Express hum and noise.

leadfootdriver · Post by **leadfootdriver** » Thu Dec 08, 2011 3:19 am

How does everyone feel about the Express layout? I'm no designer, but I've read about layout, and star grounding; where you ground each 12ax7 with the related cap.

Has anyone used their own layout where the filter cap is laid out next to the plate and cathode staging? I did this with my 1st build, and had no noise issues at all.

Discuss.

M Fowler · Post by **M Fowler** » Thu Dec 08, 2011 3:30 am

Well then you would have built a Komet 60 not a TW Express

Yes I plan to completely rebuild my Liverpool to a better grounding scheme but one will still have a hard time with preamp tube hiss even with NOS.

Mark

Clyde · Post by **Clyde** » Thu Dec 08, 2011 3:57 am

How you use the real estate isn't important, but the electrical connections are. Whether you run wires to the caps or have them on the board shouldn't be an issue.

leadfootdriver · Post by **leadfootdriver** » Thu Dec 08, 2011 8:18 am

M Fowler wrote:Well then you would have built a Komet 60 not a TW Express

Yes I plan to completely rebuild my Liverpool to a better grounding scheme but one will still have a hard time with preamp tube hiss even with NOS.

Mark

I wonder how much of that noise is due to a lack of a grid stoppers.

I have the Wizards (Merlin Blencowe) preamp book, and he says that he usually uses a 33k grid blockers, but that 10k is usually good enough. He also says that you should put at least a 100R on the grids, and that it would be totally transparent. It makes sense to put something on the 1st stage at least, so noise isn't amplified thru the latter stages.

The 1st blocker on most Marshall designs that I've seen is 68k. You'd never say a Marshall is dull in the highend. You could add a 10k right at the tube socket of each stage (3), and still be under 68k.

I think the stock mounting of the tranny's looks cool, but it makes more sense to have the PT on 1 side and the OT on the other keeping in line with the signal path. This would make it easier to do a Wizard layout.

hans-jörg · Post by **hans-jörg** » Thu Dec 08, 2011 8:41 am

leadfootdriver wrote: I think the stock mounting of the tranny's looks cool, but it makes more sense to have the PT on 1 side and the OT on the other keeping in line with the signal path. This would make it easier to do a Wizard layout.

Hi,
thats exactly what I´m doing. You can keep the sec. of OT rearly short.
But one point is important: the location of V1. Not to blow in with the OT!

Hans-Jörg

leadfootdriver · Post by **leadfootdriver** » Thu Dec 08, 2011 12:58 pm

Clyde wrote:How you use the real estate isn't important, but the electrical connections are. Whether you run wires to the caps or have them on the board shouldn't be an issue.

I've read in my searches that some people have noise issues. Does the design lend itself to this, or is it the lack of construction techniques of the hobby builder?

I'm not trying to reinvent the wheel, but just thinking out loud here. I'm open to making things better if the can be.

I wish more people would chime in.

hans-jörg · Post by **hans-jörg** » Thu Dec 08, 2011 1:20 pm

Hi,
my opinion - to get a high gain amp noisless - is, as written in the wizzard book too, only ONE ground connection to chassis.
I made it with my first high gainer and it was quiet until volume max.!

BUT I built my Dumble clone whit a simmilar grounding schem like Liverpool/Express, and its quiet too

The next is: steel or aluchassis - a big different

I think we are hereby in the aerea: what sounds better: Schellack or CD?Breath or sterility, and- we talk about guitar amps, not HiFi high ender.
Giuitar amps should breath.
Sorry for my bubbles.
Just my 2cent

Hans-Jörg

leadfootdriver · Post by **leadfootdriver** » Sat Dec 10, 2011 3:26 pm

Here's a paper explaining the Multi Star Grounding System, courtesy of the Wizard!

http://valvewizard2.webs.com/Grounding.pdf

sdp1234 · Post by **sdp1234** » Sun Dec 11, 2011 8:17 pm

My rocket is pretty quiet. Just some hiss with the gains maxed and treble maxed. Does grounding impact hiss or only hum?

fishy · Post by **fishy** » Sun Dec 11, 2011 9:02 pm

It's good to experiment with layouts and ground schemes. You might be able to improve it somewhat but tubes do make a big difference in the Express and Liverpool from my limited experience. It took two years for me to be happy with my Express but it is pretty much stock. Everything matters.....

Using a grid stopper is a personal preference and I have tried them on the first stage. It does effect the feel of the amp more than anything else in my experience with lower values. The second stage benefits more which is what KF found but it is related more to controlling oscillations.
I did a Rocket based amp with distributed capacitance in the preamp, cap cans and some other variations and it came out great but the Rocket is extremely forgiving compared to the other TW amps.

The express can be a complete PITA but when hits on, it is ON!

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