Introductions and scratch 2204 build

[RocketRob]

Hey guys,

Just wanted to say hi and introduce myself. Long time lurker, first time poster so be gentile.
After building the odd effect pedal, and an AX84 amp quite some time ago, I started to prepare for my next build. Priorities shifted slightly and free time became harder to come by, so the project was put on hold.

Well, my eldest son who is now eight has taken up the guitar in a big way, and has got me back into the swing of it, and gave me the motivation to get the build done.

It's a straight 2204 build, I was following the BillyBatz layout and incorporating SDM's grounding scheme. I've used JJ filter caps & tubes, Mallory 150 caps and CF resistors. Chassis was bent by a local shop for me, I did the drilling, board and plates were also home made. This was my first attempt at engraving a plate this big, and as you can see the back came out a bit funky (cut speed was way too fast), and there was some bleeding of the back fill on the front. I will probably redo them later on but they'll suffice for now.

Haven't given it a proper run yet, so I'm still listening to it. I do think the bass may need a little tightening up, and although there's a slight hum when dimed, I think there's too much hiss. Take out V1 or plug into the low input and she's quiet as a mouse, have checked the caps, and grid wires, I haven't yet looked at the resistors.

Let me know what you guys think, any suggestions would be much appreciated. I'm sure there's room for improvement and much to learn.







So from here, I'll build it a cabinet, try quiet it down a little, and voice it. Then start on the next build... I've actually got some F&T and sozo caps I bought from the metroamp store many moons ago which I think will be going into a plexi build.

Thanks for looking
Robert

[AJW]

Congratulations on the build, and high marks for doing your own chassis and panel fabrication! I'm not familiar with SDM's ground scheme, but I am familiar with his awesome layouts and effects loop. I used the "Larry" ground scheme on my 2203, and I think it is very quiet. Here is a link that contains the method: http://forum.metroamp.com/viewtopic.php ... 0&start=15" onclick="window.open(this.href);return false;

[neikeel]

Excellent proper 'scratch' build, impressive to do the panels too!

What next?

[RussB]

Very nice!

[OnTheFritz]

Great job, those panels look awesome!

[RocketRob]

Thanks for the kind words guys, seeing all thet awesome builds on this forum is definatly humbling, your compliments are much appreciated.

Thanks for the suggestion AJW. I basiclly followed the grounding on SDM's Silver Jub layout. In particular he runs the pot bus above the pots, and ties them all (except for the presence) along with the input, V1 cathode, and first filter cap to that cap's bracket bolt.

And as it happens, since I made the post I've changed the grounding more towards Larry's grounding scheme.
- V1 cathode and input moved to its own point.
- The bus running along the pot's has been split and the Vol pots grounded at point 2. This I have left on the cap bracket bolt under the board.
- Tone stack and PI to a third point along, and bias to point 4 all except the one exception along the front of the chassis.

All relatively simple changes, and I have to say it's SOOOO much quieter. Hum is noticeably better ( Heh, shows what I know, I didn't think it was too bad to begin with ). And to my ears at least, it seems the hiss has also been reduced noticeably! So given the results so far, I think I have to take the time to move it all over to Larry's scheme. It'll be interesting to see how much of a difference it will make from here.

So next, I was thinking of doing a 2204/1987 switching type setup on this one but I figured it'd be more fun to build another.
So with some Sozo's, F&T's, and CC resistors in the kit already I think I'll look into some Marstran or Metro/Heyboer iron and go for a 1987. Would be interested in any opinions here.

Thanks again guys,
Robert

[demonufo]

Nice.

How closely did you follow Billy's scheme? I only ask because it was incomplete.

Obviously you've discovered the missing tonestack wires, and NFB lead, but there was also a missing link wire across the input jacks, and really, the bias wiring should be changed on the standby switch imo. But I dare say you've done all this. Looks like you've done your homework.

[vanhalen5150]

The Larry ground works great.

Or as I call it, La Ground.

[RocketRob]

That's a good point Demonufo, particularly if anyone watching is planning on using the layout.

After going over the schematic and layouts I did adjust where necessary.

As you point out,
- the input jacks were missing a connection between the two jacks,
- the tone stack was missing two connections to the treble pot,
- and the NFB wire to the output ohm selector was missing.

Easy enough to fill the gaps. I also added the 5k6 grid stoppers on the power tubes.

I assume by changing the bias wiring you're suggesting running a connection directly to the diodes rather than the switch? Would save running that length of wire to the switch, will look at that when I re-visit the grounding.

I think I'll also try tidy up the wiring around the PT and filter caps a little... I'm not entirely happy with that area.


Thanks for looking guys...
Robert

[demonufo]

No, running the bias supply to the diodes is still unswitched. It needs to be directly to the secondaries on the other side of the standby, ideally.

[RocketRob]

Ah, OK.

I did a little research and found what you mean. Bias supply should be on the "hot" side of the standby switch so that the bias is present before the switch is thrown and the HT hits the plates. So the tubes are spared an inrush of current.

Thanks for that one, I'll defiantly change that.

Robert