Dual secondary taps heater supply and hum

Discussion in 'The Workbench' started by RickyLee, Nov 26, 2020.

  1. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    10,140
    Likes Received:
    3,552
    Location:
    SoCal U.S.A.
    I am considering converting my 100W Jubilee 2555 clone to a 15W to 30W power supply. The smaller power transformer does not provide much for heater current though. I will probably end up running two 6V6 in it to start, but I want to still have the heater current to pop in either a pair of EL34 or 6L6 for tonal changes. My power supply might be good for 30W if I go to the big bottle tubes if I find I need a bit more power for special occasions.

    The power transformer I have only offers 3A on its 6.3V heater tap. But it has an additional 6.3V tap at 2A that I can also use. I am running four 12AX7 including the phase inverter. So I can use the 2A tap and run the 12AX7's off that, then run the power tubes off the 3A tap. Or move the phase inverter tube over to share the tap with the power tubes so preamp and power amp are isolated.

    Question here would be: Is there any noise or hum issues running two separate heater supplies? I might even try DC heaters for the preamp or could elevate the reference to ground as well if that could help?
     
  2. thetragichero

    thetragichero Well-Known Member

    Joined:
    Jun 6, 2010
    Messages:
    2,969
    Likes Received:
    978
    Location:
    flo rida
    el34 1.5a heater current apiece so run the power tubes on the 3a tap and preamp tubes on the 2a tap. wouldn't do dc heaters for 4 preamp tubes with less than 3a of heater current. you can elevate the center tap of the 2a winding if you'd like
     
  3. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    10,140
    Likes Received:
    3,552
    Location:
    SoCal U.S.A.
    Yeah, if I run that phase inverter 12AX7 heater together with the power tubes heaters, will more than likely just give up the idea of running EL34's.

    I was considering the first one or two preamp tubes heaters for DC. Not decided though. I am just wondering if there can be any added hum issues with multiple heater taps. It is not something you see in builds, or at least I have not seen it yet.

    If I could find a 15W to 30W power transformer that gives me well under 400VDC after my solid state rectification AND plenty of heater current on tap of close to 6A, I would have my ideal power transformer. Oh yeah. And the other important feature in why I am doing this is to shed some pounds of this heavy beast of an amp lol. Can't have a huge power transformer, or I would just leave the one that it is in there now.
     
  4. 2L man

    2L man Member

    Joined:
    Sep 30, 2020
    Messages:
    59
    Likes Received:
    20
    Sorry but 6A of 6,3V is already 38VA.

    I would say an average 6V6 push pull tube amp needs at least 80VA power supply but 100VA or bit more is safer. EL34 needs at least about 130VA but even 200VA is not too much safety margin for heavy duty use.

    I use toroid power transformers on my builds because they are lightr and cheaper and also cause less electrical noise when "center hole imaginary line" is placed pointing away from the pre amp circuit.
     
  5. Gene Ballzz

    Gene Ballzz Well-Known Member

    Joined:
    Feb 19, 2013
    Messages:
    2,325
    Likes Received:
    2,083
    Location:
    Las Vegas, NV
    @RickyLee
    IIRC, the act of converting that AC heater to DC increases the AC current draw, by a bit, in the process.
    ICBFOST (I Could Be Full Of Sh!t Though),
    Gene
     
    Last edited: Nov 27, 2020
  6. thetragichero

    thetragichero Well-Known Member

    Joined:
    Jun 6, 2010
    Messages:
    2,969
    Likes Received:
    978
    Location:
    flo rida
  7. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    10,140
    Likes Received:
    3,552
    Location:
    SoCal U.S.A.
    I do not know the specs on the stock Fender Deluxe Reverb power transformers, but the standard offering from Classic Tone only has a 3A 6.3V tap. They did offer upgrade transformers with higher current capacity. The Deluxe Reverb runs two 6V6 and six 12AX7 off that heater tap.

    Do you have any links to those toroid transformers you use?
     
  8. william vogel

    william vogel Well-Known Member

    Joined:
    Dec 18, 2016
    Messages:
    491
    Likes Received:
    461
    I have some custom wound power transformers from pacific transformers that I had made up for 15 watt Trainwreck stuff (2 el84’s or 6v6) with 260-0-260 volts @ 200mA and 6A @ 6.3volts. After solid state rectifier they have 330-335 volts DC. You can run any power tube (EL34’s). I’m going to check the specs again for the 6.3. $100 plus shipping
     
  9. william vogel

    william vogel Well-Known Member

    Joined:
    Dec 18, 2016
    Messages:
    491
    Likes Received:
    461
    I just checked the specs. 6.0 amp 6.3 volt.
     
  10. 2L man

    2L man Member

    Joined:
    Sep 30, 2020
    Messages:
    59
    Likes Received:
    20
    I'm in Europe and I assume you are in NA so some what I have used do not have 120V.

    Toroidy.pl (Poland) build power transformers for 115V input and many kind special orders and their OPTs are getting name among HiFi builders

    Audiophonics.fr (France) build custom transformers the one I bought did cost only slightly more what same power stock transformer elsewhere but their manufacturing time schedule is about 6 to 10 weeks depending what day of month you buy it

    Best place for 230VAC stock toroidy buy I know is Tube Town shop (Germany). I have bought 56VA, 80VA, 106VA, 134VA 139VA and 179VA but not yet used them all.

    I have also used Indel (Poland) toroidy PTs. I am sure they can build all kind PTs and it seems like they might be best buys as their stock have cheapest VAs

    Amplimo (Holland) have few dozen different tube power toroidys but so far I have bought only and it has two 115VAC input coils which can be connected parallel for NA use. Obviously others as well so Amplimo page is worth visiting. Also I have one very nice sounding 25w 8000/4, 8, 16 ohm toroidy OPT which weights only 664g. I have test it in 5F3 but perhaps I will build AC30 circuit for it. Its HiFi rating is 25W so gor guitar use it should be good up to 40W. Toroidys are said to be critical for DC current but when I did test it using highest and lowest gain 6V6 I have I saw on oscilloscope low freguencies distort and heard distortion but it sound fine just like guitar amp.

    Menno Van Der Veen (Holland) desing Totoidy mainly OPTs and I have built 12W (VDV-2512-SEE impedance set for 5k and one EL34) single ended which sounds great. I have test VDV-4050-Guitar 50W push pull OPT which is very light only 984g but I won't install it to less than perfect circuit, light weight chassis and light weight good looking combo cabinet which I have not yet built :). It is more critical to PP bias imbalance so I might need to use Auto Bias circuit or Cross Coupled Cathode Bias circuit which I have not test yet.

    I don't know are European transformers worth shipping to NA but I have read HiFi builders have bought at least Toroidy.pl output transformers.

    Nowadays there must be NA toroidys as well when they are easy to manufacture using current machines.
     
    adew1 likes this.
  11. RickyLee

    RickyLee Well-Known Member VIP Member

    Joined:
    May 22, 2010
    Messages:
    10,140
    Likes Received:
    3,552
    Location:
    SoCal U.S.A.
    That is a good transformer.

    I solved my problem for the time being with this project. I ordered a small filament transformer. It puts out 6.3VAC at 8A.
     
  12. william vogel

    william vogel Well-Known Member

    Joined:
    Dec 18, 2016
    Messages:
    491
    Likes Received:
    461
    Like I said, I ordered them for a special purpose. There’s no shelf stock transformers with lower voltages and high current. These I have are basically Ken Fischer’s big power transformer 1/2 current. I didn’t see any reason for the 300 volt taps because it wouldn’t be needed for a 15-20 watt amp.
     

Share This Page