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Bypassing the preamp on a K100C-8 [message #14338]

Wed, 15 September 2010 00:25

RickBlacker
Messages: 133
Registered: October 2008
Location: Oregon

Senior Member

Hi all...

I just bypassed the preamp on my amp. I know where the leads from the preamp enter into the power amp due to some modifying about a year ago. What I did was put a new 1/4" jack in the place of one of the other jacks ( did not disconnect jack, just moved it out of the way).

The new 1/4" jack is wired up to go directly into the input of the poweramp. The reason I did this was because I have a Boss GT10 pedal board which has lots of preamp amp modeling as well as FX.

So, the output of my Boss GT10 is designed to go directly into an amps input or into a return on an FX loop. Seems to me that this should be ok and I have nothing to worry about.

Was hoping for some input from you guys. I really like the sound I'm getting from the bypass.

My amp : K100C-8

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Re: Bypassing the preamp on a K100C-8 [message #14346 is a reply to message #14338]

Thu, 16 September 2010 09:11

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

Yes, you should be fine with that set up as the preamp section of the amp outputs more, or about the same max signal level as your Boss unit I will guess can probibly muster up, but note that the first input transistor is of the same type used on the amps preamp section
Board(s)and can be blown out if exsessive input signal is pumped into them.
I would for this reason start out using a clean Boss patch/sound that will not produce distortion heard thru the speakers, this will than be the max volume level you can get up to with out driving the power amp section too hard. Then do not exceed that same volume level heard with any other patch/setting used from the Boss.

One thing you may need to do though will be to use a ground lift adapter on the power cord of the Boss if you get/hear a 60 hz grounding hum turn up do to a grounding loop.

The rule of thumb is with multiple items of gear plugged into to your signal chain is that you only need one of them to be grounded thru a 3 prong AC cord to have all of the gear saftly grounded.
The more of them that are grounded the better will be chances of having a 60 Hz ground loop problem drive you nuts!

If the Boss has no 3 prong AC cord you may still need to reverse the direction of how the cord plugs in to rid your self from hum and or buzz noise, even if it uses a wall wart or block type supply!

The old type AC ground lift adapters where great for doing this as they have two of the same size prongs, the new ones do not and need to be ground back with a Dremel tool stone or filed back while held in a vise which will then let you flip them around as needed.

[Updated on: Thu, 16 September 2010 09:32]

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Re: Bypassing the preamp on a K100C-8 [message #14349 is a reply to message #14346]

Thu, 16 September 2010 22:33

RickBlacker
Messages: 133
Registered: October 2008
Location: Oregon

Senior Member

Thanks steve for the input. Good to know that I can safely do this. I doubt I'll be gigging anytime soon and if I do, it wont be in a large venue. Cool

My amp : K100C-8

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