Another New 5F1 Build, First Guitar Amp Build(s) Ever

Apologies for another new post about this fine amp. HUGE thanks to Rob Robinette and his website which is a goldmine—I followed his layout/schematic. A friend over at DIYaudio.com clearly pointed me in the right direction. Anyway—first guitar amp build—can't really call myself a total noob—I've been building all manner of audio system gear to support a vinyl centric playback system based on all the fine stuff over at DIYaudio.com and specifically Pass designs—that also serves up the family movies and hi-res digital audio... So I know my way around this stuff at least a tiny bit.

Everything here in pics is from scratch—except I did purchase a blank Hammond box to use as a chassis, and a premade 5F1 turret board—for the next two builds (AA1164 Princeton Reverb as head amp with 2x10 speaker cabinet and 5E3 combo) I'll be making chassis boxes from sheet materials, and the reverb board is done, made my own turret board for that.

5F1 circuit values were close to stock I believe (except the 10W 470R)—I went with the large OT, and picked up a couple of different 12" speakers to try.

This was all a hugely awesome learning experience. And the amp sounds fantastic—but I have no other amps or guitars (my 10 yr olds Squire Strat) to compare, until I build another amp and procure more guitars! That said—I did plug it into a vintage blackface speaker at our guitar teachers place and it totally held it's own against his OG Vibrolux. Like two different beautiful flavors... There are SO many factors here however as everyone probably knows. Interestingly I have some buzz, shows up around 3-4 on the dial that grows with volume, and leaves a couple of notches before max. This wasn't present at the teachers studio with the vintage speaker (?). I think the guitar is a huge factor, still looking in to it all. If I were to build the 5F1 again I would certainly separate the power switch from signal. The grounding schema seems solid—poking around with a chopstick didn't reveal anything other than why route the signal wire from volume under the amp board?—and absolutely different preamp tubes are affecting the strength of the buzz. Also the Celestion greenback is "buzzier" than the Weber alnico—this is all without an input signal.

I built 2 of these at the same time—one is a gift. I tried a different grounding schema on one with isolated jacks etc, but reverted it back to Rob's plan. I had to refresh a few skills—particularly covering wood with fabric. I've never worked with Tolex—never covered an amp before, and I really think the secret is the right glue (and careful cuts)...which took some research (I ended up doing the corners 2 ways after really looking closely at some tweed cabinets online). I could have made the boxes 1/2" thinner if I'd made my own amp chassis. I opted not to do the canted fronts. Adds complexity—doesn't stack nicely. Light heat gun on the grill fabrics is a good thing, you can kinda see how one is crisper than the other. First post—so hopefully I get the image attachments right...Enjoy.

 

Thanks guys! The buzz could be entirely normal, or totally about the guitar? IDK. I’ve been wired to expect, and hunt for, as much silence as possible in audio amp land, I understand that guitar amps are different beasts. I already swapped out the cheap jack in the guitar for a good one, it was cutting in and out, and there was a marked improvement. Things get quieter when I touch the strings, so def some grounding stuff going on. Whatever you find @pugnax would be appreciated!
I do have a complete EMG replacement pick guard set for it (EMG is my families company) but wanted to give it all some time and not make a lot of moves at once in order to learn whatever there is to learn.

 

Thanks! Doh instinct! Might do it.... Hmmmm....5E3 first I think. It's really not that strong—i'm judging it sitting right in front of the amp from about 5', can't hear it with amp around 4 and if I max out the vol on the Strat—man—sounds awesome and plenty loud. If off axis from the amp...it's "quiet" at normal volumes. Was also considering—and have—an L-pad to put in on the speaker line—max the amp—control vol at speaker—might be cool. Breakup at low volumes.

I just scanned that thread—he's describing exactly what I hear and how. Tempting to relocate the fuse and put in a power switch. Only downside is another order from the vendors! Lol.

@jmp81sc Thanks man! Just like at the DIYaudio.com forum, nuts levels of talent abound here—I'm inspired. The tolex is stock from Amplifiedparts.com, btw. But yeah, something different.

 

Updating this... I hot wired the amp—pulling the wires off the pot and wire-nutting them temporarily. Buzz GONE!

Now, since this I've built a RobRob 5E3 and it's a ghost by comparison. SE vs P/P topology? Larger caps? The Champ has a very low level of quite acceptable hum. I redressed the wires out of the transfo and that helped a lot and put a shielded lead in for volume—also helped a bit more—I'm leaving the OG pot swtich—it's just disabled. Since I made 2 Champs at once—this has been fun to see what's what—I made the dressing in the other amp tighter by comparison—and it has been quieter out of the gate—still has the buzz though (until I make the pwr switch mod there too). Also I think the Greenback is louder by nature than the Weber Alnico? 12" speaks.

The other thing I was considering, just to try—replace the first cap with a 33uf I have on hand... I understand it might change the character of the amp—but I can't say that means anything to me yet. Plus the 5E3 just feels glorious to me—and it's not even in a box yet.