Marshall 3203

[FLHX]

Does anyone know how much the sound would change in a 3203 since it is a hybrid with 2 power tubes and 1 preamp tube?

 

[tunghaichuan]

Does anyone know how much the sound would change in a 3203 since it is a hybrid with 2 power tubes and 1 preamp tube?

I used to own one of these. Very cool amp, but I'm not sure I understand your question.

tung

 

[markb]

Hi, flhx. Strictly it's 2 power tubes and a driver/phase inverter. This is also part of the power stage and not a preamp tube. If they sound anything like the Mosfet series 52xx they'll be pretty good. I've no experience of these.

 

[FLHX]

Sorry if I'm not clear. The question I'm asking is since the amp is half solid state and half tube would changing the tubes make any difference in sound. Like make it darker or more mellow depending on what tubes are in it. I'm running it thru a 1936 2x12.

 

[tunghaichuan]

Sorry if I'm not clear. The question I'm asking is since the amp is half solid state and half tube would changing the tubes make any difference in sound. Like make it darker or more mellow depending on what tubes are in it. I'm running it thru a 1936 2x12.

There will be slight variations in tone when using different brands of EL34 tubes. You may be able to have the new JJ KT77 tubes installed, I've never personally tried them, but everyone who tries them raves about them.

The plate voltage in that amp is about 450v, so I would stay away from 6V6 tubes, although the JJ 6V6S and EH 6V6GT are supposed to work at high plate voltages. 6L6s might work, but I'd encourage you to take it to a tech to have the amp checked out and rebiased.

For the phase inverter tube, you might try a 12AX7 that has matched triodes or a 5751.

If it were my amp, I would put in Svetlana/Winged C EL34s or JJ KT77s and have a tech rebias it. I wouldn't mess around with other tube types.

One thing about that amp: the transformers are somewhat fragile. If you blow either one, it is very expensive to replace them. Hence my recomendation for staying with the tube types that came with the amp.

The schematics are on this page should you ever need them:

http://www.drtube.com/marshall.htm

tung

 

[FLHX]

Thank you for the info. I was told the 3203 were fixed biased and the tubes couldn't be biased.

 

[tunghaichuan]

Thank you for the info. I was told the 3203 were fixed biased and the tubes couldn't be biased.

The amp has a non adjustable fixed bias circuit. Any decent tech should be able to adjust the bias in that amp. It requires puting in a pot wired as a variable resistor in place of one of the resistors in the fixed bias circuit, biasing the tubes, and replacing the pot with the closest resistor value once the tech measures it.

A tech could modify the bias circuit to have a small trimmer pot in the bias circuit to make it easier to dial in the correct bias for a given set of tubes.

All tubes bias differently, even tubes from the same manufacturer of the same brand. That's why some techs match tubes: to get two close to the same ratings for use in the amp.

tung

 

[FLHX]

Thank You

 

[tunghaichuan]

Thank You

You're welcome.

Why don't you stop by the Fret Players section of the BBS and introduce yourself?

http://www.thefret.net/forumdisplay.php?f=13

This is a real friendly group of people.


tung

 

[oldguy]

Absolutely!
Tell us a little about yourself. We'd like to know what kind of music you like, what kind of gear you have, where you're from, that kind of stuff. :beer:

Oh, and welcome to TheFret! Glad you joined us here.:bravo: