6SJ7 tube preamp

157

01:21:08

Hi.  I'm hoping someone can help me.  I'm trying to understand biasing of a 6SJ7 tube as a preamp with the cathode tied to ground.  I recently acquired a Webster Chicago wire recorder and would like to learn more.  Thanks

published 3 years ago

ViolationMad

3 years ago

To simulate triodes in EC, you'll have to go the extra mile and use a proper equivalent circuit. This might help you in creating a model of your tube: http://everycircuit.com/circuit/4506102563340288. Anything else will just follow basic tube amplifier configuration, if I understand you correct.

ViolationMad

3 years ago

There is some decent literature about Class A/B/AB Tube amplifiers online. If you are familiar with BJT amplifiers, you should recognize those topologies already.

gorgut00

3 years ago

Violationmad I'm really not trying to stimulate it. I already have It functioning quite well in the real world with the wire recorder I already recapped and replaced all the resistors.

gorgut00

3 years ago

I haven't found much literate about this particular configuration, a pentode with the cathode tied directly to ground.

ViolationMad

3 years ago

With the little information you are giving, it's hard to give you an elaborate answer. My point being, simulation can easily help you to understand new concepts, since you can poke around in every node and see what happens there. This also gives you the best value to really understand what's going on.

ViolationMad

3 years ago

Anyway, a quick search on Google about your specific pentode in a preamp might give you the answer you were looking for: https://www.ampbooks.com/mobile/classic-circuits/gibson-ga-5/

gorgut00

3 years ago

Awesome. Ty. That is what I was looking for

gorgut00

3 years ago

I spent a lot of time on google searching "6sj7 preamp", or "pentode preamp cathode to ground", and didn't find anything like that. Thanks again

gorgut00

3 years ago

Alright, better late then never. I was simply not understanding fixed bias vs cathode bias. In the case of the Webster Chicago model 80 wire recorder the grid is tied to ground via a 4.7 Meg resistor. As electrons hit the grid a negative voltage is produced in reference to ground. This negative voltage along with the plate voltage can be applied to the datasheet and the load lines and bias can be calculated

gorgut00

3 years ago

I really appreciate the response. You helped me reach my answers and a greater understanding

ViolationMad

3 years ago

I'm glad you got there. This way of thinking will help you to approach most electronics issues and understand them in the best way possible. Keep up the learning^^.

add comment in editor

EveryCircuit is an easy to use, highly interactive circuit simulator and schematic capture tool. Real-time circuit simulation, interactivity, and dynamic visualization make it a must have application for professionals and academia. EveryCircuit user community has collaboratively created the largest searchable library of circuit designs. EveryCircuit app runs online in popular browsers and on mobile phones and tablets, enabling you to capture design ideas and learn electronics on the go.