Yet another 124 build

[dbharris]

I ordered the wire in my last build from here:

https://www.mcmaster.com/products/wire/wire-7/

Lots of options and it the quality was very good. I used 20Awg solid throughout except for the power tube heaters as Stephen noted at 18 awg.

-Dan

[GAStan]

I ordered the wire in my last build from here:

https://www.mcmaster.com/products/wire/wire-7/

Lots of options and it the quality was very good. I used 20Awg solid throughout except for the power tube heaters as Stephen noted at 18 awg.

-Dan

Thanks Dan. Ironically I order tools and hardware from McMaster at work fairly often but simply did not think of them for this small of wire. If I hadn't just bought what I need for this build I would order this, will definitely keep in mind for next build.

[GAStan]

Okay, the words stick in my throat, but you can find AWG20 solid core online at Ama-Satan's-Butthole-zon. You can get away with PVC sleeved solid core rated to 300V at a pinch, but 600V rated or higher is better. I'm in Europe so the supply chain is very different here, but here's an example of what is available (there are more if you dig into the site deeper): https://modulusamplification.com/cable- ... 2936-p.asp Teflon coated is not necessary except perhaps in shielded cable especially where the shielding is being soldered directly to the back of pots.

Lead dress is just much easier to control with solid core. I consider solid core especially important in the heater circuit even though the leads coming off the PT are most likely stranded. Solid core AWG18 if you can get it to fit in the sockets, can be used throughout. If your noval sockets won't permit that diameter though, you can use a AWG20 solid core on the preamp sockets; AWG18 on the power section, AWG20 on the preamp section.

The reason being a tendency for ringing or oscillation in the AC driven heater circuit. A possible source of noise you want to avoid if possible.

The ideal, silver plated AWG20 solid core, for the signal wires is more about creating a good solid lead dress. It matters

I looked on Amazon for quite some time and did not find anything I'm willing to put in my amp. Ebay as well.

The topcoat wire I got is fully tinned and bends and holds its shape like solid core, and has pvc insulation. Teflon would be acceptable but I prefer to avoid silicone.

18 AWG is what I do plan on using for heaters. Stranded is what I've got, I'm confident I can make it work. The holes in the novel socket terminals are oval shaped so the stranded will hopefully conform better but I'll find out for sure when the task is upon me.

I know what you're saying with the silicon type, I prefer PVC as well.

You might try this:
https://www.amazon.com/Silicone-Electri ... =8-24&th=1

If you are using stranded cable for the heaters my advice is to twist it tight. I've used ordinary household copper core stranded in the past and as long as you twist it so that it's very tight (almost solid) it shouldn't give you any problems. A tip though, when you come to do the noval sockets you might be tempted to tin it before you try soldering it into the noval ovals - it's a lot easier if you don't but you have to be especially careful you don't have any stray strands creating a short with the neighbouring pins.

Stephen, I didn't say it before but thank you for your suggestions. Even if I do not follow them I do appreciate them.

After a lifetime of working in the electronics and electrical fields I'm familiar with stray strands or "whiskers" as we commonly call them. Trust me, you don't want to be anywhere near 1KV industrial 3 phase when it gets energized if it has a whisker.

[Stephen1966]

I looked on Amazon for quite some time and did not find anything I'm willing to put in my amp. Ebay as well.

The topcoat wire I got is fully tinned and bends and holds its shape like solid core, and has pvc insulation. Teflon would be acceptable but I prefer to avoid silicone.

18 AWG is what I do plan on using for heaters. Stranded is what I've got, I'm confident I can make it work. The holes in the novel socket terminals are oval shaped so the stranded will hopefully conform better but I'll find out for sure when the task is upon me.

I know what you're saying with the silicon type, I prefer PVC as well.

You might try this:
https://www.amazon.com/Silicone-Electri ... =8-24&th=1

If you are using stranded cable for the heaters my advice is to twist it tight. I've used ordinary household copper core stranded in the past and as long as you twist it so that it's very tight (almost solid) it shouldn't give you any problems. A tip though, when you come to do the noval sockets you might be tempted to tin it before you try soldering it into the noval ovals - it's a lot easier if you don't but you have to be especially careful you don't have any stray strands creating a short with the neighbouring pins.

Stephen, I didn't say it before but thank you for your suggestions. Even if I do not follow them I do appreciate them.

After a lifetime of working in the electronics and electrical fields I'm familiar with stray strands or "whiskers" as we commonly call them. Trust me, you don't want to be anywhere near 1KV industrial 3 phase when it gets energized if it has a whisker.

Much appreciated. It's an open forum and this is a detail that isn't often discussed, so it's all good. I remember what it's like the first time you start building something like this, not that it's necessarily your first, but it will be somebody's. The Devil truly is in the detail with these amps.

[jabguit]

Doesn't pass signal, just makes crackling noises...

[GAStan]

Have been looking at the #124 photos quite a bit. I noticed the cathode resistors on V1 and V2 look different between the two halves of each tube. The hand drawn notes clearly show that all are 1k5 value, but why the different types of resistors?

[ijedouglas]

Have been looking at the #124 photos quite a bit. I noticed the cathode resistors on V1 and V2 look different between the two halves of each tube. The hand drawn notes clearly show that all are 1k5 value, but why the different types of resistors?

Different resistors, different tone

[GAStan]

Have been looking at the #124 photos quite a bit. I noticed the cathode resistors on V1 and V2 look different between the two halves of each tube. The hand drawn notes clearly show that all are 1k5 value, but why the different types of resistors?

Different resistors, different tone

Makes sense

[GAStan]

Looking through the notes in the pics & schematics by IC-Racer and Odourboy, there are some differences. One I am trying to decide on is the 470 ohm resistors on B+2 to power tubes.

Difference is wattage rating, 2W or 5W. I ordered both, 2W Carbon Film and 5W wire wound. The pictures appear to show Carbon Film but I could be wrong.

Will resistor type affect tone in this position? If so would the 2W be adequate?

I looked at several spec sheets for 6L6 tubes and the max G2 current I could find was 8mA. 8mA through 470 ohms results in .03 watts. Is there something I am missing? 65 mA (@30 Volts) would be required for 2 watts, is there going to be a time when the tube draws this much without damage?

[erwin_ve]

Looking through the notes in the pics & schematics by IC-Racer and Odourboy, there are some differences. One I am trying to decide on is the 470 ohm resistors on B+2 to power tubes.

Difference is wattage rating, 2W or 5W. I ordered both, 2W Carbon Film and 5W wire wound. The pictures appear to show Carbon Film but I could be wrong.

Will resistor type affect tone in this position? If so would the 2W be adequate?

I looked at several spec sheets for 6L6 tubes and the max G2 current I could find was 8mA. 8mA through 470 ohms results in .03 watts. Is there something I am missing? 65 mA (@30 Volts) would be required for 2 watts, is there going to be a time when the tube draws this much without damage?

The #124 has Dale CW5 470R resistor in that spot. Usually high wattage resisitors have specs that can handle large voltage swings and high turn-on voltage surges.

[GAStan]

Looking through the notes in the pics & schematics by IC-Racer and Odourboy, there are some differences. One I am trying to decide on is the 470 ohm resistors on B+2 to power tubes.

Difference is wattage rating, 2W or 5W. I ordered both, 2W Carbon Film and 5W wire wound. The pictures appear to show Carbon Film but I could be wrong.

Will resistor type affect tone in this position? If so would the 2W be adequate?

I looked at several spec sheets for 6L6 tubes and the max G2 current I could find was 8mA. 8mA through 470 ohms results in .03 watts. Is there something I am missing? 65 mA (@30 Volts) would be required for 2 watts, is there going to be a time when the tube draws this much without damage?

The #124 has Dale CW5 470R resistor in that spot. Usually high wattage resisitors have specs that can handle large voltage swings and high turn-on voltage surges.

Once again, Thank You Erwin!

As luck would have it the wirewound 5W I have are Vishay/Dale RS5 470R. 1% tolerance vs 5% for CW5, other specs very similar so I will use them. Appearance is very different. Both have short term overload rating of 10x rated voltage (48 volts) for 5 seconds. 2W of same types have only 4x rated voltage (30 volts) for 5 seconds.

I believe I'll put in the 5W.

[alberto.chanfreau]

Hey, Glenn (fyi, response to your earlier Q on wiring, if still in need):
If you are based in the US, for cables/wires, did you look at MojoTone.com?
FYI, more dedicated/focused than Ebay or Amazon, in their case for amp builds, repairs, components and kits, Mojo currently offers ~40 different types of wires, incl. the 18AWG bus bar (all sold by the feet or multiples, which is very convenient!) under their section Amp Shop => Electronics => Wire

(side/background comment: I've just started my first build for a #124... whereas other colleagues may bring -or have already brought- some more experience in here. Hope mine may help, if still in need. Greetings from Buenos Aires! =)

[ijedouglas]

Looking through the notes in the pics & schematics by IC-Racer and Odourboy, there are some differences. One I am trying to decide on is the 470 ohm resistors on B+2 to power tubes.

Difference is wattage rating, 2W or 5W. I ordered both, 2W Carbon Film and 5W wire wound. The pictures appear to show Carbon Film but I could be wrong.

Will resistor type affect tone in this position? If so would the 2W be adequate?

I looked at several spec sheets for 6L6 tubes and the max G2 current I could find was 8mA. 8mA through 470 ohms results in .03 watts. Is there something I am missing? 65 mA (@30 Volts) would be required for 2 watts, is there going to be a time when the tube draws this much without damage?

The #124 has Dale CW5 470R resistor in that spot. Usually high wattage resisitors have specs that can handle large voltage swings and high turn-on voltage surges.

I think #0124 has Sprague Q-Line 470R 2W in that spot

[erwin_ve]

Looking through the notes in the pics & schematics by IC-Racer and Odourboy, there are some differences. One I am trying to decide on is the 470 ohm resistors on B+2 to power tubes.

Difference is wattage rating, 2W or 5W. I ordered both, 2W Carbon Film and 5W wire wound. The pictures appear to show Carbon Film but I could be wrong.

Will resistor type affect tone in this position? If so would the 2W be adequate?

I looked at several spec sheets for 6L6 tubes and the max G2 current I could find was 8mA. 8mA through 470 ohms results in .03 watts. Is there something I am missing? 65 mA (@30 Volts) would be required for 2 watts, is there going to be a time when the tube draws this much without damage?

The #124 has Dale CW5 470R resistor in that spot. Usually high wattage resisitors have specs that can handle large voltage swings and high turn-on voltage surges.

I think #0124 has Sprague Q-Line 470R 2W in that spot

You're right, my mind is playing tricks....Might have seen it in a other Dumble. Edit: they are in #102

[GAStan]

Hey, Glenn (fyi, response to your earlier Q on wiring, if still in need):
If you are based in the US, for cables/wires, did you look at MojoTone.com?
FYI, more dedicated/focused than Ebay or Amazon, in their case for amp builds, repairs, components and kits, Mojo currently offers ~40 different types of wires, incl. the 18AWG bus bar (all sold by the feet or multiples, which is very convenient!) under their section Amp Shop => Electronics => Wire

(side/background comment: I've just started my first build for a #124... whereas other colleagues may bring -or have already brought- some more experience in here. Hope mine may help, if still in need. Greetings from Buenos Aires! =)

Hello Alberto,

Thank you for taking the time to comment on my post and make this suggestion.

I am familiar with Mojo Tone. I ordered the transformers for this build from them. I also ordered my wire from them. The wire is decent quality, not great. The pvc insulation is thick but melts easily when soldering.

MojoTone does have great customer service. When they sent an incorrect part they had a replacement in the mail 2 hours after I contacted them.