autoformer preamp

[jesserparker]

hi,
i'm contemplating attempting to build one of these transformer based pre's, but need to know more about them. first off, where do you get the parts for them (how much are they?), also, how do you wire them up (i've heard mention of one design advocated by thorsten loesch, but haven't been able to find anything out about it other than that it exists), and i would also be curious to know what all your impressions of there sound is. thanks.

 

[analog_sa]

but haven't been able to find anything out about

And where exactly did you look? Did you try diyaudio.com?
Once you find your glasses you may wish to search tweakers asylum and diyhifisupply forum at audioasylum.com. Also bentaudio and diyhifisupply.

Besides, autoformer and transformer is not the same. The only commercially available autoformer volume controls afaik are made by Dave Slagle at audioasylum

 

[ThorstenL]

Koinnichiwa,

first off, where do you get the parts for them (how much are they?), also, how do you wire them up (i've heard mention of one design advocated by thorsten loesch, but haven't been able to find anything out about it other than that it exists), and i would also be curious to know what all your impressions of there sound is.

Well, first, what I'm advocating are not Autoformer Designs (Dave Slagle advocates these), but full transformer designs. A good while ago I attempted to get Sowter to design something and I had lined up quite a substantial group order, when Sowter insisted on changing the spec, so the group order disappeard. Following this Sowter eventually released the original specification part over a year later (9300), but it has been later taken out of production again. Reputedly (I never tried the later designs by Sowter) the current parts do not sound as good as the original.

Feeling that even better performance than that should be possible tha the 9300 I got Jonathan Billington from Stevens & Billington LTD to design an Attanuator Transformer based around his exceptional TX-101 line input transfromer core design (I also commisioned an MC Stepup - the TX-103 - around the same basics) and thus the TX-102 was born.

http://www.stevens-billington.co.uk/page102.htm

It has gone through a lot of revisions and is now supplied through two OEM/Distributors to the general public and used in a number of commercial products. In case of of the Distributors and at least one OEM Customer specifically cstomised versions are supplied to each of them, differences include among others wire and also to some part winding schemes, so while the general comments about the sound with regards to ANY of the products will be similar and generally applicable, there are notable variations based on each customers desires, preferences and concept of "right sound".

Here the DIY Suppliers (both have also Kit's):

Bent Audio Canada:

http://www.bentaudio.com/parts/diy.html

http://www.bentaudio.com/parts/noh.html

DIY HiFisupply Hong Kong:

http://diyhifisupply.com/accessories/s&b_transformers.html

http://diyhifisupply.com/diy_kits/django.htm

Commercial Products (excluding above kit's which are also available assembled) around the TX-102 and with reviews available are:

http://www.6moons.com/audioreviews/audiozone/amp2.html

http://www.avtac.com/Products.htm

http://www.mfaudio.co.uk/

For myself, ever since I started using transformer based passive linestages there has not been any real, serious going abck (I have used other stuff over time between changes etc, but always have come back). I have preferred the S&B over the 9300 Sowter as well, BTW. Others have compared S&B, Silver Rock and high end switched resistor passives (sorry, normal pot's don't even get a look in, sonically).

Sayonara