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In Reply to: Xformer question mainly for Thorsten posted by Granholm on November 27, 2001 at 04:24:36:
(((Would it be the primary or the secondary that should be "fixed"??)))the primary should be fixed and the secondary winding adjusted.... this keeps the largest load on the preceeding stage.
((((Would it be ok to use one bobbin with multible outputs or should I go for multible bobbins?))))
i would use a single bobbin...
((((Would a teroide be any interesting or would it be a problem with capacity between primary and seconary?)))
i think the toroid could be very cool to keep the leakage very low... this is for the most part a step-down device where leakage becomes a major concern... i picked up a toroid winder on ebay, but haven't gotten around to getting it working... i was looking at the cobalt based amorphous toroid cores...that stuff looks to be ideal for this type of application.
((((What should be the optimum -3db freq? 30K, 50K 100K....)))
i say as high as possible...
((((( I know its not an easy to get by project and so it should not be! Thats where the fun begins.)))))
you just have to grab the bull by the horns and try it...
Follow Ups:
One attribute I have had all my life is never to be jelous, but you are testing my sanctity to the limit! Torroidal winding machine in deed!
its ancient and doesn't appear to be complete :-(whaddya want for $50 though
dave
I'll take it!
Wery helpfull! I was awake all night thinking! Your reply just gave me back some spirit. I thought it might be possible to make 23/46 individual transformers using a 4 vaffer ELMA for cutting off both the primary and the secondary!! Just a thought ;o)Rgrds
I would honestly consider a dedicated approach. How many volume settings do you need for absolute critical listening, I mean that occasion when everyone is out of the house, no hoovering, no washing machine, you turn off the door bell unplug the phone and put on your best vinyl, get into that sweet spot in your room. How many settings do you need for that moment? 3 at the most?So you can achieve that, forget all the nonsense about attaining the flexibility of a resistor network or wiper, achieve an early victory for your very best moments, and just switch in the usual stepped attenuator or pot for the times when it matters about matching volume to the needs of others.
Maybe there is just a single winding tapped choke option with 3 taps somewhere central which would give you the best possible performance at the attenuations that matter.
Actually I might make one too, keep me posted.
Paul Barker
Hi Paul,It was actually some of the idea behind using seperate transformers! Then I could start with one around my usual listening wolumen and do the experiements there and then complete the series when I got the right design.
Dave got my hart beating a bit faster too. But I got a tool fetich anyway.
Rgrds
Me too a toolaholic. Then when you come to do a job you can't find it so you have yet another one of those odd little tools that cuts through pvc plumbing for example. Try and do it any other way though?I'll be honest on the winding. If I had a torroidal winder I'd give them a try, but I don't and my supplier wants £6,000 second hand so we''ll carry on with C cores and EI like most other mortals. BUT torroidal is maybe no better than C core and is certainly less flexible.
But id Dave get's sick of trying to load that shuttle while it's inside the core he canb hurl it right out of New York across the pond please?
Regards
Paul Barker
my whole reason for looking toroidal is the bh loop of the cobalt amorphous cores, but alas they are only available in small toroids... lets just say its loop looks like it has a gap, it has a very narrow linear looking bh loop.
Hi,I must admit that in my system I use a huge range of Volume settings, both due to listening at many different hours (late listening requires envoironmentally friendly SPL levels) and due to many different sources with differing levels.
If you really make a dedicated, single source, near single volume setting system why not just calculate the gain and headroom right and use a very limited range magnetic (Tapped Grid Choke?) volume control directly ahead of the output stage? After all, the best attenuator is still no attenuator.
Ciao T
(Tapped Grid Choke?) volume controlisn't that an autoformer????
dave
Hi Dave,Yes, it's an auto transformer. If you make (as said) a dedicated, single source, single pair of speakers system it makes to move the volume control as far back as possible. As commonly the power stage has the lowest headroom, design the system for just the right gain and make the adjustments for the volume at the final point.
I find the further back the volume control moves, thebetter the overall sound, percieved dynamics etc.... But thats just me.
Ciao T
i agree with the further back you move the attenuation the better... i've been having some good results with speaker level autoformers lately... that is the place we could use the extra drive anyways....dave
Na, that would be too much like listening to solid state.
Interesting idea. I was thinking too that you could adjust with different mu valves. One might prefer the sound of a low mu valve but need the gain of a high mu valve for full power. When it comes down to normal listening levels a 6sn7 can replace a 6SL7 for example, and some people prefer the sound. Maybe better still the 76.Oh by the way. Yes late night listening is one level I need in good quality, and a little louder than the wife would like during the day when she is out, so that's just two taps on my choke, switch in a volume pot for the rest of the odd times when a tweek of the volume seems to be important. To me, those times don't allow the attention span for serious listening, so I wouldn't need the quality. Friends don't deserve it anyhow, they are content to bang on the piano or pick up the guitar what do they know about serious listening?
Regards
Paul Barker
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