EL34 compared to 6550

[TwilightOdyssey]

The 6CA7s ...  Maybe Ben's endorsement of them should be enough now that I think about it.

Yes, listen to Ben ... whoever he is!!!

[fps_dean]

no I didn't, read my post again - both times I said that 6550s require more bias voltage than EL34s.

I quote you "but the bias range that EL34s operate within is FAR too hot for 6550s so they will redplate and you'll ruin a new set of 6550s."

What does less voltage run hotter?

[HTH AMPS]

EL34s typically operate with around -45 to -25 on the grids

6550s typically operate with around -65 to -45 on the grids

as the bias voltage is adjusted towards 0v, the output valves will run hotter.  

I've actually done this procedure on amps many times, this is not just something I've read on the internet and taken as gospel.  

If anyone wants to plug 6550s into their EL34 amp without modification then go right ahead, it'll end up in the hands of a tech like myself requiring a new set of valves and possibly replacement of burnt out screen resistors and arced sockets (worst case scenario of course).

What does less voltage run hotter?

I don't know how to answer that question, it makes no grammatical sense.

 :twisted:

[fps_dean]

EL34s typically operate with around -45 to -25 on the grids

6550s typically operate with around -65 to -45 on the grids

as the bias voltage is adjusted towards 0v, the output valves will run hotter.  

I've actually done this procedure on amps many times, this is not just something I've read on the internet and taken as gospel.  

If anyone wants to plug 6550s into their EL34 amp without modification then go right ahead, it'll end up in the hands of a tech like myself requiring a new set of valves and possibly replacement of burnt out screen resistors and arced sockets (worst case scenario of course).

What does less voltage run hotter?

I don't know how to answer that question, it makes no grammatical sense.

 :twisted:

You just answered it.  Having less current makes tubes run hotter.  I always thought more current made tubes run hotter and I know 6550s require more current.

[indysmith]

where do you guys all get your amps biased, or do you do it yourself? I'm dreading having to change my valves because i'll never be able to bias my amp and i don't know anybody who can do it for me offhand. Do music shops do it? Sound Control etc.?
Actually i could just get the amp serviced by the marshall factory, but I'm thinking that might be overly expensive?

[Bainzy]

There's no point bickering over whether the tubes need rebiasing if you switch to 6550's, as even if you changed simply to a different pair of EL34's you still should be rebiasing. Just set the bias trimpot to minimum, pop the new tubes in and bias to whatever the recommended bias range is for the new tubes.

indysmith - biasing an EL34 amp isn't as hard as some people might like to make out. All you need to do is install 1ohm resistors in the power tubes (join pins 1 and 8 and put the resistor inbetween those pins and ground), then measure the current either side of the resistor, turning the trim pot to get in the range you want.

[fps_dean]

There's no point bickering over whether the tubes need rebiasing if you switch to 6550's, as even if you changed simply to a different pair of EL34's you still should be rebiasing. Just set the bias trimpot to minimum, pop the new tubes in and bias to whatever the recommended bias range is for the new tubes.

Dude, I don't know all the stuff you do.  I've always thought voltage = heat with tubes just like solid state.  I know some of the basics, as much as 6550s require more voltage than a EL34, and I have some understanding of electronics, but I haven't learned how to bias an amp yet.  I would like to, but I don't know how/where to do that.

where do you guys all get your amps biased, or do you do it yourself?

A friend recommened a semi-local tech.  I brought him my '69 Major which needed some repairs and when I got it back, it was so incredibly warm - now I understand why some people say the Majors are the best sounding Marshalls ever.  But aside from doing great work, he's a really nice guy as well!

Ask friends who play, and ask Bainzy I'm sure he'd do it for the right price.  You heard what he did with his Marshall right? ;)

[indysmith]

indysmith - biasing an EL34 amp isn't as hard as some people might like to make out. All you need to do is install 1ohm resistors in the power tubes (join pins 1 and 8 and put the resistor inbetween those pins and ground), then measure the current either side of the resistor, turning the trim pot to get in the range you want.

Whats a 1ohm resistor look like? which pins are which? what's ground? THE ground? how do yu measure current? whats a trim pot? Where's a trim pot?!
I think you can probably see that the chances of me biasing my amp are close to zero, but thanks for your help
I'm a race driver, not a pit mechanic

Ask friends who play, and ask Bainzy I'm sure he'd do it for the right price.  You heard what he did with his Marshall right? ;)

I don't know anyone around here with a valve amp; how depressingly rubbish. Unfortunately Bainzy is a few hundreds of miles north of me... :P Yeah his marshall was definately sweeet 8)

[HTH AMPS]

You just answered it. Having less current makes tubes run hotter. I always thought more current made tubes run hotter and I know 6550s require more current.

voltage and current are not the same thing and are not interchangeable terms.  increasing the idle current DOES make the valves run hotter.

I have some understanding of electronics, but I haven't learned how to bias an amp yet. I would like to, but I don't know how/where to do that.

hmmm, never biased an amp in your life yet you're willing to argue the point with someone  :roll:

 :twisted:

[Dakine]

Simmer down folks :)

Electrical 101 (gawd, going back to my Apprentiship days). VERY first thing ya learn.

Voltage is NOT what will Kill Ya, Current i.e. AMPS is what'll do it.

Just a premiss, and NOT directed at ANYONE in particular, but :), lot's of SILLY confrontations lately on this board with people arguing the fact when they have NO training/experience on what they are arguing about.

People, listen and learn. Ask and be courteous with thankyou's and responses. Being an I Know Everybloodything about guitars/music etc. but A.am still in school or B.Never opened my amp or guitar backplate or C.never listened to what music you are discussing is getting OLD!

This is an Excellent board to participate in the above;

H-C lol

Rant over :)

[March]

Heavier Than Hell has dished out some very sage advice. I've recently made the change to 6550's in one of my amps and the tech explained about the differences between them and EL34's (the chap I use as a tech is well respected in the industry, if he has advice for me more often than not I listen!).

[FELINEGUITARS]

where do you guys all get your amps biased, or do you do it yourself? I'm dreading having to change my valves because i'll never be able to bias my amp and i don't know anybody who can do it for me offhand. Do music shops do it? Sound Control etc.?
Actually i could just get the amp serviced by the marshall factory, but I'm thinking that might be overly expensive?

Indy
Go to the Marshall factory
You are already in Bucks - so distance is easier for you
They are really helpful and they do it cheaply as they like to have Marshalls running well -
And you get to look around the factory or the museum and get a feel for a bit of rock tradition

[FELINEGUITARS]

There's no point bickering over whether the tubes need rebiasing if you switch to 6550's, as even if you changed simply to a different pair of EL34's you still should be rebiasing.  

Sound advice Bainzy!!

biasing an EL34 amp isn't as hard as some people might like to make out. All you need to do is install 1ohm resistors in the power tubes (join pins 1 and 8 and put the resistor inbetween those pins and ground), then measure the current either side of the resistor, turning the trim pot to get in the range you want.

Once again - correct and sound stuff but possibly beyond the skills and inclinations of many who post here.

It is ok NOT to do all your own tech work

Do indeed consider guitar techs and amp techs to be like F1 pit crew if you like the racing car driver analogies.
Find one who you trust and who communicates well with you, & Value them and don't begrudge paying them their fees - especially if they are not being extortionate.
Then get on with enjoying playing guitar

there is nothing wrong with understanding how things work or go together and still chose to delegate the work to somebody more experienced.,

I know how to do DIY and gardening and stuff but sometimes I still employ the services of a decorator I trust simply because they can do the job quicker and more efficiently than me , with minimal mess and few complications , leaving me free to do what I like doing best

[fps_dean]

Heavier Than Hell has dished out some very sage advice. I've recently made the change to 6550's in one of my amps and the tech explained about the differences between them and EL34's (the chap I use as a tech is well respected in the industry, if he has advice for me more often than not I listen!).

Don't like the 6550s much? (I prefer EL34s too).

[March]

Don't like the 6550s much? (I prefer EL34s too).

I actually really like them and they give me a different flavour to play with which is great. Having 3 EL34 powered heads meant that I was hearing more or less the same sound when I used them. I mentioned to the tech that I wanted to try something else and he suggested them.

With yet another EL34 powered amp coming into the fold (I have a Marshall 30th Anniversary head and cab heading my way), I may have one of the other amps switched to 6L6's (is 7 amps too many?!).