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Unread 01-26-2011, 03:38 PM   #1 (permalink)
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Join Date: Jan 2011
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Exclamation New tubes Marshall 4203 Artist combo?

Hello guys,

Know there are "divided camps" about this 80s combo but I think the overdrive channel sounds pretty ok for rehearsals and home use.

Recently the amp has started hissing and buzzing and I think a re-tube
is in order, think they have been there a long time.

Current power tubes are National Electronic 6CA7s, unsure of pre-amp tubes.

Need advice - some issues

a) What are good options for both preamp-and power tubes for this model? Would like to keep the "classic crunch tone" -
speaker is Celestion G12 Vintage and Drake Electronics transformer

b) What about tube bias settings for this amp?

c) If I want to reduce the gain a tad (since there are loads...) - what do you recommend?


Feedback greatly appreciated!
Cheers / Jonas
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Unread 06-02-2011, 06:11 AM   #2 (permalink)
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Join Date: Jun 2011
Posts: 16
Re: New tubes Marshall 4203 Artist combo?

Cant offer much of a solution but Ive had a 4203 Artist combo since new in the late 80's. The power supply blew up mid 90's and was replaced by brand unknown and it was re-valved a few years ago with a matched pair of EL34s and preamp valve - again unknown brands, and it still sounds awesome : ) It has evolved fairly organically with my total absence of technical knowledge on guitar amps but still sounds great.

Quote:
Originally Posted by jonassweden1 View Post
Hello guys,

Know there are "divided camps" about this 80s combo but I think the overdrive channel sounds pretty ok for rehearsals and home use.

Recently the amp has started hissing and buzzing and I think a re-tube
is in order, think they have been there a long time.

Current power tubes are National Electronic 6CA7s, unsure of pre-amp tubes.

Need advice - some issues

a) What are good options for both preamp-and power tubes for this model? Would like to keep the "classic crunch tone" -
speaker is Celestion G12 Vintage and Drake Electronics transformer

b) What about tube bias settings for this amp?

c) If I want to reduce the gain a tad (since there are loads...) - what do you recommend?


Feedback greatly appreciated!
Cheers / Jonas
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Unread 06-03-2011, 09:13 AM   #3 (permalink)
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Join Date: Oct 2010
Posts: 96
Re: New tubes Marshall 4203 Artist combo?

JJ E34L's sound very good in these amps as well as a JJ ECC83S in the phase inverter. I would change out the 12ax7 first to see if the noise goes away. If it doesn't then swap out the power tubes. If the tubes don't get rid of the noise then it's time for some tech work. The pots and jacks, especially the effects loop, typically need to be cleaned. To bias the amp you'll need to know the plate voltage, but I think about 36mA per tube is where my friend has his set.

The amp uses diodes for clipping so the easiest way to reduce distortion is to turn the gain knob down. Being a solid state preamp you can't sub a lower gain tube.
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