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In Reply to: RE: AS250 info posted by twystd on May 21, 2009 at 12:53:18
Hi Roe:
Like I said in another post today--- primary L is important--- very important--- but not singularly important. There are 436 other factors\variables that you must also optimize to get a good to great output transformer.
On many of our products we do not publish L numbers for many, many reasons.
What your safe in assuming is that nickel will have greater L than a nickel pinstripe which will likewise have greater L than M4 which itself will have greater L than M6.
Of greater import (at least in our designs--- which will have adequate L unless otherwise stated) is that the choice of lamination types is best made from a subjective point of view--- not a solely technical bench derived measurement--- and here it is personal experience and preference that will come into play. We have some customers who love nickel--- others who prefer M4 and yet others who swear by nickel pinstripe.
Each sounds a bit different--- each has it's own colours--- their own strengths sonically--- and unless your willing to marry the girl I pick out for you (smiles here) then you need also to explore and learn of your own sonic preferences in terms of core materials and etc.
Mike
Builder of MagneQuest™ & Peerless™ transformers since 1989
Being a poor boy, I don't have the funds to "date" the beauties, so will probably have to rely on your pick. I like my transformers like my women, fast, warm, and lots of bandwidth!;-)
twystd
Even "bandwidth" is an imprecise term, I'm afraid.
Here we are talking of bass response since this is about core materials. Technically, nickel will (for example) have more inductance at smaller signals, hence deeper and lower-distortion bass. But will overload with too much deep bass. So for small signals it has more apparent bandwidth but when pushed it can seem like less bandwidth. And pushing it starts to happen at less than 1/4 of the rated power - another reason Mike is notoriously conservative about ratings.
All this is simplified to steady-state sine wave signals. Music of course in neither steady state nor sine wave, so there is no reliable way to interpret the science in subjective terms. It depends too much on your taste and your music, and how much power you demand from the amp - again your taste but also your speakers and your room. And of course your mood - none of us has only one single personality or taste!
Thanks Paul, that was very helpful. I do like very dynamic music, at pretty high volume. For example, I like Peter Gabriel's "Up" at pretty high volume with my Straight 8s. Other artists I like are Patricia Barber, Jennifer Warren, Keb Mo, too many to mention, tastes all over the place. I find my single ended 8 watt amp a little lacking, so was looking to take it up a step, to a 15-20 watt PP. Sounds like pin stripe might be the way to go, a little of both worlds.
twystd
My experiences with the AS-250...
I got a pair of the AS-250 units (M4 I guess, no nickel was offered at the time) when Mike first offered them (mid '90s?). I combined them with a pair of the MQ/Peerless Altec 17173 centertapped driver chokes and made a Brook 22A clone. (WE396 input amp/phase splitter, 5687 driver, Sovtek SP 2A3, no NFB). This made one great-sounding amp. While my speakers are quite efficient, this amp sounds more powerful than the 80W solid-state amp I was using previously. Even with zero feedback the bass is well-controlled.
If this is a relatively-simple coil wind job (compared to a 20-20 series unit), it might make a good budget offering. It sounds good to my ears, anyway.
-Dan
neat. I was just stacking a few pairs of these today from a newer run of AS-250's. These are really nice designs.
A topology such as you describe is so easy and straightforward... that with good tubes, good iron, good layout, etc... it would just plain have to sound quite good.
And funny you mention about the nickel.... I actually stacked one pair with all nickel lams. Did one other pair with M4 lams... and a third pair with M6 laminations.
I'll probably be putting these up for sale very shoortly---- look for an announcement over the next few days or so.
Mike
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Builder of MagneQuest™ & Peerless™ transformers since 1989
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