sds1
Friend of Leo's
So, put it on the ground bus or attach direct to chassis with earth?
5F6A - Build
- Thread starter pfarrell
- Start date
I'm hearing earth, which was my instinct.
Most if not all the toroids I've used in my audio amp builds have shields. Most are from Antek—in the EU they get access to Toroidy who make really nice stuff. I've built amps with and without steel can shields as well. Steel can is worth the effort—definitely quieter.
Most if not all the toroids I've used in my audio amp builds have shields. Most are from Antek—in the EU they get access to Toroidy who make really nice stuff. I've built amps with and without steel can shields as well. Steel can is worth the effort—definitely quieter.
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sds1
Friend of Leo's
I guess I should have said chassis really, on a lug separate from earth. The earth should have it's own lug.
With the one-point grounding and elevated filament CT you'd have to install a lug just for the shield.
Few more connections....Might do a little power test after a little more work...I realized that my printer needed a software update after I spent 2 days trying to figure out why it wasn't printing accurate dimensions...I assumed it was. My board is .25" shorter than what I drew out! I opened up some of the spacing as well in the file....
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To Chassis which role is Safety Earth.
Secondary "ground" role in tube amps is to collect "used" current and get back to power supply.
Fabulous so far!! Not much drama. I freaked a little when I saw a small puff of something.. but no smell… and I immediately shut down. Nothing visual to see… and it’s running normally now, could have been something benign, fuzzy or something. I should have posted a pic after I fired up the power side… but I just kept going.
I added a 1R resistor to the cathode leg to make measurements easier.. the maths where hurting my brain, and flexing the limits of my knowledge. I get it now, but fell back on what I have learned in other builds. Haha. Long story short I’m going to replace the 27K resistor in the bias part of the circuit (alligator clipped out in the pic) with a 0R resistor to get a usable range with the 6L6GCs I installed (had them on hand.) Was able to dial in 35mA on the power tubes (70mA on the single resistor) with just the 50K pot, pretty much in the middle. B+ voltages overall about 10vdc above the schematic notes.
This amp is QUIET. Super pleased. I’d say just some light (normal?) hiss with the MV dimed. One can easily dial it out with the MV down a little. Reg volume introduces no additional noise. Sounds fantastic to me at first instinct. Got better with more juice on the power tubes, sounded great running super cool too.. better now however.
I’ll build a case and see what the 15” JBL does. I had it plugged into a 12” creamback for tests.
Glad for all the chime ins about grounding schemes. Love it.
I added a 1R resistor to the cathode leg to make measurements easier.. the maths where hurting my brain, and flexing the limits of my knowledge. I get it now, but fell back on what I have learned in other builds. Haha. Long story short I’m going to replace the 27K resistor in the bias part of the circuit (alligator clipped out in the pic) with a 0R resistor to get a usable range with the 6L6GCs I installed (had them on hand.) Was able to dial in 35mA on the power tubes (70mA on the single resistor) with just the 50K pot, pretty much in the middle. B+ voltages overall about 10vdc above the schematic notes.
This amp is QUIET. Super pleased. I’d say just some light (normal?) hiss with the MV dimed. One can easily dial it out with the MV down a little. Reg volume introduces no additional noise. Sounds fantastic to me at first instinct. Got better with more juice on the power tubes, sounded great running super cool too.. better now however.
I’ll build a case and see what the 15” JBL does. I had it plugged into a 12” creamback for tests.
Glad for all the chime ins about grounding schemes. Love it.
That's a handsome, tidy build. Nice one.
Where does that resistor sit in your bias circuit? If it's the 'tail' resistor to ground, I've seen folks suggest you not go below about 10K. Why? Here's Merlin on bias: "It is good design practice to limit the range of voltage adjustment so it is impossible to reduce the bias (negative voltage) to nothing (0V)." But maybe that's not where your resistor sits.
Where does that resistor sit in your bias circuit? If it's the 'tail' resistor to ground, I've seen folks suggest you not go below about 10K. Why? Here's Merlin on bias: "It is good design practice to limit the range of voltage adjustment so it is impossible to reduce the bias (negative voltage) to nothing (0V)." But maybe that's not where your resistor sits.
gabasa
Tele-Afflicted
Great work! Did you isolate your speaker jack?
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gabasa
Tele-Afflicted
I agree, perhaps it's better to reduce the value of the pot in order to keep a resistor there.
beaut
Yes, tail resistor to ground. 10K would work. The pot isn't exposed outside the amp, so, not concerned about anyone playing with it. Not sure what other tubes I want to roll, it's entirely possible that 10K would put most of what I might try still in a usable range of adjustment—with 27K in there pot maxed at 65mA (for both tubes).
@gabasa yes isolated speaker jacks!
@gabasa yes isolated speaker jacks!
Okay—swapped in a 10K... biased back up!
Working out the details…Proportion is entirely related to the width of the chassis I had on hand and the 15” speaker. Reasonably compact.
gabasa
Tele-Afflicted
That looks great, which 15" are you using again?
Back in the old Traynor days, I had a Bass Master wired to 5F6A specs and I played it through a 1x15 cab for years. It sounded marvelous.
Back in the old Traynor days, I had a Bass Master wired to 5F6A specs and I played it through a 1x15 cab for years. It sounded marvelous.
Guys. This is a fantastic amp. I think it's hilarious that perhaps the "first" amp one should build if one was to explore amp building—the amp that birthed 1000 amps—it took me 10 builds to get to. Wow. It's got a little bit of everything to my ears—I have enough amps here to know a little about what I might like...The other amp I have that has incredible personality is the Dumble—but it's a different beast. Now I need to keep working on my fledgling guitar skills!
I'd say all the mods I decided on are worth it. Nice big difference between normal and bright channels—preferring bright at the moment (untouched). The jumper on a switch is really really cool.
On a technical note—there's a decided "pop" when switching NFB settings—and plugging in a guitar even with the fancy silent jacks—obviously not present when volumes are down. This doesn't happen on any other amp (with selectable NFB). I'm thinking this is related to the 2L man grounding scheme? Which, BTW, I kinda now feel obligated to redo all my other amps to follow?!
Anyway—the popping isn't a big deal—just noting it. In hifi-land guys freak out about "thumps" usually related to power off.
I might make straps for the top bolts... undecided, not necessary, technically...would be a visual thing. Also, I ran the grill cloth the other direction on the first try—looked totally wrong—go figure. Cool that you can see the dustcap through the cloth!
I'd say all the mods I decided on are worth it. Nice big difference between normal and bright channels—preferring bright at the moment (untouched). The jumper on a switch is really really cool.
On a technical note—there's a decided "pop" when switching NFB settings—and plugging in a guitar even with the fancy silent jacks—obviously not present when volumes are down. This doesn't happen on any other amp (with selectable NFB). I'm thinking this is related to the 2L man grounding scheme? Which, BTW, I kinda now feel obligated to redo all my other amps to follow?!
Anyway—the popping isn't a big deal—just noting it. In hifi-land guys freak out about "thumps" usually related to power off.
I might make straps for the top bolts... undecided, not necessary, technically...would be a visual thing. Also, I ran the grill cloth the other direction on the first try—looked totally wrong—go figure. Cool that you can see the dustcap through the cloth!
I'm sorry to even ask, but you mentioned fancy switching plugs. Is that the 'silentPLUG' plugged into the amp? I had the naive idea it was meant to go at the guitar end.
Again, I could be wrong. And FWIW, I doubt that'd cause an NFB 'pop' -- but neither do I think proper grounding would do that. I'll be interested to see what the smart folks can suggest.
Again, I could be wrong. And FWIW, I doubt that'd cause an NFB 'pop' -- but neither do I think proper grounding would do that. I'll be interested to see what the smart folks can suggest.
Totally—that cable has them on both ends.... belt and suspenders? Only thought about the one-ended thing recently... since those jacks are $$.
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