Fault poweramp tubes JMD 100

[macsmith]

Hi everyone

In the last days i heared strange noise from the JMD 100. Most of the time it was a sweeping and sometimes a squealing.

For testing i changed the power tubes for two new JJ and two new Electro Harmonix. The EH in the external position and the JJ in the internal.
The noise is away.

On saturday i have a gig with my band and the damage of the tubes are warranty. it will take some time. Can i use the different tubes together in the 100 watt JMD?
The technical data from the different tubes are alike. Only for one gig.

Best regards
Michael from Germany

[surfnorthwest]

Sure you can, they do not have to be matched tubes. I would bias the new tubes though to get them as close as you can.

[guitarest]

really they dont have to be matched? When did they (Marshall) start that; I thought all tube amps had to have matched tubes in the power section. Not trying to be a arz here just a question. My old JCM800 2203 had to have a matched power tubes (or so I was told). Is the JMD using new voodoo that does not require matched EL34's?

[surfnorthwest]

http://www.marshallvintagemodern.com/vi ... f=2&t=7240

[guitarest]

Cool read there about tube amps, thanks