SUNN amplifiers c. 1970

Download the ten-panel SUNN amplifiers 1970 catalog:

DOWNLOAD: Sunn_Amps_1970_Catalog

Models covered, with specs and photos, include: SUNN Dymos, Solarus, Sonaro, Sentura 1, Sonic 1-40, Sceptre, Sorado, Sentura II, Solos, 200s, 1000s, 1200s, and 2000s instrument amps; plus Sunn Concert Sound System and Coliseum Sound System.

I’ve been using a SUNN Sonaro as our ‘house’ studio bass amp for several years.  E actually found this for me, deadstock, on eBay about 10 years ago.  Since then I have re-tubed and recapped it entirely, and it is really a fantastic amplifier.  Very simple, but always sounds great.  The ‘hi boost’ and ‘low boost’ switches enable one to get some very modern sounds out of this ancient tube head; much more versatile than, say, a Bassman.  The cabinet is not so great.  insufficient low end for many songs.

Growing up we also had one of these ‘Concert’ PA heads.  We used it briefly in our teen-age garage band.  For some reason, it regularly shocked the lead singer. Even if he was not touching anything else.  It basically kept him in a constant state of terror.  sorry J.  It was all we could afford at the time.  The CONCERT is a solid-state amp and it is not recommended.

SUNN amps have an interesting story.  From Wikipedia (abridged by PS.com):

“In early 1963, The Kingsmen, a band based in the U.S. state of Oregon, became known for the song “Louie, Louie“. After their hit single, The Kingsmen soon embarked on a fifty-state national tour. Because the band was used to playing small hops and school dances, many of the members found themselves ill-equipped with the amplifiers that they were currently using. Bassist Norm Sundholm discovered that his bass amp was not nearly powerful enough to play larger concert halls. Sundholm enlisted the help of his brother Conrad to help solve his problem. By 1964, the Sundholm brothers had designed a high powered concert bass amplifier. … Thus, the Sunn Musical Equipment Company was founded.”

What Wiki does not tell you is that Conrad’s ‘solution’ was basically to add a pre-amp stage to a Dynaco Mark 3 home hi-fi amp and stick it in a big speaker cabinet.   This basic design would provide the essential platform for all the classic SUNN amp heads.  The crucial point of all of this is that all the classic SUNNs (including the humble Sonaro) use the very powerful 6550 output tubes coupled to an ultra linear output transformer.  To my knowledge, no other major instrument amp manufacturer was using ultralinear transformers in 1970.  Not even the Ampeg SVTs of the era use ultralinear operation.   This fact gives SUNN amps a real advantage in accurate low-end (bass) sound reproduction.

I’ve also owned a Sunn SCEPTRE, and other than the crappy-sounding sold-state reverb circuit, it was pretty great as well.  It is still easy to get a great deal (around $400) for many of these classic SUNN heads, and I highly recommend them, especially since you can now easily get the proper high-voltage filter caps that these amps need.   This makes it very very easy to re-cap the amps for proper operation.

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To download the original schematic for the SUNN 1200S, click here: 1200s_schem

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20 Responses to SUNN amplifiers c. 1970

  1. Robbie Nuke says:

    I have found the Sonaro bass cabinets very useful for live gigs. Although retrofitted with JBL speakers (D140-f in one cabinet; E-140 in another), they are now much more efficient and the porting offers a deep response. Their shallow pine cabinets are relatively light and make transporting a breeze. When I have a gig up a flight of stairs and feel a need for 2×15, I’ll bring these cabinets.

  2. rrusston says:

    Caps never were a problem except cosmetically: you just make a little board and stack the PC mount lytics in series with balancing resistors. Straight out of the ARRL Handbook.

  3. JIM says:

    I HAVE A COUPLE OLD TRANSDUCER 4-12 SUNN CABINETS. I USED TO PLAY THEM THRU A 100 WATT MARSHALL AMP. THE MARSHALL KEPT CUTTING OUT ON ME AND WE THOUGHT IT WAS THE IMPEDENCE. I BELIEVE THAT THE SUNN CABINETS WERE WIRED IN PARALLEL AS THE SPEAKERS ARE 16 OHM EACH, AND THIS WOULD CREATE A 4 OHM LOAD WITH ONE CABINET, AND A 2 OHM LOAD WITH 2 CABINETS. I CAN CHANGE THE OMAGE ON THE BACK OF THE AMP. I BELIEVE I HAD THE CABINETS REWIRED TO BEING RUN IN A SERIES TO TRY TO OFFSET THE MARSHALL GOING OUT ON ME, BUT THIS WOULD MEAN THAT THE OHM LOAD WOULD BE 64 OHMS, WHICH THERE IS NO SETTING FOR. CAN YOU TELL ME IF THE SUNN TRANSDUCERS WERE WIRED FOR PARALLEL OR FOR SERIES OUT OF THE FACTORY. I’M GUESSING IT HAD TO BE PARRALLEL TO CREATE THE 4 OHM LOAD. I WOULDN’T THINK YOU COULD PLAY A CABINET WITH A 64 OHM LOAD.
    THANKS!

    • chris says:

      Hi Jim. I frankly have no idea. You can easily tell what the load of a speaker cabinet it with an ohm meter. Any cheap-o digital multimeter will display DC resistance. The reading is generally going to be a little less than the actual impedance, but you can get a good sense from the reading (E.G., an 8-phm load might read as 5.7 ohms on an ohm meter). Good luck.

  4. johnny willis says:

    Rebuilding a Sunn 1200S head and need to install a reverb unit. It will have to be mounted open side up but I do not know the required ohm ratings to match this head. Can you assist ?

    • chris says:

      Hi Johnny. I assume you are referring to a vintage circa 1970 all-tube sunn 1200, yes? If so, the schematic SEEMS to indicate that a low-impedance tank (I.E., 8-ohm input) is correct. The schem is a little hard to ready, but it SEEMS like the tank is driven by a transformer stating “10Kz: 3.8Z”, so 8-ohm is close enough.

      A regular reverb tank wont work properly open-side up, though, so you may need to custom order; TubesAndMore dot com stocks the right part, make sure you get one designed for open-side up. good luck.

      • johnny willis says:

        Thank you so much for the help. Thyis is an all tube 1200S I am trying to restore for a friend. The reverb unit was removed years ago. The only place I can mount one is inside top of head cabinet – open side up, This thing has an awsome sound now and the reverb replacement will complete the project. Thanks again.

  5. François says:

    A friend of mine recently bought a Scepter, in very good condition, and he changed the tubes for brand new ones.

    I heard it and I loved it instantly!

    I want one for myself, now.

  6. Garrison says:

    DC resistance correlates to actual impedance on guitar drivers somewhat well, i.e., it is usually 60 or 70 percent of that figure, but once there is a crossover and treble units in the picture that goes out the window. Bridge methods must be used.

    That said there is a gizmo you can buy that plugs into a USB port and will plot the impedance curve of a driver across a frequency band, at least for small signals. Parts Express sells them,

    http://www.parts-express.com/pe/showdetl.cfm?partnumber=390-806

  7. Catherine Fairfax says:

    Hi, I have just purchase a storage with 2 Sunn 12,which are those large concert speakers. They are in mint condition,outside looks nice. I am pretty sure they are vintage. We also hooked them up,but we didnt have anything with enough oms to really push it to appreciate the sound.

  8. Thomas Warberg says:

    looking for information Sunn 212 cabinet, it has two diagnal 12′s with two tube ports.
    Ports look 1 5/8″, don’t know lengths. Cabinet look 28 X 28 X 14. looking for diamentions
    and port sizes.

  9. William says:

    How collectible is a Sonaro these days?

  10. William says:

    First visit to the site. Have owned my Sonaro for years. Replaced tubes and capacitor

    • bafflegab says:

      Collectibility is in the mind of the collector, but in general, Sunn amps are not in especially big demand. They are good for some uses and used, in many or most instances Dynaco transformers which are readily available new.

      Pulling up an online schematic of the Sonaro it sure looks like a Dyna Mk III with a 12AX7 pre and tonestack stage hung on the front end.

  11. Al says:

    Where can I find a readable schematic for an older (70′s) tube Sunn 1200S head?
    I’ve tried searching, and found schematic images online, but when enlarged, they become unreadable.

    Also, the amp used to connect to a cabinet with (6) 12″ speakers. But I don’t know what load the amp was supposed to see, since I don’t have the cabinet to check the resistance or verify the wiring configuration.

    I’d like to fix this beast, as it used to kick butt when it worked.

    Thanks,
    Al

    • chris says:

      Hi Al. I added the schem that you requested to the SUNN page on my site. You can download it now. The schem clearly indicates a 4-ohm load for the output transformer.

      good luck, c.

  12. Ed says:

    I have a Sunn 215m I’m looking to get a fair price on. I’m not into or up to date with music stuff and for this I’m asking for any help in pricing my amp. It is all original and is in perfect condition. Thanks in advance.

    • chris says:

      Hi Ed. Literally 15 mins ago I sold a 1969 Fender 2×15 (very similar cabinet) in ex working condition, rough cosmetics, for $150.

      As a private seller you can expect to get $100 – $300 for it depending on what city you live in and how patient you are

      good luck

      c.

  13. Bill Watts says:

    I have found that 2-15 inch cabs are worth more as two 15 inch drivers than as a single cab most of the time.

    Also as far as I know all Sunns used Dyna output transformers and had 4, 8 and 16 ohm out so if they are not hooked up it’d be esay to add a switch or additional output jacks, it’s not like they are collectible. Unlike Fenders or Marshalls there is no big demand that they be stock or cosmetically great.

  14. Frank says:

    I have a Solos II, 1973. One speaker was replace 35 years ago with no name.
    The other speaker is a transducer 128G. What speaker was used in original equipment manufactured?

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