Sunn 2000S Output Impedence

Discussion in 'Amps and Cabs [BG]' started by Rockbobmel, Nov 12, 2003.

  1. Rockbobmel

    Rockbobmel Supporting Member

    My 2000S has two speaker uotput jacks. they are labeled "16 Ohm Speaker" and "8 Ohm External Speaker" What happens when I run a 4 ohm cab..?? I was under the impression that most tube amps like 4 ohm loads. No??
    I don't want to wreck the amp. There was some discussion on this Impedence issue before, but not in reference to the old Sunn amps. Thanks, Bob
  2. Lower impedance is fine, to a point; you'll lose power and headroom and possibly overheat your output transformer at worst case, but that's usually not going to happen. If you use a 4 ohm cab, use the 8 ohm jack (or whichever happens to be the closest value to your cab without the cab being higher). Each jack is a separate secondary tap off your output transfomer.
  3. Rockbobmel

    Rockbobmel Supporting Member

    I guess that Sunn used 16 ohm cabs, so 2 in parallel went off the 8 ohm tap/jack. So if Igot both 4 ohm cabs and wired them in series "P/S box or modded cord", I'll get better headroom..??
  4. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    Here's a 2000s schematic:

    This one clearly shows a 4 ohm tap on the output transformer. Interesting. Wonder if it's in your amp? It's entirely possible they may have taped off the 4 ohm tap or not connected it in a particular year's model, but you'd have to pull the chassis to find out for sure.
  5. Look for the brown wire off your OT; that's your 4 ohm tap. The black is common to all. The white is 8 ohms. The yellow wire is 16 ohms.
  6. TimmyP


    Nov 4, 2003
    Indianapolis, IN
    That was a monster amp back in the day. I didn't know anyone who could afford one - they were a lot pricier than a Showman head (I didn't know anyone who could afford one of those, either). Word was that the power amp sections were Dynaco designs, which were quite good (if clean was what you were after). The preamp is rather lacking in fascilities by todays standards, but a competent tech could put an effects loop in it if you ever decide that you need it. It might be time to have it recapped. A keeper in any case I think.
  7. Rockbobmel

    Rockbobmel Supporting Member

    I lugged the Mesa (4 ohm) 2-15 upstairs. Plugged it in from the 8 ohm jack. I played pretty hard for 1 1/2 hrs. The trannies were warm but not real hot. You could leave your hand on either one. I don't know if this is a good test. The amp sounded outstanding..!!! I don't think I will ever play with a SS amp. Not after the way this amp sounds. When I pushed it real hard, it did break up some, but that was with a tuned 1/2 step down 5 string.The amp is very loud though. If using it with a 4 ohm tap would give it more headroom, it would be prolly KILLER. Tomorrow, The Mesa sees the 400+ for the first time. Maybe with the PowerHouse 1000 cab too.
  8. Rock&Roll


    Jul 21, 2002
    I know, I'm digging up an old thread here. If I understabd what Psycho Bass Guy is saying, I could disconnect one of the existing speaker jacks, and solder on the brown 4-ohm tap in order to make the 2000s correct for 4 ohm useage. Am I correct?

    I'm just wondering because there one for sale that I might pick up. But I was going to use it with a 4-ohm 2x15 cab. My friend said that his fender bassman sounded like crap at four ohms; it runs at 8-ohms standard. So I was given the impression that the change of ohms has a bigger effect on tube amps. Is this so?

  9. Yes. All you have to do is disconnect the colored lead from the "hot" side of the jack and swap it for whichever tap you want. Personally, I'd lose the 16 ohm tap in favor of the 4.

    Yeah. It's like I've been saying. Tube amps are designed to run at a certain average impedance and most times, that's where they will function and sound the best
  10. dhaworth


    Feb 21, 2005
    i wanna try two cabs on my there any reason to plug a cab into each of the outputs instead of daisy chain (series?)? will that effect the ohm load differently than if i daisy chained 2 cabs from one output?

    amp has one 4ohm & one 8ohm out. I have these cabs, not sure which to use for correct impedence: eden 410 (8ohm), ampeg 410hlf (4ohm), ampeg 2x15 (4ohm).

    i also have an acoustic 370...any ideas on the best amp/cab matchup with what i have for pure awesomeness?
  11. TimmyP


    Nov 4, 2003
    Indianapolis, IN
    If each amp jack is connected to a different transformer tap (as described earlier in this thread), then you must jump from cab to cab, and connect them to the one jack that is closest to the impedance of the paralleled cabinets.
  12. Rockbobmel

    Rockbobmel Supporting Member

    I finally got it open. The 8 ohm is bottom left. The 16 ohm is bottom right. The brown wire is dead ended to a board (don't know what it's called). The 8 ohm jack has a shorting switch, the 16 jack does NOT. As psycho said, should I just switch the yellow (16) for the brown wire? I took a pic. Thanks!
  13. Rockbobmel

    Rockbobmel Supporting Member

    Well, It Worked! The Henry 8x8 is no Sunn w/D140s, but it sounds pretty awsome.... Here is one of those rare examples ofte directions wer spot on!

    Thanks Guys.
  14. Hi.

    Well You certainly didn't hurry opening your amp ;).

    Glad to hear the mod worked.