Why do amp designers run EL84 valves so hot? I have seen that VOX run hot as well as fender blues JR's. My own Friedman dirty shirley mini runs them way over 100%. Do they sound better? Do you always cool the bias on them or do you ever leave them hot as they were from the factory?
That is an excellent question, Justin. It’s not so much that they run EL84s so hot, it's more that the majority of (almost) Class A amps use EL84s. The optimal bias for True Class A is 100% dissipation at idle. This will give them the maximum swing of output. When we say EL84s are a 12W tube, it does not mean exactly 12.00W. There will be manufacturing differences between tubes. For me, an acceptable variation is 95%-110%. The Elephant in the room is the Blues Junior. It’s Class AB, but still they bias it at ridiculous levels. My cynical opinion is that the mass manufacturers (I won’t speak for Friedman) intentionally bias amps too hot these days. It's about sales. Can the owner hear some luscious tube clipping on Volume 2 in the store? Of course, at gigging levels, the amp sounds like loose sh*t. I find amps sound their best between 50% and 65%, but I nearly always confirm what I hear by watching my oscilloscope, and then check the dissipation. I always ask the owner what guitar he plays and set my signal generator accordingly.
My Korg AC30 runs ridiculously hot. I think part of this is because although the ventilators are bigger than the originals, they are still too small. I use a small battery fan at the back of the amp which unfortunately cools it too much. I say that because there must be an optimum heat for the tubes to produce their best tone. I am also loathe to keep switching the amp on and off between sessions to let it cool because i don't want to shorten tube life
My Father a ETN in the US Navy & NASA Technician taught me to use a dollar bill instead of a file (of any type) except one made for the purpose, on any contact points. As it turns out the cloth type fiber the dollar in made from is a great cleaner(burnishing tool). As a bonus it holds IPA while cleaning debris any. But each his own. I do enjoy your work.THX.
Great tip Curtis. I have a great respect for the skills of a Naval Tech. My first job out of Uni was with the Royal Australian Navy. I learned SO much from the "greenies" (nickname for electronics technicians). Say HI and thanks to your Dad from me. Aussie currency is very plasticky and doesn't have the fibre content of US notes. I had smoothed down the teeth of the nail file to a gentle "grit" and the width fits nicely under the contacts. I like it because its stiff enough to not bend like the 1000-grit wet'n'dry I would fold over and use. For the Switchcraft sockets, I use the commercially available contact file.
Yeah Chris..! Fab video, lots of info for us newbies and what a cracking amp..Sounds great too..More stuff learned,..Take care and keep em' coming..Ed..uk..😀
Thanks Chris. Im absolutely stoked with the amp and sound. Ive got exactly what I was after and also the confidence knowing its been built better and more reliable. Please dont plan on retiring anytime soon😊
Iv read tht blowing a fuse can mean I need new power tubes , iv replaced said power tubes , still blowing the fuse what might be NXT on the list to CK . Thks . It's an egnater rebel 20 ,, 2el34s - 2 6v6s
Does the amp blow fuses with the power tubes out? Check the rectifier diodes. Remove the preamp tubes (from memory, they use DC heaters).Check the voltage regulators. Good luck
Great video. The final tone was something else and your mods have paid dividends. And so many people on you tube videos play their AC15/30 demos by overdriving the amp. This is pretty useless for me since I can't tell one amp or guitar from another. The only proper demo is with a clean sound.as you have done
Thank you Nigel. You have expressed my goals much better than I could have. It’s easy to get an amp to distort. Much harder to get it sounding fantastic when it’s clean while still retaining its character.
Why do amp designers run EL84 valves so hot? I have seen that VOX run hot as well as fender blues JR's. My own Friedman dirty shirley mini runs them way over 100%. Do they sound better? Do you always cool the bias on them or do you ever leave them hot as they were from the factory?
That is an excellent question, Justin. It’s not so much that they run EL84s so hot, it's more that the majority of (almost) Class A amps use EL84s. The optimal bias for True Class A is 100% dissipation at idle. This will give them the maximum swing of output. When we say EL84s are a 12W tube, it does not mean exactly 12.00W. There will be manufacturing differences between tubes. For me, an acceptable variation is 95%-110%. The Elephant in the room is the Blues Junior. It’s Class AB, but still they bias it at ridiculous levels. My cynical opinion is that the mass manufacturers (I won’t speak for Friedman) intentionally bias amps too hot these days. It's about sales. Can the owner hear some luscious tube clipping on Volume 2 in the store? Of course, at gigging levels, the amp sounds like loose sh*t. I find amps sound their best between 50% and 65%, but I nearly always confirm what I hear by watching my oscilloscope, and then check the dissipation. I always ask the owner what guitar he plays and set my signal generator accordingly.
My Korg AC30 runs ridiculously hot. I think part of this is because although the ventilators are bigger than the originals, they are still too small. I use a small battery fan at the back of the amp which unfortunately cools it too much. I say that because there must be an optimum heat for the tubes to produce their best tone. I am also loathe to keep switching the amp on and off between sessions to let it cool because i don't want to shorten tube life
My Father a ETN in the US Navy & NASA Technician taught me to use a dollar bill instead of a file (of any type) except one made for the purpose, on any contact points. As it turns out the cloth type fiber the dollar in made from is a great cleaner(burnishing tool). As a bonus it holds IPA while cleaning debris any. But each his own. I do enjoy your work.THX.
Great tip Curtis. I have a great respect for the skills of a Naval Tech. My first job out of Uni was with the Royal Australian Navy. I learned SO much from the "greenies" (nickname for electronics technicians). Say HI and thanks to your Dad from me.
Aussie currency is very plasticky and doesn't have the fibre content of US notes. I had smoothed down the teeth of the nail file to a gentle "grit" and the width fits nicely under the contacts. I like it because its stiff enough to not bend like the 1000-grit wet'n'dry I would fold over and use. For the Switchcraft sockets, I use the commercially available contact file.
A1 clip Chris.....as a non technical person, while it doesn't make me an amp tech...it explains things that make sense.
That's the best thing you could say to me, Steve! Thank you
It was worth the wait between Parts One and Two...but worth it. That Gretsch and the Vox is a match made in heaven. Thanks Chris!
Thanks Les. The Gretsch did sound fabulous. Hopefully that Vox chime came through.
I was swamped with repairs. Sorry. about that delay
Sounded real nice when you gave it a twang.
Thank you Pete. You should have been in my little workshop...it sounded awesome. 🙂
😎 dude, 🔭 the back to the future scene .. keeps running through my mind 😬 new fan big thumbs up 👍🏻
I can't call you Jesus, but I can say, "Thank you Luke"
Yeah Chris..! Fab video, lots of info for us newbies and what a cracking amp..Sounds great too..More stuff learned,..Take care and keep em' coming..Ed..uk..😀
Thank you Ed. Can you please email me on Amptech@teammania.com.au ?
I’d like your recommendation on a couple of things
Thanks Chris. Im absolutely stoked with the amp and sound. Ive got exactly what I was after and also the confidence knowing its been built better and more reliable.
Please dont plan on retiring anytime soon😊
Thanks mate! I really appreciate that. It was a pleasure working on your AC30, the star of this video.
Nah. I can't afford to retire. Exactly as the Government would prefer, I will be found dead with a soldering iron in my hand one day. 😂
Iv read tht blowing a fuse can mean I need new power tubes , iv replaced said power tubes , still blowing the fuse what might be NXT on the list to CK . Thks . It's an egnater rebel 20 ,, 2el34s - 2 6v6s
Does the amp blow fuses with the power tubes out? Check the rectifier diodes. Remove the preamp tubes (from memory, they use DC heaters).Check the voltage regulators. Good luck
Great video. The final tone was something else and your mods have paid dividends. And so many people on you tube videos play their AC15/30 demos by overdriving the amp. This is pretty useless for me since I can't tell one amp or guitar from another. The only proper demo is with a clean sound.as you have done
Thank you Nigel. You have expressed my goals much better than I could have. It’s easy to get an amp to distort. Much harder to get it sounding fantastic when it’s clean while still retaining its character.