AC30 Build Help! I'll keep building, you keep helping!

[evancorylevine]

Hey beauts! This is my first post here and I'm super psyched.

I'm building an AC30 clone from Weber and I've found that one of the caps is prohibitively large.

Should I buy a different cap? Simply move it? Move the whole board? What is the simplest way to move ahead?

Pictures attached.

[kagliostro]

IMHO Mount it and be happy


Franco


BTW which cap of the schematic is it ?

I've seen

[evancorylevine]

IMHO Mount it and be happy


Franco


BTW which cap of the schematic is it ?

I've seen

Mount it how? It won't fit under that pot!

[uki]

There are smaller caps but radial ones. The cap can't let the board to the spot due to the potentiometer with switch? Am I seen this right?

Check this ones, they are much smaller in size: https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20170228102534&SearchText=47uf+450v+capacitor

I think these are the same size also capacity:
https://www.aliexpress.com/wholesale?catId=0&initiative_id=AS_20170228102535&SearchText=40uf+500v+capacitor

How about swap the pots the one in the left side of the picture with the one with the switch?

[drew]

From looking at a couple of blurry youtube videos, it looks like you have to mount it diagonally enough to clear the pot, with the negative lead going straight to the ground buss instead of to the circuit board.  Not exactly pleasing to the eye . . .

[kagliostro]

Two different approachs





Franco

[jjasilli]

A smaller cap is an option.  OTOH checkout Doug's Library pages.  That cap may fit sideways under the pots where it can be glued to the chassis -- with hot glue or silicone glue.  Then run leads to the eyelets.  Or mount it to a terminal lag strip, e.g., and run leads to the eyelets.

[evancorylevine]

omg y'all are awesome. thanks so much for the abundance of fantastic replies!!!

<3 <3 <3

you bet yr beautiful tokheses that I'll be posting here a lot more over the coming few months. So exciting.

[MFowler]

There are e-caps physically much smaller then cap provided by Weber you can use.

[evancorylevine]

Two different approachs





Franco

Thanks so much for the help! These pics are so useful in me getting my amp together!

As for that grounding plane: What is that? A 14g brass wire? A rod? Where do I get it?

[shooter]

What is that?

[evancorylevine]

What is that?

Thank you, shooter! What I meant to ask is: What is that made out of? Is it a 14g brass wire? A rod? Where do I source it?

[kagliostro]

That is a piece of solid core wire, use what you have under hand, only use something that isn't very thin

I would like to use 14 - 12 AWG

An extreme solution is used by Larry Amps on some amps he build, he use a brass pipe as ground bus and also as a shield

(you can see some wires that comes out of the pipe on the right of the picture)



if you want to see examples of good construction go here http://www.larry-amplification.de/cms1/

Ciao

Franco

[PRR]

#14 wire is the old standard for US house wiring. (#12 is now more common.)

Any house electrician can give you a lifetime supply of #14-3 cable scraps. Peel the insulation to make bare.

A 25-Watt iron strains bad to solder #14. It will not solder to a pot body. I don't think soldering to the pot is worthwhile or wise. But if I did, I'd use the 100-Watt solder gun. (But not my 450W gutter-iron.)

[kagliostro]

Also I prefer the way Sluckey do for ground bus

he didnt solder it to the body of the pot, only to the terminal that is to be connected to ground

(am I correct Steve ?)

Franco

[Toxophilite]

IMHO Make it work well ,many fine solutions here, don't worry about how it looks unless you're building to sell. If it's for you, ultimately it's going to be all hidden and what you're really end up caring about is how fun the amp is.

[MFowler]

Insert one end of that Romex 12awg bare wire into your drill and hold the other end with a pliers then slowly let it spin and the wire will straighten out nicely to use as buss wire.


Mark

[evancorylevine]

sooooo I'm just gonna keep checking in with you because you've been so helpful!

Am I going to have problems with there being more than one grounding plane here? I've got the brass plate between the pots and the chassis, the brass wire going on the bottoms of the pots, and I also have two connections to ground on each switching jack, because I figured it increased their rigidity.

Should I move forward or should I remove the brass plate? Are the two connections on each jack (one to the NC terminal and one to the unswitched terminal) going to be problematic?

Y'all are great. thank you in advance for the help.

[PRR]

I can get you some #6 Cu wire, if you like it fat.

But really I think all small and tube audio, if a #20 isn't ground enough, you have a problem.

And with that #14/#12 wire, if you *ever* have to replace a jack or pot, you have a problem.

[evancorylevine]

I can get you some #6 Cu wire, if you like it fat.

But really I think all small and tube audio, if a #20 isn't ground enough, you have a problem.

And with that #14/#12 wire, if you *ever* have to replace a jack or pot, you have a problem.

I appreciate that! My main concern is that I'll have problems by having TOO many grounding options. Maybe the way ground loops happen in some circuitry? Or am I way off here? If I use the copper wire as my grounding buss, will that brass plate be a problem? My intuition tells me that it will just behave as an extension of the chassis and be entirely inconsequential, but I want to make sure before I start wiring stuff to the ground buss. Will there be a problem with the wiring of my jacks?

[DummyLoad]

switch places of the pots.


--pete

[evancorylevine]

Thank you for the reply, but I'm beyond that point. At this juncture I'm trying to figure out if it's okay to move forward wiring the boards to the pots with my present grounding scheme.

[evancorylevine]

Do I have the go-ahead?

[tubeswell]

Have a read of this handy article on grounding first.


Click here to view the article (360kb PDF)

[evancorylevine]

Have a read of this handy article on grounding first.


Click here to view the article (360kb PDF)

gosh! so how far behind am I putting myself by going forward with my present grounding scheme?!

Is there an explicit and concise direction that I may take if I rebuild the grounding scheme to be more in line with that impressive document?

[evancorylevine]

What I mean is: What modifications would I have to make to this layout to follow those guidelines in your document?

https://www.tedweber.com/media/kits/6v30_layout.jpg

[evancorylevine]

and if I have to figure out all those modifications myself, is it worth it? Is the noise difference really that much?

[Tony Bones]

A couple of comments:

1. What you've done is not bad by anyone's measure. It's just not the way some people might have done it. So what? It's still way good.

2. The way we learn - at least with guitar amps - is by trying things and seeing how it turns out. Then we try different things... You might as well try it the way it's already built!

Finish it. Plug in. Smile.

[drew]

I can't see clearly how you have the jacks wired.  Does it match this: http://el34world.com/charts/images/cliffjacks.gif ?

[tubeswell]

Tony Bones said it already in his last post - There are many permutations. The main reason people get finicky about grounding is to eliminate as many sources of hum/noise as possible (recognising that there are also sources of hum from factors other than grounding). Reflecting on Merlin's article, I think the main things to take from that are (if not using a single 'star ground' for the entire circuit), then:



1) Keep the respective ground returns from each different part of the circuit as close as you can to the ground return for the (respective) filter cap/supply node that is supplying those parts of the circuit (i.e. 'galactic' ground returns); and
2) make your sole chassis attachment point for a ground buss bar at the input jack(s), and keeps the input stage ('low-current') grounds close to this: and
3) keep the reservoir cap (and screen supply node cap) grounds, and the output tube grounds (and any PT centre taps) close together at the other end of the buss bar. (These are the 'high-current' ground returns)

If you're using a buss bar, these concepts will help reduce micro-rises in ground potential (that can occur differently in different parts of the ground return path/circuit). Electrolytic caps are not perfect shunters of AC to ground because they exhibit a certain amount of ESR (and therefore, where there are higher voltage swings, there are more likely to be a higher 'pull-up' of ground potential) that can produce 'micro-wobble' in the ground return path, which can cause 'cross-talk' in other (more sensitive) parts of the signal path where it is not wanted.


However, as long as your grounding isn't abysmal and your build is solid in other respects, its all a bit anal-retentive because you can't hear much in the way of ground loop hum when you're playing your guitar through the amp. It's mostly only mildly annoying in the quiet moments (between loud thrashy metal chords LoL) when you're mic'ing your equipment through a PA, or trying to do a recording and get pee'd off by the noise floor.

YMMV

[evancorylevine]

I can't see clearly how you have the jacks wired.  Does it match this: http://el34world.com/charts/images/cliffjacks.gif ?

This is all I have done of the wiring at the inputs so far. I'm waiting for the go-ahead to finish this.

Are we saying that I should connect my grounds as they are at the inputs, and then take the far end of the ground and attach it to the chassis and then run a flying ground buss over my board?

[tubeswell]

Are we saying that I should connect my grounds as they are at the inputs, and then take the far end of the ground and attach it to the chassis and then run a flying ground buss over my board?

No. Only connect the Buss bar at one end (the input jack sleeve lug). The other end (where the high current ground returns get attached to) should not be connected to the chassis. Otherwise you will get a ground loop.

Best not to solder the pot cases to the buss bar. Having pot cases attached at several different points along the buss bar can make the hum worse. Better to solder a jumper from the pot ground lug to the case, and then connect the ground lug as close as you can to the point on the buss bar where the filter cap ground return is for that part off the circuit (if you're going to adapt the concepts in Merlin's article).

[sluckey]

You have the wrong lugs on all the input jacks grounded. The lugs closest to the chassis are for the "sleeve" of the plug and should be grounded. You have grounded the "tip" lugs.

Study the pic in the link that Drew posted.

[evancorylevine]

You have the wrong lugs on all the input jacks grounded. The lugs closest to the chassis are for the "sleeve" of the plug and should be grounded. You have grounded the "tip" lugs.

Study the pic in the link that Drew posted.

oh my. of course. that is an embarrassing rookie mistake. I swear I've wired a lot of jacks successfully before. I've built an awful lot of synthesizers, recording equipment, and guitar circuits/pedals.

Thank you so much for pointing that out, @sluckey. Who knows how much further I would have gone without seeing that. ::facepalm::

@tubeswell. You are very generous with your time, energy, and information. Thank you so much! What do you make of this passage, from that document you posted:

If the amplifier has more than one high-gain channel then it may be better to make the chassis connection further into the amplifier where the two channels meet and become one. Since this increases the chances of ground loop hum when other pieces of equipment are attached, as fig. 15.15 showed, the connection should be made via a hum-loop block network.

Thank you all so much.

[tubeswell]

@tubeswell. You are very generous with your time, energy, and information. Thank you so much! What do you make of this passage, from that document you posted:

If the amplifier has more than one high-gain channel then it may be better to make the chassis connection further into the amplifier where the two channels meet and become one. Since this increases the chances of ground loop hum when other pieces of equipment are attached, as fig. 15.15 showed, the connection should be made via a hum-loop block network.

There are a couple of ways of tackling this in such a circuit. The way Merlin maps this out, with the ground return via a hum-loop blocker at the junction of the signal path of both channels, will work. So will running a single buss bar to the sleeve lug of the (hi gain) input jack of the channel with the highest gain, and running a jumper wire from there to the other input channel's hi gain sleeve jack, with that channel's preamp grounds also going to this same point (i.e. like a star-ground point for both channels at this end of the buss bar)

[evancorylevine]

@tubeswell. You are very generous with your time, energy, and information. Thank you so much! What do you make of this passage, from that document you posted:

If the amplifier has more than one high-gain channel then it may be better to make the chassis connection further into the amplifier where the two channels meet and become one. Since this increases the chances of ground loop hum when other pieces of equipment are attached, as fig. 15.15 showed, the connection should be made via a hum-loop block network.

There are a couple of ways of tackling this in such a circuit. The way Merlin maps this out, with the ground return via a hum-loop blocker at the junction of the signal path of both channels, will work. So will running a single buss bar to the sleeve lug of the (hi gain) input jack of the channel with the highest gain, and running a jumper wire from there to the other input channel's hi gain sleeve jack, with that channel's preamp grounds also going to this same point (i.e. like a star-ground point for both channels at this end of the buss bar)

Alright! So I reckon I'll do the flying buss wire to the channel with the highest gain.

So... Which of the three channels has the highest gain on a weber AC30?

Also, these jacks have their sleeves insulated from the chassis. Thick jumper to the chassis?

[sluckey]

None of the channels are considered high gain channels, but the bright channel will have a little more gain than the others.

This kit is one of Weber's more difficult kits. I highly recommend forget about all these 'improvements' and simply follow the Weber layout. You have a brass grounding plate. Use it. Later down the road when you finally power up this amp you may have to troubleshoot some wiring errors. If you followed Weber's plan that process will go much more smoothly.

[evancorylevine]

Thank you for the advice Sluckey!

One last check: am I going to be wishing that I did these alterations when I'm recording this thing?

[sluckey]

I don't see anything about the Weber layout that will prevent you from recording. Have you thought to ask these questions on the Weber forum? There's probably some folks over there that have actually built this same kit.

I'm not saying that all the grounding advise you are getting here is wrong. Most of it is good advice. I'm just saying that the Weber layout looks OK. My concern is that if you stray too far then if you have trouble getting the amp to work you may have a difficult time troubleshooting if you don't have a good layout plan to refer to. Most problems with new builds will be builder errors that can be easy to find if you have a valid layout or they may be very difficult to find if you don't have a valid layout.

Maybe you'll be lucky and not have any problems but if you do and you need some help, the first thing you'll be asked to do is show a schematic and a layout and some hi rez pics of your actual build. If your amp doesn't look like your layout, it may be very difficult to find a problem.

[tubeswell]

Alright! So I reckon I'll do the flying buss wire to the channel with the highest gain.

So... Which of the three channels has the highest gain on a weber AC30?

Also, these jacks have their sleeves insulated from the chassis. Thick jumper to the chassis?

The channel gain difference is much of a muchness on an AC30. The general principle is keep your pre-amp grounds (including the pre-amp filter cap ground return)  as close as possible to the point where you ground the buss bar (which should also be close to the input jacks if they are ground isolated).

[evancorylevine]

Hey loves! Thank you all so much for the help! I'm nearly done and I've got a few questions.

What should I do for the output? I'm building this as a head, and it didn't come with an output. Are there quarter inch outputs that can be mounted to an adjacent surface? Should I do the bass amp thing and add speakon?

Is the ground wire running from my mains cable too thin?

And finally: do you notice anything else that needs attention?

Here's an album of pictures: https://www.dropbox.com/sc/t7c06isjcpidc0u/AACUh9TXT0DpBWiytRP9elgDa

[evancorylevine]

Another thing! How should I run the output's ground?

[EKDENTON]

If your talking about the output jack sleeve, I would connect it to the Power amp grounding point. 

[evancorylevine]

I'm talking about the output transformer

[EKDENTON]

 Do you have the part number of your OT? If it is a new OT but did not come with the wiring diagram you should be able to just search the part number and get your wiring info online.

[evancorylevine]

the ground in the lower left-hand corner is the one which I'm looking to get particulars on. Anybody know how I should wire that?

[sluckey]

Connect it to the screw that's holding that terminal strip. No need to run a ground wire to any particular place since there is no NFB in this amp. In fact, it ain't necessary to even connect it to ground.

Will you just be using two wires to connect to the speaker as shown, or will you use a 1/4" jack?

[evancorylevine]

quarter inch jack.

[sluckey]

quarter inch jack.

Well there's the easy solution. Use a switchcraft jack and just connect that black common wire to the ground lug (sleeve) of the jack. Done.

Oh, and just connect the wire from the impedance selector switch directly to the tip lug of the speaker jack. Don't even use that terminal strip.

[evancorylevine]

I'm just wiring the desired impedance directly to the output, but if I wanted to put a switch in, is there one that you would recommend?

Thank you so much for helping!