Good cab match for Sunn Sonaro

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How do caps have anything to do with two knobs not working?
Find out what is really wrong with the amp before more damage occurs.

 

Why replace the caps? It's actually very seldom that the caps are in any way at fault.

 

That head is 60 watts from two 6550’s(or KT 88’s, a similar power tube), but as it is an ultralinear design, you should be able to goose a little more volume out of it. It is identical to the 200s, or Sorado. Does it have 8/4 ohms speaker outs, or 16/8? I assume the Marshall cab is 16, but check that, and check the drivers. I’d take the head in to a tech, figure out what’s going on with all the tubes, and as far ad the caps and tone problems are concerned, I’ve owned a number of these heads and have rarely had issues, but there might have been some value drift over 55 years, or a weak preamp tube.

 

The best cab to pair it with would be a 200s cab with JBL 140s of some variety, that'll allow you to get the most out of it volume wise (or any other efficient speakers in a good enclosure). Of your options, I'd grab the 2x15, and eventually replace the Eminence maybe (not that they're bad, but they aren't my thing, I'd prefer an older style efficient 15" in that cab). Do you know what model 2x15 it is? Side ports, circle ports, large middle slot port?

You have the right idea, get it serviced ASAP and it should serve you well for years with little maintenance. No sense keeping any old caps in there that may have drifted in spec. If they don't need to be replaced, fine, but if they do, don't hesitate, it's only going to improve reliability and stability. Only one of my Sunns has its original caps, and that's because it has its original everything, and doesn't get gigged. All the others in regular rotation have been appropriately brought up to modern spec.

Depending on what speakers are in the Marshall, you're probably fine. They aren't efficient cabs, so it won't get as loud as some other cabs, but they can be used. I've used 4x12s with Celestion V30s and a Sunn 2000s before, not a lot of low extension, but sold and not farty until you really start cranking, and that's at double the wattage.

And as for SWR, I played them briefly when I started, very clean but always struck me as very anemic. Just not terribly interesting sounding, polite in a not so good way. YMMV, but I know given the option between the Sunn and SWR, I wouldn't get anywhere near the SWR. Many people like SWR just fine, they have a good reputation for a reason, but it's a bit of apples and oranges between SWR and Sunn (although, coincidentally, both are currently owned by Fender and have been discontinued).

 

The 200s cab has been mentioned and I have one with the matching 200s head, that is the most natural obvious choice, it is to me the “Sunn” sound. Original Music Man bass cabs work well too, got one of those also. Whatever it needs to be very efficient as that amp is a low watt classic.

 

So, here’s the rundown...
In ‘67/‘68, the ‘Sonaro’ model name was applied to a combo unit, V/T/B controls, treble and bass boost switches, 40 watts from a pair of EL34 power tubes, one 12ax7 preamp, one 6an8 driver, GZ rectifier tube(controls power supply, not in audio path), fed into a single 15”, most likely made by CTS. By 1969 the combo concept was done away with, and the model was then split into a separate head(still 40 watts)and single 15” cab(still CTS/‘Sunn Transducer’)that looked like this(essentially half of a 200s cab in design)...

By early 1970, the power was upgraded to 60 watts by way of two KT88’s, which, as I mentioned before, made it identical to the 200s and Sorado heads. Why the different names for the same head? It was a quirky marketing move by the company; the model name changed according to what speaker cab it went with. The Sonaro then was the single 15, the 200s had the dual 15”(JBL D140’s) with the center port and unique rear baffle design seen here...

...and the Sorado(my first real bass amp)was the middle ground, budget 2x15”(CTS)with the straight forward dual round port baffle, seen below...

By late 1970, there was a change in head/cab grill cloth, from a grey woven angled pattern to a Fender-like sparkle rectangular pattern, and the tube rectifier was switched to solid state, theoretically goosing the power up to 80 watts. The single 15” cabs were still around, with a D140 option. By 1972, all the various head names were done away with, and that configuration was relabeled the 190B. The company had been sold to a conglomerate(much like Fender), and the 2x15 cab was consolidated/redesigned to the side port style...

...with just a Sunn Transducer option, and often paired with the tube Model T and solid state Concert Bass heads. From there, there were variations in cab design and cosmetics, the Model T was dropped and all amps were transistor after that, until the brand fizzled out in the early 80’s. So, if you want to be ‘period correct’, seek out one of those single 15’s(actually not found that often), or an older 2x15 will do, of course, but make sure the ohm rating matches your head.

 

If that’s the case, then most likely it’s two 8 ohm 15’s wired in parallel, pretty standard stuff. But that means they can also be wired in series for a 16 ohm load, that would match one of the taps on your head. The earliest Sunn amps featured 16/8 outs, for multiple cab capacity, and then changed to 8/4 ohms around ‘69, I believe. If you, or a tech, pull the chassis out of the case, there will be a manufacture date in marker on the side or underneath with the wiring. Also, the Dynaco output transformer should have a 4 ohm tap(not used), but not a hard and fast rule; if so a tech could install an output for flexibility.
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