New Amp Day (Sunn Content)

[johng999]

For bass I think the power supply upgrade/SS rectifier is an improvement. You get 10-15 watts additional power, but the big improvement is in the low notes. The extra capacitance makes them much more solid than the tube version. Also multi-cap can is rated for 525 volts in the day that wall voltage was under 120 volts and this cap was only marginally acceptable then. With the current higher voltages (mine is 128 at home) it often exceeds the rated voltagte. I put a voltmeter on mine and noticed surges of over 600 volts at power up - which is a time bomb on an old cap. This problem is well known and documented by Dynaco folks, of which this amp is based upon. Triode Electronics in Chicago has a write up on this issue on their site, and their power supply upgrade works very well. I have both a tube and the improved SS version, and IMO the SS rectifier is a great improvement for bass.

[Oren Hudson]

Not sure if that head has provision for a power or "slave" amp, but if does, that's a great way to pump up the power with-out losing your tone. I have an early 70's Ampeg B25B head. It's 55 watts. I have the matching cab with the two Altec 421A 15s. The head has a slave amp provision that I run a vintage Acoustic slave amp through with a single 15 Dean Markley cab. Wow - no tone loss with a big boost in power.

[edbass]

Originally Posted by vegedge

mine says 1973 in marker on the inside under the wires. but looks exactly like the OP's. only with a SS rect. has the numbers on the amp and black knobs with an arrow.

i am thinking his is the same year or around as mine.

If your amp has "1973" written on the chassis, it was probably written there by a tech who did some work on the amp in that year. Not an uncommon practice.
The "200S" was only produced until 1971, and up until 1970 no 200S was produced with a SS rectifier.
Beginning with 1972 models Hartzell changed the name of the 80 watt tube bass amp to "190B" and the 200S was gone for good.

Anomalies do abound from those early Hartzell years though. Post some pics of your amp, I've never seen (or ever heard of) a non-'67 Sunn with a numbered faceplate.
I should be able to tell from a picture what year the faceplate on your amp was made.

Originally Posted by johng999

For bass I think the power supply upgrade/SS rectifier is an improvement. You get 10-15 watts additional power, but the big improvement is in the low notes. The extra capacitance makes them much more solid than the tube version. Also multi-cap can is rated for 525 volts in the day that wall voltage was under 120 volts and this cap was only marginally acceptable then. With the current higher voltages (mine is 128 at home) it often exceeds the rated voltagte. I put a voltmeter on mine and noticed surges of over 600 volts at power up - which is a time bomb on an old cap. This problem is well known and documented by Dynaco folks, of which this amp is based upon. Triode Electronics in Chicago has a write up on this issue on their site, and their power supply upgrade works very well. I have both a tube and the improved SS version, and IMO the SS rectifier is a great improvement for bass.

I agree with you observations of first stage voltage at startup, have noticed similar readings and have read extensively about the “ongoing since day one” overvoltage issues with the Hafler circuit design.
However, that said I also have several old Sunns with untold numbers of startups on them that still have the original 40 year old cans in them that to this day test like new.
As I posted the last time this issue came up, it’s just a case of personal tonal preference, particularly since there are stock value, drop in can caps available for refurbishing old Sunns or Dynacos.

Originally Posted by edbass

I have both 2000S's and 200S's with the SDS board (which is sold by Triode) and without; stock OEM value filters. The SDS boards take the voltage to a safer 630V per section, but alter from the OEM filter spec of 30/20/20/20 to 60/60/60/60 uF and definitely changes the tonal characteristic of the old Sunns.
I like my gigging Sunns with SS rectifiers and stiffer filters but I think they sit better in a recording mix with tube rectifiers and stock values.
It's a personal preference; I'm pretty sure that JohnK has no use at all for a "fortified" vintage Sunn...

There is a happy medium though; there are can caps available that are rated 30/20/20/20 AND for 550+VDC.
It's a straight drop in for the OEM Mallory can, gets your voltage up to a safe levels and won't alter the tone of the amp.

[vegedge]

mine is identical to his. maybe more scratches but it has the numbered panel if i can ill post a picture.

what was the stock grill cloth that year? i've seen silvery, natural and mine which is black and a bit silver

[bubbastain]

Here are some more pictures. I've decided it's a keeper(for now) so I'll probably get a pair of KT88s and replace some old resistors, upgrade the can cap thing and the SS rectifier. Where can I get pretty specific details on parts list and procedures for this? I'd like it to be a as reliable as can be. I will also consider leaving as is, except for maybe a new set of tubes if doing the upgrades will be too much. It does currently work just fine, doesn't make any weird noises and sounds really good.

[lowphatbass]

Originally Posted by tabdog

Those sound wonderful. Too bad
you don't have a Sunn 2X15 to
go with it.

Happy NAD,

Tabdog

+1

The 2x15 cab makes this amp. It sounds cool through other cabs, but it doesn't reach it's full potential in terms of volume(and IMO tone) unless it's pushing an old pair of JBL's.
(edit-I don't play guitar, just bass)

[bubbastain]

I'm playing it through my Kustom Groove 8x10 4 ohm cab and it sounds pretty darn good. Would it really be much louder with the matching 2x15? I realize of course it will sound different but louder? If I had the cash, I would love the Barefaced Super Fifteen.

[bb5000]

Originally Posted by bubbastain

Here are some more pictures. I've decided it's a keeper(for now) so I'll probably get a pair of KT88s and replace some old resistors, upgrade the can cap thing and the SS rectifier. Where can I get pretty specific details on parts list and procedures for this? I'd like it to be a as reliable as can be.

Here's the Sunn 200S schematic

http://www.prowessamplifiers.com/sch...sunn/200S.html

Basically you'd want to use a full-wave SS rectifier (using 1N5408 diodes for example) and then increase the cap values of the 30 uF/525V before the choke and the 20 uF/525V after the choke. The rectifier tube could still have it's filament wires connected and you just pull the tube. But, get a tech to do it if you have not worked with amps before.

[edbass]

Originally Posted by vegedge

mine is identical to his. maybe more scratches but it has the numbered panel if i can ill post a picture.

what was the stock grill cloth that year? i've seen silvery, natural and mine which is black and a bit silver

Until the mid 70's Sunn only used two types of grill cloth;
This is mid 1969 and later grill cloth


The Sunn on the left has the pre ’69 cloth


The old Sunn’s grill cloth has seen many smoky bars over the last 45 years, it was actually a few shades lighter gray when it was new.

Originally Posted by bubbastain

Here are some more pictures. I've decided it's a keeper(for now) so I'll probably get a pair of KT88s and replace some old resistors, upgrade the can cap thing and the SS rectifier. Where can I get pretty specific details on parts list and procedures for this? I'd like it to be a as reliable as can be. I will also consider leaving as is, except for maybe a new set of tubes if doing the upgrades will be too much. It does currently work just fine, doesn't make any weird noises and sounds really good.

That amp looks relatively untouched, the only newer stuff I see at a glance are those trendy orange drops, and those are in the tone stack; the "motor" looks for the most part unmolested.
Which may be good or may be not so good. I'd leave it alone until something breaks.
A total re-do is always tempting, but the problem with that is to do it right it's all or nothing.
Although the filter caps can and sometimes do last for a looooong time, odds are the ones in your amp are probably way overdue for replacement. This would definitely explain your early distortion issues; not 100% for sure the reason, but by far the most likely reason for the lack of power.
The tube rectifier is probably the reason the filters have held up so well, SS rectifiers blast the circuit will full power instantaneously when you hit the power switch, not at all good for capacitors or many other components. Tube rectifiers slowly ramp up the juice as they heat up; kinda like using a variac every time you turn the amp on. Much more component friendly.

However, refurbishing the power supply will show the other components more current than they have seen in a long time, and failures can occur in a "domino effect" down the signal path; and upgrading to a SS rectifier will just amplify this effect.
It's like a vintage car; you replace a water pump and suddenly the previously solid heater core starts leaking.

Like I said "all or nothing". You might be fine just "bandaid'ing" a few things, or you might be opening a can of worms.

Good Luck!
PM me if you need any assistance with parts info or availability, I can point you in the right direction.

[lowphatbass]

Here's the earlier style cloth in a '67. This amp is bone stock, FWIW. Everything specd' out good and it sounds good so I optioned to just roll with it.
(I did add a 3-prong power chord and disable the polarity function)

[bubbastain]

Originally Posted by lowphatbass

Here's the earlier style cloth in a '67. This amp is bone stock, FWIW. Everything specd' out good and it sounds good so I optioned to just roll with it.
(I did add a 3-prong power chord and disable the polarity function)

That is the grill cloth mine has. Someone at some point must have sprayed it black. I can see the original color on the inside of the head shell where it wraps around and is stapled.

[OneWayPunk]

I just recapped and upgraded my Sunn Sceptre which is very similar to a 200s.
I used the upgraded cap can available here to better handle the higher voltages from the SS rectifier.

http://www.dynakitparts.com/store/product.aspx?id=312

I replaced all the rest of the electrolytic caps as well.

Here is what I did for the SS rectifier, since I wanted to be able to easily switch back to the Tube Rectifier if I wanted I just picked up one of these plug in units from Yellow Jacket so I can switch back and forth as I wish.

http://www.tubesandmore.com/products/P-YJR

Amp is dead quiet now and sounds amazing, HUGE full low end.

Running 6550's in it now, but I am thinking of upgrading to KT88's for even better low end.

[OneWayPunk]

I would also replace the Carbon Comp resistors in the Power Supply. They are the ones soldered onto the Cap Can. The ones shown in your photo is not how it should look stock. Someone has soldered additional resistors over the stock ones changing the values.
Replace them with modern flameproof 2-5 watt power resistors.

[bubbastain]

Originally Posted by OneWayPunk

I just recapped and upgraded my Sunn Sceptre which is very similar to a 200s.
I used the upgraded cap can available here to better handle the higher voltages from the SS rectifier.

http://www.dynakitparts.com/store/product.aspx?id=312

I replaced all the rest of the electrolytic caps as well.

Here is what I did for the SS rectifier, since I wanted to be able to easily switch back to the Tube Rectifier if I wanted I just picked up one of these plug in units from Yellow Jacket so I can switch back and forth as I wish.

http://www.tubesandmore.com/products/P-YJR

Amp is dead quiet now and sounds amazing, HUGE full low end.

Running 6550's in it now, but I am thinking of upgrading to KT88's for even better low end.

Thanks for the info. Happen to have any gut shots before or after of your amp?

[OneWayPunk]

I can snap a guy shot of the after, I don't have one of the before. Be aware that the guts of the Sceptre look way different than the 200s as there is Reverb and Tremolo circuits stuffed in there as well. It also has one additional filter cap.