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Kustom k200b 1 RCA jack [message #16353]

Sun, 30 October 2011 14:57

supersatisfier
Messages: 4
Registered: October 2011
Location: Pacific Northwest

Junior Member

So, I was experimenting with using a preamp with my Kustom 200 and I found that running from the output of my Presonus TubePre INTO the rca jack on the back of my amp produced signal. . . as if the jack could be used to access the power amp section. None of the controls on the front affect the volume or tone, the gain control on the preamp changes the volume. My question is. . . am I hurting anything? Has anyone else ever done this?

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Re: Kustom k200b 1 RCA jack [message #16355 is a reply to message #16353]

Sun, 30 October 2011 15:55

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

Yes, if you pump enough signal into it back feeding/bleeding into the amps driver stage harmwill be done!
The amps RCA jack was ment to feed a tape recorder and as such outputs about .750mv which is not enough to drive most modern power amps to full output with out going thru another preamp section or a mixer.
Most power amps want 1.4 volts to drive to full output.

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Re: Kustom k200b 1 RCA jack [message #16356 is a reply to message #16353]

Sun, 30 October 2011 16:29

supersatisfier
Messages: 4
Registered: October 2011
Location: Pacific Northwest

Junior Member

I figured in would be a bad idea, but it still seemed worth checking. Is there a way to mod it to be a power amp in? I ask because both channels on the front have noisy, scratchy pots (beyond needing cleaned). It seems like it would be easier to try and access the power amp directly than replace all the pots.

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Re: Kustom k200b 1 RCA jack [message #16359 is a reply to message #16353]

Mon, 31 October 2011 07:41

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

Yes, but it will require just about the same amount of work as replacing the pots.

Open up the amp and you will see two blue wires(one from each preamp board) feeding the driver board on the rear wall of the amp.
Clip these two wires and feed your outside preamp signal into eitheir mixer resistor that each blue wire feed.

Note that kustom preamp boards put out alot of signal so you may not get much output from the amps power stage, in fact I would feed your external signal into the output side of eitheir mixer resistor that the blue wires feed originally.

A tech could also wire in a switching type jack that would keep the amps normal signal path until a jack was pluged in to access the power amp section.

I find it hard to beleive that so many pots could be bad on one amp unless it had been under water or something!

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Re: Kustom k200b 1 RCA jack [message #16360 is a reply to message #16353]

Mon, 31 October 2011 10:29

supersatisfier
Messages: 4
Registered: October 2011
Location: Pacific Northwest

Junior Member

It practically has. . . years of practicing in Pacific Northwest basements! All but the bright channel's bass pot crackle noticeably when rotated, and I don't use the bright channel. The volume pots are worst, and if the bright channel's is in any position but off it make some nasty crackles. I like the idea, thanks a lot for the reply. Not something I'll do right away, but a good idea for the future. I just got schematics from a friend for a small class A preamp, I might try to have it be a switchable option! (Is adding tube tone Kustomhead blasphemy?)

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Re: Kustom k200b 1 RCA jack [message #16361 is a reply to message #16360]

Mon, 31 October 2011 10:33

Kustom_Bart
Messages: 601
Registered: October 2010
Location: Greenville, MichiGUN

Senior Member

Get yourself a good brand of contact cleaner and I normally tip the amp towards the back and spray one pot really well and then work it from side to side while pushing on the knob and then while pulling on the knob. I haven't ever had a pot that was not cleanable in one of these things. They can be trying, but normally they will clean up as they are top of the line stuff.

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Re: Kustom k200b 1 RCA jack [message #16362 is a reply to message #16353]

Mon, 31 October 2011 12:16

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

You can do anything that you want, it's your amp.

I agree with Kustom Bart, get yourself a can of Caig Deoxit and first clean the pots. After the pots are working, then listen to the amp and see what needs to be done.

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Re: Kustom k200b 1 RCA jack [message #16363 is a reply to message #16362]

Mon, 31 October 2011 16:10

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

Senior Member

Is the K200 an A or B model? Any effects? I know on the A series, a lot of ground connections were made thru the chassis. The A series had circuit boards mounted behind circuit boards, and the grounds were made thru a brass spacer. If the spacers are not making a good connection then you may have some issues with loose grounding connections. I'd also make sure all the nuts that hold the controls are good and snug behind the actual knobs.
pleat

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Re: Kustom k200b 1 RCA jack [message #16369 is a reply to message #16363]

Tue, 01 November 2011 16:24

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

Senior Member

Reread the title and I see it's a B model. Adding a line out/line in is pretty simple. There are three wires leading from the pre amps to the power amp on the back wall. Red and Green are the 8 volt wires, the blue wire is the signal from the pre amps. I use two Switchcraft 12A switching jacks. Cut the blue wire and feed one of the cut blue wires to the + tab of the first jack, jumper wire from the center lug of the jack to the center lug of the second jack. The blue wire that is left feeds the + tab of the second jack. This give you a pre amp output on one jack and the other jack is the power amp input. When I was selling Kustoms and bands wanted to add an echo to all the inputs, this was a quick way to insert the echo between the pre outs and power amp in jack.
pleat

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Re: Kustom k200b 1 RCA jack [message #16370 is a reply to message #16353]

Tue, 01 November 2011 16:32

supersatisfier
Messages: 4
Registered: October 2011
Location: Pacific Northwest

Junior Member

Awesome! Thanks for all the advice, I'm gonna add that in/out soon. It would be nice too have some more options. . . I'll let you know how it goes when I get some time. Could it drive a spring reverb tank?

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Re: Kustom k200b 1 RCA jack [message #16372 is a reply to message #16370]

Tue, 01 November 2011 16:56

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

Senior Member

The in out will allow for a wide choice of effects to be inserted. WIth the wiring of the two jacks, if nothing is plugged into either of the jacks, the amp works as normal. Fender makes a spring reverb box that is a stand alone reverb for amps without reverb.
pleat

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Re: Kustom k200b 1 RCA jack [message #16374 is a reply to message #16353]

Wed, 02 November 2011 06:24

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

If you ever do install in and out jacks make sure that sheilded cable is used and it only get grounded at one end of the cable, the jack end.

Also note like I posted earlyer, that Kustom preamps output some 4 to 5 volts, or 3 times the signal needed to drive effects and or standalone reverb units and stomp boxes.

The Fender reverb unit was desinged to normally get a input level of .250 volts, so rolling way down the input level jack will be needed.

[Updated on: Wed, 02 November 2011 06:25]

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Re: Kustom k200b 1 RCA jack [message #17829 is a reply to message #16374]

Sun, 02 December 2012 20:35

Count Bassie
Messages: 8
Registered: December 2012
Location: Rhode Island

Junior Member

Wow, great thread here. I've relinquished the thought of a in/out type loop like this, but now see that it's a pretty simple mod. Thanks for posting!

I suppose one could put an adjustable pad into that mod as well? So you could adjust for a particular use without losing input volume? Say I wanted to use an external power amp, there's one scenario; if I wanted to insert a fuzzbox, there's another; going to tape direct is another... so maybe I'd want to adjust output for each scenario. Or, would I just use the input volume for all?

Me am no tech... Confused

"Whatever we do, it is what it is, and we do it."

-Me...

[Updated on: Sun, 02 December 2012 20:37]

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