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Ez81 that rectify less volts than JJ EZ81

DrainBamage

Member
Messages
2,401
Looking for a ez 81 that will have less rectified volts than the JJ that I have now. In my 18 watt it bumps 300 ac to 350dc. I would like to brown out my amp a bit. Looking at other peoples volts charts they can get any where from 30 - 60 volts difference in their amps but did not include what rectifier they were using. Nos or current production
 

Blue Strat

Member
Messages
30,192
Wish I knew. IF the JJ meets the spec it puts out the same voltages, within 5 volts, as all the others. But we know how THAT goes. ;)
 

Blue Strat

Member
Messages
30,192
Did they all use the same power transformer? Same taps? Same AC wall voltage?

This! In addition, unless I'm looking in the wrong place, the variations don't seem to be huge. Just a different set of EL84s with hotter/cooler idle current could account for part of it.
 

EFK

Member
Messages
1,048
If you run a jumper on the rectifier socket between pins 3 and 9, you can try a dirt-cheap old 6BW4. You'll definitely drop rectified voltage. I find these to mimic the real world performance (in a miniature 9 pin) of a 5Y3 much more closely than a 6CA4/EZ81 does, so I use them in certain projects where I'm building the old Supro Super/Comet/Spectator circuit into a really compact little all-9 pin platform with no 5V winding i.e. 12AX7, 6CM6 and 6BW4. They drop around twice the voltage of a 6CA4, closer to a 5Y3, but on the downside they are rated for less current. Fine for the single ended projects with which I use them, but you may be pushing it with a dual EL84 amp. I would personally want a pair of diodes on the rectifier socket as some cheap protection in the event the rectifier gives up the ghost, but those are super easy to add also along with the 3-9 jumper.
 

EFK

Member
Messages
1,048
I think they fall between a 6CA4 and the 6BW4 I mention, at least in current capabilities, but they seem to be harder to find and pricier in the US. Another option to try, though. I don't think the OP is going to get the rectified voltage drop he's looking for simply by swapping around various 6CA4/EZ81…. Maybe a couple of 5W, 10V zeners strung off the PT center tap?
 

DrainBamage

Member
Messages
2,401
Did they all use the same power transformer? Same taps? Same AC wall voltage?
I don't know. I assume this is a old chart everyone was using when GDS reversed engineered and cloned the transformers right from the start of the 18 watt rave. But I don't think it even matters.. the chart shows ac volts in, pin 1/7, to the ez81 and pin 3, the dc out. The only difference between those voltages is what is sitting in that tube socket.
 




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