4X12 8ohms and 4X12 16ohms question ?

Discussion in 'Cabinets & Speakers' started by Kelia, Sep 15, 2019.

  1. Gutch220

    Gutch220 Well-Known Member

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    This is the email response I received from Marshall.....

    upload_2019-9-20_14-9-45.png


    So, she didn't specify other models, so maybe it's just this hybrid 1x15 bass combo. (?)

    [​IMG]
     
    Last edited: Sep 20, 2019
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  2. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    That is a solid state hybrid with one ECC83 in the preamp which is actually powered by what seems to be a voltage doubler which is attached to 1/2 of a PT HT centered tapped secondary. Man, that is a weird configuration for a power supply.

    But it has little to do with the discussion at hand.
     
    Last edited: Sep 20, 2019
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  3. Gutch220

    Gutch220 Well-Known Member

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    I asked the people at Marshall if they've ever used voltage-doubling circuitry in ANY of their amps, past & present, and this is the response I got, so read into it as you will.
    I read into it as, this is the only model they've ever used it on, but I sent a follow-up email to clarify things, and we'll see what they say.
     
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  4. santiall

    santiall Well-Known Member

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    I guess they are talking about the MB series. I designed those ones and bc have a voltage multiplier to power the preamp ECC83. I think it was used in the MB150 and the MB450 plus their variants, not in the smaller ones
     
  5. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I know. You are a trooper.
     
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  6. Gutch220

    Gutch220 Well-Known Member

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    ....but we are mostly concerned with 50/100w tube heads from 60's, 70's, and 80's
     
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  7. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    The MB was a different series.
    The Bass State series came after and on the foot of DBS series.
     
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  8. Kelia

    Kelia Well-Known Member

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    I'm still here reading you guy's and find it so interesting !......but I'm a little sad at the same time not being able to understand this great knowledge that some of you have and share !!

    Awesome Science !!
     
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  9. santiall

    santiall Well-Known Member

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    Sure but definitely the bigger MBs have a voltage multiplier, I think it was 3x or even higher
     
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  10. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    I found this. You are right and they seem to follow in line except no vacuum tube.
    No one copy this since it is protected.

    upload_2019-9-20_15-33-9.png
     
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  11. john hammond

    john hammond Well-Known Member

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    - santiall, why argue? if we are two men discussing something in a forum, why not just take a look at post 86 and break it down a little for us?
    I'm afraid, for at me at least your response is a little ....light...for someone who seems to be so revered in here.

    The observation for example, that once the centre tap is taken out of the equation we are left with a ' normal' bridge rectifier should have been, i would have thought the FIRST observation in relation to this little riddle of ours here, its actually fascinating to me..isn't it to anyone here?

    The fact that TWO methods of rectifying voltage can run concurrently ( hehe i love this shit ) is absolutely jaw droppingly interesting to anyone who realises it.

    I'll admit i'm a little curious, santiall, at how you refer to the problem as one of ' semantics' yet leave it at that..where is the play on words exactly..wait..not even exactly..just remotely?

    the semantics element comes from people who say that because the centre tap will provide doubled voltage due to the voltage doubling network of diodes and caps attached to it, that by simply removing that centre tap, at that point, H.T is derived from the remainder of the circuit comprising a simply full wave doubler.

    There is a highlighted sentence in post 86, that I would have thought would have been the first thing that was addressed by you, but instead..i see " and I won't argue at all, it isn't worth. It's fine, sorry to disappoint you"

    Instead of arguing, why dont you simply address the highlighted sentence in post 86?

    Hehe doesnt anyone here realise that by configuring diodes and caps like this, youre going to get doubled voltage somewhere?

    right there people...to unmask the bluff thats been put on ( you, not me ) just decipher that very simply network of diodes and caps haha

    i note the response from marshall themselves...youve got to be fucking kidding right? as if they were ever going to know in the first place, the people that converted that bassman to a bluesbreaker probably died years ago, they wouldnt have a clue except what cloths, vinyls and colors are good for next years models.

    Ok, santiall has told me 'to google'
    so lets go and take a look at what another gentleman in another forum who isnt afraid to let it all hang out has to say on the matter.

    Ill take a look at your question a little down the track, spacerocker...lets keep some clarity in the thread for now shall we.


    i wish we could have discussions like this here, anyway..enjoy.

    taken from metroamp forums

    authored by a fellow called 'flemingras'

    In regards to the "voltage doubler" circuit...that as has been said before is a matter of semantics. If you look at it as if you're doubling the center tap voltage, then yeah you could say it's a voltage doubler. But hooking up across the full winding without the center tap connected will give you the same end result, but you'll have to install bleeder resistors across the first stage filter caps to keep the voltage on the caps balanced. This circuit is more of a full wave voltage balancer as it is used to allow each half of the HT secondary to charge the first filter caps instead of using bleeder resistors to do it. Since each half of the HT secondary is 1/2 the voltage of the full HT secondary, you get 1/2 the voltage on each cap and each cap on the first filtering stage sees the same voltage to prevent one from going overvoltage.
     
  12. john hammond

    john hammond Well-Known Member

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    again, the centre tap has not been removed, the bleeder resistors never put in...and B+ appears courtesy of the voltage doubled centre tap.

    download (2).jpg
     
  13. santiall

    santiall Well-Known Member

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    John, I'm in the Internet since pretty much it started with the news groups in the 90s and experience tells me that 'arguing' online is a waste of time plus I feel you are looking for controversy and have a strong opinion that won't change hence my 'light' response. I'm not here to prove you wrong nor right, I have zero interest on that. I replied to this thread with my view and that's it. You claimed I'm wrong and that's also fine with me. Just a forum, not a competition of right and wrong.

    Again, sorry to disappoint.

    PS1, semantics refers to 'Internet terms' like calling a full wave rectifier a voltage doubler, cathode biasing class A, etc.

    PS2, food for thought. If I have two taps do I have a voltage tripler? Many transformers there have secondaries with multiple taps... and if I just look at 1/3rd of the secundary then I should have something like 3 times that voltage multiplied by 1.4142, isn't it?
     
  14. john hammond

    john hammond Well-Known Member

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    lets just focus on the current issue , santiall..shall we?
    why waste words? lets get to the bottom of this, and use all electrickery words.
     
  15. santiall

    santiall Well-Known Member

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    Yup, that's actually one of the first amplifiers I designed for Marshall
     
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  16. john hammond

    john hammond Well-Known Member

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    Ok, thats good, youre an amp designer..lets talk the talk, if you want to.

    If you DONT want to, then thats ok too.

    Thankyou.
     
  17. Gutch220

    Gutch220 Well-Known Member

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    So there are multiple ways to literally 'double' the voltage, so maybe you guys are talking about different ways, but calling them different things, rendering the others' wrong?
     
  18. crossroadsnyc

    crossroadsnyc Senior Moderator Staff Member

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    An acknowledgement of respect to you and the rest of the guys for remaining so respectful yourselves. Having watched this scenario play itself out time and again, it was put to rest for good this evening. I think I can speak for everyone in saying that we sincerely appreciate your 'light' responses :yesway:
     
  19. mickeydg5

    mickeydg5 Well-Known Member VIP Member

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    Not exactly so do not jump to conclusions due to so much information fying around.

    You have AC to DC power supplies which are utilized in things like our musical amplifiers. There are common types that are used most often that include half wave, full wave and bridge which is a type of full wave also.
    Power transformers are mainly used at the front end of these power supplies. These come in all forms of setups as mentioned and may include multi-taps. But the transformer does not double anything as it merely provides transformation of wattage, from one voltage and current level to another.

    Most bridge and half wave rectifiers use a plain PT secondary because simply put that is all it requires.
    Now a common full wave is different because it requires a center tap. By the way the center tap has no intrinsic voltage value until it is referenced somehow.
    So lets examine some PT secondary, one with and one without a center tap. We will use the voltage level value of 350VAC. The secondary without the centertap develops (per design) the 350VAC across the tfrom two end taps. The secondary with the center tap still develops the same 350VAC across the two end taps but can now also be referenced between the end taps and the center. When doing this 175VAC will be witnessed on each side of the center since that divides it in half.

    All of this so far has just been front end power supply setup.

    NOW we talk normal rectified voltage power supply and doubled rectified voltage power supply (the voltage doubler).
    I want to mention there are other scenarios like voltage tripler and voltage quadrupler.
    A normal rectified power supply circuit will put out like 1.1 to 1.4 times the initial supply. For 1.4 that would be like 350VAC equates to 490VDC.
    A voltage doubler rectified power supply would then as you might guess double it, times 2. For 2.0 that would be like 350VAC equates to 700VDC.

    The doubling, tripling and so on is in the power supply filter capacitor setup. It has to have the correct components and placement of those compnents to achieve the doubling and so forth. The trick is that each capacitor or capacitor bank on either side of the rectifier has to fully charge during phase changes. The fully charged capacitors store and provide that voltage which add up.

    I hope that is easy enough to understand and makes some sense of all this.
     
    Last edited: Sep 20, 2019
  20. spacerocker

    spacerocker Well-Known Member

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    Santiago - Many thanks for explaining that - it makes perfect sense! Thanks for your patience in this discussion!
     

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