Sunn Concert Lead - 1st gen vs 2nd gen red knob?

[thehornedone]

I know there are two very different looking versions of the concert lead: the more common silver knob version, and the red knob, which seems to have fewer knobs and a few obvious differences on the front panel.  Does anyone know what the differences are between these and if they sound different?

[george]

Let's see the older version (silver and black) has reverb and distortion features seperated into two channels - channels are not switchable and you will need a footswitch to turn on/off boost, distortion and reverb.

The red knob version (later) is a single channel amp with reverb and dsitortion.

I believe these amps are around 125 W RMS into 4 ohms - rumor has it that the red knob version will drive a 2 ohm load - I wouldn't advise it.

Difference in "sound"? Well these two versions of the Concert series use very similar - if not the same preamplifier designs (FETs in the input) and the output boards use transformer coupled quasi-complementary emitter followers - very slight differences (mostly to reduce cost in the later design). Oh and the red knob version has the carrying handle on the side where it belongs.

[biltmore]

I know it's a pain, but there's PLENTY about this subject that can be learned from the search function on this forum:

http://sunn.ampage.org/sdp/index.php?action=search

There's more than just a 1st gen / 2nd gen of the Concert series. There have been at least a couple of versions of both the silver and red knob Concert amps.

Here's what I've learned from JoeArthur and loudthud (and others):

The early & mid Concert series (silver knob) can produce roughly 95 watts @ 8 ohms, 150 watts @ 4 ohms, and are NOT recommended for 2 ohm operation.

The late 70s Concert series (red knob) - can produce 50-60 watts @ 8 ohms, 100 watts @ 4 ohms, and 200 watts @ 2 ohms.

rumor has it that the red knob version will drive a 2 ohm load - I wouldn't advise it.

It's not a rumor at all. The back of a red knob Coliseum Bass says it's rated @ 2 ohms. Still, that's a very iffy subject that seems to be an object of contention around here. I know that Joe Arthur is a very well informed fellow, and he doesn't recommend a 2 ohm load for the red knob Concert series. I myself have heard a red knob Concert Bass running 2 cabs with a 2 ohm load and it sounded just fine to me.

[george]

Yeah I bet it sounded fine up until the thermal switch cut the power - no way that design will work reliably under 4 ohms.

The back of a red knob Coliseum Bass says it's rated @ 2 ohms.

No it doesn't - the one I have here on the bench has a silked screened label under the output jacks that says "max output power 200 Watts - class 2 wiring may be used" There is no mention of impedance. What rumor are you starting?

I don't consider any of the revsions made to the silver and black panel Concerts worth calling major - there was a service bulletin issued in the early 70's (??) that changed some of the bias/power supply connections - the form fit and function of the series didn't change until the mid to late seventies with a new chassis, enclosure, knobs, etc. I call that a "generational" change in design (at least from an industrial/human interface point of view).

[biltmore]

Wasn't trying to start any rumors george. My friend swore that the back of his Concert Bass said 2 ohms, but it says 4.

[Walt-Dogg]

Red knob sucks, it's twice as heavy as an early 70s and impossible to carry based upon the location of the handle. I prefer red knobs though tonally.