Foreplay 3 extended kit Extremely loud popping

[Rob C]

Hey what's up I am experiencing a very loud speaker popping when I turn on the 4 play 3 w extended kit. and when I turn it off.
 I have the bent audio volume control in it.
 I can also hear when I tap on the left tube through the speaker.

[Paul Birkeland]

I would suggest turning your amp on last and off first.  Regarding tapping the tube, you can move that tube to the center socket and the microphonic issues won't be so noticeable there.

[Rob C]

Thanks for the tube swap tip. It seems that the tube is bad I see arching inside.  Is there a certain type I should replace these with? Brand wise. Is it a dual hybrid or something? Thanks.

[Rob C]

Should all three 12au7's be gain matched? Or 2 matched and one not?

[Paul Birkeland]

The outer pair of 12AU7s should be the same type, but the center can be different.  You do not need to pay for electrical matching.

[Rob C]

Thanks! I found 3 matched new EH for 45 .

[Rob C]

I'm assuming the Paramount amps are fixed bias?

[Paul Birkeland]

They are cathode biased, with the caveat that the later revision has some adjustment for proper biasing in the 2A3 version of the amp.

[Rob C]

Cool to know. 300b version here. Ty

[Rob C]

The tubes in my foreplay are 12au7a
Can I use the 12au7s I ordered?

[Paul Birkeland]

For the Foreplay circuit, there is no difference in functionality between a 12AU7 and a 12AU7A.

[Rob C]

Great thanks!