sag resistor...glassman?

[Chickenwings]

If i added a 200ohm 50watt wire wound resistor in the red highlighted part on this pic, will it work to replicate some of the sag caused by tube rectification?
http://au.element14.com/vishay-dale/rh050200r0fe02/resistor-wirewound-200-ohm-50w/dp/1369551

I chose 50w to be on the safe side, but can i get away with a different wattage value?
If i have this right, what else would i need to do to keep the amp working correctly?
Do i need to adjust the bias resistors etc?
I chose 50w to be on the safe side, but can i get away with a different wattage value?

 

[zzmoore]

Re: sag resistor...glassman?

Yeah.
As you know...tube diodes are non-linear.
I THINK a GZ34 is about 100 Ohms when pushed...and higher with less current demand.
demand.
I would think YOU are right in the ballpark with 100-200 Ohms.
Maybe get something in the 150 range so you can compare.?
good luck

 

[glassman]

Re: sag resistor...glassman?

That will give you some voltage sag...but it will be directly correlated to the power tube current which won't give you the dynamic feel of a tube rectifier. It might be cool though.

For a little more impact on dynamics, I'd remove the two center diodes (one on either side of the two groups of three) on the B+ and replace them with 50 to 100 10 watt resistors. They won't even get warm at a 10 watt rating. This puts the voltage sag before the filtering where it can have an impact on depletion/recharge timing, giving more of a "tube-like" feel. You could actually do a mixture of both if you wanted to but working before the filters is going to give you more bang for your buck and a more realistic feel.

You shouldn't have to mess with the bias at all; your quiescent current will produce very little voltage drop...the drop happens when the current starts to flow.

You'd probably be safe with 5 watt resistors in any position. If you're concerned about it, you can always bypass the resistor with a zener diode at whatever voltage you want to enforce a maximum "sag" at. You can also use the zener trick to "tune" the response to your typical level setting.

Hope this helps.

 

[Chickenwings]

Re: sag resistor...glassman?

yes thats great stuff. thank you for sharing your knowledge bro.