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previous: Bob Arbogast I'm pondering a 2x12 5E3 with a GZ3... -- 11/29/2003 1:37 AM View Thread

Re: Anyone ever build a 5E3 Plus?

11/29/2003 5:02 AM
bnwittRe: Anyone ever build a 5E3 Plus?
It sounds like you want to build a higher power tweed deluxe and I would make the following suggestion. Convert the standard 5E3 circuit to 6L6's and use the two speakers you desire for more spl's. Bruce is the guy for the 6L6 deluxe amp setup. He has helped me tremendously on a coversion I am doing to a standard 6V6 deluxe. He suggests a 5AR4 or a 5V4GT rectifier to increase the plate voltage and therefore the output power as well as the following changes to the standard 5E3 circuit.  
1.)The dropping resistor between the first filter caps needs to be replaced from 5k1-2watt to 2k7-2watt. You can go as low as 1k-2watt to get the preamp voltages up to where you get more clean sound without distortion.  
2.)The two power tube's cathode biasing resistor, 270-5watt, needs to be changed to a 270-10watt.  
3.)Install a 1k-2watt screen resistor on each power tube socket and rewire them like a 30-50watt black face Fender amp. To clarify this: Look at a Super Reverb AB763 schematic/layout. Use 470-1w to 1k5-2w values, soldered on the power tube sockets (lug 6 to 4) for the screen resistors with the screen supply B+ fed at lug 6 and. The 1k5 ohm grid stopper is moved and soldered in from lug 1 to 5. Grid (signal lead) wire is now attached to lug 1. Remove and lower the 5k ohm resistor, (voltage dropping node between the first two filter caps) to 2k2 or 2k7 ohms. This 2k2-2k7 ohm resistor would be in the same location as the choke in the Super reverb.  
4.)Using a little bigger Output Transformer(25-30watt blues Jr. trannie) will get you an additional 5 to 7 watts. Bruce has them.  
5.)Using .022 coupling caps to the volume controls  
(in place of the stock .1uf caps) and 4.7uf cathode bypass caps on the preamp tubes will net you a cleaner tone too, but using anything less than .047 caps to the power tubes seems to wreck the tweed tone too much.  
By the way, the Blues Jr. Output Transformer is rated about 25-30 watts and has a 4 and 8 ohm secondary so it can still be used with 6V6s and 6L6's. If you want the 6V6s, you'd connect the 8 ohm speaker to the 4 ohm wire to get the primary impeadance back up where 6V6s run. With the 6L6's you use the 8 ohm secondary wire. This can be setup with a SPDT toggle for switching between tubes.  
With this configuration you could have:  
a.) The 5E3 with 6V6's on the 8 ohm speaker for 12-15 watts on the 4 ohm secondary setting.  
b.) The 5E3 with the 6L6's on the 8 ohm speaker for around 30 watts on the 8 ohm secondary setting.  
c.)The 5E3 with 6L6's on the 8 ohm speaker and a 8 ohm extension speaker for a total load of 4 ohms at around 30 watts on the 4 ohm secondary setting.  
All of this knowledge is from Bruce so thanks go to him. I hope this helps you Bob. Bruce correct me if I got anything wrong.

Bruce J "By the way, the Blues Jr. Output T... -- 11/29/2003 5:15 AM