#1
I've just got a second hand peavey head, it's in reasonable condition but still has the original tubes inside so I think it's time they were upgraded.
I'm obviously happy to change the preamp tubes myself but I don't want to kill either the amp or me messing about with the power tubes when I don't know exactly what I'm doing...
There's no one that I know of in my immediate area that does this and I'd rather not have to post the head away to be done if I can help it so...
Does anyone out there have a link to a page or a video that could teach me how to fit and bias power tubes safely? If I can't teach myself to the point where I'm confident to do it I won't risk it but if I could it would be an asset?
So, any links or advice gratefully received as always
#2
I'd recommend checking out eurotubes.com. Here's a link to their info on bias probes and how to use them:

http://www.eurotubes.com/store/pc/bias%20probes.htm

I highly recommend getting a bias probe. I've used one on my head for years and have never fried myself or the amplifier. Eurotubes also has a section for videos on how to bias your head properly. And, if you really get into a bind, their phone support is great.

Everyone makes biasing out to be a really difficult process but once you have a basic idea of how it works, it should be a really easy ten minute process. And you'll save money by not having to send it to a tech every time it needs new tubes. Hope this helps
#5
Will Lane
I would imagine so, mki valveking head so I doubt it's self biasing like some if the newer heads
#6
It might would benefit you to research it first than to presume, it is cathode biased- meaning you just get a matched set of tubes, put them in, and you are ready to go. They run on 6L6 tubes which have a raised ridge on the center plastic pole piece, you can't put them in wrong.

EDIT: oops
Last edited by Will Lane at Jul 27, 2016,
#7
Quote by Will Lane
you just get a matched set of tubes, put them in, and you are ready to go.


Not necessarily. Even if it's a matched set, the bias would at least need to be checked to make sure it's in the optimum operating range. Unless the valveking has a fixed bias (although, I highly doubt it). Either way, a matched set is definitely the best bet (esp. if it has adjustable bias as this takes a lot of extra work out of the equation).
Last edited by MaidenMan88 at Jul 26, 2016,
#8
IIRC that amp has a bias adjustment that can't be wound up high enough to be too hot, just like a 6505. So you just twist it until it sounds best. So in other words it's a gimick.
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#9
Quote by MaidenMan88
Not necessarily. Even if it's a matched set, the bias would at least need to be checked to make sure it's in the optimum operating range. Unless the valveking has a fixed bias (although, I highly doubt it). Either way, a matched set is definitely the best bet (esp. if it has adjustable bias as this takes a lot of extra work out of the equation).


Since "fixed bias" means it needs to be set as opposed to cathode biased which does not I'm not sure you're qualified to give biasing advice.

Fixed doesn't mean non-adjustable, it means that it doesn't self-adjust. You still have to set (fix) it to a given point.
“Ignorance more frequently begets confidence than does knowledge.”
Charles Darwin
Last edited by Arby911 at Jul 27, 2016,
#10
Quote by Arby911
Since "fixed bias" means it needs to be set as opposed to cathode biased which does not


Sorry, I was thinking of cathode biased when I wrote that.
#11
Quote by Cathbard
IIRC that amp has a bias adjustment that can't be wound up high enough to be too hot, just like a 6505. So you just twist it until it sounds best. So in other words it's a gimick.


... It is Cathode Biased. There is no bias pot, you would have to mod one in.

...

I think. Now you guys are making me doubt myself.
Last edited by Will Lane at Jul 27, 2016,
#13
Quote by Cathbard
I can't see that link for whatever reason. Is that for the new models (MkII) or the MkI? From what I am seeing NOW, the MkII versions are fixed, adjustable bias and the MkI versions (what TS has) are Cathode Biased.
Last edited by Will Lane at Jul 27, 2016,
#14
It's from 2005
Gilchrist custom
Yamaha SBG500
Telecasters
Randall RM100 & RM20
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Atomic Amplifire
Marshall 1960A
Boss GT-100


Cathbard Amplification
My band
#15
Quote by Cathbard
It's from 2005
...

Did some more digging. I was told it was Cathode Biased, as far as the early models go. Reading the Valveking Wiki claims over and over again that none of the MkI models have a bias pot. What I found then is this:

Quote by MrCarrot
Well the schematic tells me it's a non-adjustable fixed bias. So it's just change tubes and play. Just as if it were cathode bias. Cathode bias means at an incredibly basic level non-adjustable bias designed for one tube type, ergo you just plug the new ones in with no worries at all, no rebiasing. Essentially the Valveking is set up to be the same. No bias pot that I can see.


But Non-Adjustable, Fixed Bias is different than Cathode Bias, yeah? So it has a fixed resistor rather than a Pot (Adjustable, Fixed) or Cathode Bias, which means the amp requires not only a matched set of power tubes but also to be of the same rating as the original units? And also everything I know is a lie?
Last edited by Will Lane at Jul 27, 2016,
#16
Ok so thanks for all your inputs but all the techno babble has this rookie utterly confused???
Does a mki valveking head need to be biased or will I 'get away with' just buying a matched quad set?
This entire conversation is already making me doubt I'm up to the job myself....
#17
Quote by chrislanie
Ok so thanks for all your inputs but all the techno babble has this rookie utterly confused???
Does a mki valveking head need to be biased or will I 'get away with' just buying a matched quad set?
This entire conversation is already making me doubt I'm up to the job myself....
Sorry. Now that I am doing research, I am getting a lot of conflicting information. I just do not know exactly how the amp is supposed to have the tubes biased. What really gets me is that I have not seen an explicit statement from Peavey explaining its bias style, or if it is out there it is buried. If you want to, you can read up on biasing here and here if you want to "follow along".

I thought it was Cathode Biased which means you just put the tubes in and you are good to go. But it seems like I was wrong (oh no!) and that it is Fixed, Non-Adjustable bias. All that means is you need to ask for new tubes with the specifications of the old tubes (presuming the amp has the original tubes). Really, you could just get a matched set for a Fixed, Non-Adjustable bias amp and not worry about the specifications, but you could end up with a bias either way to hot (short tube life) or way too cold (long life but sounds bad).
Last edited by Will Lane at Jul 27, 2016,
#18
Quote by Will Lane
It might would benefit you to research it first than to presume

Take your own advice here. You posted a lot of misinformation.

The absence of a bias pot does not at all mean that the amp is cathode biased. Fixed non-adjustable bias does not mean that you need an identically rated set of tubes to replace the old set. You can't find how the amp is supposed to have the tubes biased because the amp was designed specifically not to need biasing.

With the Valveking (and a lot of Peavey amps) they simply set the factory bias so ice cold that there's no danger of the bias being too hot with whatever set of power tubes you throw in. In other words, they're saving money on warranty returns and the extra parts for the bias adjustment circuit at the cost of running the power tubes super cold (which may or may not impact the sound, but certainly solves the bias problem). Except in unusual circumstances, the VK requires neither a rebias nor an identical set of tubes. It was designed to work and sound just fine with really cold power tubes. Mesa does something similar with many of their amps.

Adding a bias pot to avoid the cold Peavey factory bias is another conversation. Some people prefer it that way but it isn't necessary for the amp to function and the amp was designed not to need it. The short answer to this question is plug and play.
#19
Quote by chrislanie
Ok so thanks for all your inputs but all the techno babble has this rookie utterly confused???
Does a mki valveking head need to be biased or will I 'get away with' just buying a matched quad set?
This entire conversation is already making me doubt I'm up to the job myself....


Buy a set, put them in, play.

The rest is commentary.
“Ignorance more frequently begets confidence than does knowledge.”
Charles Darwin
#20
The VK112 is a fixed bias resistor and is not adjustable, put in a set of 6L6 tubes and play away.
#21
Quote by Roc8995
Take your own advice here. You posted a lot of misinformation.

The absence of a bias pot does not at all mean that the amp is cathode biased. Fixed non-adjustable bias does not mean that you need an identically rated set of tubes to replace the old set. You can't find how the amp is supposed to have the tubes biased because the amp was designed specifically not to need biasing.

With the Valveking (and a lot of Peavey amps) they simply set the factory bias so ice cold that there's no danger of the bias being too hot with whatever set of power tubes you throw in. In other words, they're saving money on warranty returns and the extra parts for the bias adjustment circuit at the cost of running the power tubes super cold (which may or may not impact the sound, but certainly solves the bias problem). Except in unusual circumstances, the VK requires neither a rebias nor an identical set of tubes. It was designed to work and sound just fine with really cold power tubes. Mesa does something similar with many of their amps.

Adding a bias pot to avoid the cold Peavey factory bias is another conversation. Some people prefer it that way but it isn't necessary for the amp to function and the amp was designed not to need it. The short answer to this question is plug and play.
Yup. My apologies. When I was researching the amp right before I bought my own, I was told "plug and play", which I guess translates for a lot of people as Cathode Bias. Whether or not I read that the amp was explicitly Cathode Biased is a different story, but that phrase is out there in reference to the amp. It is confusing; no where did I see what you have stated here, which is something that needs to be known.
Last edited by Will Lane at Jul 27, 2016,
#22
Thanks guys, you managed to turn a load of techno babble into clear information