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mark wrote:

with reference to the LL1627a as used in full range application in melq.you mentioned a good choice gapped at 200 ma but i would prefer 300ma but they do not do it.i had k and k check with lundhal and they will do it and at the same price 375.he mentioned that this would potentially drop the primary inductance  which could become a factor in  low frequency response.what are your thoughts on the pros and cons of using the 300ma gap in this case? i suppose a potential pro would be more headroom?

If you prefer 300ma gap, then you are out of the Lundhal’s realm as they do not have enough core mass. They can gap this transformers with any gap you ask them but you pay losing of inductance. What you want is a sensible balance between headroom for current and LF power that the transformer will be able to handle. It would however would deepens how you will be using this transformer.

Having both 200mA and 250mA LL1627A and listening and measuring both of them here is what I feel you options might be. If you willing to build a full range amp then I would go 200mA as it give enough inductance for good bass and it will allow you to drive the 6C33C at 180-190mA and moderate power. Charles from New Zealand just finks his Milq with 200mA LL1627A and he commented very positive about bass.

http://www.GoodSoundClub.com/TreeItem.aspx?PostID=5740

I personally run LL1627A with 200mA and it was nice. It was clipping approximately 3Hz above ML2 (~19Hz vs. ~22Hz) but subjectively it was incontestably better despite messured higher. I have no idea way Milq does it. The amorphous core should lose at bottom very rapidly but it does not sound like this subjectively.  The 250mA does subjectively have less weight at bottom.

From another perspective if you are willing to eventually for DSET and get a dedicated LF transformer then you should not worry about bass and lower inductance would not be a concern.  However, you might not need a lot of gap for HF transformer as you might drive only half of the 6C33C plate at 130-150mA. In this setting the 200mA transformer will be more than adequate,  even it will be too much as you will not be driving LF though it. You in fact would need to loose inductance using less turns.

There are no needs to go for 300mA gap in HF transformer; in fact you might need for HF transformer to stay with a gap close to the current you drive. For LF transformer 300mA gap is fine, I would go higher, but it obviously would not be Lundhal.

So, as you see it would be all depends to what would be your plans for your amp. I do not see a need to invest into 15H 300mA full range amorphous transformer if you plant to do DSET. From another perspective you have money to burn then a custom 300mA transforms for a full range Milq would be a very cool to try. Let me know if you found a good source and I might get it for my Injection Channel (full-range) if it were not expensive.

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