just picked up a 2000s!!

[THE COPS]

and I got a smokin' good deal. 

Just trying to find out some specifics on the amp...  i know my manufacture date is 8/69.  And it sounds incredible (i will be using it for guitar), however I only played it for a few minutes when picking it up - not being sure of the history.  I will be dropping it off to my amp dude tonight to have him go through it (recap, etc).

It has the red knobs - which i haven't seen on a 2000s in any web searching.  The rectifier tubes have been replaced with SS's.  and one of the tubes doesn't match the others.  A grounded cord has been added - and the dude I got it from said he has been playing it with some degree of regularity - and it had been working fine for him.

Anything I should be on the lookout for?  Any suggestions?  I have had (and currently have) several other Sunn's over the years.  Currently have a model t, a 412L, and 2 412 sr's.

Here are some pics!

[EdBass]

Nice score! Those red knobs are replacements, but so what? The big key to those old amps is the power supply, and from your post it's obvious that you already have your tech on that job. Depending on your tone expectations, tube rectifiers might give you a little more "brown" tone that those SS plug-in's for guitar.
It also appears that those are are some vintage GE 6550 outputs; again as long as they bias up it should be fine with the replacement tube in there with them, as before it depends on what you are striving for tonally.

[george]

Hey I'll swap you knobs - I have new knobs from the original source that made them for Sunn.

gbonosurf@yahoo.com

[THE COPS]

Awesome - thanks.  Yeah, the power cord has already been swapped out for a grounded one.  My tech has the amp now and is giving it a good seeing-to.  I think I am sticking with the SS recs for now, but he is gonna give me a set of tubes to try out in there to see what I think.  He is also testing the tubes for me - hopefully I will be keeping them.  He has some NOS GE 6550's, but suggested (like some others here have) the JJ KT88's if I need to retube.  I played it for a while last night and it sounded incredible, so I think the tubes can stay.  We will see what the professional says. 

Thanks for the offer on the knobs - but I am hanging on to these.

My dude is also putting a toggle switch to choose between 8ohm and 4ohm - which will be handy with the myriad of cabs i play through!

[THE COPS]

One other thing that struck me as odd..  there is only 1 preamp tube - and no spot for a second?  whats up with that? 

is the 2000s a hybrid or something?

[noel]

I'll try to cover the last two posts here.  I'd stay with a SS in the 2000s.  You get a little more power out of it and SS rectifiers sounds better with bass IMHO.  I think you said you'd use it for guitar but I'd still keep it.  Good work with the grounded IEC, that's crucial.  I got popped by a 2000s head when I was in college (goddamn polarity switch/ lucky I'm still hee) and it really rocked my world...ouch!!!  If those GE's are good go wtih them.  If not I've personally done JJ's and they sound very nice too. 

Now your second more interesting point.  The 2000s has 2 tubes in the preamp but you could almost consider it to have 3.  The 12AX7 is used in a pretty conventional preamp setup.  However, the 6AN8A is a pentode triode package...2 tubes in one.  The pentode side is really high gain (transconductance of about 7800 umHos).  The triode side is just used in a cathodine phase splitter setup (pretty standard).  So basically there are two gain stages in the preamp and then a phase splitter.  The interesting thing is you don't see many pentodes implimented in preamps.  2000s is without a doubt the best bass amp ever made though so mabye more people should have done it like this hahaha.  Hope that helps!

[THE COPS]

Awesome - that's the sort of explanation i was hoping for.  thanks!

[jbopper]

Noel gives some good insight on what that 6AN8 is doing.  Sort of picking nits, but just so the record is straight on what's going on in front of the 6550 power amp stage, you really have 4 tube stages with the 12AX7 and 6AN8: two triodes in the 12AX7, each functioning as a gain stage and then the 6AN8 pentode serving as the driver stage feeding into its sister triode for the phase inverter function.