1968 Sunn 200S

Discussion in 'Amps and Cabs [BG]' started by NKUSigEp, Oct 26, 2011.

  1. Well I've done it to several other people's amps on request in addition to my own. I don't go overly large, and I don't change the values in the preamp or phase inverter supplies since those ones are RC coupled and do change the tone if you change the caps. I go with 110uf in the first position (before the choke) and 50uf (plate and screen supply) in the second position. The others stay at 20uf. When I use electrolytics for those, I connect them in series and use 350v caps for a 700v rating in those spots. That puts the Sunn on par with the Blackface Fenders for filtering so I wouldn't say it makes it overly stiff. Everyone who has played or heard this setup agrees that it is superior to stock, and that would include Conrad Sundholm who is a friend of mine here locally. He heard my 200S before I sold it on numerous occasions. It also hums less but that is a side benefit. Ask EdBass what he thinks about the larger caps...he will agree with me too. The only caveat is that with the larger caps a SS rectifier or Weber Copper Cap has to be used in the amp as the filtering is then too high for the tube rectifier.

  2. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Washington, Utah
    John K Custom Basses
    two 110uf's in series gets you to 55uf. vintage fenders were two 70uf's in series for 35uf, then all 20 uf's further down the line. if you like them that way, that's great, but higher filtering just doesn't do it for me.
  3. Yah what I meant is that with the 220uf in series for the first section and the 110uf in series for the second section, I end up with 110uf and 55uf for the two respective stages in the Sunn, and it ends up being no stiffer than the blackface Fender bass amps in feel...I didn't mean that the filter cap values were the same....sorry I wasn't clear on that. Of course everyone hears differently and likes different sounds, so your choice is as valid as mine.

  4. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    uh oh im gonna try not to be too opinionated, but.......
    Nothing i mean nothing with the name weber will ever touch my Sunn amp. so getting past that.

    Uh oh, no no....dont want big 110uf before the inductors, the max capacitance allowed on a GZ34 is 60 uf. Plus that capacitor is mainly for ripple rejection. It follows pretty much textbook power supply design. Based mainly on the output impedance of the transformer and the inductive reactance of the capacitor, the value is actually suppose to be very small. the supply could see more voltage with a smaller cap than 50uf. then we trick that GZ34 as only seeing a small amount of capacitance by adding the inductor. and then you can pile up as much capacitance you want...but only after the inductor. pull those 110uf and replace with 20uf and you will see a extra 10 to 15 volts, and the GZ34 will be running within its max parameters.

    so going the opposite dirrection would be better 50uf ( actually smaller would be better 20uF) before the inductor and 100uf after.

    yanking the rec tube can raise the voltage alot, if i were going to do it, i would just use series caps to handle the voltage, and raise the screen resistors a little, i know you can pound them with higher voltage, but tube life is greatly increased when you stay with the recommended screen voltage on data sheets, and if i remember correctly kt88 / 6550 max screen voltage is pretty low.

    *edit* little of topic so lets get back....200S totally awesome Woo!
    love this pic wish i could find a better one on the net. Picture from Randy Holten's (Blue Cheer)solo album. Sunn endorsed him and i guess he wasted no time making a huge pile of Sunn cabinets. I guess he wasn't using the 12 speakers for guitar either, favored the 15" D-130's...so your looking at a all 15" band:eek: courtesy of Sunn amplifiers.
  5. Some people like Weber's products and some people really seem to hate them...no in between. I've had nothing but good luck with everything I have ever ordered from them so there you go. I've heard of some problems in the past with some products and TA and Ted before him always seem to be on top of it and trying to fix it as quickly as they can, which is good customer service no matter if you like their products or your don't. You can of course do the same thing the Copper Cap does with discrete parts but the CC is easier for those who don't know how to do that.

    Notice I said that with the 220uf in series for 110uf before the inductor, I also say that if you do that you need to use something instead of the tube rectifier like a solid state replacement. The inductor is going to give better overall performance than the cap alone would since it is resisting current and doesn't drop the voltage much, as compared to what a cap and resistor would do, but using the larger cap before the inductor gave a feel that I liked...I'm not worried about the voltage reduction as it is already higher than stock with today's wall voltages.

    I think the original 6550 was 400v on the screen, and 440v with the 6550A...the KT88 is 600v, but that is the Genelex and who knows about modern ones. I think the UL connection might have been easier on the tube anyway?

  6. bb5000


    May 30, 2006
    Sundsvall, Sweden
    Newer KT88's handle 600V at the screen just fine..I've tried Sovtek and Shuguang in my Weber AB200, 600V screen voltage.

    I've also built the Weber 6S100 that's based on the the Sunn 100S (but with SS rectifier, no UL, a EF86 instead of the 6AN8 and a slightly different NFB circuit). The GoldLion KT88's run at 505V at the screen in that one. Considering the low wattage, it's very loud. I guess that the original is just as good.
  7. Good to know, thanks!

  8. Mike M.

    Mike M.

    Feb 14, 2010
    While I never owned a 200S I heard them on a lot of occasions back in the day in very loud rock band settings. I remember the sound as being very, very distorted. A sound that had a lot of "grunt" to it like on the live tracks from Mountains "Flowers of Evil" album. But at the same time it was kind of a cool sound that had some character to it.

    Due to the low power it seemed like bass players who used them back then had to use at least two because they were trying to be heard along side Marshall stacks.
  9. chadds


    Mar 18, 2000
    Hence the 2000s.
  10. Yeah listen to one up loud with rounds and that is the sound of Geddy Lee pretty much. Quieter they have a extremely nice and full and rich tone with flats or rounds. Totally unique sound and very touch responsive.

  11. edbass


    Nov 8, 2004
    I can’t really speak from experience on power supply modifications on 200S models; all of my 200S’s are stock except for one I sacrificed for a project testing circuit mods. The 200S I normally use for gigging has stock caps that were reformed a couple of years ago and still performs great, and the rest of them, I’m a little ashamed to admit, are pretty much just gathering dust in my shop.

    I’ve got 2000S’s with three different power supply configurations, one is SS rectified with an SDS cap board installed;

    SDS Labs Mk3 Capacitor Board, with parts and instructions


    One SS rectified with a German Authenticap KTL13;

    Frag Jan zuerst- Ask Jan first: Roehren und mehr

    And the “control” in this comparison, a stock tube rectified one that amazingly still specs near new.

    They sound different, the 2000S switched to SS rectification around 1970 and the later amps (including the amps renamed “350B”) are noticeably stronger than the earlier tube rectified models.
    The SDS mod is the strongest and “stiffest”, particularly in low end response, although it still retains the same basic tonal character inherent to the 2000S IMO. The Authenticap amp sounds like a standard SS rectified 2000S, not too surprising since the values are the same as the OEM Mallory was, just rated at 550V+ rather than the underrated 525V can cap was.
    The stock tube rectified amp is a little softer; with less juice and gets a little more “Pappalardi” at lower levels than the SS rectified amps.
    Overall IMO the CE or Authenticap is the easiest to use. Also as Greg points out, particularly with contemporary wall voltages the original 525V can cap will be stressed beyond its design spec. Since the Authenticap retains the original cap values but increases the voltage rating to 550V+ for the foreseeable future I will probably use them for any vintage Sunn recap jobs. Call it "old tech", but I also recently restocked my supply of big old Sprauge 20uf 600V electrolytics...

    All of the 2000S’s will get loud and clean, you need to push them pretty hard to get the super hairy 60’s distortion like Pappalardi was noted for. I think Felix often actually used lower powered 200S amps dimed to attain that over the top fuzzy distortion, and the mudbucker equipped Gibsons contributed as well! ;)

    The SDS amp gets the most use. I use it as backup for the Reeves C225 that serves as my main gig amp; occasionally I use the 2000S and keep the Reeves in reserve, but the SDS 2000S goes out pretty much every time I play.
  12. pgk


    Aug 19, 2007
    that's my experience too, which is why i stuck to the stock power supply filter values on my bassman
  13. In a Bassman its a little different because Fenders have more value and always will, and many of the people who would consider a Fender are more concerned about originality.

    The other thing you have to consider is that back then when these amps were made, caps were expensive and the values chosen would be the minimum to do the job, in order to save money. The Sunns are basically Dynacos in a different box so they take most of their circuit design cues from what Dynaco was doing, which was trying to save money since they were selling kits for $80 or whatever. The other problems with can caps and the way the Sunns were made is that all the grounds are shared, and the grid wires are running parallel to noisy wires in the wire loom. With caps cheap these days and much better quality than what was available back then, if someone doesn't mind to modify their amp a little from stock in a reversible way like this, then they can get better performance. The grounding can be altered to get localized caps and grounding to only one chassis ground, and the grid wiring can be changed to get the sensitive grid wires away from the noisy wiring. These last two changes are not really reversible though without a lot of effort, and require a lot of effort to do. It does make for a much quieter amp however. I did this on a basket case amp since it had no value and the performance gains were very noticeable, but I don't recommend going to that effort in most Sunns due to the effort involved. Its all good anyway though. Do what you want....its your amp.

  14. Blue


    Jun 19, 2004
    Southeast Penna
    I wonder if they were used more for earth-shattering volume (and filling up the stage) as any tonal nuance ..
  15. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Washington, Utah
    John K Custom Basses
    either way, they just sound great, although i think that the 2000S was used for more thunder (over the 200S). here's a coulpe of pics my '67 200S:


    SirMjac28 likes this.
  16. chris stopa

    chris stopa

    Feb 8, 2011
    I had a 68 Sunn 200s. which I bought in 68 for $685 .Gave it to a friend when I left in 05 for Oregon and have wept nightly since. Besides the sound - which is great for projecting in the mix, the JBLs project enough to shake the audience's chest in a small club. Nothing I have come across does this. I did find however that it sounded best with a Fender Jazz bass. I tried it with guitar when first owned it and I did not like the sound but with a Fender Bass it is tops.
    J killen likes this.
  17. heavytrash13


    Oct 30, 2009
    I like my Bassman w 2/12.
  18. heavytrash13


    Oct 30, 2009
    Had a 200s -got it for$180..got a Sound City 120 pa head so id have some headroom when using an upright bass
  19. Tom Howland

    Tom Howland Supporting Member

    Feb 11, 2003

    The 200s with it's 2x15 cab is simply one of the best sounding tube amps ever.
    I used one in the early 80's, a pain to move, but a wonderful tone.
  20. taurus1


    Sep 13, 2006
    Vancouver B.C.
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