Sunn Concert Bass Amp Footswitch

[Zombie Wolf]

While searching for schematics for my Sunn Concert Bass Amp, I found this forum. Very cool and so I just joined.

I do have a question on my Concert Bass amp. I believe I purchased the amp and a 215B bottom in '75. One of the things not installed on this particular head was the 1/4" footswitch plug. They have it masked off with a plastic plug. So for many years I ponder the question can I just wire in my own plug? Is anyone familiar with this setup and basically can this be done?

Thanks,
Zombie Wolf

[MarkG]

I have a 75 also. On mine the footswitch connector is not a 1/4 inch jack. It is  twin phono plug connector labeled "Distort" . The footswitch is actually a dual footswitch,one for "distort",and one for "boost".
TO activate the distort and the boost functions,the footswitches are actually "open" .  They are "closed" to turn them off.   So with no footswitch plugged in,these circuits are open and these functions are actually normally "ON" .

Check this link below to see the backside.  

 The plastic plug you speak of would have been a second speaker output jack,that they for some reason chose not to install,probably since the matching cabinet was already at 4 ohms and they did not want to encourage a second cabinet.

check this link:
http://sunn.ampage.org/site/museum/concbass/

[ROCKETBRO2]

I always wondered why they blocked off the second speaker jack on my 73 Concert Bass. It looks exactly the same as the 75.

[Zombie Wolf]

Well after reading through almost every archived thread on the Concert Bass Head, I have part of my answer. What I have is a 2nd generation amp; the one with the red knobs. Opened it up and found the date of manufacture - 1977. Off by two years on my original post. 

The schematic found for the Concert Bass Amp on this site is labeled; D-1003. There does not seem to be any date, however I do see a couple of ECNs it went through. This looks to me like the 1st generation schematic. How different are the Concert Bass 1st and 2nd generation amps wired? Based on what I have read the 1st was 150W and the 2nd is a 200W.

So it makes we wonder more why Sunn never added the footswitch to the 2nd generation amp. I mean they went as far as labeling and putting an access hole for it. Is it just that Sunn decided to leave the circuitry out as a cost reduction? Of course, like a typical organization with great communication; no one told the Mechanical Engineer in charge of the metal housing to eliminate the footswitch hole before balls to the wall production? Just a thought.
 
It is not so much getting a distortion footswitch. That can be done with a simple pedal. It is more of understanding of what was done and perhaps why...

Zombie Wolf

[mckinnon audio]

  Hi there,I think you'll find out that they use the same chassis for both the Concert Lead and Bass,so that's probably why there's "extra" holes stamped in the chassis,for rev.,etc.Mel.

[MarkG]

Notice that the early Silver Front versions of Concert Bass had 5 knobs ,the 5th knob for the distortion.

Notice that the later Red knob versions only have 4 knobs. They removed the distortion/boost features altogether. No functions to even switch on/off for the Red knob versions.  Nothing to wire a footswitch to.

The plugged footswitch hole  on the rear of Red Knob version is there because they were built on the same chassis as the Concert Lead which did have the distort circuit as well as reverb.  Not sure what type of footswitch connection they used on the red knob Concert Lead. All Silvers used twin RCA type phone plugs.

[MarkG]

I always wondered why they blocked off the second speaker jack on my 73 Concert Bass. It looks exactly the same as the 75.

Silver front versions output circuit were minimum 4 ohms. Since the matching 2/15 cabinets typically
sold for these were at 4 ohm,they did not want a second cabinet of same attached. Would result in 2 ohm load.     

Later Red knob versions were able to handle down to 2 ohms,enabling use of a second 4 ohm cabinet.  They had both speaker jacks installed.

[pickinatit]

I'll have to check when I get home,  but I'm fairly certain that my red knob Concert bass head has a bass boost switch on the front panel.
I could be wrong though.

I don't recall ever seeing anything in the back that made me think
"foot switch",  but I'll have to check when I get home.

I have a couple of Sunn foot switches.  They each have two buttons that are double labeled:  Reverb/boost  Vibrato/Distortion
(I might have that backwards)  I have no clue what model Sunn amp they are for,  but one of them has a single 1/4" plug on the end of the wire.  The other one has the two prong (RCA??)  plug like the footswitch for  my Solarus (I bought them to see if they would work on my Solarus before I found an actual Solarus foot switch).

I'm planning on putting them up in the classifieds in the next day or two.  I'll post pics of them with my adv. 

[pickinatit]

I'll have to check when I get home,  but I'm fairly certain that my red knob Concert bass head has a bass boost switch on the front panel.
I could be wrong though.
I don't recall ever seeing anything in the back that made me think
"foot switch",  but I'll have to check when I get home.

OK, at home now.  My Concert Bass Amp (red knob).  I knew it had a switch on the front panel, but it's not labeled "Bass Boost",  it's labeled  "BRITE". 
On the back, there is a plugged hole (plastic plug)  that is clearly labeled  "Footswitch"  underneath of it.  I mean, not a paper label or hand written label,  but painted right onto the back panel at the factory.

[Zombie Wolf]

  Hi there,I think you'll find out that they use the same chassis for both the Concert Lead and Bass,so that's probably why there's "extra" holes stamped in the chassis,for rev.,etc.Mel.

After years of wondering, there is the answer... Sunn screwed the Bass player - No distortion for you!

{lol}

Thanks,
Zombie Wolf

[MarkG]

Zombie Wolf , I wouldn't cry too much about it. 

Unlike the Silver units, The ability of the Red knob units to handle a 2 ohm load ,enabling connection of  2 of the matching Sunn 4 ohm cabinets,plus a bit more power, is a benefit that outweighs the absence of any distortion feature.    Want distortion ? There are plenty inexpensive effects pedals available.