5E9 Tweed Tremolux Build Thread: Pics on Page 11

[ziess]

CAn you move the board left or right in the chassis two the jack isn't right next to a turret?

[wproffitt]

CAn you move the board left or right in the chassis two the jack isn't right next to a turret?

Zeiss,
That's another possibility, too. What I need to figure out is whether or not moving the board will create a bigger problem elsewhere than just just moving the ext speaker jack by a centimeter or two. I'll report back when I know more.

[wproffitt]

Got my grounding scheme finished up today along with doing final wiring from the OT and PT to relevant wires, grounding points, and the speaker jack. I ditched the extension speaker out, reasoning that I'd never once used it on any other amp. I'm waiting on a couple of 1K resistors for the 6v6 sockets and then I'm off to the races with the final, final, final installation of the board.

[ziess]

How much clearance is there between your ground buss and the ungrounded turrets?

[wproffitt]

There's a full half inch of clearance in most places. How does that sound to you?

[wproffitt]

Well,
Better stop for the day! I've got about 8 solder joints left, but I'm getting tired and don't want to get sloppy(er).

[Ursa Minor]

[wproffitt]

So I'm pretty close to the end on this. I'd define order more wire if I knew then what I know now. I have a lead dress question for the amp gurus out there in forum land. How big of a deal is if it I have a wire going between filament heater wires on the way to my 2nd 12ax7 tube, as seen in below with the grey wire going between the green ones?

[ziess]

Not a big deal at all. Traditionally all the board connections to the sockets are made and the heater wires go over the top but as long as the wires cross at roughly 90 degrees (which they do) you'll be fine.

Tommy.

[Racing]

One major hurdle to the novice is grounding layout.
Always,and see...there´s a remedy for that. Online even.
What you do is read up on Kirchoffs two LAWS. LAWS as in they can not be debated.

In essence the one of them tells that we should regard a given "system" as a closed entity. Ie;we ground what needs to be grounded together with the e-cap that services that part of the amp.

"The golden rule" is imperative to a well behaved amp. Noone loves a "hummer",and it is simple to cater to. As your amp is tube rectfied it brings that there´s two HT AC taps heading for said tube rectifier and in turn one centertap. That centertap is our goal of attention.
This shall run for the groundlug of the e-cap that takes the first hit out of the rectifier. This is absolutely essential and is known as "the golden rule". By doing this we have adhered to the one of Kirchoffs LAWS and it hands us a platform to work from.

Keeping this reasoning it also brings that each drop resistor within the voltage rail brings yet another potential that needs to see the capacitance of an e-cap,and ALL grounds for said node should be run for that e-caps groundlug. THEN proceed further vs chassis or whatever.
From a practical POW that for instance brings a minor dilemma as far as your Switchcraft input jack of choice as these hit ground via mechanical contact to the chassis.
This brings that the entry stage V1´s components heading for ground HAS to be run for those jacks. It is IMPERATIVE that it does as the jacks need to ground TGT with the gridleak as well as cathode resistor AND the e-cap in case to make for a "closed" system.
No.
It doesn´t matter if the amp will work anyways. It is subpar thinking,pulling it off as described per above is the electrically correct manner in which to do it. Just ask Kirchoff.

As has been pointed out it might be a wise choice to keep certain grounds apart. Above we see mention of stacking solderlugs vs chassis. Never do that,think long term. One solderlug bolted vs the chassis and one screw. Need be use multiprong solderlugs instead. Metal does oxidize over time,there´s no argument there. Do it right and do it once.

"Power" grounds,like where you let the first hit e-cap hit chassis to meet up with for instance powertube ground,bias voltage ground where applicable aso,might be wise to keep together and do so in close proximity to the powertransformer.
As has been pointed out the grounding for the entire preamp TGT with phaseinverter and what not i for one at least normally ground close to the input jacks as it´s normally diagonally as apart from the PT and thus power as it can get.
FWIW i for this very reason always use floating jacks for entry. In this manner I get to decide where the damn thing grounds... Again. Remember that we need to regard this as "closed circuits" for every node we let enter the picture,and it doesn´t matter if this all said n done is 8 preampstages or not. Kirchoff still applies.

That said preamps do not digest all that much appreciable power. True enough. There however still IS power present. Thus it might be a wise move to keep signal ground apart from preamp ditto.
Yep. That amounts to all in all three grounding points thus far. Correct. Signal ground (which in practice is AC ground only) is very very low on power and thus it can be let to ground in close proximity to preamp ground. No worries there,just keep in mind which direction the current from the preamp takes to hit main power ground through the chassis.
Ditto for shield really. Comes down to the same thing. IOW,a lot of what i present above is really about practical approach to one of Kirchoffs LAWS through common logic.
Many a times one simply has to be pointed in the correct direction,and NO. You can not overthink the practical implementation of this.

Done correctly (neither for instance Fender or Marshall is. Fenders are even known to run "chaotic grounding". Ie;grounds all over the place) you will be presented with a very well behaved amp already from the get-go. In fact,you can err on a lot of choices and still have a well working amp as long as you have put some thought and practical time into the design of the amps grounding layout.
Just take the entire lead dress debate. Very often this is a matter of NOT knowing/understanding what Kirchoff told us. Get the grounding right and the issues will go away...magic!

Point of mine here,the essential one,is read up. Them guys...like Ohm..Kirchoff et al knew their shit. It´s that simple and their LAWS applies to this day.

[Racing]

FWIW,and to point out ONE example.

Yes. Even factory designers seems to have jumped class on occasion. Be aware that what we´re doing here is nothing but quantitative physics. Period. That brings that common LAWS applies and basically anything we question within an amp can be measured. No..there IS NO MAGIC!
IDC what all the "experts" claim. This IS quantitative physics and nothing else. Period.

Factory designers. Uhu.
Regard the ill fabled Fender Super 60 and its cousins will you. Ill reputed as being noisy amps that are sub par designed. Well,yes and no.
If you want a Super 60 to turn "studio quiet" what you do is rip it open and look up the grounding point on the PCB for the first two electrolytic caps in series. These are in series to cope with the voltages at hand.
Well.
What you do is cut that ground trace on the PCB and replace it with a piece of wire that heads directly for the rectifier bridge first thing. Ie; Kirchoff..again. By the simple implement of this wire,just rerouting ground,that Super 60 will turn into one of the most well behaved amps you´ve ever run into.

Sry to say that there is just ONE out of many examples where it seems that factory designers skipped class. This,at least IMO,is electronics 101 so there really is no excuse. Sadly it´s FAR from the only example at hand.
Old Fenders..don´t even get me started. One of the prime reasons Fender get away with their chaotic grounding is the very limited amount of gainstages,but it sure as hell isn´t electrically correct none the less!
Early Marshalls and how they ground to that damn ground bus at the rear of the pots. Geeez... Wanna get an old Marshall way more well behaved? Ok..unbolt the pots and unscrew the board of that JMP or early JCM. Locate the twin cap that resides underneath the board. Cut the grounding path for the entry stages and head that together with the grounding of the entry jack directly for the groundlug of that twin capacitor...presto.
There´s way more to be said on the subject,but let´s leave it at that for the time being at least.

[Racing]

On NOS in turn.
I agree in that the old stuff is of better quality.
To claim that NOS tubes SOUND all that different tho...not so much. Again. Quantitative physics. With a good quality curve tracer we can regard all parameters of tube performance we can ever dream up and two tubes,no matter yr of production,that hands us similar numbers WILL perform similar. That simple and the numbers do not lie.

Quality wise though is a whole nother ballgame. As i see it the truth of the matter is that back in the old days the real crap was never let out the door of the manufacturers. QC made sure of that.
These days...i for instance run the numbers of a brand new JJ ECC-83/12AX7 and it isn´t even CLOSE to the reference. Ie;data sheet for an ECC-83. This for a brand new tube,right out of the box.
Per always i guess this comes down to money. Shareholders want to maximize their outcome...and these days the worst thing that´ll happen is that JJ,for instance-they´re about all as bad,gets a really PO´d musician in their face...and who are they to care.
But true is,having by now run thousands of tubes through my digital tester,that QC certainly isn´t what it used to be.

One point where it IMO really pays off to install a NOS tube is a tube rectifier. Especially so for a gigin musician. TR´s are of THAT much better QC when NOS that there´s really no comparsion.

[wproffitt]

Racing,
Thanks for chiming in here! I'd hate to get this thing wired up and have it turn into a fiery wreck or a humming mess. Forgive my ignorance of some amp terminology, but I'll proceed as best as I can. As I understand it, you have a couple of concerns with the grounding scheme I have employed up to this point:
1) my center tap is grounded, along with the ground from the AC cord and the grounds coming off of the electrolytic caps with a kept nut holding the PT to the chassis. How should I run the ground for this?
2) my input jacks are grounded to the chassis by virtue of their physical attachment to it, but this is less than ideal. Should I tie them into my ground bus wire on the preamp side?
3) my grounds to terminals that are either bolted to or screwed into the chassis. Should I have them going to terminals that are soldered to the chassis?
Thanks in advance for your guidance on this. Below are some better shots of what I've been up to. Let me know if you need to see anything else.

[Racing]

1a/ Do not ground ANYTHING to the bolts keeping the x-former in place.
Grounds are to be just that. Grounds. Not pillars working as grounds. (Read-x-formers can shift around due to for instance tossing the amp around (read-tossing in n out of a car going to gigs and what not))
b/ by EEC law the ground wire off the mains shall be run to a lug of its own. Nothing else attaches to this lug (yes..there´s ample reasons for this).
c/ read the part about the golden rule again. Do NOT sum all grounds as you´ve described. The centertap runs to the groundlug of the 1st hit e-lyte FIRST,before hitting the chassis. Again..for ample reasons (Kirchoff). Kirchoffs current LAW applies. At all times. Closed "power circles" does it.

2/ In essence,no. Again. Reread what´s written above. In reality it´s of less importance why, when and how as long as you adhere to Kirchoffs power/current law. Ie; let the preamp ground at the input jacks,by all means. Just make sure that the ENTIRE preamp does at that one point. Ie;ground for gridleaks,for the input jacks (obviously) the electrolytic cap that serves them stages and the cathode resistors/decoupling capacitors. Again. Think in "power circles". In short,for instance,the circuitry that needs to see ground for V1...ALL of it heads for them input jacks-as that IS your primary ground point for the jacks. Ie;you don´t really have any choice but to let the whole mess ground at that point do you as you´ve opted to use Switchcraft style input jacks?

3/ Bolted solderlugs (vs the chassis that is) works just fine. Be sure to torq down on the screws and do NOT use any sort of locking adhesive (loctite et al). Pure metal to metal contact does it. I use regular solderlugs for M3 screws. That´s it. No magic involved.

[Racing]

Btw.
From one of the photos above. To the utmost left on that board of yours,is that the cathode resistor for the powertubes (a black power resistor) next to an e-cap?
Reset that. Keep the capacitor WAY more distanced from the resistor. If that is the cathode resistor for the powetubes that sucker´s gonna run hotter than hell..and e-caps are normally either rated at 85degC or 105degC. Either being WAY less than what´s needed. IOW..if that there is the cathode resistor by mere install you´ve sentenced that cap to death before even starting the thing up.
Its performance will boil to crap in notime flat.