Tube Preamp - NE555

MisterBill2

Joined Jan 23, 2018
17,887
The whole reason for the tubes to be used is the desire for " their special kind of distortion" that few can describe, but know it when they hear it. All of this after the considerable effort made to produce tube type amplifiers without distortion. Sort of like running in a circle, backward. One side wants totally pure sound while the other wants that very special "coloration."
The reality is that for some pieces of music, 50% harmonic distortion is a requirement, while for other types of music a live performance is not adequately low enough total distortion.
So once again, the music is in the ear of the listener, as beauty is in the eye of the beholder.

And after seeing the schematic with the 555 IC producing the B+, I am impressed. I have one of those amplifiers with that single tube section and I wondered how they powered it. Now I see it was cheap and easy. (The amp was bequeathed to me because it was simply way to heavy to keep dragging to gigs. )
I would love to sell it, there is a limit as to how many guitar amps a non-player really needs. (contact me via pm)
 

Ian0

Joined Aug 7, 2020
9,535
For electric guitars, one has to consider both the amplifier and speaker to be part of the instrument.
Any guitarist would want the sound after that point to be recorded and reproduced without any further distortion. Once he has achieve his perfect "tone" he would not welcome a sound engineer adding has own distortion! So we get the rather weird situation of recordings done by placing a microphone in front of a guitar combo.
 

Thread Starter

rpschultz

Joined Nov 23, 2022
416
This circuit (clean channel of Matchless DC30) is only using one 1/2 of the tube. Could I utilize the other 1/2? What would adding a cathode follower do? How would that work? Maybe with an additional knob for gain control?

IMG_5177.jpeg
 

Ian0

Joined Aug 7, 2020
9,535
Look for a small-signal triode-pentode, and use the triode as a cathode follower.
You can get triode-pentodes in Noval (9-pin) bases, as the pentode will have G3 connected to the same pin as its cathode.
European part numbers start ECF.
 

MisterBill2

Joined Jan 23, 2018
17,887
Look for a small-signal triode-pentode, and use the triode as a cathode follower.
You can get triode-pentodes in Noval (9-pin) bases, as the pentode will have G3 connected to the same pin as its cathode.
European part numbers start ECF.
Possibly a 6U8 type could be used. The triode can be grid driven from the present volume control with a capacitor in series. A separate grid resistor will then be required., grid to cathode, not to common. The cathode resistor will set the output impedance. Probably a plate resistor will also be required, not certain about that. Consult the "Radiotron" book for a cathode follower guide.
 

sparky 1

Joined Nov 3, 2018
755
Don Felder talks a little bit about where an artist begins to distinguish sound effects.
Solid State based on 6L6 tube.
 
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