If this kills me, it's been fun talking gear (and shit) with you guys

[Shreddy Mercury]

I just popped the new tubes into my 3rd Power, did the contact cleaner on the pins of the old tubes and worked them in and out 3 times...those original tubes were REALLY in there!

Anyways, I just hooked up my Euro Tube bias probes and the plates are reading 508v on one and 509v on the other, but it may adjust slightly since the amp's only been off standby for a few minutes. The 508v tube is showing 29ma and the 509v tube is reading 28ma, so they are very closely matched from Euro Tubes. I'm going to let it sit here another 20 minutes or so. My Bourns trim pot tool hasn't got here yet but I can't wait any longer. I'm going to go take a really quick shower, where I won't towel off (I like being dripping wet after a shower), while it finishes heating up thoroughly, then put on all my favorite metal jewelry that makes me feel like a rock star. While my Bourns tool hasn't got here yet, I did find this nice solid metal nail in the garage where I was able to file the tip down to a small, flat edge so I can jam it around inside and adjust the bias pot. I'll probably use it to scrape off the metal legs of these big ol' capacitors too. I know the best tone comes from clean leads on capacitors, whether they're axial or radial.

 

[Shreddy Mercury]

All jokes aside, some fun info you guys might want to know:

This is why your power tubes need to cool down before touching them. Using my infrared thermometer I used for my snake habitats, the top of the tube (where the orange light is glowing) is around 330 f while the middle part is about 260 f. My preamp tubes are reading about 100 f. The covered windings of my reverb transformer are a whopping 100 f and the bells on the end of my big juicy Mercury Magnetics power transformer are a paltry 86 f. While most of this info is utterly useless, it's hard evidence as to why you do not touch your power tubes while the amp is running, or for a while afterwards.

I actually may not need to adjust the bias. The manual says they left the factory at 28ma and these probes say, after over 20 minutes, that 1 tube is 28ma and the other is 27ma. I emailed Dylana and....Dylana said (I refuse to use improper pronouns) to use the 70% rule as a guide, which would put these at about 35ma. These tubes are currently running about 59-60%, which is on the colder side, but will provide a bit more clean headroom and extended tube life. The amp has enough gain and I have enough drive pedals that I can get more drive out of it, but I really like the sounds I was getting (the clean channel is amazing on here) so I think I'll keep it on the conservative side at about 60% dissipation and get more miles out of these tubes while I'm at it.

 

[Music&Chaos]

All jokes aside, some fun info you guys might want to know:

This is why your power tubes need to cool down before touching them. Using my infrared thermometer I used for my snake habitats, the top of the tube (where the orange light is glowing) is around 330 f while the middle part is about 260 f. My preamp tubes are reading about 100 f. The covered windings of my reverb transformer are a whopping 100 f and the bells on the end of my big juicy Mercury Magnetics power transformer are a paltry 86 f. While most of this info is utterly useless, it's hard evidence as to why you do not touch your power tubes while the amp is running, or for a while afterwards.

I actually may not need to adjust the bias. The manual says they left the factory at 28ma and these probes say, after over 20 minutes, that 1 tube is 28ma and the other is 27ma. I emailed Dylana and....Dylana said (I refuse to use improper pronouns) to use the 70% rule as a guide, which would put these at about 35ma. These tubes are currently running about 59-60%, which is on the colder side, but will provide a bit more clean headroom and extended tube life. The amp has enough gain and I have enough drive pedals that I can get more drive out of it, but I really like the sounds I was getting (the clean channel is amazing on here) so I think I'll keep it on the conservative side at about 60% dissipation and get more miles out of these tubes while I'm at it.

Uncle Doug, I think, did an example and showed that the bias goes against nature in that a lower bias has less headroom than a higher bias.

 

[griff10672]

anything Neo-Classical requires at least 30mA

 

[thegame]

emailed Dylana and....Dylana said (I refuse to use improper pronouns)

One must make their own choice when faced with such a moral dylana

 

[Rottweiler]

Wow, here I was worried that you were going in for open heart surgery or going to suggest the wife look into the Ozempic or something else scary!

 

[romanianreaper]

I don't remember if it was on the HC forum or Rig Talk, but years ago there was someone that got electrocuted biasing their amp. Anyone remember that?

 

[7704A]

I don't remember if it was on the HC forum or Rig Talk, but years ago there was someone that got electrocuted biasing their amp. Anyone remember that?

Was it a Blades? I'm always worried I'm going to get zapped just from looking at pictures of them.

 

[FourT6and2]

Uncle Doug, I think, did an example and showed that the bias goes against nature in that a lower bias has less headroom than a higher bias.

EDITED:
This might be a lost in translation thing. Because a colder bias setting yields more clean headroom. But colder rated tubes supposedly yield less clean headroom than tubes with a hotter rating when the amp is biased to same plate dissipation % for each set of tubes. There's 122 years of math to support this.

If you bias so cold that you're getting crossover distortion, it might sound like you've lost clean headroom. But that's not the same thing as a power section clipping due to reaching the threshold for clean headroom.

 

[napalmdeath]

All jokes aside, some fun info you guys might want to know:

This is why your power tubes need to cool down before touching them. Using my infrared thermometer I used for my snake habitats, the top of the tube (where the orange light is glowing) is around 330 f while the middle part is about 260 f. My preamp tubes are reading about 100 f. The covered windings of my reverb transformer are a whopping 100 f and the bells on the end of my big juicy Mercury Magnetics power transformer are a paltry 86 f. While most of this info is utterly useless, it's hard evidence as to why you do not touch your power tubes while the amp is running, or for a while afterwards.

I actually may not need to adjust the bias. The manual says they left the factory at 28ma and these probes say, after over 20 minutes, that 1 tube is 28ma and the other is 27ma. I emailed Dylana and....Dylana said (I refuse to use improper pronouns) to use the 70% rule as a guide, which would put these at about 35ma. These tubes are currently running about 59-60%, which is on the colder side, but will provide a bit more clean headroom and extended tube life. The amp has enough gain and I have enough drive pedals that I can get more drive out of it, but I really like the sounds I was getting (the clean channel is amazing on here) so I think I'll keep it on the conservative side at about 60% dissipation and get more miles out of these tubes while I'm at it.

I'd try it around 32mA for starters.

 

[Music&Chaos]

This might be a lost in translation thing. Because a colder bias setting yields more clean headroom. Hard stop. But colder rated tubes have less clean headroom than tubes with a hotter rating... when the amp is biased to same plate dissipation % for each set of tubes.

This is because you need to turn the bias up hotter (less negative bias voltage) to get the colder set to pull the same current as the hotter set. This grid voltage delta directly relates to headroom. Power amp clipping occurs when the AC signal coming from the PI peaks higher than the negative DC bias voltage on the grid, becoming positive.

Because hotter tubes requires a more negative bias voltage to hit the same idle current as a colder set of tubes, they have a larger voltage "runway." The PI has to deliver a larger peak-to-peak AC voltage swing to drive the hotter tubes into clipping compared to the colder tubes.

I'm going to search and find the video.

 

[Music&Chaos]

This might be a lost in translation thing. Because a colder bias setting yields more clean headroom. Hard stop. But colder rated tubes have less clean headroom than tubes with a hotter rating... when the amp is biased to same plate dissipation % for each set of tubes.

This is because you need to turn the bias up hotter (less negative bias voltage) to get the colder set to pull the same current as the hotter set. This grid voltage delta directly relates to headroom. Power amp clipping occurs when the AC signal coming from the PI peaks higher than the negative DC bias voltage on the grid, becoming positive.

Because hotter tubes requires a more negative bias voltage to hit the same idle current as a colder set of tubes, they have a larger voltage "runway." The PI has to deliver a larger peak-to-peak AC voltage swing to drive the hotter tubes into clipping compared to the colder tubes.

Found it I think!

 

[FourT6and2]

Found it I think!

I'll give it a watch. Hour-long video, lol... I've seen his vids before and he generally knows what he's talking about though.

 

[fusedbrain]

So everybody has their ideas about where this amp or that amp should be biased.
The problem is you can't play and listen to the amp when your adjusting the bias, because it's supposed to be idle current. ( and its hard on the bias probes )
So what I started doing is I run the bias up to70% (because we all agree that that's about as high as we should go ) and I put a little dot on the bias pot with a sharpie at that setting.
Then I take out the bias probes, put the tubes back in, and play the amp while I tweak the bias for the best tone, making sure I don't go past my little high limit dot on the bias pot.
Sometimes I end up at the little 70% dot, but most of the time its quite a bit less.
Every amp is different.
Use your ears.

 

[JDs Couch]

All jokes aside, some fun info you guys might want to know:

This is why your power tubes need to cool down before touching them. Using my infrared thermometer I used for my snake habitats, the top of the tube (where the orange light is glowing) is around 330 f while the middle part is about 260 f. My preamp tubes are reading about 100 f. The covered windings of my reverb transformer are a whopping 100 f and the bells on the end of my big juicy Mercury Magnetics power transformer are a paltry 86 f. While most of this info is utterly useless, it's hard evidence as to why you do not touch your power tubes while the amp is running, or for a while afterwards.

I actually may not need to adjust the bias. The manual says they left the factory at 28ma and these probes say, after over 20 minutes, that 1 tube is 28ma and the other is 27ma. I emailed Dylana and....Dylana said (I refuse to use improper pronouns) to use the 70% rule as a guide, which would put these at about 35ma. These tubes are currently running about 59-60%, which is on the colder side, but will provide a bit more clean headroom and extended tube life. The amp has enough gain and I have enough drive pedals that I can get more drive out of it, but I really like the sounds I was getting (the clean channel is amazing on here) so I think I'll keep it on the conservative side at about 60% dissipation and get more miles out of these tubes while I'm at it.

I've burned my fingers so many times being impatient to switch tubes

 

[FourT6and2]

So everybody has their ideas about where this amp or that amp should be biased.
The problem is you can't play and listen to the amp when your adjusting the bias, because it's supposed to be idle current. ( and its hard on the bias probes )
So what I started doing is I run the bias up to70% (because we all agree that that's about as high as we should go ) and I put a little dot on the bias pot with a sharpie at that setting.
Then I take out the bias probes, put the tubes back in, and play the amp while I tweak the bias for the best tone, making sure I don't go past my little high limit dot on the bias pot.
Sometimes I end up at the little 70% dot, but most of the time its quite a bit less.
Every amp is different.
Use your ears.

The Eurotube Pro One probes can be left hooked up while you play.