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5E3 Build w/Mods Plan

Discussion in 'Shock Brother's DIY Amps' started by jejj21, Feb 13, 2018.

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  1. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    Hey Gang,

    I've been lurking on the site for several months now trying to gather as much information as possible about amp building. I have been all over Rob Robinette's site and have tried to listen to all the different 5E3 mods and determine what sound I'm really trying to achieve with this potential build. I have a habit of researching something to the nth degree to make sure I have minimal risk when it comes to putting money into play. I like to build things and create function from concept, so an amp build is something I'm ready to venture into next.

    After listening to the demo that Kley did of his "Cakepan 5E3 - Clean Blackface Tone" I was sold the mods he had there were definitely where I wanted to take this build. I reached out to Kley and he has been gracious enough to work with me the last couple weeks to dial in my layout/schematic. Every mod came from Rob's site, but I had a hard time finding the 4 main tweaks in one consolidated layout (NFB Loop, Lead Channel, Master Volume, and TB Stack). So I downloaded the DIYCL and started tinkering with a basic 5E3 Rob had put together. I then took that layout and converted it into a CAD schematic drawing so I could understand that process as well. Attached at the bottom are the two designs where they stand today.

    I'm to the point now of asking the forum for a couple more sets of eyes to look the plans over and see if there is anything wrong that I might have accidentally missed. I want to make sure the plan of attack is feasible, before I go down the path of ordering/building the amp.

    Any and all feedback is appreciated at this point and I hope this is the first of many posts as I move forward in this journey.

    Thanks,
    Joey

    5E3 Schematic v2.png 5E3 Layout v2.png
     

  2. kleydejong

    kleydejong Tele-Holic

    540
    Aug 30, 2010
    Orange City, IA
    Hey Joey, looks great! I went through my amp in person. Seems that I've done a number of mods and kind of lost track of them all. I noticed a few changes I hadn't mentioned in our PM's.

    - I am running 12AX7's in both preamp tube slots.
    - I am using .022 uf coupling caps throughout - so that would be in C3, C9, and C10.
    - Those two triodes are a bit mixed around. Looking at your schematic, the top input - J1 and J2 feeds what I would call the stock 5E3 channel or 'Bright' channel. 1.5k bias resistor and 25 uf bypass cap. 100k plate resistor is correct.
    - The bottom input - J3 and J4 feed what I call the 'Normal' or 'Mod' channel. It has Rob's lead voicings of 2.7k bias resistor and .68uf bypass cap. 220k plate resistor is correct. Tone stack with switchable mid ground defeat is correct.
    - I'll mention bright caps. Looking through my older videos and documentation, I've experimented with various bright caps. I didn't like it on the master. I recently put one back on the preamp volume control on the Bright channel - yours labeled as P1 1M Volume. I think used a 220pf cap. I go back and forth a lot on bright caps.

    My thought is that I want to have access to the stock 5E3 experience in the Bright channel. Great midrange grind. Low headroom, great distortion. Tighten it up a bit with the coupling caps.

    Then the normal channel is a very different experience. Tighter gain at higher volume. More British voicing. Switchable tone stack for better cleans and a midrange scoop. More versatility.

    Lastly, I recently got some great insight on the stock 5E3 tone control. It is kind of like combining a low pass filter with a variable bright control. Roll the tone back to cut highs. Roll it up to engage a bright cap. As you increase its volume control the bright cap becomes less relevant. I don't have that tone control in my amp because I ran out of holes in the front. So having a bright cap helps keep it from getting overly dark with the volume set lower.

    Sorry for my lack of clarity, I should really do an update video and schematic on the current state of the amp. Lots of these 'voicing' changes are pretty subjective and (I think) best to do as you spend more time with the amp and dial it in to your tastes.
     
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  3. jmp81sc

    jmp81sc Tele-Meister

    203
    Feb 6, 2015
    Orange County
    Thank You for posting the layout and schematic. This will be helpful for my next build.
    John
     
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  4. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    This is the normal channel loadline
    upload_2018-2-13_19-37-34.png
    and this the lead
    upload_2018-2-13_19-42-21.png
    Why have you chosen to have the normal channel so?

    I would use a double throw power switch, the added safety outways any reason not to.
    I would have increased the first two reservoir/filter caps to 22µ.
    And if you are using a 100Hz half boost cap on the lead input stage, I would have followed it with a coupling cap of 0.022µ instead of the fat 0.1µ.

    S2...is that just meant to be a switchable negative feedback ? I think you have that wrong ! You are disconecting the bias resistor and bypass-cap.

    Why the 12AY7 as phase inverter? have you drawn a loadline up for that? I would have thought to get the most out of an AY in that position, you would want smaller load resistors, something like 33k, and then the 1k5 bias resistor needs to be worked out to match.

    Adding 500k screen-grid resistors to the 6V6's is always a good idea.

    I haven't looked at the layout drawing, I like to get the schematic right first.
     
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  5. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    I would change the BF channel volume control to a resistive divider arrangement. You can still not feed the BF channel and load down the other channel with the BF pot. That way you will have better control when using the volume of the BF channel.
     
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  6. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    5E3 Layout v3.png 5E3 Schematic v3.png
    Thanks for all the feedback guys. I will go in tonight, make some modifications and post them to the thread.

    EDIT:
    Ok, so I have changed the three 0.1 Caps to 0.022. I have moved the TB Tone Stack from the Bright Channel to the Normal/Lead Channel. I have changed the 12AY7 to a 12AX7. I also had the V2 in the schematic labelled incorrectly as a 12AY7, vs the intended 12AX7. Is there a reason to break from the original 12AY7 in V1?

    I did have the 3-way NFB switch wired wrong on the schematic vs the layout. I think they both match correctly now.

    The 500k screen-grid resistors is a new concept, what does that change do for me?

    There was also a suggestion for a resistive divider arrangement on the BF volume control. I'm not sure what that means either so if someone could clarify, I would appreciate it.

    Thanks again for the feedback and help!!!
    Joey
     
    Last edited: Feb 14, 2018

  7. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    I edited my previous post when I should have probably replied. Please see above at revisions and questions. :eek:)

    Thanks, Joey
     

  8. kleydejong

    kleydejong Tele-Holic

    540
    Aug 30, 2010
    Orange City, IA
    A 12AX7 has more gain than a 12AY7. More output and potential clipping early in the preamp. Lower headroom. It is very much a personal preference choice. I know many who believe a true 5E3 runs a 12AY7 in V1 for good reason. My preference is for the 12AX7. I love the 5E3 bright channel for its greasy midrange grind. I want more of it sooner. I think Rob's NFB switch is a neat solution to achieve a cleaner, higher headroom tone. I also like a 12AX7 for the normal channel with the Marshall voicing on the triode and the tone stack. I only mentioned it because that's what I've had in my amp. Trying both is probably the best route.

    Some good information on screen resistors here - http://www.tdpri.com/threads/5e3-build-screen-resistors-or-not.675188/. Smarter folks than I explain it well there. I believe 470 ohm is the 'standard' choice.

    The way you have the volume on the schematic currently sends the output of the treble control onto the wiper of the volume pot. This is a little different from wiring a volume control as a voltage divider as shown here:

    [​IMG]
     
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  9. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    Hey Kley,

    This makes so much more sense!! I was having a hard time understanding the potentiometer controls in the schematic. I thought it was just a symbol, not actually how current was flowing through. I have updated all of them to be correct.

    I also added the 470ohm screen resistors, so hopefully they are connected correctly and look right.

    It feels like this is starting to come together. Getting really excited about starting this process.

    Thanks,
    Joey

    5E3 Schematic v3.png
     

    Attached Files:


  10. Preacher

    Preacher Tele-Afflicted

    Apr 17, 2007
    Big D
    Good Luck and I will be watching... for at least to get my behind out in the shop and finish mine up.
     
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  11. jsnwhite619

    jsnwhite619 Tele-Afflicted Ad Free Member

    Sep 10, 2013
    Georgia
    My 5e3 was my first build, and it's kind of been neglected lately. After fixing some crackling that I had been putting off, changing out a bad 12ax7 that was apparently dying a slow death, and adding a NFB switch, I had the chance to crank it up the other day while the wife and kid were gone. I didn't realize how much I missed it! Man, it was fun!

    I've changed the first 2 coupling caps from .1 to .047. My negative feedback is different than what Rob's site has. I used the same method as a Princeton Reverb (higher value resistor though, I didn't want to cut much) where you keep the bypass cap for the extra gain vs. only having the NFB without the cap. I like it better, but I wasn't looking for a drastic change, just tighter sound. It's not really cleaner, just a little tighter. Anyway, good luck with it. I know you'll enjoy it!
     
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  12. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    Hey Guys,

    I decided since a good deal of this build will be custom, why not just build it board and all. The addition of the board build gives me some latitude about how the turrets are laid out and overall length. I decided I really didn't like the idea of doing the tone stack caps directly on the pots, so I improvised and moved it to a new section of board, which is now 11" long total. This is the idea I have a the moment, I wanted to see if someone could look over the wire runs and let me know where I might have issues with 1) run length & 2) signal crossover.

    Once again, Thank You for any and all input on this journey.

    Thanks,
    Joey

    5E3 Schematic v4.png
     

  13. robrob

    robrob Poster Extraordinaire Ad Free Member

    Dec 29, 2012
    United States
    Very nice work @jejj21. The only issue I see is in your latest schematic is if you turn either volume full down you'll kill both channels--both channels' signals will be shorted to ground. You need to go back to how the stock 5E3 volume pots are wired to keep from doing that.
     

  14. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    Thanks @robrob for the reply. As many have iterated, your website is awesome!!

    I originally had the volume pots wired like the original 5E3 layout and it was suggested I reroute it though the pot rather than the wiper. So at this point I'm all confused on the proper way to show this. I have readopted the original 5E3 volume layout below, but it does not match the Vintage Channel Tone Stack image Kley posted above.

    Should the new tone bass stack replace the removed tone pot in the schematic or is the way I have it shown ok?

    Thanks,
    Joey

    5E3 Layout v3.png 5E3 Schematic v4.png
     

  15. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    If you are going with a resistive divider volume on both might as well put in some mixing resistors.
     

  16. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    Schematic/Dramatic mistake! If you have the two 100 Ohm R24 & R25 resistors going from the V3 6V6 filaments to the cathode, thereby floating/raising the reference ground of the heater supply, the center tap of the transformers heater winding must not be connected to ground like you have drawn it. One or the other. Like you have it drawn, the output tubes will be drawing their bias voltage setting up across the filament winding.............BUZZZZZZZZZ...which is now parallel to your 250 Ohm cathode bias resistor, making it about 42 Ohm, and the bias voltage will be low, very low, making the tubes run very hot...we're talking glowing plate, over dissipation levels here!
     
    Last edited: Feb 20, 2018 at 1:02 PM

  17. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    Thanks @Bendyha. I was trying to figure out the correct way to put the artificial center taps on the schematic. Using V3 and going from lugs 2&7 to 8 makes sense, but when I added them on the schematic side in a similar fashion, I wasn't sure if I was correct. Most of the schematic drawings I have see just have them connected to the green filament wires at the transformer, but I wanted to connect it up correctly.

    So, given all that information, what is the proper way to show this connecting if trying to add the center taps?

    Thanks,
    Joey
     

  18. Bendyha

    Bendyha Tele-Afflicted Ad Free Member

    Mar 26, 2014
    Northern Germany
    Has the transformer filament supply no center tap as you schematic shows it? If it does, you don't need an artificial one. If it doesn't, then you need to add the two 100 Ohm resistors to form a ground reference for the filament supply. This can either go directly to ground at the same place as the High-Tension center-tap.
    Or, alternativly, you can raise the ground reference by floating it on top of the voltage that is found art the cathode of the power tubes....where you have shown it joined up. This will mean that the filaments are still getting the 6.3V like they need, but the voltage between the filaments and the cathodes of all the tubes is now 25-30V higher than if it was ground referenced. This can be advantagous against hum....more of a Hi-Fi thing, or it can safeguard against problems if a cathode follower or phase-inverter cathode is raised to a high voltage....but on this amp, this is not the case.
    So... Either connect to ground, or if the supply has a center-tap...leave them away.
     
    Last edited: Feb 20, 2018 at 1:26 PM

  19. jejj21

    jejj21 TDPRI Member

    Age:
    39
    10
    Dec 19, 2017
    Louisville, KY
    The transformer i'm looking at is the ClassicTone 40-18016 which does not have the center taps but has a better voltage range for the amp so I read.

    So, in the graphical layout I have the 2-100ohm resistors connected at pin 2 & 7 and both connected to ground at pin 8. In the schematic I tried connecting the resistors from 2 & 7 into the ground coming off pin 8 to replicate the concept. Should I show it as two separate lines coming out of pin 8 in order to properly show ground?
     

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