Do Origin 20H new valves need biasing?

[rmlevasseur]

I was going for a VH vibe. I liked EH 6CA7 power tubes the best in the Ori20. I had no problem with the Marshall branded preamp tubes and kept them in V1 and v2, but I had rolled a lot and for some reason when I was most happiest with the sound I found a tung sol in v3. Not sure that v3 even affects the tone but in blind tests that's what sounded the best to me. So it stayed.

 

[PelliX]

Then you'll be too busy tuning your harp on your fluffy white cloud to worry.

That's good, hehe

Cardiac arrest is still not common, though. Generally you end up with a burn mark or a sore spot and your ego feels like it's taken a kick in the goolies, that's it... oh, and a fuse that needs replacing.

 

[ThreeChordWonder]

That's good, hehe

Cardiac arrest is still not common, though. Generally you end up with a burn mark or a sore spot and your ego feels like it's taken a kick in the goolies, that's it... oh, and a fuse that needs replacing.

Forgive me if I don't try it...

 

[Nose4Noise]

So to be clear, the O20H is cathode based and thus doesn't need to be biased, while the O50H is not, and does require biasing? Is this right?

Is there any official Marshall documentation (link) that confirms this?

This is definitely not me questioning the expertise on this board (applauding it if anything!); rather this info would be useful to have when considering a potential purchase. And really you shouldn't have to root around random forum posts to find it. So I'd be kinda surprised/disappointed if this info didn't feature on an official, easily accessible, source.

 

[fitz]

So to be clear, the O20H is cathode based and thus doesn't need to be biased, while the O50H is not, and does require biasing? Is this right?

Is there any official Marshall documentation (link) that confirms this?

This is definitely not me questioning the expertise on this board (applauding it if anything!); rather this info would be useful to have when considering a potential purchase. And really you shouldn't have to root around random forum posts to find it. So I'd be kinda surprised/disappointed if this info didn't feature on an official, easily accessible, source.

Yes.
I have both - the 20H is cathode biased and the 50H is fixed (adjustable) biased.
Marshall user manuals don't really cover biasing as I believe they assume musicians just take their amps to a tech for a tube change.
Service manuals for current production amps are generally only available to authorized service providers, and typically are not found with a Google search.

 

[Nose4Noise]

Yes.
I have both - the 20H is cathode biased and the 50H is fixed (adjustable) biased.
Marshall user manuals don't really cover biasing as I believe they assume musicians just take their amps to a tech for a tube change.
Service manuals for current production amps are generally only available to authorized service providers, and typically are not found with a Google search.

Yeah makes sense.

I guess where that info could be important is when you're dealing with the 2nd hand market. So if you get a good deal on an amp, but then discover that the power tubes are on the way out, then the money you saved might be spent on an amp tech to bias tubes if it's not cathode situation.

The learning curve continues....

 

[fitz]

Yeah makes sense.

I guess where that info could be important is when you're dealing with the 2nd hand market. So if you get a good deal on an amp, but then discover that the power tubes are on the way out, then the money you saved might be spent on an amp tech to bias tubes if it's not cathode situation.

The learning curve continues....

Buying tubes is an inherent and inevitable cost of owning tube amps.
If you want to have tube amps, get used to buying tubes and having some spares.
I wouldn't think of tubes as part of an amp purchase cost.

Both of the Origin amp types that I have are very responsive to different preamp and power tubes.
So having some different tubes available can really help dial in a tone that works for you and how you use the amp.

I have no first-hand experience with the EL84 Origin 5w combo.

Biasing power tubes does have some potential danger if you are careless when working on a live amp.
The bias probes I have make the process very simple and relatively safe if done cautiously.
I've never been zapped and have done the process dozens of times.

 

[Frodebro]

That's good, hehe

Cardiac arrest is still not common, though. Generally you end up with a burn mark or a sore spot and your ego feels like it's taken a kick in the goolies, that's it... oh, and a fuse that needs replacing.

It obviously depends on the voltage and current. The internal resistance of your body is able to protect you in many cases, but all it takes is one milliamp arced across your heart to cause very bad things to happen.

 

[PelliX]

It obviously depends on the voltage and current. The internal resistance of your body is able to protect you in many cases, but all it takes is one milliamp arced across your heart to cause very bad things to happen.

Agree. What I'm pointing out is that a lot of people have been scared into believing that any exposure to this sort of stuff will likely be lethal when the opposite is actually the case. I've had my share of zaps in my time and given how much I've worked on electrics and high voltage/high current gear there haven't really been all that many. I know plenty of people who have had a lot more than me and none of have any permanent damage except the odd scar from a burn mark or similar. Perhaps a good comparison are car accidents. Most end up in a lot of paperwork and very limited injuries. Of course some are deadly, but most of the time people walk away relatively unharmed.

 

[Frodebro]

Agree. What I'm pointing out is that a lot of people have been scared into believing that any exposure to this sort of stuff will likely be lethal when the opposite is actually the case. I've had my share of zaps in my time and given how much I've worked on electrics and high voltage/high current gear there haven't really been all that many. I know plenty of people who have had a lot more than me and none of have any permanent damage except the odd scar from a burn mark or similar. Perhaps a good comparison are car accidents. Most end up in a lot of paperwork and very limited injuries. Of course some are deadly, but most of the time people walk away relatively unharmed.

I’ve been zapped plenty myself! 120 makes my arm tingle to just under my armpit, but I don’t have a high body fat percentage so I’m not as conductive as many people would be.

 

[PelliX]

A slightly unorthodox but not necessarily uncommon practice among electricians (and HVAC engineers in particular?) is to charge a decent size can capacitor and toss it to an apprentice. They all seem to survive, though some might choose another line of work...

 

[Frodebro]

A slightly unorthodox but not necessarily uncommon practice among electricians (and HVAC engineers in particular?) is to charge a decent size can capacitor and toss it to an apprentice. They all seem to survive, though some might choose another line of work...

I may or may not have charged a cap or two and left them sitting on the bench in my college electronics lab…

 

[ThreeChordWonder]

So to be clear, the O20H is cathode based and thus doesn't need to be biased, while the O50H is not, and does require biasing? Is this right?

I used to own an O50. The tubes deinitely need biasing. I had to replace my tubes and took it to a tech to do. Coat a bloody fortune. That's also why there's a bias pot on the board.

 

[Edgar Frog]

Also wear a condom for extra protection.

 

[jmp45]

I may or may not have charged a cap or two and left them sitting on the bench in my college electronics lab…

We had a science / physics teacher in HS that kept a charged cap on his desk to toss at anyone sleeping. Those were the days

I have a clip lead with a resistor to bleed caps.

 

[ThreeChordWonder]

Buying tubes is an inherent and inevitable cost of owning tube amps.
If you want to have tube amps, get used to buying tubes and having some spares.
I wouldn't think of tubes as part of an amp purchase cost.

Like owning a car and having to buy tires.

 

[ThreeChordWonder]

Did I mention my highschool chemistry teacher was the spitting image of Beaker?

Over six foot, skinny as a rake, ginger, lab coat...

 

[Nose4Noise]

Buying tubes is an inherent and inevitable cost of owning tube amps.
If you want to have tube amps, get used to buying tubes and having some spares.
I wouldn't think of tubes as part of an amp purchase cost.

Both of the Origin amp types that I have are very responsive to different preamp and power tubes.
So having some different tubes available can really help dial in a tone that works for you and how you use the amp.

I have no first-hand experience with the EL84 Origin 5w combo.

Biasing power tubes does have some potential danger if you are careless when working on a live amp.
The bias probes I have make the process very simple and relatively safe if done cautiously.
I've never been zapped and have done the process dozens of times.

I completely get that, and I agree that if you buy a valve/tube amp then there should be an expectation that at some point tubes will need to be changed.

But I guess my point was specifically about the process and potential cost of actually doing that.

If you are new to the world of tube amps and/or don't have the requisite knowledge (and confidence) to bias power tubes, then - given the very real danger of serious injury - the smart thing to do is to engage an amp tech. However with that comes a cost (a cost that will eat into any money saved from getting a good deal buying the amp in the first place).

Now in such a circumstance, it may well be a prudent decision to look for a cathode based amp, so as to be able to change the power tubes yourself without fear of damage to yourself or the amp.

It's in this context that having reliable info out there as to which amps are fixed bias/cathode would be helpful.

 

[fitz]

I completely get that, and I agree that if you buy a valve/tube amp then there should be an expectation that at some point tubes will need to be changed.

But I guess my point was specifically about the process and potential cost of actually doing that.

If you are new to the world of tube amps and/or don't have the requisite knowledge (and confidence) to bias power tubes, then - given the very real danger of serious injury - the smart thing to do is to engage an amp tech. However with that comes a cost (a cost that will eat into any money saved from getting a good deal buying the amp in the first place).

Now in such a circumstance, it may well be a prudent decision to look for a cathode based amp, so as to be able to change the power tubes yourself without fear of damage to yourself or the amp.

It's in this context that having reliable info out there as to which amps are fixed bias/cathode would be helpful.

Cathode bias definitely makes power tube swapping as easy as changing preamp tubes.
I've lost track of how many times I changed power tubes in my O20's (and DSL20HR when I had it).
All of the Studio series 20w amps are also cathode biased.

But don't let a fixed bias amp scare you from getting the amp you really want.
A decent bias probe costs less than a trip to the tech.
I have a Eurotubes "Pro One" Bias Probe and one of their basic probes for a multi-meter.
They just plug in between the tube and amp socket and tell you what you need to know.

Bias Probes

Eurotubes Bias Probe Page

www.eurotubes.com

A little caution and safe practices when adjusting the bias pot in a live amp makes the process fairly easy.