5e3 grounding scheme

For those building and repairing amps on their own. Learna and share ideas.

5e3 grounding scheme

Postby LUC.key on Sun Feb 16, 2014 4:35 pm

I know there are some 5e3 builders in here ...
How would one properly ground 5e3 circuit to to get it nice and quiet? I've started with the star ground (and I know it may not be the best scheme) and I'm getting more hum than I'd like. I'll have to cut myself some nylon washers for input jacks - now they're grounded through chasis. Every other ground goes right to PT bolt. Following this layout:


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Any ideas?
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Re: 5e3 grounding scheme

Postby Unit_1 on Sun Feb 16, 2014 9:06 pm

this is the same arrangement that I use, after painstaking trial and error! that first power filter cap is surging like crazy being hammered by the pulses coming from the rectifier - that's why it needs to be grounded separately.

a couple other things, be sure all the wires leading to ground are 18 ga

be sure the pots and jacks are grounded LAST. if you ground them first, and then put the ground from the transformer or the power filter caps down next, you can actually cause a grounding loop even with star ground.

I ground the power transformer first, then power filter caps, then output jacks, and then after that it doesn't matter so much but the input jacks are always last since that is THE area that your signal is the smallest and therefore the most sensitive to EMF.

get some teflon plummer's tape, like what you wrap around pipe fittings before screwing together, and wrap the threads of the input/output jacks with this and it will insulate the jack from the chassis as long as you have non-conductive washers on both sides of the jack

be sure to test by checking non-continuity between the jack ground and chassis ground after tightening as this can sometimes rip the tape

regular switchcraft jacks are just a bit too short to isolate in this fashion, so I buy the switchcraft L12A (switched) and L11 (unswitched) which have a longer bushing and are SO much easier to isolate.

if the chassis you are using will allow the wider diameter bushing of cliff jacks, these are already isolated since they are plastic and don't require any special mods to isolate. they are also longer, so you have to have room in that direction as well as the width of the bushing. these don't work in a standard 5e3 chassis due to both the mentioned reasons.

capacitors: some capacitors are like freaking radio antennas - they just pull in every bit of EMF around you. Sozo's, while supposed to be mustard replacements, do this WAY more than actual mustards do (I've used both, and actually the go to 5e3 I use has nos mustard caps).

The quietest caps around are the paper in oil caps. They are very quiet to the point of being TOO high fidelity for some people. I have an all ASTRON pio cap 5e3 that I use for jazz/blues, where my mustard 5e3 is for rock.

I like to move my OT as far away as possible and at a 90 degree angle from the PT which minimizes hum, like so:

Image

uhhh..... I think that's it. If i think of more I'll post. :jam:
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The ability to play/make music is a gift that not everyone gets. Those of us who have it should use it.

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Re: 5e3 grounding scheme

Postby LUC.key on Sun Feb 16, 2014 9:42 pm

Thanks sir!
will have to look into the grounding of this thing more troughoutly :)
Those switchcraft jacks give me a headache ...I've found out that there was small resistance (like 3 -10 Ohm) between tip and sleeve on each of them = more hum ...when I grounded the inputs with a clip wire, the level of hum decreased. I had to papersand the "tip" on each swithing lug to get a good contact. Helped a bit, but still hums a lot. I've never used them Switchcrafts, probably never will again... they are old style unisolated, I have to cut some washers to isolate them and all the unnessesary work gets me mad :evil: I've got some spare cliffs ready to go, the only thing is that I'd have to redrill the holes (they are 1mm bigger in diameter) to get them there. Not a problem at all, but I'm not sure if they will fit ...unfortunately I've built it on turret board instead of eylets, so everything is bit higer and closer ...did not think of that before :(
Will redo the main filter cap to its own ground wire, It could help a bit. Also I've increased the value to 22uf instead of 16uf, also I've got a choke instead of 5k resistor in the power rail
Is that normal with 5e3 that when you turn up the volume slowly it goes nothing-nothing-insanely loud? It was like on 2 I'd say and really loud. On bedroom level the hum is not noticeable, but once I get past 2 all the way up its really annoying
I'll try to move around with the OT ...probably with another one since this one is already bolted in there with wires cut to fit ... I've got some nice old iron with 8k primary into 8Ohm that I wanted to try in 5e3 anyway :)
Thanks for tips, will see where it will get me :)
:cheers:
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Re: 5e3 grounding scheme

Postby Unit_1 on Mon Feb 17, 2014 2:56 am

LUC.key wrote:Thanks sir!
will have to look into the grounding of this thing more troughoutly :)
Those switchcraft jacks give me a headache ...I've found out that there was small resistance (like 3 -10 Ohm) between tip and sleeve on each of them = more hum ...when I grounded the inputs with a clip wire, the level of hum decreased. I had to papersand the "tip" on each swithing lug to get a good contact. Helped a bit, but still hums a lot. I've never used them Switchcrafts, probably never will again... they are old style unisolated, I have to cut some washers to isolate them and all the unnessesary work gets me mad :evil: I've got some spare cliffs ready to go, the only thing is that I'd have to redrill the holes (they are 1mm bigger in diameter) to get them there. Not a problem at all, but I'm not sure if they will fit ...unfortunately I've built it on turret board instead of eylets, so everything is bit higer and closer ...did not think of that before :(
Will redo the main filter cap to its own ground wire, It could help a bit. Also I've increased the value to 22uf instead of 16uf, also I've got a choke instead of 5k resistor in the power rail
Is that normal with 5e3 that when you turn up the volume slowly it goes nothing-nothing-insanely loud? It was like on 2 I'd say and really loud. On bedroom level the hum is not noticeable, but once I get past 2 all the way up its really annoying
I'll try to move around with the OT ...probably with another one since this one is already bolted in there with wires cut to fit ... I've got some nice old iron with 8k primary into 8Ohm that I wanted to try in 5e3 anyway :)
Thanks for tips, will see where it will get me :)
:cheers:


grounding the power tube cathode and the first filter cap separately from the rest of the amp will make the BIGGEST difference. it goes from chainsaw to purring kitten with just that change.

yes, the 5e3 really doesn't get any louder than 2, after that it just gets more breakup. I use audio taper pots instead of the linear pots to make it a bit easier to dial in the sweet spot between 1 and 2, lol...

once you separate that first stage in the grounding you'll probably be satisfied with that! :cheers:

the 5e3 chassis is really tiny to work in. make one change like turrets instead of eyelets and you MAY end up with a shortage of room.

I completely re-did the layout of a 5e3, so that it was "hiwatt style" and used turret boards and standoffs - a lot of planning and fitting with cardboard cutouts instead of actual amp pieces allowed me to see all the OOPS spots in cardboard before I ever cut the epoxy board and swagged in the turrets.

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The ability to play/make music is a gift that not everyone gets. Those of us who have it should use it.

Asimov:Individual science fiction stories may seem as trivial as ever to the blinder critics and philosophers of today — but the core of science fiction, its essence, the concept around which it revolves, has become crucial to our salvation if we are to be saved at all.
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Re: 5e3 grounding scheme

Postby LUC.key on Mon Feb 17, 2014 8:35 pm

Unit_1 wrote:
grounding the power tube cathode and the first filter cap separately from the rest of the amp will make the BIGGEST difference. it goes from chainsaw to purring kitten with just that change.




Indeed, rewiring that one filter cap to its own ground made a significant difference! Not perfectly silent, but definitely an advance ... :cheers:

I see that MM OT has the ground wire connected directly to the transformer frame ...I've got Magnetics Comp. tranys here and they did the same with the OT ...did not seem to me like a good idea, since there is some current runing right to the chassis. I've desoldered that wire, prolonged it and connected to the star ground bolt with others. Dunno if it makes big difference ... I just didn't like this aproach :?

I've used a stretched shrink tube on the input jacks treads ...works nice also :)

Your builds looks really nice! You must have built quite a few of these, right? :jam:
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Re: 5e3 grounding scheme

Postby Unit_1 on Mon Feb 17, 2014 11:32 pm

LUC.key wrote:
Unit_1 wrote:
grounding the power tube cathode and the first filter cap separately from the rest of the amp will make the BIGGEST difference. it goes from chainsaw to purring kitten with just that change.




Indeed, rewiring that one filter cap to its own ground made a significant difference! Not perfectly silent, but definitely an advance ... :cheers:

I see that MM OT has the ground wire connected directly to the transformer frame ...I've got Magnetics Comp. tranys here and they did the same with the OT ...did not seem to me like a good idea, since there is some current runing right to the chassis. I've desoldered that wire, prolonged it and connected to the star ground bolt with others. Dunno if it makes big difference ... I just didn't like this aproach :?

I've used a stretched shrink tube on the input jacks treads ...works nice also :)

Your builds looks really nice! You must have built quite a few of these, right? :jam:


Huzzah! Kapla! (Klingon for success)

Yup, I made "a few"....
Image
The ability to play/make music is a gift that not everyone gets. Those of us who have it should use it.

Asimov:Individual science fiction stories may seem as trivial as ever to the blinder critics and philosophers of today — but the core of science fiction, its essence, the concept around which it revolves, has become crucial to our salvation if we are to be saved at all.
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Re: 5e3 grounding scheme

Postby ThisLifeILead on Thu Feb 20, 2014 4:23 pm

Man Unit_1, your wiring is a friggin art form!!!
"Great spirits often encounter violent opposition from mediocre minds" - A.Einstein
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Re: 5e3 grounding scheme

Postby LUC.key on Thu Feb 20, 2014 8:56 pm

Just an update ...today I finaly cut washers to insulate input and output jacks ... now It's pretty silent :cheers: I'm going to rework some wiring which I altered when hunting the hum source and then Im finaly done!
I'm still without the cab, so it's just a amp chassis now. Played it today thru closed vertical 2x12 with only one speaker connected (8ohm) and it sounded pretty good. I have to try a few tricks to tighten the bass, because it pulls sooo much oompff ...sounds fine with strat, but my tele sound horrible :/ Then I've tried another 2x12 with Greenbacks (which I use with JTM45) .... aaand it sounded like a poop. Nothing to like with this combination :lol:
I'll post some pics when I'm finaly done :)
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