Tube Amp Cabinet Thermal Protection

[jcpcali]

Hey guys way smarter than me!

Hoping for some expert advice on enclosing my Fisher 500C into a custom made desktop. I'm designing a 24" deep x 48" wide office work station into a converted closet in a guest room. It will also contain a Hitachi sr-2004 solid state receiver. I'm worried about the heat generated.

My idea is to mount a 48x18 inch 3/4" Mdf board about 25 inches high to place the receivers on then another 48x24" board 8 or 9 inches above that so that there will be a 6 inch overhang to work on.

I have the drywall removed so I thought I'd install some sort of fan to blow into PVC installed between the studs that will run to the attic. The fan would be plugged into the fisher so that it comes on automatically when the Fisher is turned on. The space compartment will be rather tight. I'll have a wire management gromet installed above, which should provide some ventilation.

I'm thinking I should install some sort of thermal padding on the MDF above the receiver and maybe below. Please critique my design and suggest fan/blowers, thermal pads and maybe ventilation grills that will help with the heat generated by the valves. I'm in the Las Vegas area so it heats up in the summer. btw it's a single story home with easy access to the attic. The attic is insulated on the ceiling so no insulation on the floor of the attic.

Thanks in advance!!

 

[TriodeLuvr]

I would want at least a 12" space between the boards. Thermal padding shouldn't be required. Won't the fan/PVC also suck out a lot of the AC from the room and blow it into the attic? If this really needs a fan, maybe exhausting the heat back into the room near floor level would be better.

 

[Mr Boochie]

I would want at least a 12" space between the boards. Thermal padding shouldn't be required. Won't the fan/PVC also suck out a lot of the AC from the room and blow it into the attic? If this really needs a fan, maybe exhausting the heat back into the room near floor level would be better.

That's what I would look at --- like how IT people ventilate a mainframe array.

 

[century tek]

Just one of those 3 fans shown is all you would need.

 

[OldHvyMec]

It's only going to be running when your running the unit, and a single fan will move plenty of air from the ambient surrounding. Vent into the
attic in the summer and into the room in the winter. The higher the pickup in a room the more heat you'll put across the cabinet. You can reverse
the fan direction between summer and winter. Filter the attic in/out. Waffle can filter or a filter towel over an opening will work with flex hosing
HVAC, cooling/heating/vent stuff. Home Depot special!

Regards

 

[Sitka]

I installed a single fan in my tube amp cabinet, that works fine. A thermometer is used to check cabinet temps. It is a remarkable amount of heat from tube amps, without ventilation, you could almost bake bread in the cabinet!

 

[Mr Boochie]

I like overkill. My DIY computer has four internal (thermal-controlled) fans and another outside it to help push the hot air up. I have two slow-moving 10-inch fans ( behind my audio amps, which are solid-state.

With more fans, you can set one to run very slowly at temperatures (say around 30ºC). But as the amp heats to 50ºC, more fans will kick on and run faster. Then, at top-end heat (70ºC+), all fans run at full speed. I started multiple fans with tubed guitar amps that run hot --- like the Vox AC-30. In my experience, it saves the capacitors, breadboards, circuit boards, and sockets as much as the tubes.

 

[century tek]

Feeling adventurous? Grab a tube manual and see what wattage each tube is dissipating in heat. You'll get an overall average of the total amount of heat it's generating.

 

[OldHvyMec]

It is a remarkable amount of heat from tube amps, without ventilation, you could almost bake bread in the cabinet!

Especially MC60 and if they are hot rodded you could bake bread. Man those thing can run hot with any kind of a load. I had one pair close to 100wpc.
They were quiet as a mouse too. Jensen Imperials D300s. 6550 wing C vs KT88 make a difference in potential output too if I remember right.

I have a pair of Cary V12Rs, they can warm up a room too with EL34, KT88 or KT90s. That's a fun amp. 4, 8 or 12 valves. 12-115watts per rail. 6V6-KT99s
A pair, with a full complements of valves and cranking it up. Boy Howdy!

LOL they will sure make bread rise if nothing else.

Regards

 

[Mr Boochie]

Feeling adventurous? Grab a tube manual and see what wattage each tube is dissipating in heat. You'll get an overall average of the total amount of heat it's generating.

Use a point-and-shoot IR thermal gun on your unit's tubes and surrounding areas.

I once measured the temperature of my push-pull AB1 6L6GC amp (Fender Pro Reverb). At idle, after 30 minutes of use, the temperature of one of the 6L6GC was around 250ºF (120ºC), with the IR thermal gun pointed at the glass envelope. I'm sure the immediate surrounding area around the power tubes and OPT was over 120ºF. I didn't measure that.

I'd imagine a Class "A" amp would run hotter. I never measured mine.

I like the Klein IR gun. Prolly not as accurate as the Fluke, but good enough for what I used it for (electronics and auto repairs).

Klein Tools IR1 Infrared Thermometer.

 

[gadget73]

No need to calculate or measure anything. Look at the wattage number on the back of the unit. Thats basically the worst-case heat load.

the better you can have it breathe, the better the life for the internal bits will be. Tubes themselves don't care all that much about heat so long as its not absolutely crazy. The caps are going to be your limiting factor. Heat is bad for lifespan. The other parts don't love it either, anything made of plastic or phenolic will get brittle with enough heat exposure. It dries out wood pretty thoroughly too.

 

[Mr Boochie]

No need to calculate or measure anything. Look at the wattage number on the back of the unit. Thats basically the worst-case heat load.

the better you can have it breathe, the better the life for the internal bits will be. Tubes themselves don't care all that much about heat so long as its not absolutely crazy. The caps are going to be your limiting factor. Heat is bad for lifespan. The other parts don't love it either, anything made of plastic or phenolic will get brittle with enough heat exposure. It dries out wood pretty thoroughly too.

For sure! Gaming computers and mainframes have invested a lot of engineering into cooling their products. I know that solid-state devices are more sensitive to heat than tubes, but if I had the option to over-engineer anything --- proper heat dispersion in an amp would be a good option.

When I look at solid-state amps, I like the ones with over-engineered power supplies, quality heat sinks, and proper venting. They seem to be more stable and last longer.

 

[trainbuftony]

Tube amplifiers are designed to work for years with only convection cooling.
If for some reason you can't give the hot air someplace to escape, then a small fan moving air will cool them sufficiently.
I wouldn't pump the heat into the atic, I'd put a fan somewhere it can draw air across the power tubes and dump that air back at your feet. Tube receivers don't make that much heat to begin with, so a small, slow moving fan is more than sufficient.

Honestly, the best thing you can do for keeping temps under control is to verify that the power output stage is biased up correctly and drawing 70 to 80% of maximum disapation.
Play it for a while and recheck.
If the power stage is working right, heat generation will be minimal and not problematic.

 

[gadget73]

Convection cooling only works with adequate space around them. They don't really love life in a cramped box.

 

[Legrace]

My tube amps are situated on a shelf of a 3 tier shelving unit. Initially after a couple hours all adjacent surfaces would get really hot, scary hot. So I installed a low flow 120 mm Noctua brand fan behind each amp. Huge difference afterwards, barely warm to the touch now, no matter how long they are on. Noctua fans claim to fame are their low noise levels, I cant even hear them running.

 

[Bill Ferris]

Especially MC60 and if they are hot rodded you could bake bread. Man those thing can run hot with any kind of a load. I had one pair close to 100wpc.
They were quiet as a mouse too. Jensen Imperials D300s. 6550 wing C vs KT88 make a difference in potential output too if I remember right.

I have a pair of Cary V12Rs, they can warm up a room too with EL34, KT88 or KT90s. That's a fun amp. 4, 8 or 12 valves. 12-115watts per rail. 6V6-KT99s
A pair, with a full complements of valves and cranking it up. Boy Howdy!

LOL they will sure make bread rise if nothing else.

Regards

How about (4) MC275LEs with their 16 KT88, and 28 small signal tubes radiating their waste heat into a NE. FL. living room, and lets toss in a MC-60 for center channel service !
My 3.5 ton HVAC Heat pump`s thermostat often says more than "Boy Howdy" when those sonic space heaters are up and running !

 

[OldHvyMec]

"Boy Howdy" when those sonic space heaters are up and running !

They have actual circuit boards correct? Newer factory units run cooler vs the original MC275 series or paralleled. BUT they can burn the bacon
for sure. I have a pair of CE. Nice units, BUT one suffered a cable drop. First and last time for that, it blew a right transformer that I've never got
around to fixing. One of the reason I use Cary V12Rs now, I can dial back the thermals from 12 to 120 watts per channel. They can work an extra
3 months out of the year by swapping and pulling power valves. Then over to Class Ds in the summer for the mains mids and highs. I stick
with SS class Ds for bass duty, AB plates for servos subs and Dayton plates for the rest

All my Macs I'm stuck, not that I mind being stuck with MC225s or 240 as a staple in the system I listen to the most.
C11/MX110z & MC 225/240. Something about that combo is hard to get away from for me at lest the last 45 years anyway.
Both are summer/winter amps too. I'm listening to a C-11/MC240/RS IIIBs right now. Wonderful. 3-5 watts at most.

It gets HOT where I live too. We had a few 115 degree days this year and 30 or more over 110. We just don't have the horrible humidity as I remember it
as a kid in Mobile/Prattville Alabama. I was born in Waco Texas, it gets pretty hot there too. Still nothing like Vegas to work in. I worked there as a regional
Cat HD field mechanic and for Kleem, Tie Back rigs. Wonderful combination, knee deep in grout and 140 degrees in the $hitter! Imperial Valley too!
I have an idea what hell is like. Don't forget the sun screen and Thank God for retirement. LOL

Are you using the MC275s for bass duty too? If you are, YOUR TOUGHER than me by a long shot. Look nice though! Something about classic Mac.
53 years for me. Might be time to thin the heard, we'll see.

Best regards.

 

[Bill Ferris]

They have actual circuit boards correct? Newer factory units run cooler vs the original MC275 series or paralleled. BUT they can burn the bacon
for sure. I have a pair of CE. Nice units, BUT one suffered a cable drop. First and last time for that, it blew a right transformer that I've never got
around to fixing. One of the reason I use Cary V12Rs now, I can dial back the thermals from 12 to 120 watts per channel. They can work an extra
3 months out of the year by swapping and pulling power valves. Then over to Class Ds in the summer for the mains mids and highs. I stick
with SS class Ds for bass duty, AB plates for servos subs and Dayton plates for the rest

All my Macs I'm stuck, not that I mind being stuck with MC225s or 240 as a staple in the system I listen to the most.
C11/MX110z & MC 225/240. Something about that combo is hard to get away from for me at lest the last 45 years anyway.
Both are summer/winter amps too. I'm listening to a C-11/MC240/RS IIIBs right now. Wonderful. 3-5 watts at most.

It gets HOT where I live too. We had a few 115 degree days this year and 30 or more over 110. We just don't have the horrible humidity as I remember it
as a kid in Mobile/Prattville Alabama. I was born in Waco Texas, it gets pretty hot there too. Still nothing like Vegas to work in. I worked there as a regional
Cat HD field mechanic and for Kleem, Tie Back rigs. Wonderful combination, knee deep in grout and 140 degrees in the $hitter! Imperial Valley too!
I have an idea what hell is like. Don't forget the sun screen and Thank God for retirement. LOL

Are you using the MC275s for bass duty too? If you are, YOUR TOUGHER than me by a long shot. Look nice though! Something about classic Mac.
53 years for me. Might be time to thin the heard, we'll see.

Best regards.

No, each 275 is mono configured and each one drives either my purchased new in late 2003 Mc. XRT-30`s HQ high resolution digital crossover`ed tri-amplified line array speaker system`s mid range, or tweeters, with the mid range MC-275s not receiving any frequencies below 80 Hz. as that area is readily and easily handled by my purchased new in 2006 2 Mc. MC-1201 mono block 240 v rewired by me, each driving the XRT-30`s 2 bass cabinet`s twin HP/LD 12" woofers taking care of the bottom octave`s lows from 80 down to 20 or lower Hz.

The 4 Mc. floor sited music amplifying sonic space heaters were purchased new in 2010, and are still using the original OEM provided tubes with very high hundreds of operating hrs. on them have been totally trouble/issue free still delivering nice smooth and accurate wonderful sounding audio.
Here is several more pictures of my living room`s reference system amps, amps, rack, & mid/tweeter line array`s configuration.

 

[Mr Boochie]

The 4 Mc. floor sited music amplifying sonic space heaters were purchased new in 2010, and are still using the original OEM provided tubes with very high hundreds of operating hrs. on them have been totally trouble/issue free still delivering nice smooth and accurate wonderful sounding audio.
Here is several more pictures of my living room`s reference system amps, amps, rack, & mid/tweeter line array`s configuration.

This looks like the home version of the Wall of Sound.

 

[arts]

Fans? Nobody used fans back in the day. Just staple some asbestos sheets to the interior of the cabinet and you're good to go