Cathode Bias parameter... ?

D

dkijc

Experienced
Hi y'all...

I've been trying to just fiddle with advance parameters and it looks like the document says i should have a cathode bias param but I don't see it? I thought it was because it was a Matchless it doesn't have the option since it's already cathode biased amp... But I found out other amps don't have it either..

Am I missing something or is that param gone?? Or is it just an XL feature?

I was on Q3 and now I'm on Q4. (looks like Cathode Squish was changed to Cathode Bias on Q2.0)

Thanks, y'all and have a great weekend! God bless :)
 
thanks for the reply pitta!

Would you mind me asking where you found that info? I wasn't sure if Resistance and the Bias was the same parameter :)

Cheers, again!
 
dkijc said:
thanks for the reply pitta!

Would you mind me asking where you found that info? I wasn't sure if Resistance and the Bias was the same parameter :)

Cheers, again!
Click to expand...
Well on a real amp you set the cathode bias with a resistor so it makes sense.
 
Is it same as the 'PA Cathode Resistence' in the Advance page in the amp block? I don't use AxeEdit.... lol.

But if that's the case it seemed like it was a different parameter to Cathode Bias. According to the Wiki.
 
Release notes for Quantum 2.0 (from the wiki http://wiki.fractalaudio.com/axefx2/index.php?title=Axe-Fx_II_firmware_release_notes):
Improved cathode bias algorithm for “Class-A” amp models (i.e. Class-A 30W, AC- 20 Dlx, etc). In conjunction with this the Cathode Squish parameter has been repurposed as “Cathode Bias” and controls the value of a virtual cathode resistor. A value of 50% is “optimum” and biases the power tubes at true Class A operation (neglecting any bias shifting due to supply sag, screen droop, etc.). Values greater than 50% increase the resistance and therefore bias the power tubes “colder”. Values less than 50% bias the tubes beyond Class A. In a real amp this would probably destroy the tubes but that limitation does not exist in our virtual amp. Most real amps of this type actually operate far below Class A and the default values for the models will reflect this. Note that the Power Tube Bias value should be set to 1.00 for these amp types (since that parameter controls the grid voltage and the grid voltage is at a maximum in these types of amps). Existing presets will be automatically updated with new default Cathode Bias and Power Tube Bias values.
 
Really appreciate the response but that still doesn't explain to me where the "Cathode Bias" parameter is in the amp block.. (on the axefx itself)

pitta said:
n conjunction with this the Cathode Squish parameter has been repurposed as “Cathode Bias”
Click to expand...

This is confusing as well. It sounds like Cathode Squish have been changed to Cathode Bias.. and no where does it say PA Cathode Resistance is same as Cathode Bias.. :( :(

Thank you!
 

"Cathode Bias" is now "PA Cathode Res"... look at the AC30TB, under the ADV tab in the AMP BLOCK and you will see it set at 70%.
 
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