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choke instead of resistor in power supply


 
5/6/2002 1:13 PM
scott c choke instead of resistor in power supply
has anyone tried this?
 
5/8/2002 2:45 AM
frankenstein

Ya. I have a deluxe running with choke rather than 5k1 screen resistor. I do have 450 ohm resistors in the screen lines and have been advised to move these up to 1K or 1K5. Probably a good idea as the screens don't like to run at such high voltage as the plates. Also..the preamp tubes are running a bit hot as they also don't have benefit of the dropping resistor. I will probably increase the 22K preamp supply resistor as well.  
But...so far this amp has run many hours without complaint. The high screen voltage at idle shows up as high bias...but the voltage drops when notes are played...  
I'm running the 6V6EH tubes...they are VERY robust. Don't try this with NOS 6V6GTs.  
I've also just finished a standard resistor input power supply Deluxe and am only waiting for a cabinet...at which point I'll A/B/A the two units and give a full report.  
/ frankenstein
 
6/6/2002 5:37 PM
frankenstein

Scott: Finally got the cabinet for the second 5E3.  
Comparing the sound of the stock circuit to the one that has a choke in place of the 5k rail resistor ( 470 ohm 2 watt resistors in the screen lines as the screen supply is so close in voltage to the plate lines) shows an interesting difference in sound.  
The stock circuit exhibits more compression (not surprising). This gives tighter chords and a more controlled sound... probably better for recording purposes where a lot of chording is used.  
For a lead solo, however, the more WILD sound of the choked version is probably preferable. I built the choked version for a VERY able lead player and he LOVES the way it sounds. When he's got the volume set where he wants it..the chords are a bit rough ... which requires a lighter touch than would be needed with the resistor input power supply.  
The difference is subtle... but effective in the right hands. The lead solo work on the choke version is capable of near 'melt down' sounding tone... very nice for that purpose.  
The preamp tubes are running a little hot in the choke version and for that reason I will substiture a 30k 1 watt resistor for the 22k preamp rail resistor to help tame them down. Also, I'm gonna replace the screen line resistors with 1K5 2 watt resistors... in an effort to prolong final tube life. The EH 6V6GTs are VERY stout and have stood up to 300 + volts on the screens... which is amazing. Who knows how long they would last like that ?  
Will report more after the resistor changes.  
My own 5E3 is resistor input power supply. I think the overall sound is better...more 'together' for my style of playing - rhythm/finger picking/occasional lead fills. Summing up: For a WILD solo machine..the choke substitution without preamp voltage compensation is dramatic but not fatally harsh to the 'chording mode'.  
/ frankenstein
 
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