question on order of electronic components

glasshand · Tue Sep 07, 2021 7:30 am

I have what seems like a really simple question, but I'm not sure how to look up an answer. Imagine that you want to have a resistor going from a voltage to ground, and you want it to be switched so you can take it out of the circuit or not as you want. Is it better to arrange the components
voltage - resistor - switch - ground
or
voltage - switch - resistor - ground
?

I realize that mathematically, they're the same - the resistance is either the value of the resistor, or it's infinite because of the open path - but is there any "best practices" reason to do one or the other?

LancerTheGreat · Tue Sep 07, 2021 8:06 am

I think you'd go voltage > switch > one position has the resistor added|other position is no resistor > ground.

But I'm not for sure on this one, I haven't considered circuits for a while lol.

mozz · Tue Sep 07, 2021 9:45 am

Either is correct. If you are talking high voltage it may matter.

ID10t · Tue Sep 07, 2021 10:15 am

Always listen to @mozz and I agree with @LancerTheGreat. I'd go to Voltage-Switch-Resistor-Ground.

glasshand · Tue Sep 07, 2021 11:48 am

Thanks, all! A couple other people I talked to suggested that it was usually better to have the hot side switched, so that the component(s) are completely unpowered when the switch is off.

mozz · Tue Sep 07, 2021 5:43 pm

Is it running voltage through it or audio?

"Always listen to @mozz " Except when i live to be a hundred years old and get interviewed on TV. "So what's your secret to a long life?" "Well, i eat a pinecone everyday."

Tue Sep 07, 2021 5:48 pm

mozz wrote: ↑Tue Sep 07, 2021 5:43 pm Is it running voltage through it or audio?

"Always listen to @mozz " Except when i live to be a hundred years old and get interviewed on TV. "So what's your secret to a long life?" "Well, i eat a pinecone everyday."

Yep, what are we talking about? Voltage? Audio? RF? Digital?

glasshand · Wed Sep 08, 2021 7:29 am

This is for a power tube's bias resistor. The particular mod I'm looking at is https://robrobinette.com/Special6UltraM ... _Tube_Bias

mozz · Wed Sep 08, 2021 9:41 am

It doesn't matter but you might get a pop if you switch on the fly. If you're using it to bias another style tube no problems. What amp is it?

glasshand · Wed Sep 08, 2021 10:33 am

mozz wrote: ↑Wed Sep 08, 2021 9:41 am It doesn't matter but you might get a pop if you switch on the fly. If you're using it to bias another style tube no problems. What amp is it?

Can't really see why I would switch on the fly, other than for testing purposes (it's not like you're switching power tubes with the amp plugged in and turned on!) It's for the VHT Special 6 (non-Ultra).

mozz · Wed Sep 08, 2021 12:03 pm

Most any output tube you use besides 6V6 draws more filament current. If the power transformer is not rated for that increase, you can burn it out. El34 draws over 3 times what a 6V6 draws. I doubt very much the factory transformer is overbuilt, it's the most expensive part and the most often to meet bare specs so the company can profit more.
Unless those amps are well known to not overheat when doing that, I would stay away.

Robs site has a lot of info but to me it's a cluster fuck. He is like" cut this wire, solder this to here, remove this add this" He has very little schematics showing me actually what he is doing with the mods.

honyock · Wed Sep 08, 2021 12:42 pm

I did not see any point in running an EL34 in my Classic 6 or Special 6 (both non and ultra versions) after asking a VHT tech about it. They said it would work, but it did not sound good to me. It also sat too close to the speaker for my liking.

I had a Kustom Defender 30 that had a switch for changing power tubes, but it came stock with the EL34s and you flipped a switch for the change to the 6L6 tubes.

I only did it because the EL34s were out of the Defender and curiosity got the best of me. Never tried it in either of my Specials.

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mozz · Wed Sep 08, 2021 6:04 pm

Kind of off topic but the single ended 6v6 was the most popular when it came to SE. Champs were made for about 50 years total? Gibson and Ampeg also copied them. When it comes to single ended EL34/EL84/6L6 I don't think there were many made and therefore the sound of those particular tubes may not be as common or familiar. You have beam power tubes, pentodes, tetrodes, triodes, etc. They are all gonna sound different and have different distortion/harmonic signatures. 6V6 and 6L6 are not in the same family (same pinout though) and therefore will sound different.

Small increase in wattage may be slightly noticeable but a more efficient speaker will do wonders. I have read about 6l6 and EL34 in SE mode and didn't get the impression people liked the sound. That all being said, i do have a 6550 single ended here being built to see what i can push out of it. It has 440vdc (with a solid state rectifier) so a 6v6 won't do. I may end up using 2 6v6's to get 10 watts if this 6550 doesn't work out. If i can get 15w out of the 6550 i will be joyous. I hope it frys the old alnico speaker which is only 10-15 watts because it will sound good right before it blows up.

glasshand · Thu Sep 09, 2021 12:58 pm

mozz wrote: ↑Wed Sep 08, 2021 12:03 pm Most any output tube you use besides 6V6 draws more filament current. If the power transformer is not rated for that increase, you can burn it out. El34 draws over 3 times what a 6V6 draws. I doubt very much the factory transformer is overbuilt, it's the most expensive part and the most often to meet bare specs so the company can profit more.
Unless those amps are well known to not overheat when doing that, I would stay away.

Actually, this amp is known for being over-engineered and to run well even with the added current draw; this sort of mod is officially approved. I know it's rare, but it is apparently the case here.

Robs site has a lot of info but to me it's a cluster fuck. He is like" cut this wire, solder this to here, remove this add this" He has very little schematics showing me actually what he is doing with the mods.

No argument there. It's a decent source for ideas, but I would kill for some better diagrams.

mozz · Thu Sep 09, 2021 5:29 pm

Lots of times you can sort of judge if the power transformer is oversized, by the overall size/weight and the gauge of the wire used for the filaments. They may have used a larger transformer and also used that same tranny in other amps, you get wholesale discounts if you buy larger quantities, so why stock more than 1 item if tranny X covers a bunch of amps and we get better pricing. Best way to tell is by temperature, if it gets a lot hotter running a EL34 and you can't keep your hand on it, it will burn out.