Katana 50 Mod - Monitor on speaker while using Rec Out

Started by KeldAmpworks, January 09, 2018, 01:03:58 PM

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KeldAmpworks

Hi,

I took my Katana 50 apart to find out if I could get the speaker to still work in rec out mode. Turns out you can. My hunch was that Roland would have used a jack back contact to tell the microcontroller to defeat the speaker - sure enough, when you insert a 1/4in stereo jack into the rec/phones out, the sleeve back contact is pulled up to 3V3 and the speaker is defeated. If you ground that connection again then the speaker plays and the sound still comes through headphones.

To my way of thinking that's a good permanent mod - since you can put the amp in standby if you want silent headphone/rec out usage anyway.

Firstly - before I make this permanent, have a I missed a setting in the tone studio that would allow this to happen unmodded?

Points to note:
The headphone level increases (EDIT: by 8dB) - The channels might be summed, I couldn't immediately tell from the program material I tested with.
The master volume controls the output level of the phones/rec out and the speaker simultaneously.

Pics on my website:http://www.ampworks.co.uk/experiments/boss-katana-mod-midi-mod-rec-mod/

And also on the midi 5 pin thread:
https://www.vguitarforums.com/smf/index.php?topic=19575.msg162978#msg162978

Cheers guys,

vtgearhead

Nice writeup - thanks!  I'm now waiting for a way to disable the speaker emulation on REC and LINE out for those of us who use IRs rather than mics. 

KeldAmpworks

Interesting point - I can't be sure that the cabinet emulation remains with this mod. Id have to measure the frequency response before and after. If it disappears then it's bad for me and good for you!

vtgearhead

I'm 99.9% convinced that cabinet emulation is always on the REC and LINE outputs.  Just go into BTS and toggle the "style" setting and you should always hear a change.

As a temporary workaround, I've started using a Y-connector on the loop jacks (in their infinite wisdom, Roland decided it was a great idea to disable loop send unless (a) the loop was engaged through pedal and (b) a connector is physically connected to the return).  By plugging the volume pedal into the FX jack on the my GA-FC I can get pre-loop level control and make this arrangement practical. 

The only downside is that I now have to leave the loop active all the time and can no longer use it as a poor-man's boost.

admin

#4
CAUTION - If ANY Speaker (+) wire or (-) wire touch each other - or Chassis ground while powered ON -  - you fry the Katana Power amp

( BTW - this is true for ANY Solid State Power Amp, and many Tube Power Amps too.

KeldAmpworks

Quote from: admsustainiac on February 12, 2018, 11:59:45 AM
CAUTION - If ANY Speaker (+) wire or (-) wire touch each other - or Chassis ground while powered ON -  - you fry the Katana Power amp

( BTW - this is true for ANY Solid State Power Amp, and many Tube Power Amps too.


You're dead right of course (though solid state current drive amps are an exception), but that's not a big issue with this mod. You just need to modify the rec out PCB,

admin

#6
Quote from: KeldAmpworks on February 12, 2018, 01:06:35 PM
You're dead right of course (though solid state current drive amps are an exception), but that's not a big issue with this mod. You just need to modify the rec out PCB,


And its a great mod BTW -

Just spreading caution ( and CYA from Roland / Boss tech support) for some naive  Katana Owners


  , as some folks reveal they have a misunderstanding with solid state power amps and  electronics and speaker wires , and often foolishly apply their own idea of the ultimate mod - with no experience = smoke

Specifically to prevent this

Katana - HELP NO SPEAKER OUTPUT AFTER SWAP OUT.!
https://www.vguitarforums.com/smf/index.php?topic=22774.msg165602#msg165602

KeldAmpworks

Agreed. I only attempted this because I've got a lot of experience in solid state design and repair.

rolavin

I did this mod on my Katana 50 mk2, the easy way. I removed the 6 screws that go to the standoffs that support the  board that has the headphone jack in it. Using a small soldering iron and some leaded solder (it melts at lower temps and is easier to use), I soldered a short between the two headphone jack terminals closest to the board. I didn't remove the  board, just pushed it over to the side to do the terminal closest to the side edge of the board, and soldered the other end of it, with the small iron right through one of the holes that the jacks go through. By doing it this way, I avoided disassembly, and the risks, of removing the heat sink and wooden pieces. I was going to take some pics, but i put it back together to see if it works and it does. As stated the standby switch mutes the speaker with the headphone out still working, so there was no need to add any sort of switch. I just used a piece of 30 gage wire wrap wire to make the jumper as it carries ground, but still a good idea to keep insulation on the wire, except for the short end that solder to the terminals. Pretty easy but don't try it with a soldering iron that is too large to fit through the jack holes.

specialbat

Would it be possible to just modify the headphone PLUG is some way to accomplish this (retain speaker output while headphone jack engaged)?



admin

Needs an internal mod -ground the Amp Mute control line PCB trace for the cable present switch contact on the Headphone/Line Out 1/4" switch jack.

As described  here

https://www.vguitarforums.com/smf/index.php?topic=22474.0#msg254301

specialbat

I was hoping there was a way to do it without messing with the amp.  If I attemp this I would need diagrams & photos as I have limited skills and knowledge in this area.
I did something similar on my old micro cube but there were detailed instructions and less at stake.


specialbat

Re my preceding post there is a way to do this.  A guy in the private facebook group "Boss Katana Amps" shows how he filed away part of the plug so that the speaker stays on