Choke for 6100

Discussion in 'The Workbench' started by Setneck, May 13, 2011.

  1. The Dose of Harmony

    The Dose of Harmony Well-Known Member

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    Hey what whats the result of the choke on the 6100 ?
     
  2. john hammond

    john hammond Well-Known Member

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    The more ohms in the choke your using for this application, the cheaper the choke is going to be. There is no practical reason for what you're doing, to get the lowest resistance choke you can find.
    Henries, is possibly more of a consideration.
    The more inductance, ' Henries' ( H ), the more ripple ( hum) is taken away.
    taking hum away from the output tube screens, and preamp is the sole job of the choke that you want to put in your amp.
    If you use a 5H choke, and then use a 25H choke, you may notice a difference..one will be ' faster' than the other, and you may hear less hum with the larger 25H one.
    I doubt you would though.
    i recommend any choke 5-25h, and 100-150ma for a 100 watter, 60ma for a 50 watter.
    i once noted there is no choke in this jcm900 amp i have here, so i put a choke where the resistor was, it sounded better with the resistor.
    This poster is very dubious about any benefit from changing out the resistor for a choke in any guitar amp that is made with the resistor.
     
  3. ampmadscientist

    ampmadscientist Well-Known Member

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    A. The choke is used in conjunction with the filter capacitors to filter ripple out of the power supply.
    (ripple is HUM which results from the AC power being changed into DC)

    B. The DC resistance is very important because it tells you how much voltage drop will occur based on the load.
    The factory specification of a choke always gives you the DC resistance.
    When an engineer designs a power supply, the DCR is ALWAYS considered.

    C. Choke / filter power supplies were always used in older amplifiers. Using the choke means that the filter capacitors can be a smaller value, compared to a power supply that has no choke.
    (the choke makes the power supply filtering more efficient - to attenuate ripple, thereby reducing HUM)

    D. The Choke can radically affect the sound of an amplifier because:
    Combined with filter capacitors values, the power supply choke can develop a resonant frequency.
    This may be a good or a bad thing depending on what frequencies are in that result.

    For example: adding a choke may cause major overkill in the low sub sonic frequencies....depends on the value of the choke, combined with the value of filter capacitors in the power supply.
     
  4. john hammond

    john hammond Well-Known Member

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    thankyou ampmad, point d) is educational for me, and explains why a resistor instead of a choke is sometimes a good idea ( merc mag and other choke manufacturers would simply never tell you that or imply it)

    i think however, point b) moreseo apples to choke input power supplies, whereby instead of a capacitor placed right after the rectifiers, you put a dirty great choke or two ( much larger than a typical marshall or fender choke ).

    these choke input supplies, to give you an idea, if the rectified voltage is 500v, the voltage after the first choke is only 450v...instead of 600v if you were using a regular capacitor input power supply. but( importantly..this is the money shot), they HOLD that 450v during say, a bass transient)

    the reason why more resistance is less desirable in these ' choke input' power supplies is that the higher the resistance, the more voltage drop and the poorer the regulation ( regulation is the chokes ability to ' maintain' the same current under load..which is the whole point of 'choke input power supplies'

    back to small typical guitar amp chokes ...of course, you dont want zero resistance in a choke. the value they use in a resistor which is what 100? ohms...would make a choke small enough for typical guitar amp application more expensive to buy than say.. a 150 ohm choke..( if both chokes were say 5H) it just doesn't matter that much when filtering just the screens and preamp supply, which is what marshall/ fender chokes do.

    you can use all sorts of things for chokes in a guitar amp ampmad, ever used a filament transformer? just one side of it? they work perfect, absolutely perfect.
     
    Last edited: Sep 9, 2019
  5. marshalltsl

    marshalltsl Member

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    I tryed some choke's in one TSL100. 10H, 6H, 5H, ... It change your tone just a little. IMO If the amp it's designed properly it's a waste of time use it. I think it's not must have in your LM6100.
    :cheers:
     
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  6. anitoli

    anitoli Well-Known Member

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    Resistor does the same thing as a choke and costs so much less according to Santiago. He stated that somewhere in this forum.
     
  7. ampmadscientist

    ampmadscientist Well-Known Member

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    Start the reactor. free Mars!
    It's pretty wreck-less to just buy and install a choke without understanding what it's going to do or not do.
    But theoretically the choke could work better than a resistor if the circuit is designed to do so.
     
    Last edited: Sep 9, 2019
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  8. ampmadscientist

    ampmadscientist Well-Known Member

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    No, a resistor definitely does not do the same thing as a choke, no matter what Santiago says.
    The choke has a definite purpose for filtering power which is not the same.

    The choke filters the ripple more efficiently with less voltage drop compared to a resistor. (if the power is correctly designed)
    The choke can work with smaller value capacitors, and with a better result compared to the resistor.
     
    Last edited: Sep 9, 2019
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  9. santiall

    santiall Well-Known Member

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    I never stated that... a resistor and an inductor aren't the same and the characteristics of an LC filter (2ns order) are not the same as the ones of a RC filter (first order).

    What I did state is that once the capacitance is large, like in a JVM, having a LC or a RC filter isn't too different because the large capacitance 'swamps' the response of the filter. That applies to any amp that has a relatively large capacitor after the choke or resistor. With small capacitor values then the the differences start to show.
     
  10. Fender

    Fender Active Member

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    For the record, I did replace the choke resistor with an inductance on my 6101 (Hammond 194F). I didn't hear the difference :D
     
  11. marshalltsl

    marshalltsl Member

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    I didn't buy anything, just a crazy friend with his TSL
     
  12. The Dose of Harmony

    The Dose of Harmony Well-Known Member

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    I really would like to hear your opinion on the 6100lm !

    If you would modded what would you do to it?

    I believe the 6100 is one of the best amp ever and many people says what are you gonna modded if it sounds good but i the way i think its what if it can give more?

    I been just thinking on putting a choke, better PT and OT!

    And some time i feel the presence knob should be more sensitive but i havent put brand new tubes until that i wont touch

    By the way i love my Jvm it took me a while to dial it
    now i am using it for recording a lot!

    Great job
     
  13. john hammond

    john hammond Well-Known Member

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    -if you think its the best amp ever, then changing o/t, p/t and choke will give you another amp sound. bit of a risk wouldn't you say? ( who says marketing doesn't work?)

    i suggest that if you've found the best amp ever, don't change a single thing on it.

    there is a strange problem that people get when they find gear they truly love

    " what do i do now?"

    Unfortunately, sometimes the wishes we have, actually come true.
     
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  14. The Dose of Harmony

    The Dose of Harmony Well-Known Member

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    Yeah I know !!!!
    But a am lucky that i have two 6100 lm and one for cheap so i been bitten by bug ?

    Its just that you know we guitar players we want more and more , i been enjoying a lot my JMP and my Mesa v and i dint know why i dont think about moddind them
    but with 6100 lm its different because i can do so many things with that i just think

    what if ?
     
  15. john hammond

    john hammond Well-Known Member

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    if its good, very good just the way it is..youll be throwing your money away at people who have told you lies.And, you may just well wreck the sound you now love.
    - less, is very much more in this guitar and amp world, sometimes.
    by adding frequencies to the mix, you will probably create mud.
    too many frequencies in the same bandwidth just doesn't work.
     
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  16. marshalltsl

    marshalltsl Member

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    If I had two LM6100 I wanted one with EL34 and the other one with 5881 tubes.
     
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  17. anitoli

    anitoli Well-Known Member

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    I have both and there isn't much of a difference. The real difference is in channel 3.The LE's and Anniversary heads had different parts that made that channel sound anemic compared to channel 2. The LM's have a mod done that rectifies this.
     
  18. Micky

    Micky Well-Known Member VIP Member

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    I have passed on 2 6100's with burned boards inside. I don't know which versions, one was purple/blue with a gold faceplate but is there a mod to keep these from burning up?
     
  19. santiall

    santiall Well-Known Member

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    I wouldn't change much tone-wise but I'd change all the biasing circuit and sort out the heaters hum. The way of deriving the bias from the HT is not reliable at all, I have a 6101 and it was breaking all the time until I modified that. Also, the hum is gone after powering the heaters with DC.

    The last touch was to replace the old micro and eprom with a modem micro. I haven't had that much time to finish that part though :)
     
  20. The Dose of Harmony

    The Dose of Harmony Well-Known Member

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    can anybody elaborate and breakdown to a simple mortal all this that Santiall said

    "I wouldn't change much tone-wise but I'd change all the biasing circuit and sort out the heaters hum. The way of deriving the bias from the HT is not reliable at all, I have a 6101 and it was breaking all the time until I modified that. Also, the hum is gone after powering the heaters with DC."
     

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