5E3 coupling caps question

Discussion in 'The Squawk Box' started by ARandall, Sep 1, 2017.

  1. ARandall

    ARandall Senior Member

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    I am in the process of finishing a 5E3 build, but know already from clips that the stock form will be too bassy for the LP's - which I play most of all. But I do play strats and Teles quite often - as well as having a Jag and JM too.
    A fix for the farty bass seems to be replacing the 1uF coupling caps are going for a lower value - but for a strat say it sounds great with the higher values.

    What I'm most interested in is knowing if with a DPDT on,on,on switch or similar if you could have a switching operation for say the normal channel coupling cap. Where you could have 2 caps as an: A, B, A+B possibility.
    Would the switching action have popping issues.....what (if any) grounding would be needed for the housing??
     
  2. Leña_Costoso

    Leña_Costoso Senior Member

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    Well.... I think what I'd try, because its easy, is to separate the cathodes of the input 12AY7. Use a pair of 1500 ohm resistors to ground. Use the 25uf bypass capacitor on the "normal" channel, and no bypass capacitor on the "bright" channel. You may find that the loss of gain on the bright channel (with no bypass capacitor) is a little too much, so you can try smaller values of bypass capacitor there to help keep the gain up a bit. I don't think you'll need to do that, but just in case, I mentioned it. Ditto if its a little "too bright". (edit in afterthought: You can leave it too bright, and jumper to the normal channel and "mix" them with the volume controls too).

    If you're intent on messing with the coupling capacitors, I'd only replace the ones at the input to the phase inverter. There are two .1 capacitors there. Try something more like .01 or .005. I put a Tremolux head into a 2x10 cabinet once, and it sounded like crap-o-la. No bottom at all. I noticed that it had (from memory) a 500pf coupling cap on the input of the phase inverter (yah, I know, different inverter, but still...). The Tremolux was voiced for a closed back, not open! Change it to .01 and it sounds great.

    So, you can do a lot of "voicing" with the phase inverter input, but I seriously would try the cheep and easy to do "split the cathodes" at the input for your Lester/Strat situation.
     
  3. ARandall

    ARandall Senior Member

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  4. Splattle101

    Splattle101 V.I.P. Member

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    I ended up changing the coupling cap between the preamp and the vol control / tone network. I did the mod only on the bright channel, and the normal channel remains stock. The only difference between the bright and normal channels in the stock amp is the bright cap on the volume control, and that becomes irrelevant once the volumes are up. So the stock amp is still hiding in there...

    But I digress. I replaced the big cap with a 0.047 uF on the bright channel. I did this some time ago and I've kept it. The amp still has oodles of bass to spare, but the mod definitely tightens up the bottom end when the vol is above two thirds (which, for me, is all the time).

    Calculations and discussion here:

    http://www.mylespaul.com/threads/5e3-build.218859/page-12
     
  5. sonar

    sonar Senior Member

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    I played around with all sorts of coupling cap values on my 5E3 build. In the end the stock values not only sounded best, but felt right. That's including my LP which gets a lot of its attention with the 5E3. I just crank up the 5E3 tone knob with the LP.

    For me lower value caps just choked the sh*t out of the amp, and it ended up playing like a constipated and weak Marshall.

    Sure the bass can get a little wooly, but it's not an amp that you kick into drop D, chugga, chugga stuff. It's a 12 watt amp that grinds and growls.

    A lot of the early ZZ Top recordings were done with a 5E3 and MPG. It's pretty hard to find a better LP -> amp match, imo.
     
    Marshall & Moonshine likes this.
  6. ac/dcfan87

    ac/dcfan87 Senior Member

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    I played around with the coupling cap values on my Mojo 5E3 - it neutered the amp. It did tighten up the bass, but it took away the magic and the buttery sparkle of the amp. It dulled the amps character completely. You really have to keep this amp stock IMO or just mildly tune it so it sounds a good old one.

    Ron at the tweed deluxe shop modded my amp, and it was never the same after that. I don't regret it one bit. Now it sounds like it should IMO, but it just "slightly tuned" it so that the character of the amp shines. Changing the couple caps a few times showed me that it had too much of an affect on the amp and that wasn't going to get what I wanted.

    My amp in stock 5E3 form- it was too much farty bass early on and high up on the dial it got worse. The overdrive was glorious but it was only usable in certain spots. It could fall apart very easily and difficult to use. And the treble response - it was too grainy at high volumes, guitar volume on 10 - back off the amp tone control and then it became too bassy- so that was another complaint. It had some great tones, but those tones were difficult to use and lacked some amount of versatility.

    Ron's modifications on the other hand, just enhanced and refined everything about the amp. And I think it's important not to change the architecture of the amp too much because it is what it is. Making it 20 watts and fixed bias and stuff like that is completely changing the amp IMO. So I'd rather a dead nuts clone or someone (like Ron) who really knows what makes these amps sound good. Most of the 5E3 clones I've heard, they don't sound like they should.

    There are many different reasons why many of the new clones do not sound like a good old 5E3. It could be voltage differences, old components that have drifted values, not the right speaker, not the right tubes, not the right transformer, new components that sound different to similar NOS components, etc.
     

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