Hi guys! I have a question.
What's your favorite transformer for chip amp and gainclone?
My fav is Stancor "NV" style, like this one.
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=9288566
It works well for designs like 47 labs: ". . .where only the simplest. . ." have such limited power supplies that transformer choice is critical.
So what transformers do you hold in high regard? Let's see em'
What's your favorite transformer for chip amp and gainclone?
My fav is Stancor "NV" style, like this one.
http://www.alliedelec.com/Search/ProductDetail.aspx?SKU=9288566
It works well for designs like 47 labs: ". . .where only the simplest. . ." have such limited power supplies that transformer choice is critical.
So what transformers do you hold in high regard? Let's see em'
It doesn't matter, just to be built OK. The toroid which is used in my GC is a 400VA monster and even if I stick my ear into it I cannot hear anything. Now take a look at this cutie:
http://www.selectronic.fr/article.asp?article_ref_entier=90.3223-9999
http://www.selectronic.fr/article.asp?article_ref_entier=90.3223-9999
I did find some R-Core on ebay.
One thing that the Toroid and R-core can do better than my fav Stancor NV series is. . . the smaller toroid and R-core are so short in height that the amplifier enclo$ure cost$ much le$$.
On a recent discussion, a friend and I, who hardly ever understand each other, both agreed on a minimum 80VA capacity and that larger 120VA to 160VA capacity would be better. Neither of us illustrated all the details as for why. For me, it relates to bass response, and I do not know the details, except that the errata does exist.
Power supply boards with extra poles and sufficient caps (at each pole) can help, but they don't completely cover the issue. A "right sized" transformer gets it done more easily.
This makes for 3 amper to 4 amper EI core transfos in sizes of about 4 x 4 x 3.5 inches (plus an extra 3" clearance away from signal-in/amp); however, Toroid and R-core are sized conveniently smaller at equivilent strength.
I had assumed that I'd simply use wooden enclosures (they have plenty of room for the EI core and there's plentiful insulation); however, the timeframe for me to make a seemly-looking wooden box was unexpectedly huge, and, in fact, a barrier to completing projects.
Compare the VA capacity requirement for doing it the easy way, to the cost of enclosures, and you'll see the point.
Its this:
If you're a good carpenter, you're "home free" on saving some cool cash on your transformer. Otherwise, you'll need the R-core or Toroid that will fit into a prefabricated enclosure.
I find this out the hard way.
One thing that the Toroid and R-core can do better than my fav Stancor NV series is. . . the smaller toroid and R-core are so short in height that the amplifier enclo$ure cost$ much le$$.
On a recent discussion, a friend and I, who hardly ever understand each other, both agreed on a minimum 80VA capacity and that larger 120VA to 160VA capacity would be better. Neither of us illustrated all the details as for why. For me, it relates to bass response, and I do not know the details, except that the errata does exist.
Power supply boards with extra poles and sufficient caps (at each pole) can help, but they don't completely cover the issue. A "right sized" transformer gets it done more easily.
This makes for 3 amper to 4 amper EI core transfos in sizes of about 4 x 4 x 3.5 inches (plus an extra 3" clearance away from signal-in/amp); however, Toroid and R-core are sized conveniently smaller at equivilent strength.
I had assumed that I'd simply use wooden enclosures (they have plenty of room for the EI core and there's plentiful insulation); however, the timeframe for me to make a seemly-looking wooden box was unexpectedly huge, and, in fact, a barrier to completing projects.
Compare the VA capacity requirement for doing it the easy way, to the cost of enclosures, and you'll see the point.
Its this:
If you're a good carpenter, you're "home free" on saving some cool cash on your transformer. Otherwise, you'll need the R-core or Toroid that will fit into a prefabricated enclosure.
I find this out the hard way.
The recent discussion took place between you and AndrewT, isn't it? I'm not a carpenter at all, but my enclosure is made of wood and it costed me around $5 at a local store, including cutting at the size I specified. As you can see, it isn't _that_ expensive.
Now, regarding the sound, IMO no juice, no life. Let's say that my amp is capable of 40W output, audible undistorted. The true efficiency of AB class is around 40...60%, so I took the worst case, 40% efficiency for a LM3886. This means that at full continuous power I will draw 100W per channel, right? Two channels equals 200W. But at 30V per rail as I have, the maximum peak power can be 30^2/4 = 225W. Two channels equals 450W. Now, instead of drawing this amount of power from the filtering caps, why not to have this power available all the time? So that's how I ended with a custom made 400W toroid.
I'm not a carpenter at all, but my enclosure is made of wood and it costed me around $5 at a local store, including cutting at the size I specified. As you can see, it isn't _that_ expensive.Now, regarding the sound, IMO no juice, no life. Let's say that my amp is capable of 40W output, audible undistorted. The true efficiency of AB class is around 40...60%, so I took the worst case, 40% efficiency for a LM3886. This means that at full continuous power I will draw 100W per channel, right? Two channels equals 200W. But at 30V per rail as I have, the maximum peak power can be 30^2/4 = 225W. Two channels equals 450W. Now, instead of drawing this amount of power from the filtering caps, why not to have this power available all the time? So that's how I ended with a custom made 400W toroid.
ratza said:. . .
Now, regarding the sound, IMO no juice, no life. Let's say that my amp is capable of 40W output, audible undistorted. The true efficiency of AB class is around 40...60%, so I took the worst case, 40% efficiency for a LM3886. This means that at full continuous power I will draw 100W per channel, right? Two channels equals 200W. But at 30V per rail as I have, the maximum peak power can be 30^2/4 = 225W. Two channels equals 450W. Now, instead of drawing this amount of power from the filtering caps, why not to have this power available all the time? So that's how I ended with a custom made 400W toroid.
The diodes will still drop, unless. . .
You could have quad secondaries, or a pair of dual-secondaries transformers. That would make 4 rectifiers (16 diodes). Just a thought. I'll do it someday, but the way I make power supplies, it would have 35 capacitors (only 16 big caps). Only? LOL!
Okay, I have to laugh at myself sometimes. Now is good.
Well....just for the sake of not arguing and getting back to the original subject...I have had very good luck with this company - www.antekinc.com. In my last gainclone I used a fairly large 400VA toroid with dual secondaries and it is dead quiet....and is now one of my "reference" amps.
I would love to try an R-Core, but have not really found any that were reasonable (price wise) or "up to-snuff".
I would love to try an R-Core, but have not really found any that were reasonable (price wise) or "up to-snuff".
Sound versus power = apples and oranges consideration.
They weren't disagreeing on anything except the method used to measure resonance.
It seems that a lot of people enjoy the resonance of the bigger 300va and 400va transformers for unregulated linear power supplies, especially with, but not exclusive to, the gainclone styles.
They weren't disagreeing on anything except the method used to measure resonance.
It seems that a lot of people enjoy the resonance of the bigger 300va and 400va transformers for unregulated linear power supplies, especially with, but not exclusive to, the gainclone styles.
paulb said:
Um. . . No, not really.
But, I'll try it just for fun.
Even after rectification, there's no such thing as perfect DC. The source of it always has a size. This rings exactly like a wind chime works. That is a resonance. Each different size has a different resonance. Choose one that's pleasant for your application.
You can calculate a zobel for a transfomer exactly like you would calculate a zobel for a woofer. Both a speaker driver and a transformer have a copper coil around either metal or a magnet. The same caveats and calcuations apply as they would to any inductor.
You can alter the resonance with a power supply board if you had one--but since a "gainclone" (meaning, the style of 47 labs) doesn't have a power supply board, then the transformer selection becomes more important.
In contrast, observe the series resistors in the carlosfm power supplies (and many others). These can use much smaller transformers with quite good results. The resistor has created a pole. This changes the resonance of the power circuit. But that's not a gainclone style anymore.
That's almost as far out on a limb as I'm able for at the moment.
wboyd said:
Hi. I'm wondering if that's Antek's AN-4255 (pair 25ac sec) or their AN-4222 (pair 22ac sec)? Those look nice. Wow. Big.
The 2.7" x 5" sort of puts an end to my theory about the Stancor NV being too big at 3.5" x 4" x 4". The Toroid requires clearance on the top for an air gap, in order to avoid the shorted turn phenomena, wheras there's no such requirement for the EI. There was actually no difference in the required size for the amplifier enclosures. Now, I feel so silly for complaining about that.
I recommend these guys in the UK, extremely proffessional and fast, will build a transformer at your own specs and at a very reasonable price.
I have had 2 toroids built for a Class A project They are centerpotted and with a steelband screen the absolute best transformers I've seen dead quit.
I have tried them out with my Dual mono GC's performing outstanding....
Airlink Transformers
I have had 2 toroids built for a Class A project They are centerpotted and with a steelband screen the absolute best transformers I've seen dead quit.
I have tried them out with my Dual mono GC's performing outstanding....
Airlink Transformers
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