What line voltage do you run amps at / bias the tubes for?

BlueTele

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Sorry...I don't have a copy to post or a website, but as I cruised around the web on the same topic, I actually came across a website that has the proper bias for each type of power tube. I never knew such specs existed. Just search for: "Guitar amp tube bias values"...you'll find it.
 

Jon Snell

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If you cosider that as the mains voltage rises, the HT or high voltage DC supply from the power supply within the amplifier rises, the Anode current, if left unattended, will increase.
If you now consider the -ve DC bias voltage. However it is derived, comes from either a separate tapping on a winding, a separate winding or directly from a reverse biased diode off the main HT supply winding through a potential divider.
As the AC voltage increases, so does the HT and as does the -ve bias voltage, largely cancelling out the effect.

Why worry about something that unless you make the mistake of using a regulated bias supply. It is self compensating to a large extent.
Set the bias as per the service manual and at the rated line voltage.
In the UK we have 240v mains so I rewire the mains transformer for 240 volts and set the bias. Why they think we have 230 volts is still a mystery.
Bias current is purely a personal requirement. As they say, some like it hot, (Fender bluesy sound) some like it cold, (Marshall super lead). Some like it warm.
A matter of taste and transformer specification. Too much quiescent current causes output transformer saturation and distortion, not enough causes crossover distortion and non linearities at lower volumes.

Edit; more information supplied ...
 
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Euphonica

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As the AC voltage increases, so does the HT and as does the -ve bias voltage, largely cancelling out the effect.

Why worry about something that unless you make the mistake of using a regulated bias supply. It is self compensating to a large extent.
You’re saying a wall voltage that swings between 116 - 125 does not result in any perceivable or audible changes in tone, as long as the bias is set at an average value? I’m paraphrasing of course, but trying to understand. Apologies I am so dumb.

I still want a proper voltage regulator, but I’d prefer to spend less than a grand or so.
 

rdjones

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You’re saying a wall voltage that swings between 116 - 125 does not result in any perceivable or audible changes in tone, as long as the bias is set at an average value? I’m paraphrasing of course, but trying to understand. Apologies I am so dumb.

I still want a proper voltage regulator, but I’d prefer to spend less than a grand or so.
Either Tripp-Lite or Juice Goose should have something in that price range.

 

Euphonica

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Either Tripp-Lite or Juice Goose should have something in that price range.
Where? I scrolled through all the products on Markertek, then all their products on both of their sites. I emailed both of them asking about it.

I feel like only laboratories need any voltage regulation in the real world. Guitar amps just sound a little different, but no damage is happening. And that’s why no one makes this product at my price point.
 

Euphonica

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Either Tripp-Lite or Juice Goose should have something in that price range.
Actually, they don’t! They referred me to a company called Sola. He said I need a “constant voltage transformer.” All the Sola products I saw were for 120 volts, but they say “+/- 3 VAC.” Which could either mean the output is adjustable, or it’s not a steady output. I can’t find an email for Sola so I’ll have to call them when I’m done working nights.
I use a buck transformer (The Amp Preserver) to drop line voltage to around 117vac. Vintage amps only.
Not a voltage regulator or a variac, but if your wall *doesn't* vary too much, Keen's vintage voltage adapter (Rob's bucking transformer) is great for vintage amps and the many too-hot 'clone' PTs…
But my wall voltage does vary, every few seconds… I have a few variacs, but I’d need to tweak em constantly to get anything steady. Ah well.

Especially since according to some (who haven’t deigned to reply yet haha!), it’s a non-issue… Which I just don’t have the expertise to have an opinion on. But I have “distinct feeling” that wall voltage has to affect the sound / HT of the circuit.

I’ll stop. I apologize for all of these redundant posts.
 

King Fan

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But my wall voltage does vary, every few seconds…
Right, I wasn’t suggesting a VVA for the 'regulate' question. And I’m under the same impression as you — a lockdown regulator is expensive. It may not help, but have you talked to your power company? Maybe even a home electrician? Is it possible your neighbor or even your home is running a big load that switches on and off?
 

dougstrum

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Clearly strings have a large effect on tone. Just put a new set on and the difference is apparent.
I don't notice much difference between brands of strings, but another string type makes quite a change. An extreme case would be flat vs round wound~
 

Euphonica

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Right, I wasn’t suggesting a VVA for the 'regulate' question. And I’m under the same impression as you — a lockdown regulator is expensive. It may not help, but have you talked to your power company? Maybe even a home electrician? Is it possible your neighbor or even your home is running a big load that switches on and off?
Thanks for the thoughts! I have spoken with Sola who makes constant voltage transformers, and they’re not crazy expensive, a 6.25 amp one is $1700. My thought was I’d put a variac after that and dial it in. However, the specs say “+/- 3 VAC” which funnily enough would be the exact amount of swing my wall provides haha!

So I have put the whole dang thing to rest for now, possibly forever. Seems way too much of a hassle. Which is *crazy* to me since all I want is a steady 117 volts. Ah well…
 




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