concert bass questions

[year of the horse]

Hey there, I'm new to this forum and to Sunn equipment. I just purchased my first piece, a 70's silver face concert bass.
My first question is, it looks like the speaker 2 input on the back panel has been blocked off by the previous owner. What might be the reason for this?

Also, the distortion feature requires a dual RCA footswtich. What footswtich options or substitutes would you guys recommend? How easily can one be home made? Any and all help would be greatly appreciated. Thanks!

[wildbill96]

I can't address your question regarding why one of the speaker out jacks has been covered up by the previous owner but I can advise you regarding your footswitch question.

I ran into the same challenge with my Coliseum 880 head.  After searching everywhere for a vintage footswitch (they do pop up from time to time on eBay) I cobbled together a solution with a generic dual latching footswitch (I purchased an Apex AFS2 since it was silver similar to the originals) along with a stereo 1/4" cable and a 1/4" stereo female to dual RCA male mono adapter cable from Radio Shack.  One of the two switches activates the distortion and the other activates the boost.  I put the whole thing together for less than $40 which is considerably cheaper than what the vintage footswitches are going for these days.

There's also a guy on eBay (VoodooMan) that is building replacement footswitches.  Here's a link to his posting for his Sunn version that would work for this application.  Note that his $39.99 price does not include cables. 

http://cgi.ebay.com/Sunn-RCA-2-Button-Replacement-Footswitch-VoodooMan-/110625925077?pt=LH_DefaultDomain_0&hash=item19c1d1a7d5

[Isaac]

I use a Peavey foot switch. It terminates in a stereo plug, but I bought a stereo jack to dual RCA adapter from Radio Shack, and I've been good to go ever since.

[Walt-Dogg]

Fender makes dual RCA jack footswitches.

[year of the horse]

Thanks for all the help everyone!

[django7866]

I use to own a silver faced concert bass, The 2nd speaker out was blocked on mine as well. I thought that the person I got it from did the same. So my guess is that this was done at the time of manufacturing. I had a speaker jack installed, be careful you don't run this amp any lower then a 4 Ohm load.

[ROCKETBRO2]

I bought mine new in 1974 and it had a blocked extention jack too.

[year of the horse]

I use to own a silver faced concert bass, The 2nd speaker out was blocked on mine as well. I thought that the person I got it from did the same. So my guess is that this was done at the time of manufacturing. I had a speaker jack installed, be careful you don't run this amp any lower then a 4 Ohm load.

Thanks for the tip. Is there any place you guys know of where I could find a solid yet simple explanation of ohm loads and whatnot? I've got a vintage Kustom 3x15 Tuck n Roll and the speakers are each rated at 16 ohms. What is my ohm load at that point?

[django7866]

My guess would be 16 Ohms. I only going by this because I had a 4x12 cab that was 16 Ohms and all 4 speakers were rated at 16 Ohms. I know that, how they are wired makes a difference. But I can not remember, if the speakers are wired parallel  the cab should rated at 16 Ohms. Or if the speakers are wired in series. then it would be a 16 Ohm load.  I don't remember how this works!!! but Here is a link that could be of some help:
http://www.prestonelectronics.com/audio/Impedance.htm

[mckinnon audio]

   Hi there,the Kustom 3 x 15" cab should have the 3 spkrs. wired in parallel,giving you a total load of 5.2 ohms.Run it on the 4 ohm tap and you'll be fine,good luck,Mel.

[Isaac]

Here's the formula for impedances in parallel:

1/(1/R1+1/R2+...1/Rx)=Z

In the case of the Kustom, that works out to
Z=1/(1/16+1/16+1/16)=1/[3*(1/16)]=1/(3/16)=16/3=5.33 ohms

[EdBass]

Hey there, I'm new to this forum and to Sunn equipment. I just purchased my first piece, a 70's silver face concert bass.
My first question is, it looks like the speaker 2 input on the back panel has been blocked off by the previous owner. What might be the reason for this?

Also, the distortion feature requires a dual RCA footswtich. What footswtich options or substitutes would you guys recommend? How easily can one be home made? Any and all help would be greatly appreciated. Thanks!

I have a Vibrato/Distort, Reverb/Boost pedal with RCA plugs on a 6' cord for sale. Works fine, some minor paint chipping and very light surface rust on the back.
I know it works for the Vibrato/Reverb on the old tube 100 and 1000 series amps, and I'm pretty sure it works on the Concert/Coliseum? series amps for Distortion and Boost.

$45 shipped CONUS