Input 1 & 2 Footswitch for an Original Mark 1

[kdove]

I have never used the input 2 and never had the footswitch.

I have an idea to use the 2nd input with a TS9 on the 2nd input for another sound option. But I need to understand how that switch was set up.

 

[Shep]

i am pretty sure that the mk I's didn't have a channel footswitch.. only a reverb i think..

the mk II was the first dual mode amp...

 

[kdove]

No ... I was just looking at my original instructions from '78 this weekend and it described running two leads (one to input 1 and one to input 2). The input 2 lead skipped the first pre-amp tube and it warned the "clean tone" would be much less volume ... which it is.

My idea is to put a TS9 in between the switch and input 2. Kind of like running into an older Fender designed amp without that first pre-amp. It works pretty good when I set it up that way. However, I want to be able to switch back and forth. Both sounds would be overdriven ... not clean ...but different.

 

[Shep]

i don't competely understand what yo uare trying to do..

guitar A/B box A to input one and B to a TS-9 and then input 2?

what are you trying to switch

 

[kdove]

gtr----------------------> input 1 (like I've been playing)

OR

gtr---------TS9--------> input 2



Both would be overdriven. The input 1 has all of the pre-amps cascading. The input 2 has all but the V1 preamp stage and instead has the TS9 (kinda like an old Fender bassman with a TS9).

They both sound good and I'm just trying to be able to switch between them both.

 

[Shep]

A/ B box?

 

[kdove]

That's what I was thinking ... I don't have an A/B box ... was considering Boss LS-2. If I hook up both cables without the A/B switch only the 2nd input functions.

I'm curious if there is anything special about the old Mesa box (the one I could have bought back in '78 ) that is different from an A/B switcher. Surely somebody has one of these. At least that's what I'm hoping.

 

[kdove]

I found my answer on the Mesa/Boogie website ... the Mark I "Reissue" manual is almost word for word from the instructions I have from '78 (including the volume drop). But the new instructions specifically mention the A/B box on page 2.

http://www.mesaboogie.com/manuals/Mark1 Reissue.pdf

 

[JOEY B.]

I would try a garden variety a/b box if you have one on hand. If you have to buy one, get the correct one from Boogie. They still sell it. Depending on how they are internally wired, not all a/b switchers will work with the MkI. My Lehle, for example, won't channel switch my MkI. Maybe the TS-9 will help overcome some of the volume drop.

 

[kdove]

I just ordered the LS-2 from Musicians Supply last night. I guess I didn't think about the Mesa version. You are correct ... they still sell it Mesa Box cheaper than the LS-2 box.

Anyone know either ...

... if the wiring is different on a Boss LS-2 and the Mesa Box?

... whether the LS-2 will work?

:?

 

[kdove]

the LS-2 is on it's way via UPS ... let you know tomorrow ... if anyone's interested.

 

[PRS-Ian]

The LS-2 has a few more functions than just switching A and B. Each of the channels has a volume control and you can select the option to blend both channels if required.
Ian

 

[stokes]

The one Mesa has is easy to make, for a lot less than $69.One switch,a couple of jacks and a box.

 

[kdove]

So the Mesa/Boogie is a simple ... nothing special ... A/B box?

 

[kdove]

As I suspected, the LS-2 doesn't work out of the box to do what I want.

Setting it on the OUTPUT SELECT:
- Right side of pedal: input the guitar to the INPUT
- Left side of the pedal:
------ cord going from A-SEND to INPUT-1 of the Boogie
------ cord going from B-SEND to INPUT-2 of the Boogie

Results:
-- Select A: Very muffled sound (works correctly if I unplug B-Send cable from the box)
-- Select B: Works OK

Conclusion: There is something in the Mesa pedal that effectively "unplugs" the B-Send cable and it is grounded somehow on the LS-2 box. Anybody know how the mesa box is wired? It must not be a simple A/B box but I'm no tech.

Note: If I plug the A-Send to the Boogie and the B-Send to another amp it works fine. So the Mesa pedal has to be slightly different to deal with the INPUT-1 and INPUT-2 wiring on the Boogie.

 

[JOEY B.]

That's exactly how my Lehle acted. As if the signal was always going through both input 1 and 2. It would not switch between the two.

 

[Boogiebabies]

It's got to be an A/B switch, not an A and B.
Once you engage the A and B it's basically a series loop.

 

[kdove]

If I hook up the LS-2 to two amps it works.

If I hook it up to Input 1 & 2 ... inputy 2 works but input 1 does not unitl I unplug input 2 from the pedal.

So the Mesa pedal designed to switch input 1/2 must be slightly different from and A/B.

The LS-2 has A+B, A<>Bypass, B<>Bypass, A>B>ByPass,

 

[kdove]

I think the secret is grounding in the two input circuits when 1/4" jacks are in BOTH input-1 AND input-2. Here's a picture of my original schematic (just the input section). Any techs see what's doing it?

Remember ... INPUT-2 always works fine ... INPUT-1 is still OK when a 1/4" jack is placed in INPUT-2. However INPUT-1 goes silent when the other end of INPUT-2 cord is inserted into the LS-2 pedal.

I have a set of those planet waves cables that you can touch a button and short the circuit. If I run through INPUT-1 and insert the cord in INPUT-2, it still works but as soon as I close the circuit on the cord on INPUT-2 ... INPUT-1 goes silent. I think the Mesa pedal must NOT ground INPUT-2 when it's not in use. Possible?

 

[Shep]

you might be finding that the stereo jack off input 1 is grounding out the input 1 ciricuit.. my mk III and mk IV does this..basicly when you un plug a lead from your amp your input 1 will cut out most of your pre amp section reducing noise..i think your amp is doing this when you are pluging into 1 and 2 inputs..It's hard to explain typing it... lol

the best way to test is plug only into input 1 turn your preamp vol,treble,mid,bass up to 10 and your master so you can softly hear a hiss ( doesn't have to be to loud) .. have your guitar volume and 0 so there isn't any pickup noise.. now unplug the lead from the amp and if there is a drop in preamp noise then that might be your problem..( well it's not a problem ) as i said if i did this with my mk III/IV then they will go quite with no hiss.this will explain why your amp isn't doing what you want...your amp might be different..I might be wrong but it's just an idea..

Anyway good luck..