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Davemade 2x4 (let the beatings begin...)

Discussion in 'Amplifiers' started by TheRealPorkchop, Nov 19, 2018.

  1. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    I'm gonna ask this question because I want either an opinion or actual knowledge from experience...

    I know this is gonna open the proverbial can of worms and the opinions will vary. For the record, yes I am talking about overdriving the ever-loving-dog-snot out of it too, with a Magnum S9.

    So... how much average and PEP power should one of those put out if everything is in working order? I've ran across one in a pile of "junk" that I've recently acquired and I don't have a lot of experience with 2x4's. I personally prefer a straight 2 or a straight 4, so here we go...



    It appears to be a "stock" amp, nothing has been changed and it has 2 red dot 2290's driving 4 red dot 2879's. I know you need to know what the output of the radio is, this will also open a can of worms but let's try to just look past the whole radio issue and focus on the amp itself (if possible). My testing radio is a Magnum S9 with dual 1969's, the PEP swing of this radio is in the neighborhood of 55 watts. The radio has had a full alignment to factory spec or as close to it as possible anyway.

    Now, what I'm seeing is about 600 watts average and 1200 watts peak, ran at 14.5 volts off a Cosel power supply, the 125 amp version. The radio is being ran at 14.2 volts and the supply is a 30 amp Astron unit. Neither supply is dropping voltage while being pulled on, not according to the volt meters connected to each unit. I'm unsure of the amperage being drawn, especially off the amp supply, I don't have that option at the moment.

    So... does this sound about right or should it be more? I kinda feel like it should be a little more but then again... eh... maybe it's right? And yes, I know I'm technically overdriving it and all that goes along with that, I get it... I understand. But it's what's sitting in the shop at the moment and it's what I'm testing with. I'm thinking of gutting it and using the parts for smaller builds, I have no use for a 2x4.
     

  2. 543_Dallas

    543_Dallas Sr. Member

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    The 2x4 is really a waste of parts IMO. A one pill will beat all the watts you're going to get out of 4 2879s. 600 average and 1200 pep is about all it will do on 14 volts. A comp tuned cobra 25 or 29 might get a little more average power out of it but you're out of headroom. The pep has hit the wall.

    Crank it up to 20 volts and it should make around 2kw in short bursts. I used to deadkey a 1x2 at 900 swinging back to 400 avg and 1100 pep on 21 volts. Nasty nasty but it would key all over my friends 6 pill.:ROFLMAO:

    I ran an s9 with a straight 4 pill for years. It made 125 watts carrier, 300ish average and 650 pep. It was a nice combo. The dave style amps are easy to reconfigure. You could pull the 2 pill section out of it and make another amp. Jusy bypassing the driver and making it a straight 4 will take about 15 minutes.
     
  3. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    I wonder how hard it would be to make it a straight 6?
     
  4. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    Well I’m not going to use it at all, I just found it in the box and wondered if it was working correctly. That’s kinda disappointing that that’s all it’ll do, not very impressive. I’d expect more, or I did kinda considering what it is and knowing its “dirty”.

    I was thinking of making 3 amps out of it, if anything. But yeah you’re right, a few minutes and it would be a straight 4 easily. That’s a lot less work, maybe I’ll do that and fiddle with the “driver” part as another project.

    I too am now curious as to what would be involved in making it straight 6. Probably be crappy or impossible since you can’t put the driver section beside the 4 section AND the fact that you’d have to replace those 2290’s with 2879’s.
     
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  5. jessejamesdallas

    jessejamesdallas Sr. Member

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    I had one...(Joe-made in NC) 1100-1200w is going to be about max...However, those are really meant to be ran with a single final radio that only swings around 6 or 7w's (10 max) and you would see about 850-950w, and sound good!

    OR. With long key-down time using a dual-final radio you risk releasing the 10 ohm smoke genie...
     
  6. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    Will that genie look like Jennie from “I dream of Jennie”? If so, I’m going out to the shop to feed my 98vhp into it that’s sporting those 4 2879’s... haha.
     
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  7. jessejamesdallas

    jessejamesdallas Sr. Member

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    If so...at her age now it might scare the hell out of ya!:eek:
     
  8. kopcicle

    kopcicle Sr. Member

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    [​IMG]
     
  9. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    I think I have seen some amps where the double sections aren't lined up so that might be ok. After the transistor swap, the input and output combiners would have to be reconfigured but I am not sure how to do that.
     
  10. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    Y’all do me wrong, so wrong. I meant back-in-the-day Jennie not today. Y’all are wrong, so wrong, haha.

    I think I’ll convert it to straight 4 and maybe sell it, I really have no use for it. Then again, I might just put it back in the box and forget about it. You never know what I’m gonna do, neither do I.
     
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  11. jessejamesdallas

    jessejamesdallas Sr. Member

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    You could sell it...boxs with Toshiba pills sell for good money, that one could easily fetch $500. maybe more.
     
  12. 9C1Driver

    9C1Driver Sr. Member

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    Since it has good finals make it a straight 4 and keep the 2290's for a future repair on a nice 2 pill. Or sell it as is, would bring strong money.
     
  13. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    Well I just looked closer and one of the 2290’s isn’t a red dot, so that means a repair was done and I guess the value just decreased.

    I’ll figure something out to do with it. At least far as it’s output goes, it seems inline and working correctly.
     
  14. kopcicle

    kopcicle Sr. Member

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    again?

    "
    Early design Toshiba 2SC2879 do not have the small red dot on the package (lower right). In contrast, the later “A” version has the dot to identify that it uses a
    different insulator between the chip and the flange base.

    The 2SC2879A meets all specifications on the Toshiba Data Sheet, however, we believe
    the heat conductivity from chip to flange with the original 2SC2879 part is better.

    Also, we found that the 2SC2879 had a bit higher Collector to Base breakdown voltage,
    which would be of interest it the transistor was to be pushed beyond factory specs."

    Matched means they hopefully have been checked for similar gain specs."
     
  15. jessejamesdallas

    jessejamesdallas Sr. Member

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    That's a easy fix...Get you some RED Nail Polish, and just....:whistle:
     

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