How to cool down your hot GT amps

soundofvoid

WBF Founding Member
Apr 22, 2010
173
11
365
Athens/Greece
The same article has been posted in the DIY section but here is more focused on the GTA SE-100 tube amps:

I use modified GTA SE-100 tube amps with KT90s in place of the original EL34s and reliability has always been a concern to me...
"Thermionic" is a old tube term that describes exactly that:you need heat to get those electrons fly!
Also massive transformers working on high voltage and resistor banks exude heat!
The result is a very hot device that:
a)Plays music the way no SS amp can!
b) works great as a heat source on cold winter nights!
c)It's internals operate in a very unforgiving environment that
stresses their reliability and shortens their life span!
I have seen too many amps destroyed by heat or poor heat management!
Usually some weak parts start to blow,you replace them and after a while it happens again!
If changing a resistor or a diode is not a big deal,what about a transformer or a board itself?
Having the privilege to start the modification from scratch i had taken great consideration on dealing with the heat issues that tantalize every tube amp.
I have hand picked all parts to work safely up to 105 deg Celsius (e.g.most of the original caps
were of the common 85 deg variety),upgraded critical resistors to the next wattage level,
installed separate heatsinks on all big wirewound resistors,used silicone wires and arranged them away from overheated places inside the amp and sometimes moved parts so i could keep a constant air flow from bottom to top.All this worked nicely and have produced hot running but reliable amps.
BUT my mind was not at rest...Sometimes on hot days and long listening sessions i could measure chassis temperatures over 55 deg!That is an amp casing that is way too hot to touch!
Forced ventilation was troubling my mind but i had to find a way to implement it effectively.
A quick search in the net provided various solutions (in the form of 12V fans) and i had to pick a winner.After a lot of consideration i decided on buying 3 fans (12X12cm version) from Scythe.
These are model S-Flex SFF21D.
They are guaranteed for 150000 hours, work on 8000 rpm/12V,6000rpm/9V, consume only 0.1 amps on 12V, they have absolutely NO vibrations and a noise level of ONLY 8.7dbs!
This is all achieved with the use of a Sony patented "Fluid dynamic bearing".
Next step was to make sure that i had taken all reasonable precautions to make sure that no
electric "pollution" was entering the amps chassis.
I glued together a round piece of copper sheet and mu-metal sheet
(mu-metal to the core and copper to the amp)and then glued them on the fan side facing the amp.
Next i had to decide where exactly to put it!
Cutting the amps chassis was out of the question but the good thing is that the amps bottom is
"grilled" so i could force the air to come into the amp from the underside.
My amps are on dedicated platforms made from solid steel/lead feet with bronze spikes and cups and 3 cm thick HDF shelves.Their weight is around 15 kilos.
With the use of a Parts Express sourced jig, designed to cut round holes in speaker baffles
i have cut 12cm diameter holes through the HDF, exactly where the amp needs the most cooling
(in the middle from front to back and at two thirds to the right side).The fans were screwed on position from the underside of the HDF
with a in-between layer (2mm) of silicone.
A small multiple voltage (15-12-9-6V)power supply was used to power up the three fans.
Without the amps in position, i could hear nothing from a distance of 30 cms from the fans.
I placed my hand on the platform and again could feel no vibration at all.
The amps weigh in present form around fifty kilos each and could certainly damp a little vibration with their mass
but it's a good thing to start without vibration at all!
Then i placed the amps on their position and fired up everything.
Tubes are very picky with vibrations and EMI penetrates easily into circuits and although i had taken every precaution you can never know what will happen...
I couldn't hear anything - not from near the amps and certainly not from the speakers.
I turned on and off the fans with music program playing and without, to see if there was any difference, audible or other...
I couldn't detect one!
Of course the real test is the temperature drop and after a four hour -high volume- listening
i can report that the chassis was never more than 45 deg!I could not expect anything better!
If anyone of you has similar problems with heat soaked tube amps or even class A SS amps
this is a solution that you could seriously consider.It's cheap, easy to install and works!
Of course before you cut any holes in your rack you should check with a working fan in hand
to see if your equipment picks up noise from the fan.If not, you can go on and do it!
Success is guaranteed!
There may be more elegant solutions out there but this one works,it's cheap and you can
do it easily on your own!
 
Last edited:

kach22i

WBF Founding Member
Apr 21, 2010
1,591
210
1,635
Ann Arbor, Michigan
www.kachadoorian.com
BUT my mind was not at rest...Sometimes on hot days and long listening sessions i could measure chassis temperatures over 65 deg!

55 degrees Celsius = 126 degrees Fahrenheit

Yes, that would be too darn hot.

Okay, post us some photos when you get a chance.
 
Last edited by a moderator:

soundofvoid

WBF Founding Member
Apr 22, 2010
173
11
365
Athens/Greece
George,i have posted some photos and further explanations in the DIY topic.I urge you to do this if you have no problem with cutting a hole in your audio furniture!
It's like adding a bigger intercooler on a higly tuned turbo engine!It will last longer!
 

kach22i

WBF Founding Member
Apr 21, 2010
1,591
210
1,635
Ann Arbor, Michigan
www.kachadoorian.com
Yea, I saw your photos in the DIY section.

The only way I would do this hole with a fan thing is if I were to replace my wood rack top with a custom cast concrete top. I would also then brace the floor joist in the basement of my home to support the extra weight.

Like I told you in the e-mail, I've had bad luck with the failure rate of cheap computer fans. I will look into this new fan you rave about, seems like a serious upgrade from what I've used in the past.
 

amirm

Banned
Apr 2, 2010
15,813
37
0
Seattle, WA
Great write up although if there were more paragraph breaks it would make it easier to read :).

I have hand picked all parts to work safely up to 105 deg Celsius (e.g.most of the original caps were of the common 85 deg variety)
This is great advice and generic to many more situations. Caps are made up of chemicals that create the functionality of a capacitor. Put them next to something warm though, and the chemicals dry out, losing their functionality. The caps look like this btw:


Look at the top of any of these electrolytic caps. If it is not flat but bowed out, it means the above has happened to it.

As noted, caps come with different temperature ratings. In a tube amp, they must be the 105 degree variety. Anything else is criminal :). It is a hot environment and even if you don't hit 85 degree, it is still warm enough to dry it out over time, significantly shortening the life of your gear. Once the cap goes, it might take other devices with it!

The issue is not limited to tube amps. Next time you are buying a PC power supply look inside it and see if you can see the cap temp rating (it will be either 85 or 105 as mentioned). If it is 85, put it down and don't buy it. Likewise, if you ever buy a piece of electronics and have the opportunity to open and see the inside, find where the heatsinks are and look next to them. If there is an electrolytic cap very close to the heatsinks, then it is a bad design. If the rating is only 85, then it is a terrible design!

Here is a picture from a short little article explaining the same:http://images.google.com/imgres?img...&ndsp=21&tbs=isch:1&ei=TZrhS6jiDojAmQP_sKz-Dw



You can see the 105 degree rating after the PL letters (which don't mean anything). Just look for degree C symbol and the number next to it is the temp rating.

There may be more elegant solutions out there but this one works,it's cheap and you can
do it easily on your own!
This is a very good solution. The only thing that would make it better is an alarm that would tell if you if the fan is stuck. The problem with active cooling (i.e. using a fan) is that when the fan stops, it makes the situation worse than no fan at all. The fan blocks convection so damage occurs that may not happen otherwise. You are using pretty high quality fans but still, failures occur, including the wiring or the power supply to the fan.

If you have an automation system like Crestron/AMX, it is easy to wire that up to provide this feature (path I am taking). Otherwise, the circuit is dead simple and you could build one yourself if you are handy at all with soldering iron. There are also various temperature activated sensors that could be used to say turn on a buzzer. All require some type of DIY skill but that is what this thread about, no? :)
 

soundofvoid

WBF Founding Member
Apr 22, 2010
173
11
365
Athens/Greece
Thanks Amir,for the input on the subject!As the fans are located on the amp platform and not the amp itself,if one stops to spin then the amp is as it was and not worse in any way!
I do have a routine to check every hour on the amps temp!I don't want to be a couch potato!I walk up to the system pretty often as i change records and cd's...
In fact if i put my hand over the amps top, i can feel a warm breeze coming upwards!
The idea about a buzzer connected to a thermal probe is a cool (!) one!I will look into it!
Regarding the capacitor quality-you are right:pplacing an 85 degree cap in a tube amp is poor choise and will soon lead to failures!
Another trick i do to beef up cap quality is to place if i can (space wise) a cap of higher voltage rating:ie in place of a 680uf/16V, i use a 680uf/25V.
It takes a little longer to break in but it's usually sturdier!Also picking ones with the lowest ESR helps too!
John
 

amirm

Banned
Apr 2, 2010
15,813
37
0
Seattle, WA
it is hard to say that increased voltage rating helps unless the designer didn't know how to design things :). Lower ESR though may help as that could have been a design choice to save money.

A word of a caution. Capacitors hold their charge even if the unit is off! So you could be subjected to an electric shock if you touch their leads in the process of replacing them. The higher the voltage, the higher the risk. A 12 volt unit would be harmless but one at 60 volts -- now that is another matter. When we attempt to repair such gear, we use a screwdriver and short out the pins on the cap first to discharge the electricity held in it. This can cause a spark which may startle you but it is better than getting killed :). So strong caution is needed here for people not familiar with electronics and what could go wrong.
 

soundofvoid

WBF Founding Member
Apr 22, 2010
173
11
365
Athens/Greece
Of course Amir!This is basic precaution to anyone attempting to change a cap or laying a hand inside an amp!I had too many fine screwdrivers blackened by capacitor shorting sparks!
Nowdays i use a BIG (as in 50Watts big) resistor to short the leads.
Less fireworks-just a little warmth!
Regarding the GT amps upgrade:I have ordered from Farnell and Mouser the total kit for three SE-100's! (A third -in stereo- for me and two -as mono- for a friend).About 1000$ worth of components.
Add to this Solen tin foils tube coupling caps and PIO bypass caps and the bill is rising!As soon as i start the stripping of old caps ,resistors,diodes,pots etc ,
i will start a new post with step by step pics.Should be an interesting read...
 

amirm

Banned
Apr 2, 2010
15,813
37
0
Seattle, WA
BTW, how about writing a version of all of this for the Tweaks forum? When I think of Tweaks, I always think of things you could do on the inside of a unit like a car hobbyist would do by adding turbo and such. Yet most people use it for external tweaks which tend to make far less difference.
 

soundofvoid

WBF Founding Member
Apr 22, 2010
173
11
365
Athens/Greece
Ok then! From now on i will repost these in the tweaks topic.It's a thin line between tweaks/mods/diy.I am not shure where the borders are...
For example if i post on a completely redone turntable do i post on tweaks or diy?Or for a given speaker that i have changed the crossover,doubled the mids and tweeters,
added a low-mid woofer,changed wiring,binding posts,sound absorbing materials, is this under tweaks or diy?
 

amirm

Banned
Apr 2, 2010
15,813
37
0
Seattle, WA
Sorry, didn't mean to confuse you :). What is here should be here. But thought we should also carry some of common themes that apply to many devices over to more common areas that more people read.
 

soundofvoid

WBF Founding Member
Apr 22, 2010
173
11
365
Athens/Greece
Okay,no confusion!If anyone of you feels that something that is being discussed here should be on other topics too,please feel free to use copy/paste on the whole post or any parts of it that you feel appropriate!
Hmmm:"Spread the word"!
 

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing