200S with multiple filter cans?

[Anonymous]

On its way to me as I type is a (advertised to be) '69 200S.  All external details point to '68-'69 time frame.  

My experience with Sunn is limited to the '67 200S and '70 2000S I own.  Those, as well as every Sunn schematic I have seen, show a single multisection filter can, sometimes supplemented by internally-mounted axial capacitors.

This amp clearly has *two* multisection cans.  From the pictures they both appear to be original as 1) they both seem to be riveted in, and 2) the amp still has the original Sunn-branded GEC KT88s - I can't imagine recapping an amp that is still on its original tube set.

Ever seen one like this?

[Ryan Phelps]

Guest,
Your experience matches mine. I've had a dozen or more Sunn heads dating from 1966 through 1974 and have never seen this configuration. One possible clue though......the grille cloth appears to be the early style that was discontinued in 1967. Of course the chassis could have been placed in an older cabinet. Check the knobs......if original (Rogan), do they have numerals or pointer arrows (with the numerals silkscreened on the face plate)? Pointer arrows would indicate an earlier chassis. So this amp may be a 1967. Also check the stampings on the second filter can. Near the bottom should be the date code. See if it matches the code on the larger filter can. This might provide a clue to the originality on the smaller filter can. Perhaps Sunn was experimenting and later decided that an internally mounted axial cap was more cost effective? Perhaps some of the old Sunn employees on this website will weigh in on this question.
Ryan

[AdmiralB]

(Forgot to login!)

I haven't received it yet (still en route), but it is the old-style cloth.  The chassis is dated '69, so I believe that.  It's got the numbered knobs/plain faceplate.  That, coupled with the KT88s, makes me think early '69.

Should see it midweek.

[Isaac]

My guess is that the second can was added when a cap job was done on the amp.I opened mine last night, and found several new, larger caps inside. Whoever did this simply used a different technique.

[Anonymous]

OK, it arrived.  The amp is actually from 8/68.  The caps are not original, at least the wiring on them isn't.  They are a pair of 2x20uF/500V.  What is rather unusual is that the date code on the caps is late '68 and early '69, and they appear to have been in the amp for a VERY long time.

While I don't think they are original, it is obvious that the chassis was originally punched for the second one - the hole is perfectly formed and the chassis plating was done after the hole was punched.  So *something* was there originally and the only thing I can think of that uses a 1" hole is a filter.

This amp is also unusual in my experience as my others have CDE coupling caps, but this one is full of Sprague Black Cats.

[AdmiralB]

Ahhh!  It doesn't remember my login!

[Soundmasterg]

I have seen a couple with the Black Cats in them. I like them better than the CDE's, but since they're paper/polyester caps just like the CDE's, they probably are leaky by now. As far as the second can, I haven't seen any like that from the factory but it wouldn't surprise me. Depending on how the caps are hooked up, they are being hit with voltages that are higher than what they are rated for. The amp has somewhere around 550v on the plates and screens, so the caps should be rated for higher than that unless they are hooked up in series. There is so much room in the chassis that you could just leave the can caps in places for appearances and hook up some axials inside in series to get a high enough voltage rating. You could also use the 600v Sprague Atoms in here with no size issues since there is room. I'd replace all the electrolytics in the amp myself. I'd also check every coupling cap for leakage and replace if necessary. On my 200S I modified the first two filter cap values and went with 110uf instead of 30uf, and 60uf instead of 20uf. I used series connected caps to get a 700v rating, and going with the larger values made the bass response tighter while keeping all the highs too. I haven't done this to my 2000S yet, but plan to at some point.

[AdmiralB]

I've been lucky I guess in that none of mine have leaky coupling caps.

This one has the two cans - both 20x20/500V.  So they are definitely overvoltage at the first two stages.

I like the stock values - I prefer to keep the tube rectifier and that limits you to 50uF at the first stage (100uF for the 2000S), but I stay at 30.  I use 60uF/350V Atoms, two in series for 30uF total before the choke, a single 20uF/600V after the choke, then I replace the can with an LCR/F&T/JJ 32x32/500V can.  It's close enough.

My 2000S, oddly enough, had no cathode bypass cap on the 12AX7.  Sounded a LOT better after I fixed that...

[Soundmasterg]

I liked the higher cap values in my 200S, but I haven't worked on my 2000S yet, so I may go stock with that...which ever sounds better. My 200S was missing the cathode bypass cap too on the first stage, and I ended up going with a 300uf there. Not much different, but it was just enough to make the bottom end a little smoother. I'm using a Copper Cap WZ34 in my 200S and it sounds better than the tube recto in there, which is good since I can't use the tube anymore with the higher filter values. I get lots of compliments with the 200S when its taken out live, but its only used for bass.

Greg