Do you re-bias your amp after changing your power tubes?

Make it loud here.

Do you re-bias every time you change your power tubes?

Yes, every time.
14
64%
I don't, if I use a properly matched fresh pair
3
14%
Never, who cares if the amp still sounds great?
5
23%
 
Total votes: 22

User avatar
øøøøøøø
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 5984
Joined: Sun Jan 06, 2008 8:26 pm
Location: Los Angeles
Contact:

Re: Do you re-bias your amp after changing your power tubes?

Post by øøøøøøø » Sun May 08, 2022 5:51 pm

zhivago wrote:
Sun May 08, 2022 2:10 pm
øøøøøøø wrote:
Sun May 08, 2022 1:39 pm
Yannis, I'd really recommend getting a Bias-Rite or similar. Then you can check bias without even opening the amp... it might be pretty close to in range already, and that'd save you a trip to the tech. And if it does need adjustment for the new tubes, it's just about being comfortable adjusting an internal trimpot
Good advice there, Brad...I contacted a tech earlier and I am waiting to hear back...I will check youtube to see if there are any videos showing the process using that gadget. It sounds pretty straightforward, but I do get nervous whenever I open an amp! :o :D
If you like, you can think of it like a “bias monitor” of sorts, which wouldn’t require opening the amp at all.

Insert the device between tube and amp, read plate current, cross-check against online references (or calculator).

If it looks out of range, then you can decide whether you want to learn an easy DIY adjustment or delegate to a professional—but it would save you a trip to the tech just to find out if bias needs adjustment or not :)

Full disclosure—I monitor my bias “the hard way” and so don’t own a bias-rite, but for people who don’t have the inclination for a lot of tech work, it really is the way to go

User avatar
zhivago
Mods
Mods
Posts: 21926
Joined: Tue Sep 12, 2006 6:18 am
Location: London, UK

Re: Do you re-bias your amp after changing your power tubes?

Post by zhivago » Sun May 08, 2022 11:38 pm

øøøøøøø wrote:
Sun May 08, 2022 5:51 pm
If you like, you can think of it like a “bias monitor” of sorts, which wouldn’t require opening the amp at all.

Insert the device between tube and amp, read plate current, cross-check against online references (or calculator).

If it looks out of range, then you can decide whether you want to learn an easy DIY adjustment or delegate to a professional—but it would save you a trip to the tech just to find out if bias needs adjustment or not :)

Full disclosure—I monitor my bias “the hard way” and so don’t own a bias-rite, but for people who don’t have the inclination for a lot of tech work, it really is the way to go
I will get a monitor for payday I think...sounds like it will be a good investment! Many thanks for the encouragement! The Friedman shall roar again soon! 8) 8) 8)
Resident Spartan.

User avatar
Dr Tony Balls
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 476
Joined: Thu Mar 12, 2015 10:05 am
Location: Brooklyn, NY
Contact:

Re: Do you re-bias your amp after changing your power tubes?

Post by Dr Tony Balls » Mon May 09, 2022 4:56 am

øøøøøøø wrote:
Sun May 08, 2022 1:39 pm
There's a good reason for not making bias easily user-adjustable.

Some users might think it's another way to "tweak tone" and then complain when their amp burns up output tubes.

There's a less-good (but totally-understandable) reason for not including test point jacks on the rear of an amp that's designed to emulate a vintage design: guitarists are way too superstitious and are irrationally-suspicious of anything that deviates in any way from 'vintage correct" (see: volute, Gibson).

There's a high likelihood that a manufacturer of vintage-style Marshall-clone heads would sell fewer amps by adding such a useful feature.

Yannis, I'd really recommend getting a Bias-Rite or similar. Then you can check bias without even opening the amp... it might be pretty close to in range already, and that'd save you a trip to the tech. And if it does need adjustment for the new tubes, it's just about being comfortable adjusting an internal trimpot

Yeah, BUT.....wouldnt these same maniacs just get a bias-rite or other similar tools and do this on their own accord?

I look at it in two ways 1) it makes re-bias much easier for both user and tech, and 2) it provides a safe channel to do this, keeping users from poking around inside the chassis. One can always take a perfectly functioning amp and screw it up with their own misunderstanding. I had a guy blow an OT by putting a chorus pedal between the head and cab once! People are animals. I also write the ideal bias measurement on my amps, to hopefully guide people into setting it correctly. Have external jacks and adjustments isnt fool proof, but I think it's more right than wrong.

Image
Instagram: thetonyballs

User avatar
sessylU
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 534
Joined: Sat Oct 03, 2015 9:33 am

Re: Do you re-bias your amp after changing your power tubes?

Post by sessylU » Mon May 09, 2022 4:57 am

I know this is basically an impossible question, but how many tube changes would it take for the Bias Rite (or similar) to pay for itself? Like, what expect to pay for changing tube and rebiasing? I know that varies wildly, even within the same city, so it's a silly question.

I'm assuming it's something that a tech would do in less than an hour, so whatever bench rate is?
a total idiot jackass

User avatar
luau
Admin
Admin
Posts: 10020
Joined: Tue Dec 12, 2006 7:07 am
Location: Ft. Lauderdale, FL, USA

Re: Do you re-bias your amp after changing your power tubes?

Post by luau » Mon May 09, 2022 5:26 am

I've never done it because I don't really feel the need, but there are a few videos on youtube demonstrating how to build your own bias probe and it looks pretty easy to understand and do.

User avatar
øøøøøøø
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 5984
Joined: Sun Jan 06, 2008 8:26 pm
Location: Los Angeles
Contact:

Re: Do you re-bias your amp after changing your power tubes?

Post by øøøøøøø » Mon May 09, 2022 5:54 am

Dr Tony Balls wrote:
Mon May 09, 2022 4:56 am
øøøøøøø wrote:
Sun May 08, 2022 1:39 pm
There's a good reason for not making bias easily user-adjustable.

Some users might think it's another way to "tweak tone" and then complain when their amp burns up output tubes.

There's a less-good (but totally-understandable) reason for not including test point jacks on the rear of an amp that's designed to emulate a vintage design: guitarists are way too superstitious and are irrationally-suspicious of anything that deviates in any way from 'vintage correct" (see: volute, Gibson).

There's a high likelihood that a manufacturer of vintage-style Marshall-clone heads would sell fewer amps by adding such a useful feature.

Yannis, I'd really recommend getting a Bias-Rite or similar. Then you can check bias without even opening the amp... it might be pretty close to in range already, and that'd save you a trip to the tech. And if it does need adjustment for the new tubes, it's just about being comfortable adjusting an internal trimpot

Yeah, BUT.....wouldnt these same maniacs just get a bias-rite or other similar tools and do this on their own accord?

I look at it in two ways 1) it makes re-bias much easier for both user and tech, and 2) it provides a safe channel to do this, keeping users from poking around inside the chassis. One can always take a perfectly functioning amp and screw it up with their own misunderstanding. I had a guy blow an OT by putting a chorus pedal between the head and cab once! People are animals. I also write the ideal bias measurement on my amps, to hopefully guide people into setting it correctly. Have external jacks and adjustments isnt fool proof, but I think it's more right than wrong.

Image
It’s objectively better.

The volute also made Les Paul necks objectively less likely to break, but it was still roundly rejected.

On a new design that’s not trading on being “as close as possible to identical to vintage spec,” your test points (and plate current spec written on chassis!) is clearly way better; a major improvement.

On a vintage clone, it would probably drive away some percentage of customers who base technical decisions in part on “irrational fear of change”

User avatar
JSett
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 8803
Joined: Mon Jun 01, 2009 1:33 pm
Location: Old Hampshire, Old England

Re: Do you re-bias your amp after changing your power tubes?

Post by JSett » Mon May 09, 2022 6:59 am

sessylU wrote:
Mon May 09, 2022 4:57 am
I know this is basically an impossible question, but how many tube changes would it take for the Bias Rite (or similar) to pay for itself? Like, what expect to pay for changing tube and rebiasing? I know that varies wildly, even within the same city, so it's a silly question.

I'm assuming it's something that a tech would do in less than an hour, so whatever bench rate is?
I mean, when there was actually any tech's around where I live it was about £40-60 just to get your amp on their bench for the first hour. I think I paid about £130 for my BiasRite so it paid for itself within 2 visits if we include my fuel and time to drop off and collect it (hell, now an hour out of my day would cost me £90 so it'd only take one trip to pay for itself!).

And you don't have to be without your amp for any amount of time.
Silly Rabbit, don't you know scooped mids are for kids?

User avatar
stevejamsecono
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 4552
Joined: Tue Oct 17, 2006 10:55 am
Location: Brooklyn, NYC
Contact:

Re: Do you re-bias your amp after changing your power tubes?

Post by stevejamsecono » Mon May 09, 2022 11:08 am

zhivago wrote:
Sun May 08, 2022 11:38 pm

I will get a monitor for payday I think...sounds like it will be a good investment! Many thanks for the encouragement! The Friedman shall roar again soon! 8) 8) 8)
When it does I'd love to hear some clips. I've been looking at Marshally types lately and those one... intrigues me :ph34r:
And you find out life isn't like that
It's so hard to understand
Why the world is your oyster but your future's a clam

Resident Yamaha Fanboy

COYS

User avatar
Larsongs
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 2414
Joined: Mon Aug 18, 2014 9:39 pm

Re: Do you re-bias your amp after changing your power tubes?

Post by Larsongs » Mon May 09, 2022 12:40 pm

On recent Fender & Vox Amps which I’m using I’m not sure how you adjust Bias? Would someone be good enough to elaborate on this?

Thanks

L

User avatar
JSett
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 8803
Joined: Mon Jun 01, 2009 1:33 pm
Location: Old Hampshire, Old England

Re: Do you re-bias your amp after changing your power tubes?

Post by JSett » Mon May 09, 2022 12:54 pm

Larsongs wrote:
Mon May 09, 2022 12:40 pm
On recent Fender & Vox Amps which I’m using I’m not sure how you adjust Bias? Would someone be good enough to elaborate on this?

Thanks

L
The Vox should be cathode biased so no adjustments necessary...just pop in a pair of good quality, matched tubes and go for it. If there's something going wrong to cause the tube to blow aside just wear and tear it's a case of swapping resistors to adjust the bias point - which is too complicated to go into here. Modern reissue Fenders (DRRI, PRRI, etc) I think the bias pot is in the traditional spot on the underside of the chassis, behind the power tubes and next to the PT. You need to take readings and do the maths, or use a bias reader, then adjust to suit.
Silly Rabbit, don't you know scooped mids are for kids?

User avatar
zhivago
Mods
Mods
Posts: 21926
Joined: Tue Sep 12, 2006 6:18 am
Location: London, UK

Re: Do you re-bias your amp after changing your power tubes?

Post by zhivago » Mon May 09, 2022 1:01 pm

stevejamsecono wrote:
Mon May 09, 2022 11:08 am
When it does I'd love to hear some clips. I've been looking at Marshally types lately and those one... intrigues me :ph34r:
Sure thing, I can do that...nowadays I play my amps through a Suhr Reactive Load IR, so I can record incredible guitar sounds straight into the computer. 8)

I haven't heard back from the amp tech, by the way...so I am very tempted to buy that gadget now and test the tubes. :D
Resident Spartan.

User avatar
JSett
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 8803
Joined: Mon Jun 01, 2009 1:33 pm
Location: Old Hampshire, Old England

Re: Do you re-bias your amp after changing your power tubes?

Post by JSett » Mon May 09, 2022 1:09 pm

zhivago wrote:
Mon May 09, 2022 1:01 pm
stevejamsecono wrote:
Mon May 09, 2022 11:08 am
When it does I'd love to hear some clips. I've been looking at Marshally types lately and those one... intrigues me :ph34r:
Sure thing, I can do that...nowadays I play my amps through a Suhr Reactive Load IR, so I can record incredible guitar sounds straight into the computer. 8)

I haven't heard back from the amp tech, by the way...so I am very tempted to buy that gadget now and test the tubes. :D
If I was a little closer to you I'd swing by and show you/do it for you.
Silly Rabbit, don't you know scooped mids are for kids?

User avatar
zhivago
Mods
Mods
Posts: 21926
Joined: Tue Sep 12, 2006 6:18 am
Location: London, UK

Re: Do you re-bias your amp after changing your power tubes?

Post by zhivago » Mon May 09, 2022 1:09 pm

This will also work, right?

https://www.hotroxuk.com/tad-biasmaster ... s-bm2.html

I thought I'd check before I pull the trigger! :)

It is a bit cheaper than the one that does 4 valves at the same time. My amp runs 2 EL34s only, and I doubt I will ever go up to 100 watt amps (running 4 power valves) ever again. My late 20s/early 30s are waaaaay behind me! :D
Resident Spartan.

User avatar
zhivago
Mods
Mods
Posts: 21926
Joined: Tue Sep 12, 2006 6:18 am
Location: London, UK

Re: Do you re-bias your amp after changing your power tubes?

Post by zhivago » Mon May 09, 2022 1:10 pm

johnnysomersett wrote:
Mon May 09, 2022 1:09 pm
If I was a little closer to you I'd swing by and show you/do it for you.

Yes it is a shame we are not any closer...if you're ever in London drop me a line...would be great to hang out! 8)
Resident Spartan.

User avatar
JSett
PAT. # 2.972.923
PAT. # 2.972.923
Posts: 8803
Joined: Mon Jun 01, 2009 1:33 pm
Location: Old Hampshire, Old England

Re: Do you re-bias your amp after changing your power tubes?

Post by JSett » Mon May 09, 2022 1:11 pm

zhivago wrote:
Mon May 09, 2022 1:09 pm
This will also work, right?

https://www.hotroxuk.com/tad-biasmaster ... s-bm2.html

I thought I'd check before I pull the trigger! :)

It is a bit cheaper than the one that does 4 valves at the same time. My amp runs 2 EL34s only, and I doubt I will ever go up to 100 watt amps (running 4 power valves) ever again. My late 20s/early 30s are waaaaay behind me! :D
That's the exact one I have.

You can buy the extra 2 probes later if you ever have need to.
zhivago wrote:
Mon May 09, 2022 1:10 pm
Yes it is a shame we are not any closer...if you're ever in London drop me a line...would be great to hang out! 8)
I am often up in the city, but it's always for a specific reason (normally a gig). Waterloo is only 35mins on the train though, so it's not all that far really.
Silly Rabbit, don't you know scooped mids are for kids?

Post Reply