Guitar Pedal Design EE Senior Project

[fischbro]

Hello everyone, this is my first time posting on this forum. I currently working on my senior electrical engineering design project. My partner and I are working on designing a guitar effects pedal. Essentially we are working on something like this Blackbird Vacuum Tube Preamp | effectrode, where the pedal has a vacuum tube for pre-amp gain, and then it goes it to several bands of analog EQ filtering. Right now we are just trying to write out the basic specifications for our proposal.

What is the maximum allowable voltage signal for the input of a guitar amplifier? We are trying to figure out what the maximum gain and output voltage for a project can be and we can't quite seem to figure it out. Any help or tips you all can give us would be greatly appreciated.

 

[JMFahey]

Design your preamp for 100 mV RMS signals, and 1M input impedance.
It should stand 1V RMS without clipping.
Will be fine for 95% guitars out there.

For a classic reference, study the input jacks and first triode in a Fender AB763 schematic.

 

[thoglette]

For a classic reference, study the input jacks and first triode in a Fender AB763 schematic.

If you're not referencing existing designs (and existing papers/books on the subject) your supervisor should be marking you down. And hard - a literature review is Step 1 in any project.

If you have some leeway to get off the beaten track, remote cutoff pentodes allow vibrato and compression effects (at the front end), plus asymmetric distortion if used at larger voltages (at the higher voltage end).

Power management is the biggest challenge in pedals - you can't use mains directly and the classic 9V cell won't last long on heater duties.

 

[kevinkr]

This will get much more attention over in the Instruments & Amps forum where I will now move it.

Interesting project.. Do your research as suggested for existing practice.

 

[jazbo8]

It seems like way too easy for a senior EE project - in the analog domain with vacuum tubes! Most of the interesting projects/researches on guitar amplifier distortion are done in the digital domain now...

 

[JMFahey]

You are right, of course, but today "everybody designs digital" so I bet his 50's technology tube based analog project will be quite a sensation .

 

[jazbo8]

So yesterday's high school shop project = today's senior EE project... man we are really going backwards... who's gonna design our new toys?

 

[thoglette]

. man we are really going backwards...

At least they're letting them play with soldering irons!

I'm hoping that the supervisor is hoping that they'll learn a lot about power, space and heat budgets.... Oh, and noise coupling (I hope there's a SMPS to convert from 9V to B+)