Pentodes again.

[Mark1406]

I have been doing a bit of spring cleaning on my 18 watt amp. It’s served me well for a long time but I’m looking at what I can improve.

I’ve seen a few signal pentode stage threads in this forum, but people who I have met who have an 18 watter with a pentode in the normal channel say the pentode has too much output and is sensitive to vibration.

I have thought that perhaps the pentode stage is best suited to the tremolo channel. With the extra output there could be more filtering to get rid of the thump from the oscillator. Thus you’d get the pentode fatness without the excessive output.

The Gibson Les Paul GA-40 tremolo circuit would go into an 18 watter if one were prepared to give up a triode in the normal channel of the amp.

I have even wondered if a pentode could be added in lieu of the triode in the tremolo circuit. The screen grid circuit would have to be added and the cathode resistor would have to be increased in value.

http://www.prowessamplifiers.com/schema ... Ga_40.html

My chief concern is that this might have already been done in which case there is no point in reinventing the wheel.

I would like to hear about your thoughts and observations on this matter.

Regards

Mark

https://www.18watt.com/viewtopic.php?t=17898&start=15

[KagliostroAmpwww]

Usually the reference tube when talking of a pentode in preamp Is ef86 but you can give a try to other tubes (with less gain) like 5879 (see some Gibson) or 6ak5 or 5654 (used by Telefunken in some tube mic)
Both this tubes are used in various configuration on preamp as V1 or V2

If you perform a Google search you can find examples

K