Marshall Amp Forum - View Single Post - Preamp Tubes?

RiverRatt · 07-02-2009, 11:38 PM

I like new production tubes in V3 and V4 - the Mullard and Raytheon 12AT7's I have sound great there as well, but the new tubes seem to have a bit more presence or maybe they are a little more aggressive. It's hard to explain. I'm mainly just worried about Marty's info about Tung-Sols failing in V3.

There's a guy on the Les Paul forum who knows his stuff who insists that the PI tube can't have any affect on the tone of the amp. My experience seems to say otherwise. I can hear a difference and feel a different response from the amp with phase inverters that have different gain factors, or even between different makes of the same value.

Josh, I hear what you're saying about the bias setting. I've always thought that the JCM 2000 EL34 amps are biased way too hot at Marshall's recommended setting. Like I said, My DSL50 likes to be around 36-37mV instead of the 45mV that Marshall uses. One of these days I've got to open up my amp and measure the plate voltage. I suspect that 45mV is going to read somewhere between 80-90%.

07-02-2009, 11:38 PM	#547 (permalink)
RiverRatt Senior Member Join Date: May 2008 Location: Between Memphis and Nashville Posts: 517	Re: Preamp Tubes? - Who, What, When, Where, Why, and How? I like new production tubes in V3 and V4 - the Mullard and Raytheon 12AT7's I have sound great there as well, but the new tubes seem to have a bit more presence or maybe they are a little more aggressive. It's hard to explain. I'm mainly just worried about Marty's info about Tung-Sols failing in V3. There's a guy on the Les Paul forum who knows his stuff who insists that the PI tube can't have any affect on the tone of the amp. My experience seems to say otherwise. I can hear a difference and feel a different response from the amp with phase inverters that have different gain factors, or even between different makes of the same value. Josh, I hear what you're saying about the bias setting. I've always thought that the JCM 2000 EL34 amps are biased way too hot at Marshall's recommended setting. Like I said, My DSL50 likes to be around 36-37mV instead of the 45mV that Marshall uses. One of these days I've got to open up my amp and measure the plate voltage. I suspect that 45mV is going to read somewhere between 80-90%.