# Help me ground this YBA-1 for high gain



## glideon2 (9 mo ago)

Now that I've replaced with shielded wiring at the input, the only thing left to consider are the Filter Caps grounds themselves.

From the factory, many Traynor amps had the filter caps installed right near the input jacks. Conventional wisdom says this is a horrible idea, yet despite the
amp has historically been very quiet. Might have something to do with the cans being practically welded to the chassis.

Mine is no exception and I've replaced (dremeled out) the old Mallory cans with F&T 50/50 500v all around, soldered the grounds to the cap clamp lugs and thought nothing of it since. Think I did that sometime in 2012 and they are still going strong.

However, now that I've added shielded wire grounds right near the (-) of where the Screen and PI Filters are, I'm debating of rethinking the whole thing.










I've observed and read that in old Fenders, the ground wires for the Filters travel at least 8-10in back towards where the HT ground is to avoid inducing hum into the preamp area.

So, I went ahead and wired up this way using 22 guage Gavitt wire I had on hand, but hesitant to try it out because instinct says to keep ground short. Think I ended up using 10in-11in of wire, supposedly it handles up to 600v. Will it work?

Alternative is using some CE Multcap Can and try to mount like so near the HT ground under the PT:


















There is an empty socket where earlier models had tube rectifiers, but it is a little to small to accommodate a cap can unfortunately.

Reason I ask is because with higher gain from the preamp (Marshall value cathodes, higher plate resistance, higher treble peaker, V2 fat cap, cascade), this thing is quickly starting to make hiss and noise unacceptable for studio/recording use.

Any bit more can help.


----------



## Latole (Aug 11, 2020)

There is on DC voltage on filter caps no AC
It is the AC produce hum


----------



## glideon2 (9 mo ago)

Yes, and?


----------



## Latole (Aug 11, 2020)

glideon2 said:


> Yes, and?


And ? Filter caps may stay there, near the guitar jacks


----------



## glideon2 (9 mo ago)

Explain?


----------



## Latole (Aug 11, 2020)

What I wrote ( AC and DC) say all. 
Do you look for electronic course ?


----------



## glideon2 (9 mo ago)

Latole said:


> What I wrote ( AC and DC) say all.
> Do you look for electronic course ?


No, but I took several Engish courses and I can't decipher a single phrase of what you're saying


----------



## Latole (Aug 11, 2020)

Sorry I didn't want to bother you but to help you and I see that it doesn't work. So let's just forget about it ok?


----------



## dtsaudio (Apr 15, 2009)

I'm not entirely sure what you are asking. But comon ground practice is to ground all the power supply caps to the same point. Google star grounding. That is usually not practical in a large chassis, so what Fender and others do is to ground sections, and then take those sections and ground those to a common point.
You mention shields from the cables. Connect the shield to amp ground at one end only.
If you are getting hum (60 or 120 hz,) move the grounds around to find the quietest location, but i suspect the original grounding scheme will be the best.
Hiss is a function of gain, parts quality and current flow.
If you are getting excessive hiss, it is most likely caused by the amount of gain you are asking the circuit to produce or noisy tubes.
Those old carbon comp resistors will add significant hiss as well.


----------



## glideon2 (9 mo ago)

dtsaudio said:


> I'm not entirely sure what you are asking. But comon ground practice is to ground all the power supply caps to the same point. Google star grounding. That is usually not practical in a large chassis, so what Fender and others do is to ground sections, and then take those sections and ground those to a common point.
> You mention shields from the cables. Connect the shield to amp ground at one end only.
> If you are getting hum (60 or 120 hz,) move the grounds around to find the quietest location, but i suspect the original grounding scheme will be the best.
> Hiss is a function of gain, parts quality and current flow.
> ...


Firstly, thanks for the detailed reply and I'd be happy to clarify:



The amp is far from stock. Mods include:


Shielded/grounded input cable to V1.

Split cathodes (1.5k/8uf --- 3.3k/.68uf).

270k Plate on V1b Bright channel.

.033 normal channel coupling.

.0047uf bright channel coupling.

Cascade mode on DPDT switch, added 270k stability resistor to keep from oscillating.

33k/500pf treble peaker circuit.

.68 boost cap on V2b cathode (push/pull engaged on a Peavey 50k mid pot).

Type 3 PPIV Master Volume (sheilded).

50k NFB.

500pf/470k fixed resonance.

50k pot/25k bias circuit for power tubes.

IEC Grounded Power Cord.

1k 5w screen grid resistors.

F&T Filter Caps 50/50 all around (paralleled to 100uf for mains.

Almost all resistors save for the PI section replaced with Metal Oxide.



It's fairly hissy and there's some mild hum.

It's the same plugged into any outlet in any building.

It was quieter before the mods but didn't sound as clear and as rich before.

You are correct in that Filter Cap grounds (especially mains) should be as close to the Power Transformer or HT ground as possible. But they are at the other end of amp near the input.

I just finished with the shielded wiring at input and had to make new ground, but in pace of where Screen and PI Cap Can was grounded at one of the clamp lugs.

So I based on historic advice about grounding neat HT/PT, I used some leftover 22awg Gavitt wire and made leads approx 11 inches away to one of the PT lugs, literally an inch away from HT soldered to chassis ground see pic). Fender seemed to pull it off, why not me?

Multimeter says grounds are all good and she's ready to fire up, however what concerns me is:

Is the cap ground wire guage too small/leads too long?

Or should I just ground back to the Preamp/Jack area and call it a day?


----------



## dtsaudio (Apr 15, 2009)

22ga is pretty light. I would ground it back toward the input jack, or possibly the first filter cap.
You've added a ton of gain, there's your hiss, but you may also be getting induced hum that is being picked up by the high gain circuit.


----------



## 2N1305 (Nov 2, 2009)

I do believe that dtsaudio is right. Try that and see what happens. I also heard that lead dressing is important and has been the cause of many amplifier noise problems. For this I recommend reading the following from geofex: lead dressing

One thing though: May I ask, as a matter of curiosity: May I ask what those two white alligator clip bodies are doing near the second stage?


----------



## Alan Small (Dec 30, 2019)

Maybe not in your plans but may assist.....change heater supply to DC


----------



## glideon2 (9 mo ago)

That's testing out a 470k resistor in parallel with the Resonance cap. It extends the low-mid punch a bit. I like it so far, but I'm always experimenting with values


----------



## glideon2 (9 mo ago)

Alan Small said:


> Maybe not in your plans but may assist.....change heater supply to DC


Nope, not going to add DC heaters. Not enough room and too complex to implement.


----------



## Paul Running (Apr 12, 2020)

glideon2 said:


> There is an empty socket where earlier models had tube rectifiers, but it is a little to small to accommodate a cap can unfortunately.


Why don't you file-out the hole to accommodate the filter cap?


----------



## glideon2 (9 mo ago)

Paul Running said:


> Why don't you file-out the hole to accommodate the filter cap?


For one, the chassis is warped inwards so any tall cap can will lean into and potentially rest on the Power Transformer which already runs warm.

Also, by principle I don't begin dremeling or drilling any performing any permanent modification unless absolutely necessary - save for the Power Plug socket which was already previously hacked at by prior owner, so that was easily shaped into a slot big enough for an IEC power socket where an ordinary power cord would be hanging loose.

I might be okay with a shorter standard F&T 50/50 can as a Mains there which is Power Tube socket sized.

But there's room inside for the Giant CE Cap Cap in between turret board and pots, would just have to fashion a mount from one of the existing Transformer bolts.


----------



## glideon2 (9 mo ago)

Went ahead and wired it up, went surprisingly well and looks, feels legit. Haven't turned it on yet because I realized something...

I used my older CE Cap Can which I think I purchased sometime in 2011 making it *11 years old*. It's been in a cool dry, place in a tupperware bin with other misc caps and components and the readings are...somewhat high, but it looks virtually mint and identical to the newer can I just purchased.

I think it will be fine as it's as robust a cap as humanly made these days (made in the USA).


















Reading for Mains: 116uf (80+20 on can, paralleled with 100k bleeder to ground)










Reading for screen: 53uf (40uf on can)










Reading for PI/Phase Inv: 51uf (30uf on can)

Screen and PI have 4.7k between them on the board as well as the Screen grid resistors. That's how it came and I felt no need to change the layout.


----------



## glideon2 (9 mo ago)

Bump


----------



## glideon2 (9 mo ago)

10 year old cap, tuned it on.

Not a single issue.

Sounds simultaneously tighter and squishing than before. And quieter!

Success!


----------



## Whammer Jammer (Sep 7, 2019)

Latole said:


> There is on DC voltage on filter caps no AC
> It is the AC produce hum


You mention "conventional wisdom" this and "historic advice" that, but that's all the wisdom you need.


----------



## glideon2 (9 mo ago)

Whammer Jammer said:


> You mention "conventional wisdom" this and "historic advice" that, but that's all the wisdom you need.


Then why bother commenting?


----------

