Welcome to Solid State Guitar Amp Forum | DIY Guitar Amplifiers. Please login or sign up.

March 29, 2024, 08:11:22 AM

Login with username, password and session length

Recent Posts

 

Want SS triode VA curves?

Started by KMG, August 05, 2011, 08:11:07 AM

Previous topic - Next topic

KMG

I think all remember how switched triode/pentode modes in tube PA.
Yes, by connecting second grid to plate.
So we need to find SS tetrode. It is RF dual gate mosfets
http://www.nxp.com/documents/data_sheet/BF998.pdf
So, by connecting Gate2 to Drain (through resistor for safe) we will get SS triode.
Also we must add grid current emulation, it can be done by "Kempf" method.
There are simulation examples
Single common cathode stage

common cathode + cathode follower + tone stack

Today I tested real single stage, it matches exactly with simulation model from NXP

phatt

Hi KMG,
          This stuff I get lost with but the shapes do show that distinct triode plot.
Here's a little challenge If I may Ask? 8|

http://www.ssguitar.com/index.php?topic=2226.0

The PhAbb FPV floor schematic is producing some stunning results.
The BIG Q?
Could one of your trick fet triode circuits replace the AX7 that is used in my circuit?

There are 2 audio clips on that page,, the first is passing though a soaked Valve Amp but the second clip
is the FPV unit passing through my all SS DDC circuit. (Dynamic Distortion Controller)
DDC is just a hot rodded nobels cabsim/OD circuit but does a great job of replicating the crunch from
a Valve power stage.

So if I can replace the Triode in the FPV unit with something that replicates a triode,,,,,,,,,
Then Hey It would be All SS  0:)

Then we can all throw another party.
Thanks,,Phil.

joecool85

Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

KMG

QuoteCould one of your trick fet triode circuits replace the AX7 that is used in my circuit?
Yes, but HV versions requires negative bias voltage, or biasing grid potential (VR100, R103, R107 in your schematic).
Look there for new info.
http://www.ssguitar.com/index.php?topic=2039.msg15437#msg15437

phatt

Quote from: KMG on August 10, 2011, 03:26:49 PM
QuoteCould one of your trick fet triode circuits replace the AX7 that is used in my circuit?
Yes, but HV versions requires negative bias voltage, or biasing grid potential (VR100, R103, R107 in your schematic).
Look there for new info.
http://www.ssguitar.com/index.php?topic=2039.msg15437#msg15437

Thanks for the input,
Well that might be a lot simpler than making your whole Amp. ;)

It will depend largely on how easy it is to find parts and then the time to test and build,, but I will certainly look into it all in more detail when time permits.

Can I take it that the small -bias Voltage is a low current drain and could be easily created much like a bias voltage in Valve circuits.

Phil.

phatt

Quote from: joecool85 on August 08, 2011, 02:05:42 PM
Quote from: phatt on August 06, 2011, 09:56:15 AM
Then Hey It would be All SS  0:)

I like your thinking!

I try,,, oh how I try :loco

The 2 clips on My FPV post will give some idea as the first is running through the Valve power Amp.

The second one is relying on the triode in the FPV driving the all SS DDC and it's very close to the same sound.
So rather than reinvent the Valve power stage (which is a little too optimistic for my limited knowledge :-[)
I just wish to try recreating the triode in the FPV unit.
Don't expect results tomorrow as this will take a fair amount of time to breadboard,,, If I can find the parts.
Phil.