Jadis, It seems odd that your transformer would gain that much heat. In Manila, are you running 220 volts and 50/60hz? I wander if the transformer is designed for your voltage or is a US version 110 volt unit? Do you have a step down transformer that you are using?
What Audio Research power amps have you owned or admired?
- Thread starter Jay_S
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Jadis, It seems odd that your transformer would gain that much heat. In Manila, are you running 220 volts and 50/60hz? I wander if the transformer is designed for your voltage or is a US version 110 volt unit? Do you have a step down transformer that you are using?
Will do, Sparky. It's just hard to pin down the proper office hours in Mn as I am half way around them. Usually in my 'free time', they are closed, and when they are open, I'm sleeping.
Hi Davey,
Well, allow me to qualify a bit. I live in a tropical climate where it is generally hot all year except for a few months when it rains. During summer time, my room temperature is around 90+F or 30 to 32C. Sometimes the airconditioner does not cool the room as fast on a hot day and slowly the amp tranny goes from warm to hot if the room has not reached a cold temperature. That is when I notice the heat of the power tranny. With my VS110 and VS115 it's easy to check as they are exposed. With old ARCs they are inside a chassis so I never was able to try to feel them. Perhaps it's a curiosity that killed the cat thing, but I'd rather be safe than sorry in knowing if these trannies are built to withstand high heat levels, as Don mentioned, it's actually a very high temperature really. And, my amp is an export model, running 220v and 60hz.
Jadis, my ARC also gets a little warm after about 45 minutes, but the transformer never gets too hot to touch. I think Sparky's advice is sound. The ambient temperature in your room is, or should be, pretty irrelevant to the operating temp of your transformer.
Ok, Davey. I'll give ARC a call one of these days and see what they have to say about this. I noticed this starting with my old ARC VS110 amp which I bought around 2004 and sold it just last April 2010, and good thing, no tranny problem with that unit though it did get very hot to touch also, as with my new VS115.
I just talked to a tech man in ARC now and described to him my concern about the very hot power tranny on the VS115 after a couple of hours. The guy said it's normal, and yes, it does run very very hot. I asked if it's ok to run that 'hot to the touch' transformer condition at about 5 hours and he said, 'yup, they're designed to handle that kind of heat'. That should make be feel better now.
I just talked to a tech man in ARC now and described to him my concern about the very hot power tranny on the VS115 after a couple of hours. The guy said it's normal, and yes, it does run very very hot. I asked if it's ok to run that 'hot to the touch' transformer condition at about 5 hours and he said, 'yup, they're designed to handle that kind of heat'. That should make be feel better now.
HI jadis,
Outstanding. That's what I expected. You should feel better now.
Sparky
Surely, but once you have all in a complex system such as an amplifier it is difficult to separate contributions and know the sonic attributes of each of them - it is why I referred to it.
Back to tubes I have seen noisy tubes that after half an hour warmup became silent - may be cathode "cleaning" of micro-needles or some similar surface effect . Break-in of tubes has very reasonable explanations and was deeply studied in the past.
Considering the high temperature of the filament, it is not easy to accept that the relatively small rise of temperature of the glass envelope can have a large effect in the sound quality - after all the tube is in vacuum. A minimal variation of the filament voltage can have much higher effect in the cathode emission and does not lead to so noticeable variations in sound quality. IMHO, contributions from other circuit components must also be responsible for the long warmup effect.
HI All,
Concerning warm up, I have a theory. The greatest thermal mass that must reach temperature stability are the output tranformers. On the D250 these are huge. It's very hard for me to imagine that the smaller components such as resistors, capacitors, diodes, etc., aren't ready to go at full performance after, say, 15 minutes. They should be fully up to temperature.
Tubes have very little thermal mass. On a good tube tester, they settle out in a matter of minutes.
What's left? The output transformers, that's what. Also, in the D250, the transformers are not in the direct air flow of the four fans. So, they would not get the full benefit of the heat produced by the 6550's much less the general heat produced by the power supply. They receive their heart from simple radiation from the output tubes and only on one side at that. Of course, they do have intermally generated heat but that is small potatoes. Ultimately, it's the intermally generated heat that does bring the transformers up to temperature. Maybe that's why the warm up period on all these amplifiers is so long.
I have often wondered what would happen if a person installed small electriic heaters over the tranformers with a thermostat and timer control. This might allow the transformers to come up to temperature much faster but then would switch off after some predetermined time, say 1/2 hour. There is no reasonable way to redirect the fan air flow over the transformers so there is no help there.
I see a whole new tweak market here. You know, transformer heaters complete with tip toes, detachable power cords, fancy finishes, precision thermostats and timers, and cat proof. How could it miss???
If the VPI Brick could make it as a "must have" (yes, I have bricks too!!) audiophile item, why not a "Precision" transformer heater?
Sparky
I have to say I feel the same about my large VTLs : they sound good when the output transformers are hot or, should I say when the transformers are hot they sound good?
I have to say I have used your ideas in the past. One of the worst sounding amplifiers in the world from cold was the old Krell KSA250 - it sounded really bad for the first three-four hours depending on the playback volume and speaker efficiency (the Apogees would speed it). After half a day it was a great sound. For the little time I owned such an amplifier I had it above a 750W heater - the type you have under tables to keep your feet and legs warm, now not allowed anymore - just to speed warmup!
Classe Audio is now selling an "intelligent" amplifier - the output transistors are assembled in a low mass tunnel heat-sink with a fan controlled by microprocessor that always keeps the optimum temperature after a very short time.
HI Don and microstrip.
While it must be true that other components contribute to warm up time in general, I'm trying to account for the extremely long warm up times. In this case, thermal mass may be the dominant issue. I'm looking for the smoking gun that is over and above the relatively small thermal masses of the much smaller components which will not take multiple hours to stabilize. What's illogical about that? Clearly, something is taking multiple hours to stabilize. I'm hypothesizing it's the output transformers.
Are you in disagreement here?
Sparky
While it must be true that other components contribute to warm up time in general, I'm trying to account for the extremely long warm up times. In this case, thermal mass may be the dominant issue. I'm looking for the smoking gun that is over and above the relatively small thermal masses of the much smaller components which will not take multiple hours to stabilize. What's illogical about that? Clearly, something is taking multiple hours to stabilize. I'm hypothesizing it's the output transformers.
Are you in disagreement here?
Sparky
Not necessarily in disagreement as I do not know. What I know of transformers (not a lot) leads me to believe they would get worse, not better, as they warm up, but my gut says other things probably contribute significantly if not dominate. I have no proof of that.
As for thermal mass, my counter argument was that convective effects may outweigh thermal mass considerations in tube electronics. That is, rather than looking to component with the most thermal mass, look to the ones that are most likely to influence circuit performance and are likely to have the longest thermal settling times in the system. For example, elements under the chassis that heat up only gradually as the tubes warm up the box. Lower thermal mass themselves, but take longer to heat up because they are isolated from the heat sources. Arguably, changing the bias point would have more impact than heating the transformers. Does that make sense?
Aside: Since B+ usually routes through the output transformers, there could be some coupling going on...
I do not believe I ever said your transformer theory is illogical; it is as good as any other theory and would be interesting to test. The tempco of wires tends to be very large but is typically offset by their low resistance. I do not know anything to speak of about the tempcos of magnetic materials save they tend to get lower in field strength as they get hot. It would be fun to set up an amp with some thermal probes, a decent spectrum analyzer, and some test signals then have at it with a heat gun to see what changes are caused by heating up various components.
Not arguing, more like thinking out loud, via the 'net... - Don
As for thermal mass, my counter argument was that convective effects may outweigh thermal mass considerations in tube electronics. That is, rather than looking to component with the most thermal mass, look to the ones that are most likely to influence circuit performance and are likely to have the longest thermal settling times in the system. For example, elements under the chassis that heat up only gradually as the tubes warm up the box. Lower thermal mass themselves, but take longer to heat up because they are isolated from the heat sources. Arguably, changing the bias point would have more impact than heating the transformers. Does that make sense?
Aside: Since B+ usually routes through the output transformers, there could be some coupling going on...
I do not believe I ever said your transformer theory is illogical; it is as good as any other theory and would be interesting to test. The tempco of wires tends to be very large but is typically offset by their low resistance. I do not know anything to speak of about the tempcos of magnetic materials save they tend to get lower in field strength as they get hot. It would be fun to set up an amp with some thermal probes, a decent spectrum analyzer, and some test signals then have at it with a heat gun to see what changes are caused by heating up various components.
Not arguing, more like thinking out loud, via the 'net... - Don
Hi to all,
W/ regards to the amp i currently have( A pair of D79B's, D 250MK2 Servo, Classic 150 monoblocks) the power transformers are warm to touch but not hot. The output transformers barely gets warm, even if they're use for more than 5 hours. I have not tried touching the D79's output nor power transformer because its enclose inside the chassis. Could the size of the transformer related to how hot it will be when its operated for long hours? The power transformer of the D250 and the Classic 150 are huge. The output transformer are likewise humongous in both this amps.
tdh888
W/ regards to the amp i currently have( A pair of D79B's, D 250MK2 Servo, Classic 150 monoblocks) the power transformers are warm to touch but not hot. The output transformers barely gets warm, even if they're use for more than 5 hours. I have not tried touching the D79's output nor power transformer because its enclose inside the chassis. Could the size of the transformer related to how hot it will be when its operated for long hours? The power transformer of the D250 and the Classic 150 are huge. The output transformer are likewise humongous in both this amps.
tdh888
Also just thinking loud, it is a been a while since the last time I looked at magnetism. IMHO magnetic permeability of usual ferromagnetic materials should change less than 5% between 25 and 100º Celsius, I would not anticipate great changes from the core magnetic properties.
Although my space vessel does not have an electromagnetic shield, I would risk that temperature would dilate the copper wire and core lamination making it much less microphonic as the winding and even the core would became more compact - transformers usually have high-Q mechanical resonances - see this Mudorff figure about their own coils.
Although my space vessel does not have an electromagnetic shield
, I would risk that temperature would dilate the copper wire and core lamination making it much less microphonic as the winding and even the core would became more compact - transformers usually have high-Q mechanical resonances - see this Mudorff figure about their own coils.Attachments
As a Johnny-come-lately to this thread, as someone who has never fiddled with valves, but is deeply concerned about the temporal nature of SQ, that is, the sound of a system keeps changing from start up time till as long as you want to keep listening, the whole business of warmup and stabilisation is a huge can of worms. My own experiences are that every system is too complicated in terms of all the subtle factors that add to and subtract from SQ, so the best thing is either have a setup that never sounds really good so that you become used to generally lower order of quality and never expect to hear better, or elevate the components and finesse their connections to such a level where the audible significance of the ongoing variations of SQ is very minor in as far as how you perceive it in your mind. So, either end of the spectrum in SQ for a collection of gear will keep you satisfied; it's only in the middle where the up and downing of SQ will be very apparent and possibly irritating, so you'll want to keep trying to do something about it ...
Frank
Frank
HI All Who Are Interested In The Transformer Discussion,
Probably most of you have not seen a D250, especially with the cover off. I'm attaching a picture from the ARCDB that shows the innards. From this you can imagine the air flow through the amp. Four fans are located at the bottom of the amp and the air flow is vertical up through the tubes. There are 20 6550's (8 per channel and 4 regulators) in this monster along with 12 small signal tubes. It's quite a light show.
Note that all the components are located in the air flow. That is, they are mounted on the inside surface or each of the three large PC boards. In effect, this layout forms a chimney. The transformers are mounted directly behind the front panel but are not in the airflow directly. The output transformers are those that are on the outside while the power transformer is in the middle.
The last picture shows this arrangement.
The first picture shows the bottom of the chassis. Note, the bottom of the output transformers have no bottom cover.
The second picture gives a side view showing that all the output related components are mounted on the inside surface of the board.
I wanted to show you this so you can calibrate your ideas in this discussion for this particular amplifier.
Sorry about the order of the pictures. I didn't download in the correct sequence so it's a little messed up.
Sparky
Probably most of you have not seen a D250, especially with the cover off. I'm attaching a picture from the ARCDB that shows the innards. From this you can imagine the air flow through the amp. Four fans are located at the bottom of the amp and the air flow is vertical up through the tubes. There are 20 6550's (8 per channel and 4 regulators) in this monster along with 12 small signal tubes. It's quite a light show.
Note that all the components are located in the air flow. That is, they are mounted on the inside surface or each of the three large PC boards. In effect, this layout forms a chimney. The transformers are mounted directly behind the front panel but are not in the airflow directly. The output transformers are those that are on the outside while the power transformer is in the middle.
The last picture shows this arrangement.
The first picture shows the bottom of the chassis. Note, the bottom of the output transformers have no bottom cover.
The second picture gives a side view showing that all the output related components are mounted on the inside surface of the board.
I wanted to show you this so you can calibrate your ideas in this discussion for this particular amplifier.
Sorry about the order of the pictures. I didn't download in the correct sequence so it's a little messed up.
Sparky
HI All Again,
Since the site would not let me download more than three pictures, I could not complete the set. So, here is the final picture of the D250 showing the front of the amp. This will give you an idea of its size.
Sparky
Since the site would not let me download more than three pictures, I could not complete the set. So, here is the final picture of the D250 showing the front of the amp. This will give you an idea of its size.
Sparky
Sparky, On another thread, there was a considerable discussion about the need to replace all my Caps in my ARC D70Mk2 due to the age of the amp. Since your amp is appx. the same age, are you considering cap replacement soon? I was told by my tech, that the caps have a very long life and should not need replacement for many more years, however, many of the members here did not agree. So far, I have resisted the idea of cap replacement....I would guess in your case, the cost would be even more astronomical!
....I would guess in your case, the cost would be even more astronomical!HI Davey,
There is a certain madness running around about capacitor replacement. I'll tell you what I think about this.
Generally, all plastic caps will essentially last forever. These include Mylars, Polypropylenes, and Teflons. I have also had no problems with Tantalum's and Ceramics. Why people replace these types routinely I have no idea. They do not wear out.
Electrolytic capacitors, OTH, present a different case. They do have a life span. But from extensive experience in my repair shop, they don't wear out nearly as often as people think they do. Further, electrolytics come in different grades. Typical consumer type products use the cheapest capacitors they can. But even so, their lifespan is quite long; maybe 30 years. Out of many, many amps I have seen and fixed, I have seen exactly one fail on a amp that was about 30 years old.
Audio Research uses the best professional grade capacitors available. Their life span should be considerably longer that typical consumer grade capacitors-maybe 50 years? The big blue ones in your D70 are your electrolytic filter capacitors.
So, to answer your question, no I have not replaced my electrolytics and have no plans to do so. Since your D70 uses the same grade components as my D250, I don't think you need to replace anything (except tubes-always tubes!!) . You are fine.
Sparky
There is a certain madness running around about capacitor replacement. I'll tell you what I think about this.
Generally, all plastic caps will essentially last forever. These include Mylars, Polypropylenes, and Teflons. I have also had no problems with Tantalum's and Ceramics. Why people replace these types routinely I have no idea. They do not wear out.
Electrolytic capacitors, OTH, present a different case. They do have a life span. But from extensive experience in my repair shop, they don't wear out nearly as often as people think they do. Further, electrolytics come in different grades. Typical consumer type products use the cheapest capacitors they can. But even so, their lifespan is quite long; maybe 30 years. Out of many, many amps I have seen and fixed, I have seen exactly one fail on a amp that was about 30 years old.
Audio Research uses the best professional grade capacitors available. Their life span should be considerably longer that typical consumer grade capacitors-maybe 50 years? The big blue ones in your D70 are your electrolytic filter capacitors.
So, to answer your question, no I have not replaced my electrolytics and have no plans to do so. Since your D70 uses the same grade components as my D250, I don't think you need to replace anything (except tubes-always tubes!!
) . You are fine.Sparky
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