The PI Tube Matters!

[s2]

"S2, you have convinced me to switch to a star ground...can you describe your strategy?"

Well... It would be easier to show you...

One of the biggest complaints about star grounds is they are messy. If you look through my gallery, you will see it can be done neatly. Most of those amps have star grounds.

Essentially, I make 2 stars--one for the high current grounds (power amp) and one for the lower current grounds (preamp). I locate those several inches away from each other.

Power Amp Star - This chassis ground point is located near the PT and gets all the center taps from the PT, the cap can ground, and the cathode ground of the EL84s. This keeps all the high current grounds together and away from the sensitive preamp grounds, which helps keep things quiet.

Preamp Star - This chassis ground ends up with about 10 wires running to it in a full-blown 18 Watt.

I ground each set of input jacks together and run a single wire to the star for each set.

The volume and tone of each channel also contribute one wire (run the bleeder cap off the tone over to the volume then use one ground wire from there). I've found you can generally jump the pot grounds together on the TMB and use one ground wire for all of them.

On the board, I run a dedicated wire for each of the higher current grounds which are filter caps and 12AX7 cathodes. For the lower current grounds like signal bleeders, I try to tie to the nearest higher current ground.

If I look at the Tsunami board, I see 6 ground wires plus 4 from the jacks and pots = 10 total wires. Starting at the left side of the board, that is one for the filter cap plus the driver ground, one for the PI ground, one for the second filter cap plus the voltage divider, one for the cathode follower's cathode, one for V1's second triode plus the tone stack bleeder, and one for V1's first triode. When you tie grounds together, run the wire to the higher current of the two and let the other one just be kinda parasitic.

That's about it. I think it is actually easier than buss ground and is more consistent--at least for me.

[s2]

Here is a pic of a build I just finished using a star ground scheme.

[NitroLiq]

S2,

Thanks for posting the link. I'm going to do a bit of studying between yours and Nik's layout this weekend.

Pete

[MooreCowbelle]

S2 - awesome description! Thanks.

Now all I need are those sweet S2 trannies, and I'll be all set...

[s2]

S2 - awesome description! Thanks. 8)

Now all I need are those sweet S2 trannies, and I'll be all set...

You're welcome. I have trannies in stock whenever you are ready :)

[MooreCowbelle]

S2 - well, I ordered them a couple of weeks ago, so I HOPE they are already on their way...

[s2]

S2 - well, I ordered them a couple of weeks ago, so I HOPE they are already on their way... 8O

Well, isn't this a little more than embarrassing?! Hi Dale! You are boxed up and ready to go! I just didn't realize who you were before! Now that I have your secret identity, I can stalk you properly!!!

[MooreCowbelle]

YIKES!!!

A stalker with mad amp skylz...well, I guess it could be worse.

[bitsandvolts]

Correct me if I'm wrong but from my research EVERY tube matters in distinguishing the final sound of the amp. Even the rectifier....

After completing my Ghia build this afternoon, I'm inclined to agree with you about the recto.

This amp used to be an 18lite...with a copper cap.....just prior to the amp being converted to a Ghia....I tried a real ez81...I couldn't hear a shred of difference between the two...but I could feel the difference. I haven't changed my opinion after playing this ghia-clone with the 5y3GT.

Sorta like the difference between playing a POD and playing the real thing, but certainaly not as drastic.

The recto *does* make a difference...and I discovered that this week.


Ironically, putting the ez81 into my 18watt lite is what actually sealed its fate in being converted to a Carmen Ghia. I loved the sound of the 18 with the real tube recto, that I have decided to build a TMB...so the lite chassis (which really looked more like a Z anyway) got the heave ho...