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.

Simplified 5E8a Layout

Discussion in 'Shock Brother's DIY Amps' started by nathanh, Dec 27, 2018.

  1. Lynxtrap

    Lynxtrap Tele-Holic

    Posts:
    821
    Joined:
    Feb 29, 2016
    Location:
    EU
    From a pure technical standpoint, two parallell perform better than one large with the same net value.
    You get distributed consecutive filtering without the drawbacks of having to add large capacitances to compensate.
    For one, ESR will be halved - or down to 1/10 if you parallel ten 3uF caps ;)
     
    robrob likes this.
  2. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    That would be one insane dog house haha
     
    robrob likes this.
  3. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    But seriously, is the upside to this negligible or are the chances of hum greater with a single?
     
  4. Lynxtrap

    Lynxtrap Tele-Holic

    Posts:
    821
    Joined:
    Feb 29, 2016
    Location:
    EU
    I can't really say how much it matters in this type of amp.
    It's a whole science in itself, with impedance, capacitance, resistance, currents, temperatures and what have you.
    I wouldn't worry about it. I might be more concerned in a single ended amp.

    On the other hand...if you have the space in the chassis, why not? The feeling when powering up a new build and thinking there's something wrong because you don't hear noise is worth the cost of a cap and couple of extra solder joints. ;)

    Every cap works against hum of course, progressively so with every cap added. That's why you tap V1 from the last one.
    I did parallel caps in a preamp I built recently where I wanted to make sure the noise level would be as low as possible.

    Fender might have done it for the reasons mentioned above, small caps being cheaper.
     
    nathanh likes this.
  5. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    I never thought about V1 that way! It's these little nuances that I love about exploring circuits. I'll probably roll with 4x16uf.

    Whats left:
    1) Calculate the correct NFB
    2) Replace the worn Tolex with shellacked or lacquered tweed. Should be a fun learning experience.
    3) Design a face plate (any info here would be great)

    Now to start looking for a hole in the "budget" and building a shopping cart at tube depot that I can stare at longingly. Thanks for all the help and letting me ask questions. I've learned a lot. Will report back when theres actual movement if anyones interested.
     
  6. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    8,330
    Joined:
    Dec 29, 2012
    Location:
    United States
    When changing the feedback source from one output transformer secondary to another you change the feedback resistance by a factor of 1.41 for one step change (for example going from a 2 ohm speaker tap to 4 ohm), a factor of 2 for 2 steps (example 2 ohm to 8 ohm), or a factor of 2.83 for 3 steps (example 2 ohm to 16 ohm).
     
    SSL9000J, nathanh and Lynxtrap like this.
  7. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    So the 4 ohm has a 56k NFB resistor therefore the 8 ohm would need 79k ohms of resistance. It looks like theres only 82k resistors available but I bet I could find one that's tolerance leans south.
     
  8. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    8,330
    Joined:
    Dec 29, 2012
    Location:
    United States
    You most likely wouldn't hear a difference between 79 and 82k.
     
  9. nathanh

    nathanh Tele-Meister

    Age:
    35
    Posts:
    285
    Joined:
    Oct 13, 2016
    Location:
    Bama
    Copy that. It will probably take me a year to get ahead enough to buy everything but I'm looking forward to coming back and posting the amp and some clips.

    I've got a type 4 MV in my 5F6a build and I'm debating adding it to this one while I'm at the drawing board. I just noticed that on a Cathodyne Phase Inverter you should remove the grid leak and ground the MV pot at the tail, replacing the resistor. Should I be doing the same thing for an LTP setup?

    Edit: In hindsight that would be a no.
     
    Last edited: Jan 7, 2019
    robrob likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.