Metropoulos Forum

So, I have ordered the 50 kit and await for its arrival.
I do have a couple of questions:

1. What steps can I take during the build to keep the amp as noise free as possible?
2. I have seen on some Clone amp sites a red coating on the solder connections, any idea what this is? Insulation of some sort to keep noise down? Must be a pain to rework.
3. Still need to pick up a higher watt iron as my is only 15 watts, any suggestions?
4. Has anyone done the soldering on their stove and use the hood as a fume hood? I am the only one in my house so not a problem for me to take over the kitchen. Plus I can sit on a stool or stand and have the amp at a good level.
5. How many hours to do a complete build, not days, but average hours? I have worked as Field Service Engineer, working on Semiconductor Equipment, thus I have experience with wiring, routing wires...components...and such.
6. I saw a jig to hold the amp somewhere on this site. Does anyone have drawings to make this jig?
7. Still haven't decided on where to mount the PPIMV. Will the length of the wires be a source of noise?
8. Why do some builders use the Bradley CC resistors as opposed to the standard resistors in the kit?

Sorry for so many questions, I just want to get a running start before my kit arrives. Any other suggestions would be great.
Thanks,
Guy

I do have a couple of questions:

This is far more than a "couple" of questions...sorry, just calling a spade a spade. lol jk

1. What steps can I take during the build to keep the amp as noise free as possible?

Ground the rectifier circuit as close to the fliter caps as possible. Don't make the mistake of grounding it to the back of the pots (huge ground loop...been there, done that). Another thing you can do is join all the circuit grounds together, then ground them to one spot on the chassis while grounding the mains ground to another spot on the chassis, thereby making it so there are only two chassis grounds. This is known as a "star" or "spider" ground system and virtually eliminates any possible ground loops.

Also another trick I do is pick the wire up that runs from the 470K mixer resistor to pin 2 of V2 off the chassis and keep it as far away from the chassis as possible.

2. I have seen on some Clone amp sites a red coating on the solder connections, any idea what this is? Insulation of some sort to keep noise down? Must be a pain to rework.

I've seen it too, but not sure what it is myself. Don't think it has anything to do with noise (I think it's more like an anti-corrosive or something).

3. Still need to pick up a higher watt iron as my is only 15 watts, any suggestions?

The Weller WLC-100 soldering station is a relatively inexpensive soldering station with adjustable temperature. Power is adjustable from 0-45 watts. Comes with a sponge and a nice tip and works quite well.

4. Has anyone done the soldering on their stove and use the hood as a fume hood? I am the only one in my house so not
a problem for me to take over the kitchen. Plus I can sit on a stool or stand and have the amp at a good level.

Fumes for me were never a problem so never saw a need for a fume hood.

5. How many hours to do a complete build, not days, but average hours? I have worked as Field Service Engineer, working on Semiconductor Equipment, thus I have experience with wiring, routing wires...components...and such.

I've done a complete build in about 10-12 hours...I'm sure there are some on here who can do it quicker whereas others take their sweet time. It's not a race...quality definitely matters here.

6. I saw a jig to hold the amp somewhere on this site. Does anyone have drawings to make this jig?

These heads believe it or not sit upside down on their transformers quite well...not like a Fender.

7. Still haven't decided on where to mount the PPIMV. Will the length of the wires be a source of noise?

No because the PPIMV is working with two signals that are out of phase with each other, so any noise here will get cancelled out.

8. Why do some builders use the Bradley CC resistors as opposed to the standard resistors in the kit?

Tonal preferences.

Sorry for so many questions, I just want to get a running start before my kit arrives. Any other suggestions would be great.
Thanks,
Guy

Keep the questions coming! We enjoy answering them. Lookin' forward to the progress and hearing the final build.

flemingmras wrote:I do have a couple of questions:

This is far more than a "couple" of questions...sorry, just calling a spade a spade. lol jk

1. What steps can I take during the build to keep the amp as noise free as possible?

Ground the rectifier circuit as close to the fliter caps as possible. Don't make the mistake of grounding it to the back of the pots (huge ground loop...been there, done that). Another thing you can do is join all the circuit grounds together, then ground them to one spot on the chassis while grounding the mains ground to another spot on the chassis, thereby making it so there are only two chassis grounds. This is known as a "star" or "spider" ground system and virtually eliminates any possible ground loops.

Also another trick I do is pick the wire up that runs from the 470K mixer resistor to pin 2 of V2 off the chassis and keep it as far away from the chassis as possible.

2. I have seen on some Clone amp sites a red coating on the solder connections, any idea what this is? Insulation of some sort to keep noise down? Must be a pain to rework.

I've seen it too, but not sure what it is myself. Don't think it has anything to do with noise (I think it's more like an anti-corrosive or something).

3. Still need to pick up a higher watt iron as my is only 15 watts, any suggestions?

The Weller WLC-100 soldering station is a relatively inexpensive soldering station with adjustable temperature. Power is adjustable from 0-45 watts. Comes with a sponge and a nice tip and works quite well.

4. Has anyone done the soldering on their stove and use the hood as a fume hood? I am the only one in my house so not
a problem for me to take over the kitchen. Plus I can sit on a stool or stand and have the amp at a good level.

Fumes for me were never a problem so never saw a need for a fume hood.

5. How many hours to do a complete build, not days, but average hours? I have worked as Field Service Engineer, working on Semiconductor Equipment, thus I have experience with wiring, routing wires...components...and such.

I've done a complete build in about 10-12 hours...I'm sure there are some on here who can do it quicker whereas others take their sweet time. It's not a race...quality definitely matters here.

6. I saw a jig to hold the amp somewhere on this site. Does anyone have drawings to make this jig?

These heads believe it or not sit upside down on their transformers quite well...not like a Fender.

7. Still haven't decided on where to mount the PPIMV. Will the length of the wires be a source of noise?

No because the PPIMV is working with two signals that are out of phase with each other, so any noise here will get cancelled out.

8. Why do some builders use the Bradley CC resistors as opposed to the standard resistors in the kit?

Tonal preferences.

Sorry for so many questions, I just want to get a running start before my kit arrives. Any other suggestions would be great.
Thanks,
Guy

Keep the questions coming! We enjoy answering them. Lookin' forward to the progress and hearing the final build.

Hey another CA guy. Thanks for the help. Great reply to my questions.

Another question
1a. Is there a picture of the "Spider" ground (I will search but if someone knows where it is then great).

gitman59 wrote:

flemingmras wrote:I do have a couple of questions:

This is far more than a "couple" of questions...sorry, just calling a spade a spade. lol jk

1. What steps can I take during the build to keep the amp as noise free as possible?

Ground the rectifier circuit as close to the fliter caps as possible. Don't make the mistake of grounding it to the back of the pots (huge ground loop...been there, done that). Another thing you can do is join all the circuit grounds together, then ground them to one spot on the chassis while grounding the mains ground to another spot on the chassis, thereby making it so there are only two chassis grounds. This is known as a "star" or "spider" ground system and virtually eliminates any possible ground loops.

Also another trick I do is pick the wire up that runs from the 470K mixer resistor to pin 2 of V2 off the chassis and keep it as far away from the chassis as possible.

2. I have seen on some Clone amp sites a red coating on the solder connections, any idea what this is? Insulation of some sort to keep noise down? Must be a pain to rework.

I've seen it too, but not sure what it is myself. Don't think it has anything to do with noise (I think it's more like an anti-corrosive or something).

3. Still need to pick up a higher watt iron as my is only 15 watts, any suggestions?

The Weller WLC-100 soldering station is a relatively inexpensive soldering station with adjustable temperature. Power is adjustable from 0-45 watts. Comes with a sponge and a nice tip and works quite well.

4. Has anyone done the soldering on their stove and use the hood as a fume hood? I am the only one in my house so not
a problem for me to take over the kitchen. Plus I can sit on a stool or stand and have the amp at a good level.

Fumes for me were never a problem so never saw a need for a fume hood.

5. How many hours to do a complete build, not days, but average hours? I have worked as Field Service Engineer, working on Semiconductor Equipment, thus I have experience with wiring, routing wires...components...and such.

I've done a complete build in about 10-12 hours...I'm sure there are some on here who can do it quicker whereas others take their sweet time. It's not a race...quality definitely matters here.

6. I saw a jig to hold the amp somewhere on this site. Does anyone have drawings to make this jig?

These heads believe it or not sit upside down on their transformers quite well...not like a Fender.

7. Still haven't decided on where to mount the PPIMV. Will the length of the wires be a source of noise?

No because the PPIMV is working with two signals that are out of phase with each other, so any noise here will get cancelled out.

8. Why do some builders use the Bradley CC resistors as opposed to the standard resistors in the kit?

Tonal preferences.

Sorry for so many questions, I just want to get a running start before my kit arrives. Any other suggestions would be great.
Thanks,
Guy

Keep the questions coming! We enjoy answering them. Lookin' forward to the progress and hearing the final build.

Hey another CA guy. Thanks for the help. Great reply to my questions.

Another question
1a. Is there a picture of the "Spider" ground (I will search but if someone knows where it is then great).

It's just called a spider ground because all the ground wires in the amp all ground to the same spot on the chassis, which makes it look like a "spider" with many legs.

BTW you're in Livermore. I boat at the delta all the time (store my boat at Orwood Resort in Brentwood).

1) If you follow the layout for your amp, plus look at pictures of other nice builds your amp should be about as noise free as possible.
There are tricks to lead dressing and knowing what wires are critical and what wires to keep away from other wires is a matter of experience.
The tube grids (inputs) for example are pretty sensitive so they need to be run down close to the chassis floor with other wires kept away from them as much as is practical.
Heater wires of course are ac voltage and as such have 60 Hz current on them.
This 60 Hz noise can find it's way into the signal chain if you aren't careful about the way your route the heater wires.
That is the main reason for tightly twisting the heater wires, to cancel out the hum.

2) the red coating you see on solder joints is a holdover from the military wiring style.

Originally it might have been to coat the solder to prevent corrosion.
And then red loctite on the nuts to prevent them from vibrating loose.

Nowadays I like to use a red Sharpie when I am troubleshooting an amp.

I go over each solder joint and inspect them.
Sometimes if the soldering isn't that great, I will re-flow all of the solder joints.
As I go along, I mark them red with the Sharpie to keep track of where I have been and I know if it is red it has been inspected and or touched up.

Plus it kind of gives a cool look to the amp.
Like I said, it's a military thing and a lot of the old school amp techs were trained in the military.

I haven't heard that grounding style called a spider before but it makes sense.
It is most commonly called star grounding.

Having just finished a successful JTM-45 build, I am glad I had spent ALOT of time on this forum reading through thread after thread. Use the Search function whenever a "what if" question arises.

Review the build pics on the site-if it looks good and neat-chance are it will be nice and QUIET.

It took me about 24 total hours-but I am disabled with spinal injuries and standing is tough at times-after 2 spinal fusions With your experience it should be fun. Take your time and double check everything!!