs - fairly similar to screamin' eagles. I have a 5A3 Deluxe and really like the squishy grid leak biasing sound on that. I'll try and get a circuit diagram up in a few days.

    Keep those thoughts and comments rolling in - this will be my Xmas build so lots of planning happening at this point.
     

  10. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    You can have the grid leak channel switchable to cathode biased with a double pole switch.
     

  11. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    The only thing about the grid leak channel is that it doesn’t like drive pedals. At all.

    But it also doesn’t need one either. At all.
     

  12. Mat

    Mat Tele-Meister

    282
    Oct 14, 2003
    Australia
    Parts beginnings to arrive. I have been pondering whether to do something with negative feedback or a presence control. If I did would want it to be switchable so that it is on or out of the circuit. To locate it I was thinking to relocate the fuse to the lower chassis and free up the hole for a switchable pot.

    Anyone have any thoughts or experience with this mod
     

  13. Mat

    Mat Tele-Meister

    282
    Oct 14, 2003
    Australia
    Hi

    A quick (hopefully) question regarding NFB.

    The 5D5 schematic shows a 1m resistor in the NFB loop whereas the 5C5 and 5E5 had none.

    That's a lot of resistance does anyone have experience with a 5D5 as to how much of a dampening effect this loop has - my initial reading would be not a lot given other Fender loops often have 820R to 1K resistors in the NFB. I understand that the insertion point will also have an effect on the effectiveness of the loop.

    Please feel free to chime in.
     

  14. Nickfl

    Nickfl Tele-Holic

    888
    May 24, 2016
    Florida
    If I understand it correctly, that resistor is part of a voltage divider, so its role in determining the amount of negative feedback isn't dictated by its measured value, but by the ratio between it and the tail resistor. Note that the 820r in the AB 763 is paired with a 47r tail resistor to ground. In the case of the 5d5, I guess the tail is the combination of the 220K and 50K to ground? So the 1M series resistor isn't as big as it initially seems when you take into account the 270K (I think?) tail.

    I don't fully understand the NFB on these amps though as the paraphase PI seems to complicate things as compared to the common LTP PI implementation, and calculating the actual amount of feedback you would be getting is definitely over my head. Aiken amps has quite a bit of information of the subject if you are interested in some in depth reading: http://www.aikenamps.com/index.php/designing-for-global-negative-feedback

    Cool project BTW, I'll be interested to see how it comes out and I hope you post some sound clips when its done. I'm very interested to hear the comparison between the octal and noval channels in the same amp.
     
    Last edited: Dec 12, 2017

  15. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Mat, I am not able to give a full explanation of that loop, but.....it would be simple to test this with the circuit built. Simply lift the resistor to hear the difference. And....know that in a NFB loop, higher resistances limit the amount of cancellation by a negative feedback loop while lower resistances increase the cancellation effect. With no loop...total resistance, right?...there is no cancellation of signal. That 1M resistor is less resistance than an ‘open circuit’...no negative feedback, but it is much more resistance than say 500k or 100k.
    I am not familiar with that loop, it’s insertion point, or the effect in that circuit. The 5D5 is one Pro that I have not been around.
     

  16. Mat

    Mat Tele-Meister

    282
    Oct 14, 2003
    Australia
    Hi Wally & Nickfl

    Thanks for chiming back. I'm thinking a switched 1m pot so turned "off" it's out of the circuit ala 5c5 and 5e5 and "on" then I can go from stock 1m and apply more NFB as the pot resistance is decreased. Seems to be the best option in terms of flexibility
     

  17. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Mat, 1meg may be a bit much there. I would think that a 50k or 100k pot would do the trick. If you have some different pots you might experiment, but I am thinking that most of the sweep of a 1meg would be so close to being like no NFB that you would be wasting time turning the pot.
     
    D'tar likes this.

  18. FenderLover

    FenderLover Friend of Leo's

    Jun 11, 2009
    Minnesota
    I think Nick is right here, and the fact that the insertion point is the grid of the output stage, it is generally pretty ineffective. (Notice, no one does that any more....) NFB is generally more effective when injected into a stage that has more gain.

    I'd do what Wally said and disconnect it after the fact, determine the effect, and go from there. It's all part of final tuning.

    Cool project, by the way. I've been meaning to change one of my builds to what Screamin Eagle has for quite a while now...
     
    Wally likes this.

  19. screamin eagle

    screamin eagle Friend of Leo's

    Oct 9, 2008
    S. CA
    You should. You definitely should.
     

  20. Mat

    Mat Tele-Meister

    282
    Oct 14, 2003
    Australia
    OK so here is the NFB plan.

    I will include the 1M NFB resistor on the board and then connect / disconnect it to see how it sounds / works. If there is a good difference I will wire in a pot and play around with values to get something usable.

    Should I adjust the resistor so that the total resistance (resistor + pot) is a maximum 1M eg. 750K resistor + 250K pot or just add a pot in series and see how I go (this doesn't seem the best course as there is already a high resistance so adding more resistance intuitively is not the way to go - have I missed something in my logic)?
     

IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.