1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

5E3 Location of .022 Coupling Caps

Discussion in 'Shock Brother's DIY Amps' started by timewaster1700, Apr 28, 2019.

  1. timewaster1700

    timewaster1700 Tele-Meister

    Posts:
    324
    Joined:
    Feb 17, 2016
    Location:
    Utah
    I apologize because asking these questions feels like beating a dead horse but I couldn't quite find the answer I was looking for searching the past threads.

    I'm getting ready to do my second amp build and want to get some .022 uF couple caps in case I decide the stock .1 uF allows too much bass. I noticed the Edge deluxe puts the .022 uF caps on the two legs of the phase inverter while most suggestions seem to put it on the first gain stage. I would think the first gain stage would essentially filter the bass out for the second gain stage and phase inverter whereas the Edge mod is filtering it at the end. Has anyone compared the sonic differences between these locations?


    EDIT: IGNORE THIS I'M AN IDIOT. THE TONE CONTROL IS INDEED SHARED.
    Also one more question. I notice the suggestion is usually .022 uF on the bright channel for humbuckers and play single coils through the unmodified normal channel. But having never played a 5E3, I'm curious wouldn't you miss having tone control on the amp when playing single coils? Do most people just resort to the tone control on their guitar when using the normal channel?

    Thanks!
     
    Last edited: Apr 28, 2019
  2. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,491
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    First: the plate of the gain side of the 12AX7 is an .022. I put another .022 on the Bright channel. So far, I'm happy with the result.

    Why do you think you don't have a tone control on the normal channel? The tone control on the 5E3 is shared and works on both channels.
     
  3. timewaster1700

    timewaster1700 Tele-Meister

    Posts:
    324
    Joined:
    Feb 17, 2016
    Location:
    Utah
    Wow you're right I feel like a complete idiot. Its been too long since my last build. I need to spend some time looking at schematics again before asking dumb questions. The tone control is indeed shared.

    But I guess my first question was still the tonal difference between changing the .1 to .022 uF on the plate of the first gain stage versus waiting until the phase inverter where you've allowed all the bass to be amplified and then you filter it at the end. See what I'm saying?
     
  4. Snfoilhat

    Snfoilhat Tele-Afflicted

    Age:
    39
    Posts:
    1,396
    Joined:
    Apr 8, 2016
    Location:
    Oakland, CA
    The math for 5E3 equalization and the common wisdom (based on many people who really have the amps in hand) don't totally agree. I don't know what to make of that. Best thing to do is probably to install the smaller caps when you build your amp, then clip additional caps in parallel and listen for the behavior you like more.

    But here's what the 5E3 should do on paper.
    deluxe_5e3.png
    For reference, low E on a guitar is 82 Hz.

    Starting with the purple filter. Vintage 5E3 vs Edge 5E3. The 0.1 microfarad cap and 220k resistor have a roll-off frequency of 7 Hz. The roll-off frequency for the modded 0.022 microfarad cap and 220k resistor is 33 Hz.

    I wouldn't expect to hear much difference.

    Next, the gold circle. One of the special characteristics of the 5E3 is this volume control. Move the wiper (the little arrow) up and down in your mind, and see that the resistance to ground goes up and down. So the resistance part of the filter depends on the volume control setting.

    For vintage 0.1 microfarad cap and 100% volume (1M), roll-off frequency is 1.6 Hz. Turn an audio pot down to 50% and the resistance to ground will be 1/10th, so 100k**. Roll-off Frequency is 15 Hz. Turn it way down to let's say 10k resistance and the roll-off frequency is 159 Hz. We're finally cutting out a substantial band of guitar frequencies.

    **or less, since this pot is always in parallel with the other channel's controls.

    For modded 0.022 microfarad cap and 100% volume (1M), roll-off frequency is 7 Hz. For 50% on the audio taper volume control (100k**), roll-off is 72 Hz. Getting close to guitar frequencies. Therefore with the 0.022 cap in the gold area, volume control settings below 50% might substantially cut low and low midrange frequencies.

    Having a volume control cut bass at lower settings doesn't seem like a really desirable trait. Most people seem to want to cut bass at higher volumes, and let more through when they are playing quietly.

    Then there is the issue of frequency-dependent behaviors of the first gain stage because this odd 5E3 volume control is loading the stage differently at different settings, unlike the more constant load presented by more normal circuits.

    Then there is the extraordinary interactivity of the two channels in the 5E3 and the EQ changes brought on by the two different volume settings working together.

    :eek::eek::eek::eek::eek::eek::eek:

    If it were my amp, I wouldn't change the caps at either of these places! o_O

    I would change the cap right before the phase inverter, the one that is unmarked in the schematic, because the impedance of the phase inverter is known and constant. Then you can pick any cap or combination of caps you want and pick any roll-off frequency you want to control the bass.
    http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php
     
  5. AJBaker

    AJBaker Friend of Leo's

    Age:
    33
    Posts:
    3,880
    Joined:
    Oct 3, 2010
    Location:
    Switzerland
    Interesting, will follow this thread. I picked up someone's build with the Edge coupling caps mod, and I'm wondering whether it's worth trying the original larger value.
     
  6. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,491
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    The one I circled? I've got a .022uf/600v in there now.
    Inkedimage_LI.jpg
     
    timewaster1700 and Snfoilhat like this.
  7. theprofessor

    theprofessor Poster Extraordinaire

    Posts:
    5,498
    Joined:
    Aug 8, 2016
    Location:
    Chattanooga, TN
    That is what I would start with also. Having swapped out all the schematic .1μF caps on my 5e3 at some point for lower values, I noticed the biggest difference with the ones right around the phase inverter. I ended up with .047μF caps everywhere the schematic calls for .1μF.

    I also lowered the first cathode bypass cap and noticed little difference. Again, the most dramatic difference was at the two legs of the phase inverter.

    I do think the .022μF coupling caps in the Edge Deluxe sound good, but in my opinion, the amp sounds too little like a 5e3.

    The speaker for a 5e3 is critical and also has a lot to do with how well the amp holds together. I have finally landed on what I believe to be the ultimate speaker for a 5e3: the Tweed Deluxe Speed Shop A12Q. See here: http://www.tdpri.com/threads/new-speaker-day-rec-pro-audio-tweed-deluxe-speed-shop-a12q.940330/
     
    Last edited: Apr 28, 2019
    timewaster1700 likes this.
  8. jman72

    jman72 Tele-Afflicted

    Posts:
    1,575
    Joined:
    Aug 31, 2013
    Location:
    Central Florida
    Here's my 5e3 clone board, and I LOVE it. Swapped out the first three coupling caps for 0.022 and the last two for 0.047. Can't remember exactly where I got the idea to do it that way, but I read it somewhere on this forum back when I put it together. Has a great bass response and no flubbyness at all. One thing to note is the location of the third cap...it doesn't change the circuit, but eliminates the need for the wire under the board connecting the empty turret with the turret where the cap is shown here.

    board.jpg
     
  9. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    8,172
    Joined:
    Dec 29, 2012
    Location:
    United States
    I like to reduce the first coupling cap in one of the channels so you still have a true 5E3 in the other channel (warts and all). You can go smaller than you'd think because intermodulation distortion will fill in the bottom end, especially when pushed into overdrive. You can go as small as a .0022uF and still sound surprisingly "normal". I currently recommend a .0047uF for my lead channel mod. Both sound great with high output pickups and humbuckers. Jumpering the channels and playing with the volume and tone controls also yield some unique tones.
     
  10. timewaster1700

    timewaster1700 Tele-Meister

    Posts:
    324
    Joined:
    Feb 17, 2016
    Location:
    Utah
    Sorry for the late response to my own thread. Been a busy couple of days.

    I love this forum. There are some incredible people here will to share their knowledge and experience and I'm very grateful.

    Wow thank you so much for taking so much time to share such a detailed explanation. This makes total sense and I can follow all the math. Super helpful. I don't know why I didn't think of the coupling cap and volume pot forming a high pass filter. I also totally get what you're saying about putting it before the phase inverter since the 1M resistor is fixed. But if I put a value there like most suggest (.022 uF) that only really changes the rolloff freq from 1.6 to 7 Hz which seems like it wouldn't be much of a difference. So I would have to use much smaller caps in that spot to trim off bass. Hmm interesting.

    Very interesting and helpful to hear what you found trying all those different values and positions. I already ordered a Celestion Blue and am anxious to try it against my 10" Weber 10A125 and see the difference between a more traditional American style and a british style speaker many rave about. At the end of the day I want what's going to sound the best with authenticity taking a back seat if it must.


    Makes a lot of sense. I remember reading about your lead channel mod. In fact I can't count the number of times I've read most of the mods on your site. I can't begin to thank you enough for creating that resource. I've learned a TON from your site and probably wouldn't have built an amp if it hadn't been for that site.


    So one more thing on my mind that I want to ask those knowledgeable. After the signal is amplified with V1 and is coming off the plate its faced with a 100k plate resistor or a .1 coupling cap and so its always made sense to me that the AC frequencies that are high enough will pass through the cap as if it weren't there compared to the resistor which is a big load. But on the other side of the cap there is likely a load. For instance the volume pot could be set at 50/50 giving 500 ohms to ground and 500 ohms to the next gain stage and of course the tone pot is likely up at a higher value of resistance too. These two would easily couple to a much larger load than the 100k plate resistor. So it seems like in normal use there is usually a lot greater resistance for the amplified signal to overcome in the next gain stage than for it to dump to ground through the plate resistor. Like 10:1 in the case I just mentioned. So is there really just that small of a percentage of the amplified signal making it to the V2 grid?
     
  11. Tom Kamphuys

    Tom Kamphuys Tele-Holic

    Age:
    41
    Posts:
    630
    Joined:
    Sep 18, 2018
    Location:
    The Netherlands
    Volume pot is 1M (iso 1k), so the loading of V1 (output impedance roughly 40k) is very small.

    Not sure from your post whether you're problem understanding might come from this, but a larger resistance value is a smaller load. Voltages love high resistances, currents don't.
     
    robrob likes this.
  12. timewaster1700

    timewaster1700 Tele-Meister

    Posts:
    324
    Joined:
    Feb 17, 2016
    Location:
    Utah
    Hmm I guess I'm thinking of it in terms of Ohm's law but the problem is the tube is an amplifier so using ohm's law kind of breaks down as extra energy is being added to the system. I'm thinking that high voltage off of the plate has to drop across the resistors to push the small amount of current into the next grid but I guess there isn't really much current at all. Hmm this stuff is kind of confusing even after I thought I understood it.
     
  13. Tom Kamphuys

    Tom Kamphuys Tele-Holic

    Age:
    41
    Posts:
    630
    Joined:
    Sep 18, 2018
    Location:
    The Netherlands
  14. timewaster1700

    timewaster1700 Tele-Meister

    Posts:
    324
    Joined:
    Feb 17, 2016
    Location:
    Utah
    I had a bit of an epiphane laying in bed last night. I keep confusing electron flow with conventional current flow. Voltage drops happen across a resistor in the direction of conventional flow but in the case of electron flow the resistor effectively increases the voltage so that helps quite a bit but I also want to check out the link you posted and gain a deeper understanding. Thanks
     
  15. Snfoilhat

    Snfoilhat Tele-Afflicted

    Age:
    39
    Posts:
    1,396
    Joined:
    Apr 8, 2016
    Location:
    Oakland, CA
    I don't think AC signals need be thought about as 'flow' at all. Places that are connected, even if there are some series resistors between them, are going to be at about the same potential. Differences in current through the tube (it's most basic job) mean differences in current through the load resistor, which makes the voltage flicker -- those waves of higher or lower voltage across time are the signal. Everywhere connected to that plate load but not also (parallel) connected to a different potential (like ground), is going to experience those changes in voltage simultaneously. It's not a single wave top moving from one place to another, it's the whole water surface changing from rollers to chop to flat (etc) all at once. Like Tom says, in the 'voltage amplifier' part of the circuit, currents are so small that series resistors barely matter at all. Those resistors are doing other jobs (like managing how much resistance lays between that part of the circuit and its parallel connection to ground, of which amps have many because power supplies are also AC grounds, voltage dividers use connections to other potentials like ground in useful ways, etc).
     
    Last edited: Apr 30, 2019
    timewaster1700 and Mr Ridesglide like this.
  16. timewaster1700

    timewaster1700 Tele-Meister

    Posts:
    324
    Joined:
    Feb 17, 2016
    Location:
    Utah
    This is super helpful thanks! Great way of thinking about it
     
  17. Paul G.

    Paul G. Friend of Leo's

    Posts:
    3,491
    Joined:
    Mar 17, 2003
    Location:
    Rhode Island
    Where I'm at now. Amp is usable even with humbuckers. Bass is not flubby or distorted. It is still heavy, but not objectionable and the amps still sounds like Deluxe.

    No change to bypass caps. First coupling cap (Normal channel) .047uf. Second coupling cap (Bright channel) .022uf. Third coupling cap (second stage to PI) .010uf (may still do something here). Fourth and fifth coupling caps (to power section) .047uf/.047uf.

    I may go to an .0047uf in the Phase Inverter. I feel I've lost some gain when changing this cap to .010uf, so I am a bit reluctant to lower this further.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.