RE: My first attempt at using Tube Cadd

johnsciolino · 4th October 2011, 02:03 AM

OK, please be easy on me since this is my first attempt at using Tube Cad.
I plugged in some tubes sitting in my stash to experiment with various gains. It appears (and correct me if Im wrong) that I should have plenty of headroom since the first gain stage is 7.1 (about 17db) and second is about 13. Unfortunately, Tube Cadd doesnt calculate the whole circuit. Now wouldnt that be great! I thought about direct couple from first to second but was sure what the resistance would be at the grid of second tube. For now, lets not worry about the quality of power supply, I can do that part easily. But as an FYI, the 26 and the 76 would be driven DC, and the JJ would be AC heated. I'm calculating about 3 watts with 2v in.
I'm starting out with this scenario since its probably the easiest to understand, from there I'll move to the next level.

VictoriaGuy · 4th October 2011, 05:25 AM

I can't offer advice, but I'll be watching, since my first (recent) experiences with TubeCAD, SEAmpCAD, and the TubeManual were all negative.
Perhaps you'll encourage me to have another go!
EDIT-I don't know if its easily done, but larger images of your schematic would be a help, I think.

dsavitsk · 4th October 2011, 07:44 AM

Maybe it's just how the program works, but it looks like you don't have the input tube's grid referenced to anything, and instead you have the "ground" input connected to ground through a 22K resistor.

4th October 2011, 02:03 AM	#1
johnsciolino diyAudio Member Join Date: Aug 2004 Location: florida	RE: My first attempt at using Tube Cadd OK, please be easy on me since this is my first attempt at using Tube Cad. I plugged in some tubes sitting in my stash to experiment with various gains. It appears (and correct me if Im wrong) that I should have plenty of headroom since the first gain stage is 7.1 (about 17db) and second is about 13. Unfortunately, Tube Cadd doesnt calculate the whole circuit. Now wouldnt that be great! I thought about direct couple from first to second but was sure what the resistance would be at the grid of second tube. For now, lets not worry about the quality of power supply, I can do that part easily. But as an FYI, the 26 and the 76 would be driven DC, and the JJ would be AC heated. I'm calculating about 3 watts with 2v in. I'm starting out with this scenario since its probably the easiest to understand, from there I'll move to the next level.

4th October 2011, 07:44 AM	#3
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	Maybe it's just how the program works, but it looks like you don't have the input tube's grid referenced to anything, and instead you have the "ground" input connected to ground through a 22K resistor. __________________ http://www.ecpaudio.com

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4th October 2011, 05:25 AM	#2
VictoriaGuy diyAudio Member Join Date: Dec 2008 Location: Victoria, BC	I can't offer advice, but I'll be watching, since my first (recent) experiences with TubeCAD, SEAmpCAD, and the TubeManual were all negative. Perhaps you'll encourage me to have another go! EDIT-I don't know if its easily done, but larger images of your schematic would be a help, I think.

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