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Discussion in 'Amps and Cabs' started by EL84 Abuser, Jun 12, 2019.
If you really want to keep your tubes running cool, clip the heater wires that run to the sockets.
I don't know about the new ones, but the original Peavey Classic 50 from the early 90's ran a fan. I gigged the ever loving daylights out of one for many many years and never had any tube trouble...or any trouble at all for that matter. Still have it, still works.
Not mine, but same vintage..
There is an easy workaround.
Set your amp to your liking.
Use angeled plugs on your wire.
Turn your amp upside down.
It´ll probably last forever.
I prefer tubes amp in a chassis...but I've never had an issue that stemmed from tubes down.
When I rehoused my Crate VC50 I flipped it. Stays MUCH cooler than my other VC50. Bob
I remember SRV mentioning that he wished Dumble had NOT put the knobs on top like SRV requested - said they got too hot to touch when running.
This is one of those If you think it matters, IT MATTERS! things. I built an impractical combo for a show with the tubes horizontal in the front of the case. Found a 19dB 6v computer fan and mashed it into the case as well no issues. I generally don't put backs on head shell builds but I do mill in non visible slots in the face plate for air flow.
My Rivera M100 is 29 yrs old and never had a prob
The elusive ampstrument slots!
The less stress, the better, I reckon.
The other thing I'm thinking is that mounting upside-down probably eases tube replacement. Egnater got around this by putting a removable metal vent atop the Tweaker 15. Top-mounted tubes and vents are no problem for me.
I haven't set any drinks on an amp since 1995, when one walked off the amp onto my leg due to vibrations. I also ran the same 71 Bassman head as my #1 for eleven years without a tube failure, despite bottom-mount tubes and no venting.
There's an argument that went around for a few years that Vox amps sound better when the EL84s are really hot-fans hurt the sound. Is it true? I dunno, I'm not going to mount a fan in my AC30...
Everyone agrees that upside down works, and has worked for a very long time.
If you know basic physics and electronics, you can agree it's the least thermally
efficient orientation. As a combo designer (talking brands that will add cost if it makes
a better design) why wouldn't you orient the tubes and chassis for maximum thermal
efficiency? The steel chassis of the amp also acts as a thermal conductor for the heat
that builds up inside of it. Mounting it upside under a piece of wood is a terrible thermal
Again, not saying it doesn't work. Of course it does. It's just not optimum, and given the choice, why would you consciously go that route? The #1 enemy of power generating electronics is heat. Always has been. Still is.
I think I learned that hot air rises even before I got tying my shoes down pat.
You’re not wrong, you’re just way overblowing it
Just making discussion. It's obvious Leo started this way for ergonomics. "Controls must be on top!" I like how Swart does it with some of their amps. Also think a sideways orientation is a good compromise.
Many Mesa amps have fans as well.
That late-'40s/early-'50s Valco design has always appealed to me for combos:
It is important to note that for some larger tube types, manufacturers specified tube pin orientations if the tube is to be mounted horizontally. Check out the GEC KT-66 installation notes on page 3, plus the diagram on page 4: https://frank.pocnet.net/sheets/084/k/KT66_GEC.pdf Or another example, from Tung-Sol, with their 5R4GYA rectifier datasheet stating that horizontal operation permitted if pins 1 & 4 are in a vertical plane.
When mounting horizontally, if plate orientation is not as specified, it can set up a situation where heat rises up from one plate and adds to the heat load on another. This can overheat the grid assembly within, with gravity sagging it until it shorts.
My personal preference is for a tubes-up head amp.
In terms of a combo, isn't there a fair amount of air being moved (cooling) inside the cabinet at higher volumes by the speakers?
Speakers move air but in a constant push and pull motion. They move the air within the enclosure a bit but don't really do much at all for cooling. Learned this the hard way years back when we mounted amp chips to an aluminum port tube thinking the air movement would be enough. The fire during power testing proved otherwise.