i have vitavox S2 and also altec 288c.i am trying to source the fane studio 8m,just missed a pair by 1 day on uk diy.until i get the fane and make a horn for it,i will use altec 515c in vot.i also have jbl 2405.yes i will definitely build the full range first,that is common sense.but i want to be able to switch the full range to low pass at 550hz and high pass a single stage from 550hz up.eventually i might follow the full 4-6 channel setup eventually but for the next year this is as far as i want to go.since the sourcing and shipping is a pain for such small quantities i am going to order sufficient quantity of the smaller harder to get parts(diodes,950 caps etc.) to last me for several units.right now i would like to know what transformer you would reccomend for the single stage 550hz up as i am ready to order the LL1627a from k&k and would like to get the single stage transformer ordered and shipped together.as soon as i get the full range done i really want to experience the dset midrange.one step at a time.

Well, the LL1627A is very good universal transformer with phenomenal flexibility (properly done - with section not with tabs) to load the output stage. It might be a good choice for a full-range amp at 200mA, though I would still prefer to have a transformer gaped for 300mA – so you would need a larger core and they do not do it. I do suggest to by one LL1627A as you would need to know how to load your 515c, your S2 and how Milq might sound all together.

For LF transformer you need nothing fancy but juts with a lot of core mass. In my case Jack from ElectraPrint did very well, it is else very inexpensive but there is a catch in there – you do not know what kind ration you would need to damp your 515c driver properly (do not forget –Milq is no feedback amplifier). You might use the LL1627A to investigate your bass channels’ needs – that what I would do. Alternatively you might try to do what I am trying to do now with my 1Ohm (amorphous?) bass transformer – to make the secondary interchangeable. It has some complexity as the coils would not fill up the core as they use to and the person who would wind the thing would need to make the necessary corrections in order to hit the target impedance.

I have a left over bass transformer from my project but it would not be useful to you primary because my transformer dies at 800Hz and it would be too low for you. If I was you I would go for top roll of at minimum 2000Hz as 550hz is very high crossover point.

For above 550hz you might use the same LL1627A if you wish, for MF the 200-250mA gap will be fine. Yes it would be reasonable to desire less inductance in the transformer, mean less turns but honestly I personally did not detect that it very much affects sound, at least in context of the S2 bandwidth.
Well, Mark, there are a number of manufactures out there who made amorphous transformers, I did not try them, I am sure you will found a lot of people out there who had more exposure then I did. I kind of had an easy ride with LL1627A.

For a single stage amp you would need a transformer with ~40mA and the inductance enough to care 2-3 octaves under your crossover point. Here is fragment of email that I was sending to transformer manufactures when I was searching my MF transformer.

1) Amorphous 'C' cores (there is different type of amorphous material, I
would need with higher permeability)
2) Ratio 15:1
3) Minimal amount of turns on primary, juts enough to built up inductance to support high-pass roll off at 500Hz.
4) Gaped for 40mA
5) The most minimalist phase shift above 10Khz.
6) 300V on primary.
7) Lowers DCR on primary
8) <5w carrying power.
9) Inclosing and appearance of the transformers are irrelevant
10) The secondary sections (>7 sections)go out (with marked polarity) allowing secondary remapping.

Still, if I was you I would not think about the transformer for a single-stage amp or about anything else. Get a single LL1627A if the equivalent amorphous, it will cost you $350. Build a single mono Melquiades around this transformer, powering it from your bench PS but with the Milq biasing schematics. It would take you one evening to do as Milq is very simple amp. If you found the full-range result worth you attention then you might think further. While you do so you will see how you bass channel react to 8H of the LL1627A’ inductance.

Romy the Cat wrote:

For above 550hz you might use the same LL1627A if you wish, for MF the 200-250mA gap will be fine. Yes it would be reasonable to desire less inductance in the transformer, mean less turns but honestly I personally did not detect that it very much affects sound, at least in context of the S2 bandwidth.

Still, would like to keep the thread about Melquiades as it is a Milq dedicated forum. If you attention is only S2 driver then move to an appropriate thread about S2 – there are plenty of them at this site.

mark wrote:

what indicators or criteria would make my particular drivers more or less amicable with amphorous cores?(with reduced inductance only?)is it strictly an issue of varied lots of alnico used throughout  decades of production?

Good question. I do not know the answers. I did matching of drivers to the amp channels not vice-versa.

mark wrote:

the thing that really hit me like a 2x4 was romey saying of 12 s2 only 3 were usable in his opinion.

I would say 3 of 6 as the 4 of them I keep with metal and 2 with “old” plastic suspension.

Mark, generally in order you to have anything that I say in perspective of even better do not listen what I say at all and to use own judgment I proposed you to make/buy/borrow a full range SET (it might be a Milq prototype with AM core) and  to see how you driver will react to your expectations. Without it any conversations are groundless.

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.