Duncan Tone Stack calculator & D-style tone stack

[tubenit]

In the Duncan Tone Stack Calculator, there is a program for Vox amps where the tone stack is off a cathode follower.

Can that tone stack calculator program be "adapted" for D-style tone stack configurations?  I realize it won't be completely accurate but if it could be reasonably accurate in how changing tone stack values impact the tone shaping then that would be useful to me.

IF so, I am presuming Zsvc would need to be different then 56k  and R5 would need to be different then 600k?

Can anyone help me with this, please?

The schematic on the right should be considered what I have in the amp.  The Duncan TSC image on the left is what I am wanting to match up.

With respect, Tubenit

[PRR]

> tone stack is off a cathode follower.

No. In that case Zsrc would be 1K-2K. 50K suggests plate loading. For Fender-type 100K-12AX7-1.5K stage, Zsrc is about 39K. The 56K default suggests Vox used 150K-200K plate load, but the result won't be much different.

Full 250K mid resistor makes little sense-- hardly any boost available. It makes sense as a 250K audio taper, because at "5" it will be 25K-50K allowing B and T to add-back a bunch, while at "10" the tone-stack is 90% defeated for instant Screaming Solo tone.

[tubenit]

PRR,

As always,  thank you for the response and information!  I do appreciate it. 

The tone stack looked like the one off the AC30 which I thought was off a cathode follower?  I may have misunderstood or presumed incorrectly?

I am understanding your response to mean the Duncan Tone Stack calculator is somewhat reasonable to use as sort of a guide to see how changing component values in a Dumblish inspired tone stack would react.  Looks like I can substitute Zsrc as 39k instead of the 56k.

with respect, Tubenit 

[jojokeo]

I will change Zsrc all the time to get relative comparative responses as I tweak stack values to suit what I’m looking for. It works very well and I do not care about “exactness” it’s the comparative results that matter to me. It’s the best way to compare apples to apples IMHO.


For amps I will many times change it to 33k for example, then hit sweep then take a snapshot. Then I will change color and value(s) and repeat up to three or four times. Any more and things get fuzzy and hard to make out. Also when done and come up with what I like or want to see at a later date you can save the file or use control + print screen and save to a bitmap file which then can be converted to jpeg, png, etc...


I’ve spent tons of hours on the program and wiring different things into my amps & pedals both. It’s an invaluable program and resource to me.

[jjasilli]

Richard Kuehnel has a free online cathode follower output impedance calculator:  https://www.ampbooks.com/mobile/amplifier-calculators/cathode-follower/


That's enough reason to buy his new book right there!