new sim schematic

[Gus]

Simmed this after reading this thread
http://www.diystompboxes.com/smfforum/index.php?topic=92824.0

Replaced the JFET circuit fragment with a bootstrapped NPN fragment I drew up and changed two tone section values.

http://www.aronnelson.com/gallery/main.php/v/PenPens-stuff/Bassman_Fetzer.png.html

Changed 50k to 100k potentiometer and a .1uf to a .047uf.  Adjusted gain to about x14.4.  A number of transistors should work fine I would try something like a 2N5088, 2N5089, MPSA18 first.  I have not built it yet.


C1 .68uf


C1 10uf


The high end peak is from the input sim (left of R17)
Note what changing C1 (bootstrap cap)does

.68uf think low end closed box peak.

R12 and R11 are a 100K log volume control

R10 and R11 are a 100k lin tone control

Have Fun

[Gus]

Look at the C2, R5, R1, R2, R3, R4, R6, R16, C1, C7  and Q1 section.    What I am sharing is a high input resistance NPN transistor gain stage that can be used instead of a JFET stage.   I adjusted C1 to .68uf for more a low end bump note the change with .68uf to 10uf in the graphs.  I even have the gain controlled to about x14.4.  The tone pot is being simmed at different places in the rotation for the different curves.  You could adjust the gain up by swapping R2 and R16 about x26

IMO a well designed bootstrapped BJT circuit is more repeatable without transistor selection than simple JFET circuits.

You can often drop in different transistors Si and even Ge and the bias should be in a workable range with out trimming if you need to trim you can adjust one resistor in the bias section.  

I have posted other circuits at this forum with sims and do not seem to get much of a response.  

If R.G. or Mark  posted  something like this would there be more response?

[John Lyons]

Looks very interesting Gus.
Being able to use a BJT is nice!

[Brymus]

Hey Gus I have been following all your sims and saving them.
I just dont have the knowledge level to add anything useful to the disscusion.
BUT I do appreciate what your doing,especially the graphs and component subs you list for modding.
So dont stop.

[harmonic]

Hey Gus I have been following all your sims and saving them.
I just dont have the knowledge level to add anything useful to the disscusion.
BUT I do appreciate what your doing,especially the graphs and component subs you list for modding.
So dont stop.

+1 — exactly the same as my situation and response!

[WGTP]

Yes Gus, appreciate all your posts, but your operating several levels above me.  I'm watching and learning. 

[joegagan]

gus, all of your sims are too tempting, seems like if i dive in  i am gonna be swamped with intrigue , am really busy trying to get inventory built for the pedal hut ( plus a busy summer for const in my dayjob). can't wait to get to these and the wah stuff we talked about.

[Gus]

I have been posting the sims so people that do not have decades of building and measuring and fixing things might start using sims as a way to understand what is going on with circuits.

I don't post the .asc files but I do post the screen shots with notes.  I think you learn more by doing.

FWIW I finished building the NPN BOOST ver. 2 it sounds interesting.  Ver2 was the result of using LT spice and changing values and looking at the interactions on the graphs.  

An interesting thing is making a model of a guitar and cable and sweeping a parameter and/or changing a value and seeing on the graph what is going on.

There is a simulation section at this forum

 

[rnfr]

looks very cool, Gus.  I'll be giving it a try. 

[Gus]

I see an error on the schematic

should be "Try C1 as .33uf, .47uf, 1uf, 10uf"

I don't know if this is a good sounding circuit. I have not built it yet.

Interesting link I found looking for guitar pickup measurements. 
http://terrydownsmusic.com/technotes/guitarcables/guitarcables.htm