#183 5th Generation ODS Skyliner. Layout/Schematic discussion

[UltraHookedOnPhonix]

What gauge wire do amp builders generally use for the ground bus?

I use 16AWG in my builds. For what it's worth, I think it's the same gauge the D-man uses.

[donvan]

I use 16AWG in my builds. For what it's worth, I think it's the same gauge the D-man uses.

That is very helpful info. Thanks!
I also read somewhere that if the bus wire is copper you can tin it with soldier to prevent corrosion. Not sure if that is really necessary.

[sluckey]

I like using this pre tinned 16AWG copper bus...

https://www.ebay.com/itm/NEW-16-Gauge-T ... xyNo9Sq4X9

[donvan]

I like using this pre tinned 16AWG copper bus...

https://www.ebay.com/itm/NEW-16-Gauge-T ... xyNo9Sq4X9

Thanks for the tip. I just ordered a roll of this.

[donvan]

Can anyone help with a part number for a 50/100 watt switch - round hole type? I was using the 124 BOM from the files section for part numbers but it seems to have a mistake for the half power switch. It calls for a Carling 691-110-73 but that is a SPST.

I believe I need a DPDT that can handle the voltage and current of EL-34 cathodes and it needs to fit in a round hole since I have no means of making a square hole. What part do you all use?

Thanks,
Don

[pompeiisneaks]

Really almost any DPDT switch will work, as it's running at milliamps of current at sub 10 v readings. Most 4 power tube setups measure like maybe 200mA max in a bad situation for 6L6's (you'd have to check for other tubes) but cathode biased at say 400VDC they shouldn't exceed like 48mA for 100% diss. X4 is 200mA. Wattage rating then becomes 2 watts at the 'worst case I can think of' at 10v. Most times, I believe they sit more like 1 v so it would be .2 watts.

I'd suggest getting a second opinion, but something like this from alpha has up to 28VDC and 2A current rating:

https://www.mouser.com/ProductDetail/Ca ... g99lAqo%3d

I had one at home that was 2A I think and it was a pretty small switch, but I used it for mine with no problem. (some tubes may have more than 28V at the cathodes so be sure you match that value as well as the actual current to ensure the switch can take it.

~Phil

[donvan]

Thanks for the response Phil. I think the switch that you are suggesting will work fine.

[donvan]

It appears that it is common to use an electrolytic cap in the FET circuit for the RS bypass cap. Is that considered good practice? Since that capacitor affects frequency response I would think that an electrolytic would be avoided there. If it is good practice could someone explain why?

Thanks,
Don

[erwin_ve]

It appears that it is common to use an electrolytic cap in the FET circuit for the RS bypass cap. Is that considered good practice? Since that capacitor affects frequency response I would think that an electrolytic would be avoided there. If it is good practice could someone explain why?

Thanks,
Don

Rs bypass cap is similar to a Rk in a 12ax triode. Electrolytics can be used . Tantalum is a commonly used for this application(JFET).

[donvan]

Rs bypass cap is similar to a Rk in a 12ax triode. Electrolytics can be used . Tantalum is a commonly used for this application(JFET).

I'm glad I asked. Even though it's not in the direct signal path, I assumed that since this cap shaped the signal frequency response it shouldn't be tantalum or electrolytic whether it was Rk for a triode or Rs in a FET circuit.

Thanks for setting me straight on this!

Don

[donvan]

What type of cathode bypass electrolytic caps did Dumble use? Were they low ESR?