Heat and tube preamps

[kach22i]

I took the cover off my tube preamp a while ago because it was just getting so hot. I'm not sure what too hot is, just that it felt like I could not only keep a meal warm on it, I could cook it part way too.

It takes a lot longer for the sound to soften up and sound sweet with the cover off. There is some glare on the first LP or CD that I can't seem to avoid, even after warming up the system for an hour before hand.

There is a green circuit board on this preamp, and the transformer is also inside. I don't think these parts really like or need heat all that much.

Choices:

1. Cover on - like the designer intended.

2. Cover off - will extend the life of the unit.

3. Modify the cover by drilling some holes in it, starting at 10% open area and working my way up to the perfect spot.

I should note that there are downward facing louvered vents on the side of the preamp. They are small and few in my opinion. There are no vent holes in the bottom of the unit, but I could be wrong - going off of my aging memory. There are no vent holes in the top of the unit at all. The metal finish is very nice you may think it was anodized black if the manfacturer did not tell you it was the same black paint Ferrari uses. Oh and it's Italian in origin of course - maybe it's just meant to be hot tempered.

 

[aliveatfive]

IMHO, I'd leave the cover on. You might be changing some mechanical vibration-damping characteristic with the cover off. Tube preamps run very hot. I've not noticed any sonic degradation over the years which I could attribute to the heat. The original Dyna PAS had no vent holes at all and tubes were reputed to last in these units for years.

 

[roberto]

I took the cover off my tube preamp a while ago because it was just getting so hot. I'm not sure what too hot is, just that it felt like I could not only keep a meal warm on it, I could cook it part way too.

It takes a lot longer for the sound to soften up and sound sweet with the cover off. There is some glare on the first LP or CD that I can't seem to avoid, even after warming up the system for an hour before hand.

There is a green circuit board on this preamp, and the transformer is also inside. I don't think these parts really like or need heat all that much.

Choices:

1. Cover on - like the designer intended.

2. Cover off - will extend the life of the unit.

3. Modify the cover by drilling some holes in it, starting at 10% open area and working my way up to the perfect spot.

I should note that there are downward facing louvered vents on the side of the preamp. They are small and few in my opinion. There are no vent holes in the bottom of the unit, but I could be wrong - going off of my aging memory. There are no vent holes in the top of the unit at all. The metal finish is very nice you may think it was anodized black if the manfacturer did not tell you it was the same black paint Ferrari uses. Oh and it's Italian in origin of course - maybe it's just meant to be hot tempered.

Hola...you might have a problem in your unit. We know that the tubes are hot, but not that much. It seems, by your description, that you have a bad component there. The transformer gets warm, but not so hot, if you have this, could be because the transformer is bad or another component is draining too much current. My advise is, take it to good service qualified tech. or send it to the factory for test and repair. Hope this can help...happy listening,
Pura vida,
Roberto.

 

[kach22i]

I think I need to find out how hot other tube peramp run - I have no watermark or standard to go by for this.

Any tube preamp I can think of has vent in the top. I did a quick search - wow, I've alway liked the ones that exposed the tubes, but this is X-rated!

Here is more more typical tube preamp - vented, just like my old solid state preamp.

When I mentioned the heat issue to the store/shop once before, they said it was fine.

I really need to see what other tube preamps feel like after they have been running for a couple of hours - that sums it up.

 

[risabet]

Leave the cover on!

Both the tubes and the transformer generate heat. If the unit is working okay then leave it be. The cover not only protects the unit from you, it protects you from the unit. Some of the voltages are lethal in there. This is another case of looking for a problem where none exists. Audiophilia Nervosa at its finest.

 

[kach22i]

Both the tubes and the transformer generate heat. If the unit is working okay then leave it be. The cover not only protects the unit from you, it protects you from the unit. Some of the voltages are lethal in there. This is another case of looking for a problem where none exists. Audiophilia Nervosa at its finest.

A case Audiophilia Nervosa is someone without first hand knowlege giving second rate opinions. Something risabet apparently is an expert at.

 

[tonyc]

Kach, I discovered quite by accident that my Sonic Frontiers SFL2 sounded best with the cover off. It ran pretty hot. I also experimented with Pearl tube coolers and Ensemble tube sox-these seemed to increase the heat coming from the top of the preamp due to increased cooling of the actual tubes. I thought the tube sox sounded better in my sytem and these may be an alternative option. My arc LS 25 ran cooler than the Sonic Frontiers (fewer tubes). My Ref 3 runs hot-so much so I had to rearrange my rack to give it more room. I have not tried tube coolers of any kind on the Ref3 (YET), but probably will if I can find tube sox to fit 6H30's. It is nearing time to retube the Ref 3 and I may listen with the cover off just for grins if I can summon the courage to mess with success!

 

[kach22i]

Thanks for the information tonyc, I did not mean to go off on risabet either.

Perhaps these diagrams will help explain my situation to everyone. I am of couse Scheme-1, and I want to know if ther is any advantage to keeping the tubes in what I've termed a "thermal pocket".

 

[roberto]

Thanks for the information tonyc, I did not mean to go off on risabet either.

Perhaps these diagrams will help explain my situation to everyone. I am of couse Scheme-1, and I want to know if ther is any advantage to keeping the tubes in what I've termed a "thermal pocket".

Hola Kach22i...if you want to keep your tube system running a little bit cooler, try to take the hot air out, instead of inserting cool air to them. Tubes like to be hot, but not too much. If your tubes are too hot, the bias adjustment of them is a must. There are not benefits of running the tubes too hot in a sense for better sound and also too much heat will shorten their durability. When I had a furniture without good ventilation, what I did was, with the help of three silenced fans (you could hear them only at late night and without music) that you could get them perhaps at Radio Shack...taking out the heat was the best! Hope this can help!...happy listening,
Pura vida,
Roberto.

 

[MiTT]

The only problem I see with that Merlin pre-amp kach22i showed us above is all the drool that would flow down onto the exposed tubes. Actually that looks like a computer rendered image to me.

I had a similar problem with my BAT VK31-SE as what tonyc described. When I moved from my old SFL-1 Sig to the BAT the BAT put off significantly more heat. I had kept the Sonic Frontiers underneath my turntable in my rack, but with the BAT stoking the fire I needed to move it to a seperate rack so that it could also be in the top position. For what it's worth, the BAT is vented on the top.

Also, for what it's worth. I am the director of Product Development for a major high end lighting company. High quality lamps are very much like audio tubes when you think about their construction. My engineers are constantly challanged with the issue of keeping thermals in a range where the lamp is able to operate in optimum conditions (lamps actually "like" to see a certain amount of heat), without exceeding the thermal characteristics of the lamp and sending the ballast into a current cycling/thermal runaway situation. My longwinded point here is that if your pre-amp has been "properly engineered", then the high heat you are mentioning may actually be appropriate for the tubes you're using. BTW, I am NOT an engineer myself (my degree is in Industrial Design), I just manage them so feel free to treat this as a bunch of hooey.

Happy Listening

 

[kach22i]

BTW, I am NOT an engineer myself (my degree is in Industrial Design),

I'm an architect, so my understanding or perspective is much like yours MiTT. I understand what you are saying, it reinforces exactly what I had suspected.

For the record, with the cover on the unit the preamp sounds great right from the begining and keeps sounding better the more it heats up.

For reference a link to my system:
http://www.martinloganowners.com/forum/showthread.php?t=531

Preamp image:

The BrightStar "stone" over the preamp did not seem to have any effect on cooling or heating - much to my suprise. The UFO disk shaped thing is for some remote wireless speakers. Both the "Stone" and the UFO have been relocated while the cover has been off. I use an old record with it's cardboard sleeve to keep dust off the innards of the unit while not in operation. I of course let things cool down before putting the record over the preamp (covers up about 80% - a temporary measure until I had things figured out.

The part about the heat which worried me the most was not the top of the unit as you would think. It was the control knobs, such as the selectors and volume control being "HOT" to the touch after a long and serious listening session.

Hot knobs.............don't go there - please.

 

[MiTT]

I'm an architect, so my understanding or perspective is much like yours MiTT

Yes, I would have guessed that or an Industrial Designer from your sketch above...

The "hot knobs" situation on your Graff sounds very odd to me. I'm sure that they are just using metal shafts on all of the controls and they are actually transfering the heat to the knobs, also obviuosly metal. Just think of them as decorative heat sinks I guess.

 

[kach22i]

Yes, I would have guessed that or an Industrial Designer from your sketch above...

The "hot knobs" situation on your Graff sounds very odd to me. I'm sure that they are just using metal shafts on all of the controls and they are actually transfering the heat to the knobs, also obviuosly metal. Just think of them as decorative heat sinks I guess.

I was thinking the same thing, it's as if the whole mass of the component is a heat sink as well. The metal knobs being the heaviest and most massive parts.

 

[aliveatfive]

Kach, I discovered quite by accident that my Sonic Frontiers SFL2 sounded best with the cover off. It ran pretty hot. I also experimented with Pearl tube coolers and Ensemble tube sox-these seemed to increase the heat coming from the top of the preamp due to increased cooling of the actual tubes. I thought the tube sox sounded better in my sytem and these may be an alternative option. My arc LS 25 ran cooler than the Sonic Frontiers (fewer tubes). My Ref 3 runs hot-so much so I had to rearrange my rack to give it more room. I have not tried tube coolers of any kind on the Ref3 (YET), but probably will if I can find tube sox to fit 6H30's. It is nearing time to retube the Ref 3 and I may listen with the cover off just for grins if I can summon the courage to mess with success!

tonyc -

Some reports say that 6h30s can last for 10,000 hours. ARC says that they have a much longer life span than 6dj8s. So does BAT. Have you that many hours on your REF 3 already?

 

[tonyc]

aliveatfive, the owners manual for the Ref 3 says tubes should last around 4000 hours. According to the timer on The Ref3 I have already logged 2800 (I tend to leave the system powered up all weekend, which is when I am most able to actually listen!).