Metropoulos Forum

Does anyone use shielded wire for the input jacks (like the 2203) to reduce noise? I know why it's used for the 2203, given the cascading gain stages, but was just wondering whether there would be any benefit for a 1987.

Cheers

Nope. Keep the wires from the board short and neat.

Arclight wrote:Nope.

Why - because there isn't enough gain to cause noise?

kdmay wrote:

Arclight wrote:Nope.

Why - because there isn't enough gain to cause noise?

Yes, IF you keep your lead dress short and neat. You can get more noise on a lower gain amp than this one with the same input setup with bad lead dress. If you build it like the instructions you should be fine.

Also it's important to pay attention to your lead dress on the wire from the vol mixer R junction to v2a's grid, that can give you a lot of noise if sloppy.

Keep the v1 & v2 grid wires elevated and away from the heater wires too.

Last, if you have the chassis out of the cab and think you have too much noise, put an aluminum oven pan or whatever over the open chassis as a shield.

This all from my experience building my 50..

Dave

elronhoover wrote:

kdmay wrote:

Arclight wrote:Nope.

Why - because there isn't enough gain to cause noise?

Yes, IF you keep your lead dress short and neat. You can get more noise on a lower gain amp than this one with the same input setup with bad lead dress. If you build it like the instructions you should be fine.

Also it's important to pay attention to your lead dress on the wire from the vol mixer R junction to v2a's grid, that can give you a lot of noise if sloppy.

Keep the v1 & v2 grid wires elevated and away from the heater wires too.

Last, if you have the chassis out of the cab and think you have too much noise, put an aluminum oven pan or whatever over the open chassis as a shield.

This all from my experience building my 50..

Dave

Good advice - thanks.

After playing it last night, the biggest issue re noise was the fact that the bare chassis was sitting on top of a 400w cab and susceptible to vibrations. Last night I had a standard Marshall cab with G12T-75s and moved the amp away from the cab and it made a massive difference. I also moved some wires around (e.g. making sure plate and grid wires were as far apart as possible). I was able to max out everything and not get any crazy noise. The presence is still a little touchy, so might check the dressing out again, but I've heard maxing out the presence at full volume is never going to be nice on a plexi. Not sure though.

When you say grid wires elevated, what do you mean. Actually physically raised? Sorry for my ignorance.

Will check out the vol mixer junction.

The oven pan is a winner! I thought about this (being exposed would create noise) and this is a great solution. My wife won't be happy though.....!

Anyway, thanks again and here are some clips and shots I've just posted.

http://forum.metroamp.com/viewtopic.php ... 42#p318742" onclick="window.open(this.href);return false;

kdmay wrote:
When you say grid wires elevated, what do you mean. Actually physically raised? Sorry for my ignorance.

Will check out the vol mixer junction.

The oven pan is a winner! I thought about this (being exposed would create noise) and this is a great solution. My wife won't be happy though.....!

RE. the grid wire elevation, yes, physically raised up off the chassis. I lift them up and come down to the tube pin connection kind of like an arc (I keep all socket wires in general as clear from each other as possbile using a 3D layout). Also, look under the board on the socket side and separate them from the plate & cathode wires as much as possible.

RE. the vol mixer junction, the slightest bit of baseline noise (i.e. when both vols are down) I have in mine I attribute to this grid wire (I can pull v1 and still have the baseline noise the amp has). Moving this wire just a bit can have a big difference on your noise level. Again, check under the board to make sure it's clear of other wires..I thought briefly of trying a shielded wire here, but the noise level is so low it's not even an issue.

RE. the oven pan, I noticed that this amp is more sensitive to not being fully shielded, and I reduced what was a 'I gotta fix this' niose level to practically nothing by just dropping a shield on. I keep one of those .99 throwaway oven liners under my bench for this purpose. Them's my kind of easy fixes; spend the .99, keep the wife happy (she's also gotta deal with this 50 blasting, remember!).

Saw your other post re. presence; if you mean the scratchy noise when you turn it, thats normal in this amp. I like it around 5 or so for both strats or gibs, I wouldn't dime it tho..

Enjoy your build, this is a hella great amp, loud as all git, but well worth it for that tone. It'll smooth up a bit as your caps break in, so just keep sawing away on it!

Dave