ANTEK transformer quality is quite good
Even Nelson Pass uses them in the SIT 1's and he used to be a PLITRON guy. I feel sure he uses them both.
In my experience, ANTEK offers EXCELLENT service and quality.
Of course, the fire slowed him down and I have not ordered since that happened but I suspect when he says something is in stock and you order it you better want it because it will be on the way.
I have never used the shielded version.
I am not a fan of toroids - I think their most important feature is ease of packaging. But after hearing that the SIGNAL EIs buzz and figuring SIGNAL about as high quality an EI as one can get and if that is the case I have little choice but to use a toroid.
Since the toroids are notorious for their transparency to the AC outside world I wish I had a choice of another format. The R cores are not easily acquired and I cannot find any in a stout VA rating. Wish LUNDAHL made a C core for SS voltages ...
Even Nelson Pass uses them in the SIT 1's and he used to be a PLITRON guy. I feel sure he uses them both.
In my experience, ANTEK offers EXCELLENT service and quality.
Of course, the fire slowed him down and I have not ordered since that happened but I suspect when he says something is in stock and you order it you better want it because it will be on the way.
I have never used the shielded version.
I am not a fan of toroids - I think their most important feature is ease of packaging. But after hearing that the SIGNAL EIs buzz and figuring SIGNAL about as high quality an EI as one can get and if that is the case I have little choice but to use a toroid.
Since the toroids are notorious for their transparency to the AC outside world I wish I had a choice of another format. The R cores are not easily acquired and I cannot find any in a stout VA rating. Wish LUNDAHL made a C core for SS voltages ...
I have used Antek transformers with no issues. I have also recently used a Signal EI core with no problems at all, no hint of buzzing; that was in a Salas BiB for an OpenAmp1 phono preamp. It is dead quiet. Hammond also have an excellent reputation, and are made in Canada.
I really don't see how a circuit that draws a constant current of less than 200mA could benefit from an increase in xformer rating to more than 50VA.
I really don't see how a circuit that draws a constant current of less than 200mA could benefit from an increase in xformer rating to more than 50VA.
IMO, this is something that unless you have personally done the experiment (change out a 50VA for, say, a 160VA and then listen), you will not believe there is a sonic benefit.
10 years ago when I bought a ss phono stage from a local dealer (a copy of the Bill Beard BBP100, from the '80s), I queried him - the dealer - why he had used a 160VA transformer when the currents were so low. His answer was ... that it gave you deeper bass.
So I decided to swap out the 30VA toroids I had used in my active XOs and replace them with 160VA toroids. Sure enough, deeper bass was the result!
) Which just proves the late, great Allen Wright's dictum ... "Nothing succeeds like excess!"Regards,
Andy
And why is 50VA your boundary? My guess is that it is pretty much psychological since 50VA is still way above the 2-3VA that should be enough for allowing such a circuit to function.
Oh and we do not have a constant current, but frequencies... Peak to peak demands could be different than the mean 200mA that our DMMs give.
I can vouch for bigger transformers giving big improvements. After experimentation with various sizes, I am using dual 160VA for my phonoclone and my DCB1. And yes the difference is significant. Rather subject to diminishing returns after the 100VA as expected, but still...
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I was being generous, since 50VA is at least 10x the required power.
No, the shunt regulator in the circuit uses a constant current source; it will never draw more current that that, under any circumstances, even a dead short (thank goodness, that saved my bacon once).
OK, well I have never done the experiment, so I can't gain-say your experience. Still, I am the sort who wants a reason (not even a good one) why a grossly over-spec'ed transformer would change the behaviour of a shunt regulator. Does the bigger transformer have a lower output impedance, and is that somehow reflected through the regulator (with its constant current draw), changing the output impedance of the regulator? Has anyone got any data that supports this?
(My Mezmerize DCB1 uses, as I recall, a 30VA transformer, and it sounds just fine. That even powers an extra input-selection circuit. If it was seriously hotrodded I could see going to something like 50VA or a little higher, but it's only consuming about 80mA per rail. My current phono preamp, powered by a pair of BiB shunt regs biased to 280mA per rail, uses a 56VA transformer which never gets warm. I bought that 56VA unit because Mouser had exactly one in stock, and it was about $12. I was going to repurpose it for this build, but the OpenAmp1 is so darn good with MM carts that I can't bear to break up the PS for it, so I'll probably try to find a couple of nice 25-30VA units for the new build.)
Not looking for an argument, but I wanted to offer an alternative opinion before all new builders of this circuit start thinking they need a pair of transformers better suited to a power amp. In his build guide Salas spec'ed a pair of 30VA transformers, which any technical analysis would suggest is a very generous, conservative suggestion (like an order of magnitude beyond the circuit demands).
True. I was thinking about actual consumption from the circuit after the psu.
RJM tries to give a rather reasonable explanation here.
http://www.diyaudio.com/forums/blog...ower-transformer-than-you-think-you-need.html
I just don't understand why the builders do not inform themselves before selecting transformer power rating.
A DCB1 using a 15+15Vac transformer feeding into a constant current of 200mA requires an absolute minimum rating of 12VA. This will run hot, possibly very hot.
The recommended minimum is 24VA so that the continuous loading is 50% of the rated maximum.
Anything more than 24VA is by choice, not for technical safety/performance.
Yes 50VA, or 160VA, could be used. Yes there may be slight Bass handling changes.
But the mis-informed should never be stating that 3VA or 5VA is adequate. They deserve to be .... !!!! There's no more polite way of saying it.
Make informed decisions, don't guess and don't mislead.
A DCB1 using a 15+15Vac transformer feeding into a constant current of 200mA requires an absolute minimum rating of 12VA. This will run hot, possibly very hot.
The recommended minimum is 24VA so that the continuous loading is 50% of the rated maximum.
Anything more than 24VA is by choice, not for technical safety/performance.
Yes 50VA, or 160VA, could be used. Yes there may be slight Bass handling changes.
But the mis-informed should never be stating that 3VA or 5VA is adequate. They deserve to be .... !!!! There's no more polite way of saying it.
Make informed decisions, don't guess and don't mislead.
AC input 121V, out for each channel 50V DC.
The transformer has an additional piece of core material around the outside and a static shield connected to the core.
Thank you Andrew for the perfectly in tune post.
IMHO, using higher VA Tx, with higher quality build and also high Q capacitors can really make a difference when we use these shunts.... it may seem strange but the difference can clearly be heard.
I did not find a big difference going from 120VA to 160VA and I started to have problems during power on due to inrush currents... also bigger tx tend to be bulky and emit stronger magnetic fields that can be picked up by our preamps.
But I must say, the difference is not restricted to a slight bass handling change... it extends to the whole spectrum, providing a wider soundstage and overall increased ease in the reproduction.
Not a must, but the way to go if you really want to get full on results.
I suspect there is a best value for VA - not simply the biggest
I think it is fairly well accepted that the bigger transformer will have better bass but one has to wonder if there is a loss elsewhere and I bet there is.
Just as has been found that an unlimited amount of supply capacitance is not a panacea. Makes me think going too far overboard with the power transformer for anything but a 100 hz low pass electronic crossover is probably not a good idea for a wideband device.
I think it is fairly well accepted that the bigger transformer will have better bass but one has to wonder if there is a loss elsewhere and I bet there is.
Just as has been found that an unlimited amount of supply capacitance is not a panacea. Makes me think going too far overboard with the power transformer for anything but a 100 hz low pass electronic crossover is probably not a good idea for a wideband device.