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I have a jolida 302 a with three transformers. Two small ones on the left/right side and a large one in the middle. The large one buzzes quite bad. The left has a slight hum and the right is silent. Any ideas of what is going on? Thanks! Thanks a bunch even if its the worst of news :( I'd just be happy to know it can be fixed :)
I auditioned one of these for about 2 weeks and the transformers buzzed and rang so badly they would keep us awake. With the amp running push down on the top of the transformer caps to see if the buzz stops. The flimsy steel caps work like megaphones, I ended up with about a pound of weight on each trans. by the end of the audition.This kept them quiet. Needless to say the amp went back to the store.Regards, Joe
It is the quality problem on transformers. You must return it for repair. It will not blow if it not overt heat. It may be the design problem espcially on power transfomer. It is not enoght turns/V.
Dear Scott,
just thought I would also mention that if Dave's suggestion doesn't work, it COULD be a defective transformer. Given that Jolida is about the lowest priced valve gear you can find, and that I'm quite sure that it is built in China (If not the whole thing then certainly the transformers), you shouldn't expect perfection. The buzzing is NOT a sign that the transformer is about to fail! Two other reasons account for transformer buzz:
1) The transformer windings were not wound snugly enough around the core and have worked loose.
2) The transformer is made with insufficient or substandard iron, and the core runs close enough to saturation due to insufficient magnetic headroom to make a slight buzz. This is more common than one might think. Quicksilvers, anyone?
A third possibility is magnetostriction, but this is experienced when a steel cover on an amp is too close to the top of the transformer. I don't have much experience with Jolida, but I think I can assume that you are not running it with a cover, assuming that one is even available.
Can't see how the 2 smaller transformers would buzz at all, it may just seem that way. Your ears can have a hard time pinpointing location of sound below 200c/s. Good luck, doesn't sound serious.
***just thought I would also mention that if Dave's suggestion doesn't work, it COULD be a defective transformer. Given that Jolida is about the lowest priced valve gear you can find, and that I'm quite sure that it is built in China (If not the whole thing then certainly the transformers), you shouldn't expect perfection. The buzzing is NOT a sign that the transformer is about to fail! Two other reasons account for transformer buzz:
1) The transformer windings were not wound snugly enough around the core and have worked loose.
2) The transformer is made with insufficient or substandard iron, and the core runs close enough to saturation due to insufficient magnetic headroom to make a slight buzz. This is more common than one might think. Quicksilvers, anyone?This is all true, but the twist is that such transformer is probably not defective - it is doing what it is supposed to be doing, it is designed that way. It was designed to meet some incredible low cost objective and that means humongous flux densities. One can't expect a transmission in a $5000 subcompact work as smoothly as the 540i 6-speed. You sort of get what you pay for, of as a firend of mine likes to say: You pay for what you get. For instance, you can buy very reasonably priced Signal power transformers that, without an exception, consistently buzz under their rated load - when you look at their iron weight it is not surprising.
While no one can guarantee 100% quiet transformers, some people do come close to that, but usually in the higher price echelon. Power transformers with low flux density are expensive.
Your options include tightening the screws first of all, then screaming and bitching about it to the manufacturer. Some companies will replace a buzzing tranny with no questions asked.
There is one last possibility and it is usually outside of anyone's control, though. A good transformer that is normally quiet will become noisy given very distorted power line - so don't discard that possibility as well. In one case that I am familiar with, three or four parts were replaced one after another, all verifiably quiet, with no good results. A sufficient amount of power line harmonics can be damaging. Of course, the toroids are more sensitive to that, but the more common E-I's are not immune either. To rule out this possibility, take the amp to a different location and try it there.
speaking of transformers what is strength and weaknesses of EI v. C core v.double C core v. cut core v.toroidal for both power and output. At what point do they saturate, what is their speed & responsiveness and what is their freq. response typically. I know their are a lot variables so feel free to speak as generally or specifically as you like. many thanks for your valuable contributions to this group
***speaking of transformers what is strength and weaknesses of EI v. C core v.double C core v. cut core v.toroidal for both power and output. At what point do they saturate, what is their speed & responsiveness and what is their freq. response typically. I know their are a lot variables so feel free to speak as generally or specifically as you like. many thanks for your valuable contributions to this groupOne way to look at it is from the position of an "ideal component". It is often repeated that the closer a component is to the ideal model, the better it is. Few people would intentionally introduce in the signal chain a less-then-ideal thing.
If you take this approach then toroid wins hands down. Of the three types above it has the lowest flux leakage and the best primary-to-secondary coupling. Think of flux leakage as a blood flow thrugh your body - the less you lose the healthier you are. A toroid is much closeer to an ideal transformer than the other two ( I lump the two C-cores together, and I am not sure what you mean by the cut core, I presume it is still a C-core).
Because of its being closest to ideal, it is also most efficient, meaning the lighest and smallest for the same function and power rating. It also contaminates the surrounding area with stray magnetic fields least of all.
The main reason the toroid is not used more often is of course, its cost. It can be as high as double of the cost of a traditional E-I type.
The C-core parts are essentially lower cost toroids and are placed in between the two types. These enjoy many benefits of the toroidal transformers at much lower cost. They do lose some qualities, of course. But because they are highly manufacturable and can be configured many different ways (depending upon the bobbins shapes), they are very popular, mostly in Asia and Europe - have been for decades.
If your main concern was bandwidth, then using a toroid would provide for the widest one - because the leakage inductance is the lowest.
In my view (and I put my money where my mouth is), all high end products simply should have toroidal power transformers. Magnetically shielded ones.
When it comes to an optput tranny, there it is all about a particular sound the designer is trying to achieve, and the transformer is a significant sound-shaping tool. So the E-I type has more right to exist in this particualar area.
You are right ! torodial is good on Power transformers but no good for Output transformers. Is is difficult to insert a thin paper on each layer. It have low leakage but high capacitance. So It high frequency still not good enought for output. It also don't have a air gap. It become not good for Single end output transformers. It will saturated due to DC current.
***You are right ! torodial is good on Power transformers but no good for Output transformers.I don't think that is true. There ARE some incredibly good toroidal outputs.
***Is is difficult to insert a thin paper on each layer.I presume you are talking about air gap. The core is cut in two and the gap introduced, much like in the case of the C-core part.
***It have low leakage but high capacitance. So It high frequency still not good enought for output. It also don't have a air gap. It become not good for Single end output transformers. It will saturated due to DC current.I believe all those issues are addressable in the toridal outputs. For example, Plitron makes toroidal outputs with high frequency going into 350kHz - so it can be done. Also, the air gap CAN be introduced if required, it is not too hard. I have not seen anyone make toroidals for the SE amps, but suspect it can be done too.
I am not a believer in the SET's in general, otherwise, based on my positive experience with other toroidal parts, I would be quite tempted to try a toroid there too. I suspect one would have to experiment with the best way to arrange the windings - there are many ways of reducing the capacitance, if that is your requirement. Look at the way high frequency coils are wound.
I hear the very same statement every day: toroidal output transformers are problem. We have been using them with great results for about six years now and they work as advertised. During the initial tests, a prototype toroidal part worked better in every respect compared to a very fine E-I model.
I realy wish more people took the plunge and seriously investigated the toroidal output transformers. Plitron makes a very nice line of the general purpose parts suitable for a DIY'er.
Band Width 35Khz ? Do you know it have never told you how many -db ? It is no meaning spcification. Some manufacturer just told you Band width xxx Khz but never told you -db !!!!
You are right ! It is from China as I know but some amplifiers from China don't have such problem. It only the poor material , poor design & poor quality control.
The two outside ones are the output transformers which feed the speakers, and the center one is the power transformer. The power tranny has a 120v/60Hz primary winding and multiple secondary windings that convert the 120volts to 5-7volts typically for the filaments and several hundred volts for the B+ voltage for the plates.In simple terms, your power tranny has laminations that can vibrate due to the strong 60Hz magnetic field variations of the power from the wall.
If these laminations are loose, things can vibrate and resonate. First thing to do is to check the machine screws at each corner of the tranny that hold the laminations together - make sure they are tight.
The tranny could be going bad, but loose laminations and mounting are the first things to check.
I once had an early version of the Mac1900 Receiver that was eventually upgraded from a power tranny with 4 machine screws holding the laminations together to one with 6 screws. The change got rid of the mechanical hum coming from the unit that was bugging me. A little mechanical hum is normal, especially with less expensive transformers.
Dave van Harn
We have same problem 4 years ago. It is cause by turns/V not enought. Also the induction to Iron Cover. (I'm not sure is it a Iron cover). It can not solve by any method.
nt
I will try to tighten the screws down, but I think It might be more serious. They don't feel too loose, it could be that I really need a power line conditioner, if not it'd still be a fun toy. I'm thinking triodes would be my best bet driving efficient speakers in a near field listening layout.I would strongly consider solid state but my room isn't planar friendly :( I've been reading your posts about your fascination with tubes. I think your going to need to part with your Apogees for some more efficient speakers if you go the full triode route. Good luck
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