Neutrik xfmrs and mixed feedback circuits

[bigugly]

Hey Everybody,

While I was looking through the Transformers Meta I noticed that Neutrik has a couple that would work for a pre. So, being the silly fool that I am I whipped up a schematic and a PCB layout using them for i/o around an OPA604. I have a couple of questions though.

1. Has anyone heard these things? I really don't care if they're kinda crappy. I just haven't heard anyone talk about them and maybe some has but not mentioned it.

2. I'm using a mixed feedback topology. (Jensen Trans. calls it "feedback through the transformer") On Jensen's site they have a pdf, #as025, that shows this and Lundahl has a short pdf on it also. In both instances they use an inverting opamp. Mine is non-inverting. Is that going to be a problem? re: Is there a reason both show an inverting amp that I'm not aware of?

If anyone wants they can go to my Yahoo Photos @
http://pg.photos.yahoo.com/ph/[email protected]/detail?.dir=/5585&.dnm=9782.jpg&.src=ph
to check out my layout and schematic.

thanks,
James Lee
Bigu Ugly Van Audio

 

[pucho812]

file unexcessable :sad:

 

[bigugly]

wow, thats odd pucho. I can acces the link on both my PCs and a Mac.

PM me so I can send them to you.

Unfortunately I have no real place to host these.

J. Lee

 

[pucho812]

asks for my log in.

 

[paranoidandroid]

I made a board using the 1:4 ratio neutriks as the frontend to a hamptone pre. Unfortunately, the two transformers i got on ebay a while ago and when i rigged them up i realized that the primaries are blown or something to that effect, no readout with my ohmmeter. there's a datasheet on the neutrik website, tho it's a little confusing as to what corrosponds to what. They are about the same size as the UTC ouncer series, maybe a little smaller, and rectangular.

 

[peterc]

I've used the Neutriks quite a bit, & like most of their products they are very good. As far as I know, the NTM 4 is about $50-00, which I think is a bit pricey when compared to a Lundahl.

I've pulled some from an old card & messed up the connections to the windings - they seem to be very sensitive to heat.

Peter

 

[bigugly]

peterc, thanks for the info. I'm glad to hear that those xfmrs sound good. If you're interested I can send the schem and PCB layout. It's a pretty simple circuit and the board dimensions are 3in X 1.7in, with the iron on the board.

If anyone wants to host these so everyone can take a look just drop me a line.

cheers,

James Lee
Big Ugly Van Audio

 

[bigugly]

Okay,

For those that are interested I took my schem over to Avedis @ B. Averill's
and he looked it over. We made some changes to Rs and Rf to get a good gain structure and last night I added a current buffer (BUF634) after the OPA604.

I also changed the board layout but made sure to keep it the same overall dimensions.

I've been thinking about a version with a discrete class A buffer instead of the BUF634 I just need to read some more about this.

cheers,
James Lee
Big Ugly Van Audio