EL84/6V6 switch

[jeff]

SE amp. 6V6 and EL84 sockets parallel excpet for cathode. Switch grounds one or the other's cathode resistor.

Is it OK to flip this switch while the amp is running?

[sluckey]

Probably OK, but it might be dangerous if you are playing a guitar while switching.

[TIMBO]

Hi Jeff,This is how it did it and had no problems switching between tubes while amp was on but can't say what would happen if switch while playing.I would guess that a break in the signal when the SW. flicked would give a snap/pop but a SW. that has a make before break might reduce this and could work. 

[jeff]

Cool, thanks guys.

[jeff]

Got it going. Sounds good. Thanks.
 EL84 seems louder than 6V6.
Not as much as a difference in sound between the two as I expected, maybe I'll notice it more when fully cranked(during daytime). I suspect it's because the bias voltage is lower on the EL84 than on the 6V6 that the EL84 will have more of a power tube to preamp distortion than the 6V6.

 Cool to see the which is the "on" tube by the blue glow.

Thanks for the help
     Jeff

[HotBluePlates]

... EL84 seems louder than 6V6. ... I suspect it's because the bias voltage is lower on the EL84 than on the 6V6 ...

The reason the EL84 seems louder at the same "volume control" setting is that the EL84 has a smaller bias voltage. Really, because the EL84 has a higher Gm, which results in a smaller bias voltage for the same idle power.

That means that while the 6V6 and EL84 create the same total output power, with similar loading, the EL84 requires less input signal to reach that full power. The 6V6 seems less powerful, but it really only has a smaller Gm, requires somewhat more bias voltage, and therefore more input sginal to reach the same power output.

The same general effect applies to EL34 vs 6L6.

[Jaakers]

Can somebody still open the attachment from Timbo?
* PLEXI GAIN - 20 power amp V2.sch

I was unable to do so but I would like to see the schematic on how to do this.

If someone being able to open this, can he please make a jpg from this and send it to me?

[DummyLoad]

Can somebody still open the attachment from Timbo?
* PLEXI GAIN - 20 power amp V2.sch

I was unable to do so but I would like to see the schematic on how to do this.

If someone being able to open this, can he please make a jpg from this and send it to me?

will a PDF do?


attached.


--pete

[TIMBO]

Hey mate, this is the free program to use.
https://www.expresspcb.com/expresssch/

[Jaakers]

thanks a lot both for the input given!

[jjasilli]

Hotblue's Reply implies that you can keep the amp as is, and use the EL84's for an automatic boost. Or, drop signal voltage to the EL84's to equal the output volume of  the 6V6's.  The latter might be done with a series resistors, certainly with a voltage dividers.