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Thread: Resurrection

  1. #1
    Site Janitor tboy's Avatar
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    Arrow Resurrection


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    -tb

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    That is fantastic!!! You are the best. Thank you very much.

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    Quote Originally Posted by tboy
    Playing around I noticed my username and password from the old site appears to work as well. That's cool... not having to register to yet another site!

    Thanks Tboy!!

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    Fantastic!

    I am very thankful to tboy for volunteering when I asked. I saw the posts on the old Sunn site about it going down and no one seemed to be stepping up, and I thought about who I knew that could possibly take care of it and make it work. Tboy was the first I asked and it looks like I made an excellent choice! If I would have known how to do web hosting myself I might have volunteered myself, but I'll stick to helping out fellow Sunn-setters, and making my own projects work.

    Thanks again Tboy!

    Greg

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  5. #5
    Senior Hollow State Tech Bruce / Mission Amps's Avatar
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    Quote Originally Posted by tboy
    ********************************************************
    I just rebuilt a Sunn tube amp, what I think is a 200s but using two KT88s and a couple 9 pin tubes...
    The Sunn brochure says it is +250 watts of program music or some such nonsense....
    At a B+ of around 540vdc with a 5AR4 rectifier, we are getting is about 65 watts, dead clean into an 8 ohm, 100 watt dummy load.
    It sounds great but is the RMS = to 25% of "program music" rule appplicable here?

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    Bruce

    Mission Amps
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    I don't know anything about RMS to program music equivilants, but the power out sounds about right. I rebuilt and modded my 200S and with about 560v B+ it was putting out right around 70W RMS. I'm using higher filter cap values for the first two stages to get a tighter bass response, and using a Weber Copper Cap WZ34. All the E caps are now discrete caps with a higher voltage rating instead of that over-stressed can cap that was stock. I use the amp for bass only and it has a very nice sound.

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  7. #7
    Senior Hollow State Tech Bruce / Mission Amps's Avatar
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    Thanks...
    I also built up a series parallel cap circuit with 270K bleeder resistors for about 50uF@1000v on the plates and 50uF@1000v on the screen node, eliminatiing that stingy FP cap and only used the last two sections for the preamp B+ filter.
    Still, with the 5AR4, and the older KT88s that it came with, 62-65 watts clean is all it will do and that is probably correct then.

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    Bruce

    Mission Amps
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    Hi Bruce. In mine I went with a 110uf @ 700v and 60uf@ 700v series caps w/ bleeder resistors for the first two cap sections, and then discrete 20uf 500v caps for the next two. The third one needs the 500v but the 4th section is ok with a 450v cap. I actually liked the sound better with the Weber CC in this amp than with the 5AR4, and I used a lovely pair of blue glass JJ KT88's. The JJ's really make these Sunns perform.

    I've got a 2000S that I haven't gone through yet that is using GE 6550A's, but my 200S sounds better. You may check with Bob at Eurotubes if you're wondering about the power out. He's a Sunn fiend and has several. I haven't met him yet and only know this by reputation and hearsay, but he's less than 15 miles away from me so one of these days I'll go meet up with him.

    Greg

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  9. #9
    Senior Hollow State Tech Bruce / Mission Amps's Avatar
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    Very good.
    I am using four, 100uF/500v F&T axial caps in the B+ rail's PI filter network.
    Two pairs of series 100uF caps and the choke in between the two sections.
    The AC ripple is fairly low and I'm pretty happy with it, considering on a 90-100w Twin Reverb I would not use anything less then 70uF to 110uF@600v anymore.
    As a matter of fact, I have been using two 220uF@300v F&T caps in series for those old Fender amps lately.

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    Bruce

    Mission Amps
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    Hi Bruce. I love those F & T caps...very well made. I used some Xicons in mine, with the same layout as stock, but just with the larger values. I have no idea what the ripple is, though with larger values, its probably less that the one you fixed. I was mainly going for an improvement in the bass response, which I got of course. I always thought the Sunns (and Dynacos) were a little soft in the bass response stock, and they have plenty of high end with those nice transformers, so upgrading the cap values a little helped to even out the tone to my ears. If I was using it for guitar I wouldn't have bothered though.

    I was thinking in my 2000S of going with Solen polypropylene caps, since there is soooo much room in the chassis. Maybe I'll wire them up first though and see how it sounds before I cut holes. I've heard that you don't need to go with as large a value of a cap if you're using polypropylene as compared to electrolytics, but have no idea if it is true or why the reason might be. Better ESR maybe?

    Greg

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    250 watts program power was optimistic hype from their marketing dept. remember this was made during the days of music power +/- 1dB.

    the tube manual is your bible here; 2 KT88/6550 should deliver about 60w RMS.

    The amplifier is a dynaco MK-III, right down to the secondary feedback loop from one of the output tube screen grids.

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  12. #12
    Lifetime Member Enzo's Avatar
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    Hi u-a, welcome to the forum.

    You might check the posting dates of the threads, this one has been dormant for two years now.

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