Hello one and all,
Yesterday, I got a 2nd hand isolation transformer to use with my integrated amp (2000va/8.2A).
I stuck a large 250v-rated varistor across live and neutral to soak up spikes, but when I turned it on I blew the 5A fuse on my mains reel which it was plugged into. Any ideas why? I have used varistors across L+N (on other equipment) with no problems, and an increase in sound quality. These were smaller ones bought from a different place however...
The sound btw is quite markedly different, with a much richer tone, deeper bass etc. I have lost some attack and excitement, maybe I can put this down to crap wire from transformer to wall, which I will change to something better ASAP...
TIA for suggestions
-Simon
Yesterday, I got a 2nd hand isolation transformer to use with my integrated amp (2000va/8.2A).
I stuck a large 250v-rated varistor across live and neutral to soak up spikes, but when I turned it on I blew the 5A fuse on my mains reel which it was plugged into. Any ideas why? I have used varistors across L+N (on other equipment) with no problems, and an increase in sound quality. These were smaller ones bought from a different place however...
The sound btw is quite markedly different, with a much richer tone, deeper bass etc. I have lost some attack and excitement, maybe I can put this down to crap wire from transformer to wall, which I will change to something better ASAP...
TIA for suggestions
-Simon
possible inrush current
It is quite large!
I had thought about inrush current, but where is the current rushing to get to? It wasn't connected to any load! Will a transformer pull some current just to sort of 'load' the wiring? And would that be enough to blow a fuse? (I noticed the internal fuses are rated at 32A/400v!!) Ooh, also, why would a varistor make it draw extra current?
-Simon
It is quite large!
I had thought about inrush current, but where is the current rushing to get to? It wasn't connected to any load! Will a transformer pull some current just to sort of 'load' the wiring? And would that be enough to blow a fuse? (I noticed the internal fuses are rated at 32A/400v!!) Ooh, also, why would a varistor make it draw extra current?
-Simon
if a transformer doesn't have any load on the output the outputvoltage rizes till ... who knows ... so the VDR wil do its job, but if the VDR have to work ik wil act as a short-circuit, actually it will destroy itself in that short time, so you need to add a load to test or just use a higher voltage VDR
( this if you placed the VDR on the secundairy side, dunno if on primairy )
just my thought
( this if you placed the VDR on the secundairy side, dunno if on primairy )
just my thought
Is there such a thing as a DC varisistor?
I had a similar issue, I think, w/ a 220 step down transformer I threw together.
It was a big Hammond step down that I put in a box w/ a pair of duplex outlets on it. When I first plugged it in, BLEWY! All the lights went out. I should have tested it before leaving town. After the hotels floor matron showed me where the circuit breaker was, I found that I could operate the transformer, if I switched off the circuit breaker, plugged in the transformer, and then switched the circuit breaker back on. Inrush currents being the culprit, this was a mild work around.
I don’t think the varisistor should be giving you issues unless its just specked out wrong like Joe-D was suggesting. (Is there really such a thing as a DC varisistor, or is that a zenor-diode?
I’ve heard other interesting reports about iso-transformers here before. I don’t know if I’ve seen anyone hypothesize about the change in the source impedance between the transformer and the amplifier.
Without the iso transformer the amplifier in most cases will be facing a rather large transformer feeding a myriad of homes, and apartments. This to the amplifier will look more or less like an ideal voltage source (methinks?). The iso-transformer will have a substantially lower source impedance with respect to the amplifier, subsequently looking much more like a current source.
I think this may start to explain some of the perceived differences in sound quality that are observer when these devices are used. If we extrapolate a bit from here we may be able to make some parameters for ideal audiophile grade isolation transformers for various applications. (KVA, K ratings ect.)
Fred Dieckmann did you catch any that? I'd love to know what you think. Am I close to the issue, or talking out my back end (again)? If I got any of it wright, I think it was with your assistance.
Thanks.
-Dave
I had a similar issue, I think, w/ a 220 step down transformer I threw together.
It was a big Hammond step down that I put in a box w/ a pair of duplex outlets on it. When I first plugged it in, BLEWY! All the lights went out. I should have tested it before leaving town. After the hotels floor matron showed me where the circuit breaker was, I found that I could operate the transformer, if I switched off the circuit breaker, plugged in the transformer, and then switched the circuit breaker back on. Inrush currents being the culprit, this was a mild work around.
I don’t think the varisistor should be giving you issues unless its just specked out wrong like Joe-D was suggesting. (Is there really such a thing as a DC varisistor, or is that a zenor-diode?
I’ve heard other interesting reports about iso-transformers here before. I don’t know if I’ve seen anyone hypothesize about the change in the source impedance between the transformer and the amplifier.
Without the iso transformer the amplifier in most cases will be facing a rather large transformer feeding a myriad of homes, and apartments. This to the amplifier will look more or less like an ideal voltage source (methinks?). The iso-transformer will have a substantially lower source impedance with respect to the amplifier, subsequently looking much more like a current source.
I think this may start to explain some of the perceived differences in sound quality that are observer when these devices are used. If we extrapolate a bit from here we may be able to make some parameters for ideal audiophile grade isolation transformers for various applications. (KVA, K ratings ect.)
Fred Dieckmann did you catch any that? I'd love to know what you think. Am I close to the issue, or talking out my back end (again)? If I got any of it wright, I think it was with your assistance.
Thanks.
-Dave
Hi Dave,
Fascinating reply. I searched and found a recent thread on inrush currents/transformers/blown fuses. The general concensus appears to be that any transformer can pull a lot of current when first connected/turned on - and 2kva is quite large!!! It's like having my own little substation
I suppose my main point originally was concerning the MOV/VDR as it only blew once in several times being plugged in - and that was when the MOV was attached.
The varistor is rated at 250vac, and it says: "max 8000 A Energy, transient 140 J, Voltage, varistor at 1mA 360 V Voltage, clamping max 650 V." It is quite a large one, I think. Here is the url...:
http://uk.farnell.com/jsp/search/searchresultstwo.jsp?action=0&ImgDisp=Y&QText=580247
Interesting musings about why a transformer can change the perceived sound. I always thought, personally, it was just because of the potentially massively reduced common-mode and 'whats the other type?' noise reduction.
For UK readers, there are more of these babies going on Ebay now, though I think they'll end up less of a bargain this time around
-Simon
Fascinating reply. I searched and found a recent thread on inrush currents/transformers/blown fuses. The general concensus appears to be that any transformer can pull a lot of current when first connected/turned on - and 2kva is quite large!!! It's like having my own little substation
I suppose my main point originally was concerning the MOV/VDR as it only blew once in several times being plugged in - and that was when the MOV was attached.
The varistor is rated at 250vac, and it says: "max 8000 A Energy, transient 140 J, Voltage, varistor at 1mA 360 V Voltage, clamping max 650 V." It is quite a large one, I think. Here is the url...:
http://uk.farnell.com/jsp/search/searchresultstwo.jsp?action=0&ImgDisp=Y&QText=580247
Interesting musings about why a transformer can change the perceived sound. I always thought, personally, it was just because of the potentially massively reduced common-mode and 'whats the other type?' noise reduction.
For UK readers, there are more of these babies going on Ebay now, though I think they'll end up less of a bargain this time around
-Simon
I suppose that the MOV could be reacting to an induced spike from the inrush current, and popping the CB. Geesh that almost sounded good. Watch out, its a bit dangerous when I start believing my own drivel.
I emailed the mods, looking for Fred, as I’ve always enjoyed his background and ideas on these issues. Meanwhile, if anyone else spots any errors in my often flawed suppositions, please jump in.
-Dave
I emailed the mods, looking for Fred, as I’ve always enjoyed his background and ideas on these issues. Meanwhile, if anyone else spots any errors in my often flawed suppositions, please jump in.
-Dave
Yeh, that sounded quite good
Assuming that is correct, and I have no reason to doubt it is, then it looks like I can't actually use normal MOVs for removing spikes
I just (haha, optimistic it now seems) wanted a cheap, simple, and comprehensive way to clean the power going to my amp.
I also have some x and y caps I got just for it, not put those in yet.
ooh, just remembered, I drew a pic whilst bored at work!
Attachments
Nah, it's one of those old-fashoined ones
An 'I' core I think.I measured the resistance across the primary ends, at about 0.7ohms - sounds like nearly a short-circuit to me!!
Now that I've been using this for a couple of days I'm not going back!! The plug, extension, and the wall socket are all rated for 13A, which seems to be enough....unless you meant big leads going in and out of the transformer, in which case - yes! Will do it, maybe with some Chord Odyssey - thick silver-clad, teflon speaker cable. I bet that makes excellent mains wire.
-Simon
I was thinking something al little more pedestrian, like an industrial grade 10-3 SJ jacket from Carroll or Belden. A good Hubble connector. . 10 Gauge is likely a little overkill, but that’s the point after all, isn’t it?
Do you know the make of the transformer?
What kind of receptacles do you use? I think I'm familiar w/ two types, but I'm not sure what they are called. One is the shutco (sp?) , that has three big square pins and the over has two round pins and sometimes a ground built into the case. I'm not sure what that one is called.
-Dave
Do you know the make of the transformer?
What kind of receptacles do you use? I think I'm familiar w/ two types, but I'm not sure what they are called. One is the shutco (sp?) , that has three big square pins and the over has two round pins and sometimes a ground built into the case. I'm not sure what that one is called.
-Dave
Dave,
The transformer comes from this via an MK toughplug and standard wire, which is hard-wired/choc-blocked to the 'former. I have (probably) 16awg good, braided wire to my amp, again hard-wired at the transformer end.
I have already asked for some speaker wire from the shop I work PT at, which I will use to replace the wire to and from the transformer. When I install that I will use Deoxit contact enhancer to help get good connections.
I wouldn't normally consider £17/m cable for this, but at trade price it's rather cheaper...
I'm hoping for some change.
-Simon
Burrows Electrical I think. It is fairly old.
Err, a fairly standard, fairly new switched wall box. This leads to a modified (no internals, and cleaned contacts) 8-way Belkin computer strip via very thick braided wire.
The transformer comes from this via an MK toughplug and standard wire, which is hard-wired/choc-blocked to the 'former. I have (probably) 16awg good, braided wire to my amp, again hard-wired at the transformer end.
I have already asked for some speaker wire from the shop I work PT at, which I will use to replace the wire to and from the transformer. When I install that I will use Deoxit contact enhancer to help get good connections.
I wouldn't normally consider £17/m cable for this, but at trade price it's rather cheaper...
I'm hoping for some change.
-Simon
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