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Discussion in 'Shock Brother's DIY Amps' started by pfarrell, Feb 3, 2021.
Yeah! Thanks Rob. I have learned an absolute ton from your site. So, thank you.
Yea!!!!! No real listening impressions yet (sounds fantastic for a bare speaker on the floor)—but as an amp I can't imagine it being more quiet. Just hearing tube rush, some additional light noise when the guitar is plugged in—but I think that's fair—and there's a lot of variables there. Kinda of insane really considering the Champs i built—I'm thinking I need to experiment with taking the AC off the pot in the Champs—the 5E3 is so quiet—as I would expect(?) and want it to be...
I may (may) put feedback switch in place of standby...
So, are the phase dots actually wrong on the output transformer diagram? Outputs are swapped, so I started up with the inputs "correct" per schematic...and no noises—that means I was in the rare 10% correct zone? ;-) LOL.
Going to take some more readings but B+ voltages are: 386, 353, 323
What a great saying. I can vouch for it's accuracy!
I already did that. Andy Rooney seems to have said it.
I have a suspect 12AY7! It's NOS, and I don't have another... first power up last night took a while and I didn't immediately see the heater glow... thought something was wrong, verified a few voltages, then all suddenly came alive, post wiggle and prod...today, it's definitely intermittent. I cleaned the pins. Put it back, nothing... then flicked it and it slowly came alive. I'm trusting my soldering and a new socket more than the tube—but don't know if that is fair. Then I decided to pop in an 12AX7 and it fired right up after ever so slight delay. Hmmmm.... I don't know enough to know if these tubes are interchangeable in this design... I've read that they can be—and the 12AX7 is "warmer" with less gain. Then someplace else I read the opposite. To me the 12AY7 seems warmer—and quieter...but could be the tubes themselves...
EDIT: Whoops @robrob site says the opposite of some suspect places on the internets (good grief) 12AX7 for higher gain in 12AY7 position.
12AX7 has more gain. The 12aY7 usually has a warmer descriptor do to less gain.
I used the Classic Tone 40-18022 for a 5e3 with a NFB option.
Green to 6v6 with plate feed of the PI. V3
Yellow to 6V6 with cathode feed of the PI. V4
Speaker jack: Blue to tip and black to ground.
iirc the NFB location for a 5E3 involves another 180 degree of phase than the Deluxe Reverb. The OT dots do not line up the same on the different amp circuits.
Exactly what I did. Love this mod. Where did you put the switch? I'm leaning towards taking out the Standby switch and putting NFB in its place, carefully routing the wires, using coax per Rob's advice.
I used a push pull 1M pot for the NFB switch. I changed the standby switch to a mute. Used shielded wire for the mute.
Standby delete—NFB in it's place. Used the hole where the mini switch was to add back in the AUX jack! Yea!
Okay. This amp and MODs are incredible—I have super limited experience, electric guitar-wise—but this amp is freaking awesome. Some observations: The options with the NFB, tone control, jumpering the various jacks are just nuts. LOTS to explore here. It sounds different than the Champ! I have the same speaker in the Champ and what's on the floor in the image—plus a Greenback in the other Champ. Taste test in the house: My daughter and I preferred the Greenback—mom preferred the Weber Alnico in Champ. Cool! Need to get 5E3 in a cabinet to really evaluate this. But it's really neat for sure—maybe this is obvious to all you guys, these differences—new to me.
I never really understood with using shielded cable and guitar amps what the deal was with what most people are doing with the shield—I'd think it needs to be grounded on one side to be effective—my experience has always been when using the shield as an actual ground (connected both ends) in hi-fi amps and preamps, RCAs etc—here it's just for adding some noise reduction barriers (?) on single point connections. So you can see my solution—involving a hot knife I happen to have—single point ground of course. I tried un-grounded—and then my group-fast-ground solution—I feel that the amp got quieter. Might be subjective. This thing is quiet for sure. Bridge PU in the cheap strat has some buzz. But all the other positions are quiet—no other guitar to try (yet!).
Awesome. Tolex-in cabinet next. Front panel from FPE should be here Friday.
Nice build. You've made it neat and yet made it all your own with component choices and wiring touches.
Re OT phase dots: They *do* tell us what's in phase (as long as the guy at the factory uses the right wire color). We just have to figure out what's driving our power tubes (eg, the PI here) and whether there are any phase swaps in the chain. So despite the powerful 50/50/90 rule (which I learned here from @clintj some years back) the dots should work to prevent PFB in NFB amps. Oh, phase dots I also learned here, in this case from @elpico.
But sadly, we won't have phase dots to kick around much now that ClassicTone is gone; seems like most of the other major OT makers don't use 'em.
I was thinking about this NFB polarity thingy. Can't we just hook up an oscilloscope and determine the correct phase?
It always amazes me when someone says it's their first or second build and then does such a clean, stellar job.
Yeah! thanks, that's VERY kind—but to be fair to the world—and myself—I've been playing with the audiophile side this equation for a couple of years now—built half a dozen Nelson Pass amps and turntable decks and pre amps and speakers, hunting for my version of audio perfection, and blowing my own mind in the process over at diyaudio.com. I can't call myself a noob (in "life" always, but not 100% technically with audio). Second and third tube projects ever though—so that's way fun and challenging. AND recently started playing guitar (acoustic)...and am hooked on that for life—electric guitars are too awesome—I'm connecting dots—and my daughter is musically gifted, blah blah.
Two nice builds under your belt, looks like your hooked. Planning your next build yet?
Princeton Reverb AA1164!
Oops—actually did this just after Champs—but threw 5E3 into the mix at the last minute—glad I did though—it's a keeper and a good project stepping stone—PR is pretty complex. The plan with the Princeton is to build it as a head amp—plus 2x10 cabinet... This one I staked the board by hand, which was fun.
Very nice amp and the PR board looks good too.