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K200 PA Disconnecting 1 Channel from Line Output [message #21032]

Thu, 31 July 2014 14:30

janalex
Messages: 11
Registered: May 2013

Junior Member

Hi,

I'm using channels 1-3 of my K200 for vocal amplification and would like to use channel 4 for micing the Leslie speaker. I run the Kustom head line out into a Peavey monitor amp. I'd like the Leslie to not be heard through the monitors. Can one channel by removed from the line out signal and if so how?

Thanks

John

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21033 is a reply to message #21032]

Thu, 31 July 2014 16:11

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

I don't think that it can be done. At least not easily.

The 4 preamp channels are mixed together at the reverb board and the mixed signal is sent to the input of the power amp, where the signal is routed to the power amp circuit and to the monitor jack.

In order to separate out the one channel preamp, you would need to bypass the reverb and mixer circuits and then mix the Leslie signal back in to the power amp after the monitor jack.

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21034 is a reply to message #21033]

Thu, 31 July 2014 21:16

pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi

Senior Member

Not a tech by any stretch of imagination, but the PC105 board has two versions one with the bright switch and one with the reverb control.
What if the reverb control was removed and a bright switch in it's place. Could you bypass reverb board and the only thing left to do is make a blocking filter to keep the signal from going to the RCA jack?
pleat

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21035 is a reply to message #21032]

Thu, 31 July 2014 22:05

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

It might be doable!
Bill what do you think about this?
You would have to remove the blue wire for channel 4 where it enters the 803 board, bypass Q700 on the 703 board and then feed that channel 4 output thru 10 uf cap on the input side of Q702.
The issue I see is the drop in signal level due to channel 4 bypassing Q700!
That being said, the channel preamps do have a good amount of output all on there own and if you are not running the other channels up too loud you may just have to open up channel 4 a good amount more.

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21039 is a reply to message #21032]

Fri, 01 August 2014 01:49

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Steve, that's what I thought of, but there are two gain stages on the mixer board based around Q804 and Q805 and then the input to the power amp at Q700. I don't know if there would be enough signal straight from the preamp board to drive the power amp directly. But it might be worth a try.

Pleat, the four signals from the separate channels are mixed together before going into the reverb/mixer board. Once the signals are mixed together, I can't think of any way to unmix the one channel from the monitor send. What Steve is suggesting is to remove the channel from the mix before going into the reverb/mixer board and running it directly to the power amp.

janalex, if you want to try it let us know and we can suggest a way to do it.

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21041 is a reply to message #21032]

Fri, 01 August 2014 07:06

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

I hear ya, but my though is that since this same basic board is used the non effects type amp (200B-1 and such) that it would be worth a shot!
I know from testing these boards that they have about 4 volts of signal output and that might do it at least up to a certain volume level in regards to the other channels used?
Or, if his channel 2 works, take that output of 4 run it down into 2 and then do the mod you (Bill) and I have been tossing about?

[Updated on: Fri, 01 August 2014 07:11]

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21043 is a reply to message #21041]

Fri, 01 August 2014 08:33

pleat
Messages: 1452
Registered: June 2004
Location: Belding, Mi

Senior Member

A good brain teaser on janalex original question, of seperating out the signal from channel 4 that is being used to mic a leslie cabinet to the RCA out jack that is feeding a peavey monitor amp and monitor cabinets.
Would it be easier to tap the signals from the first three channels and route them to a seperate output jack that would feed the peavey monitor amp?

pleat

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21044 is a reply to message #21043]

Fri, 01 August 2014 08:54

janalex
Messages: 11
Registered: May 2013

Junior Member

Thanks for the suggestions. As long as the gain level for channels1-3 is not affected, I don't think it would be too much of an issue if the modded channel had a little less gain. The Leslie just needs a small boost apart from its own amplification.

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21045 is a reply to message #21032]

Fri, 01 August 2014 09:13

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

Well if your game than give what I posted a try out as you will not harm the amp if done careful!

Cut the blue wire on the pc803 board, the blue wire that is at the junction of r816 and r817, but cut it so there is enough lead left off the board to use a butt splice and a crimping tool to re- join them if need be.
Next extend that blue wire off of preamp 4 and at its end solder on a 10 mfd or uf @ 35 to 50 volts or better cap with its positive end on the wire.
Next on the pc703 board tack solder the other end if that cap to the junction point of c702 and r707 and take a test drive!
Note that you can use any of the pc703 schematics listed on this site to wire from.
Please report back on your outcome!

[Updated on: Fri, 01 August 2014 09:16]

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21046 is a reply to message #21045]

Fri, 01 August 2014 13:25

janalex
Messages: 11
Registered: May 2013

Junior Member

Will do and report back!

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Re: K200 PA Disconnecting 1 Channel from Line Output [message #21087 is a reply to message #21032]

Sat, 09 August 2014 11:14

janalex
Messages: 11
Registered: May 2013

Junior Member

Hi

We tried the mod but unfortunately the signal is still being fed back through the monitor output. Maybe there is another hookup point that is buffered from the monitor out?

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