Help with identification!

[Slomo]

Greetings!
Recently got this beautiful solarus but year of production and wattage still unknown to me.
Output tubes are 2X6550.
Footswitch and reverb onboard.
It has 5AR4/GZ34 rectifier tube, which, i assume, is typical for pre 70's models (?).
But it also has a mid boost switch, which is a post 70's models' common feature (isn't it?).

Any help with identification of age and wattage will be appreciated!

[Ryan Phelps]

Nice clean Solarus....great amp! I think you meant tremolo and reverb onboard.

The Solarus began as a combo amp in 1967. The mid-boost switch was added in 1969. The Solarus changed from EL34 tubes (40 watt rating) to 6550 tubes (80 watt rating) in 1970 (the transformers are physically larger). By 1972 The Solarus was gone and so was the tube rectifier for the remaining tube amps! So your amp is likely 1970 - 1971. If you pull the chassis from the cabinet, you will probably see a date written in red grease pencil.

FYI....all this info is on The Sunn Catalog Thread at the top of this page.

Have the AC cord repaired or replaced (3-prong) and see if the filter caps have been replaced too. If the amp sounds mushy or lacks bass, the filter caps should be replaced (if you plan to actually play the amp).

Good Luck!

[EdBass]

As has been discussed here before, there were lots of anomalies in the old Sunn tube amps. I think they probably were using up parts stock in that  '70-'71 time frame as they were transitioning away from EL34 amps and simultaneously into SS rectified amps which could account for a tube rectified 6550. Of course in the past 45 years someone may also have put 6550's in an EL34 Solarus in an ill advised attempt to get more power. Wouldn't be the first time that had been tried...
The chassis dating Ryan suggests is the sure fire answer to the actual age of the amp, also some had a green inspection sticker rather than the grease pencil markings.

If it has the bigger transformers and is tube rectified the rating would have been 60 watts. Can you post a pic Slomo?

[Slomo]

Ryan, Ed - thank you SO much for being helpful!!
Ed, did u mean a pic of that number written there?
Sure, i think ill be able to do it as soon as chassis removed
(with the help of my fellow tech. dont want to do it myself (scared) :/

i HOPE its at least 60W, because its pretty heavyweight, very heavy i should say!

(P.S. also wondering whats the technical/sound difference between plugging into normal or bright inputs?
what's the actual use for those 4 inputs? Im confused a bit because it reminds me of Hiwatt or Plexi-superlead inputs...)

[EdBass]

That's a 60 watt amp for certain, those are the big transformers. That amp is essentially identical to a late '69 Sceptre or 100S w/ reverb, it would be interesting to see if there is a date on the chassis.
Taking the chassis out is pretty easy, just pull the 4 bolts on the bottom and it slides out to the back.
It's heavy, and might take some "elbow grease" to get it out. Sometimes the control panel where it meets the faceplate of the box it a little snug, but if you remove the 4 bolts on the bottom there is no other physical obstruction to sliding it out.

She's as clean as a whistle, very nice looking 45 year old amp!
One thing though; it looks like it was dropped pretty hard on the output transformer end at some point. That power transformer mount is tweaked good, but doesn't necessarily mean that there is anything wrong with the amp.
Those old Sunns are built like tanks!

Be sure to let us know if there is a date inside!

[Isaac]

The reason for the four inputs is that Sunn was cheap. It was easier, or cheaper, or more efficient to get all of their chassis drilled at the same time. The PA head (like my Concert PA) had four inputs, four volume controls, bass, treble and master volume. On guitar amps, those seven controls became volume, bass, treble, contour, reverb, and tremolo rate and depth. They already had four holes drilled, so why not four inputs? Each input has its own isolation resistor, so there's not much interaction. The difference between the normal and bright inputs is that the input resistor for the normal inputs is 47K, while for the brights it's 270K, bypassed by a .001 μF capacitor. The high input impedance tends to reduce loading, which then tends to improve high end response. The bypass capacitor passes more highs through above about 600Hz. The result is more midrange and treble, for a brighter sound.