Sunn 190b

[Bill]

I was checking out a Sunn 190b (I'm pretty sure of the
model number) a guy has for sale locally.  It is a head
with a 2-15" cabinet.  The grill cloth on both the head
and cab are tear free and in good shape.  Both the head
and cabinet show some scrapes and such from use, but no
major problems.  The power tubes are two 6550's.  

Now the questions:

Watts (RMS)?
Was it originally equiped with 6550's
Pre-amp tubes?
Speakers, they look original and OK, but there is
distortion when the thing is cranked (actually 3/4
cranked), what can you expect out of these old
speakers?  WHat can they handle?  Should they be
replaced?

Also, I have little experience with tube amps.  Is the
distortion most likely fron the amp or the speakers?

Finally, does anyone have an idea on the going price
on these amps?        

[Tom Loizeaux]

1) 60 watts rms
2) came with Tung-Sol 6550s
3) If you want loud and clean, replace the original speakers (unless they're JBL D 140Fs) with higher quality speakers,
   ie: EV, JBL, Eden 15s, etc.
4) Tube amps do produce distortion... but what you're hearing is most likely speakers being over driven.
  The over-all sound is a combination of a number of things. Check the tubes, check the bias voltage, compare the speakers to known clean speakers.

This amps sounds "big" for a 60 watt amp, but don't expect it to fill large rooms.

Tom

[mike]

: I was checking out a Sunn 190b (I'm pretty sure of the
: model number) a guy has for sale locally.  It is a head
: with a 2-15" cabinet.  The grill cloth on both the head
: and cab are tear free and in good shape.  Both the head
: and cabinet show some scrapes and such from use, but no
: major problems.  The power tubes are two 6550's.  

: Now the questions:

: Watts (RMS)?
: Was it originally equiped with 6550's
: Pre-amp tubes?
: Speakers, they look original and OK, but there is
: distortion when the thing is cranked (actually 3/4
: cranked), what can you expect out of these old
: speakers?  WHat can they handle?  Should they be
: replaced?

: Also, I have little experience with tube amps.  Is the
: distortion most likely fron the amp or the speakers?

: Finally, does anyone have an idea on the going price
: on these amps?        

Definitely pick up on it if it's the $400-$500 range for both head and cabinet, but going to high end of this range depends on how cherry it really is, and the depth of your pockets. If less, by all means, run, don't walk, and snag it immediately. As Tom said, new speakers will be in order, as what's in there now are probably Emminences, so figure that into your expenditures. Carvin makes a pretty decent cast frame 15" for about $100 each if you're on a budget. Now, tubes. If you really want to get this thing pumping, kick out another Franklin and get a pair of Czech KT88's. Much more power than 6550's(which were used as substitutes when the 88's originally went out of production)--88's are now back! Have a reputable tech do a bias job/tune up, 'cause I'll betcha there'll be a capacitor or two needing replacement. Put in a new 6An8 driver tube, and then try this preamp tube trick:instead of the standard 12AX7, use a 12AT7(601221f AX's gain value) or even a 12AU7(20%). Why, you ask?  Well, unlike a guitar setup where hot gain and overdrive is desirable, for bass, theoretically, you want as clean a sound as possible, and this is achieved by not running as hot a signal through the preamp tubes onto the power tubes. With a lower gain preamp tube, you can open up the volume a bit more and make the power tubes work to their full potential. Passive bass pickups do put out quite a bit of voltage, and if you're using actives, that's plenty of juice to push lower gain tubes. If you can find the Nov.'91 issue of Guitar Player, there's an article entitled "Tube Mysteries Revealed" that explains all of this in depth. Good luck on your deal.  

[Tim]

: 1) 60 watts rms
: 2) came with Tung-Sol 6550s
: 3) If you want loud and clean, replace the original speakers (unless they're JBL D 140Fs) with higher quality speakers,
:     ie: EV, JBL, Eden 15s, etc.
: 4) Tube amps do produce distortion... but what you're hearing is most likely speakers being over driven.
:    The over-all sound is a combination of a number of things. Check the tubes, check the bias voltage, compare the speakers to known clean speakers.

: This amps sounds "big" for a 60 watt amp, but don't expect it to fill large rooms.

: Tom

I've played a 190b thru accompanying 2X15 cab for 10 years. Until the orig. tubes burned, and replaced with svetlana 6550's. Good for large and small venues. A bitch to lug that cabinet.