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What will higher voltages do to a 5E3?

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  • What will higher voltages do to a 5E3?

    I have a completely stock 5E3 with voltages bang on using the 240vAC tap (UK mains at 240vAC usually) of a MM tranny. But wondered what I would hear if I raised the B+ by switching to the 230 or 220 taps?

    Would it just increase the voltages throughout and hence the headroom? Would it damage anything? Would it have the same effect as stepping up to a bigger rectifier?

    Last edited by ad30; 01-28-2010, 09:58 PM.

  • #2
    The main difference compared to swapping the rectifier (ie 5V4) will be you will probably increase the heater voltage over the spec (6.3+/-10%) - not a great idea.
    With either method, the 6V6 plates will run even hotter, and with a 5E3 they are pretty much at max anyway.
    You could accomodate the additional voltage by increasing the value of the cathode resistor, ie 330ohms, but then you go further towards class B at high signal levels and crossover distortion may thin the tone down and go 'reedy'.
    Higher B+ levels tend to give the 5E3 tone a harder edge - more like a mini marshall, losing the soft warm response.
    If you want to stay clean but get louder, the most effective way will be to double up on the speakers, which, assuming that you keep the correct load impedance (and all else being equal), will give you another 3dB sound pressure level, which is equivilant to doubling the output power of the amp.
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    • #3
      Simplest way to raise B+ would be to use a stiffer rectifer & rebias as Peter suggests (shouldn't be any problem with excessive crossover distortion witha 330ohm cathode resistor, as long as plate current is over 30mA).

      5V4 is a very common choice for rectifier upgrade in a 5E3. The amp will also take GZ34 or SS rectifiers as long as you bias accordingly & watch for tube & caps running over voltage.

      This won't affect th heater voltages like changing the PT primary taps.

      Fixed bias (or a cathode/fixed bias switch) is another option for a cleaner, louder 5E3.


      • #4
        Just to clarify.

        The Hi-V and Heater voltages are from separate windings in the Tranny and have separate leads.

        The rectifier only changes the Hi-Vac to B+ Vdc.

        The 5v and 6.3v heater windings respectively only supply voltage to the filaments of the rectifier and power/preamp tubes and are not affected by changing the rectifier, therefore changing the rectifier won't change the heater voltage.

        I have a preference for Weber CopperCaps which don't use the 5V heater, less demand on the Tranny.

        I like using a 5V4 in my 5E3's to bump-up the B+ voltage under load(tubes in)by approximately 20-30volts. The 5V4 is more efficient having less sag(voltage drop on demand)the resulting tone is slightly cleaner, but all that is not that noticeable unless you are really listening for it.

        I was using "Custom Wind" Tranny's from Hammond(just up the road from me)which are a little under the spec'd for voltage and over spec'd for current in-regards to a Tweed 5E3 PT, therefore another reason for the choice of a 5V4.

        I might add, since Hammond have come out with their "Guitar Amp" line I may go with those in the future, but then again, I'm not a fan of chassis-thru mount Tranny's, maybe they can change them to standup.

        Last edited by GrungeMan; 01-30-2010, 05:37 PM.


        • #5
          I got it. Not much to gain it doesn't seem.

          Thanks for the replies.


          • #6
            Well not much increase in volume, but in relation to what GrungeMan implied but did not quite spell out, if you change the primary winding, you will also change all the voltages you get on ALL the secondary windings (not just on the High Tension winding). Tubes have some (but not a lot) of tolerance for difference in voltages needed to operate the filament windings - Usually 6.3V +/- 10%. So you need to be mindful of what changing the primary winding voltage does to that. There's only a 4.5% difference between 220 and 230VAC on the primary, and that won't affect the heaters much in they are otherwise around 6.3VAC (i.e. it will become about 6.6VAC), but if the heaters were already sitting at say 6.7VAC on the 220 Primary, then the heaters will be hitting 7V on the 230V primary, which is not too good.
            Building a better world (one tube amp at a time)

            "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo


            • #7
              A little bit off topic and question...

              Originally posted by ad30 View Post
              I have a completely stock 5E3 with voltages bang on using the 240vAC tap (UK mains at 240vAC usually) of a MM tranny. ......
              What is the stock 50's "bang on voltages"?
              The original tweed Deluxe amp's schematics had very little or no documentation stating B+ voltages so I'm wondering what the consensus is on this?

              Mission Amps
              Denver, CO. 80022


              • #8
                Nothing useful to contribute about a real one, but to start the ball rolling, the schematic for the RI puts the B+ plate node / reservoir cap at 370Vdc (with heaters at 6.6Vac), cathode at 21.2Vdc across 250ohm.
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