Neve transformer enamel. Strange conclusion

Hello everyone,

It's been quite some time since I have posted here but I figured this one would be worth a post...

I did a fun experiment last week where I took a Heritage Audio Classic 1073 module and wired it into a 19" case. For the most part the same layout is used. The same transformers and even the same wire. Not much was unsoldered during the transfer except for the transformers for re-positioning in the 19" frame.

I had several reason's for doing this, one was that I was selling a rack I didn't need that someone wanted. Secondly I have tons of custom 19" 1073 metal work around so I figured why not, sounds fun.


Here's where things get weird. After the transfer into the new case the preamp sounded completely different. Almost like a blanket was over it.

I quadruple checked everything and then checked again. Ran AP test and sweeps and measurements, everything looked good on paper but it didn't sound as good anymore.

So after countless hours of research there's only one thing I can think of that would cause this. The transformer enamel on the windings. I use lead free solder witch requires my iron to be at 850F.

After really thinking about it and being this is the only thing I unsoldered and soldered again, I think the enamel on the windings might have been burned. This would affect the capacitance of the transformers and also the high end if this is really the case, resulting in the "blanket effect".

I figured this was worth sharing. I guess the only way to be sure is to fit new transformers in the unit with a much lower iron temp and see if it sounds any different. Unless anyone can think of anything different.

Thoughts?

Aaronrash said:

This would affect the capacitance of the transformers and also the high end if this is really the case, resulting in the "blanket effect".

Click to expand...

Howdy Aaron,
like in this thread http://groupdiy.com/index.php?topic=54748.msg699205#msg699205  it seems unreal to me that your measurements if proper made still don't show a loss of high end you could hear.

Aaronrash said:

I figured this was worth sharing. I guess the only way to be sure is to fit new transformers in the unit with a much lower iron temp and see if it sounds any different. Unless anyone can think of anything different.
Thoughts?

Click to expand...

Then you would compare differents Tx. Not a proper comparison IMO.
Try to put it back in the HA module to see if you can get back the sound you want. Did  you think of grounding your 19" case ?

Btw how  do you think of the sound of the HA one vs the ams ones you have ?  do they also have that sheen on the top end you want so bad ?  ;D

There's been lots of things I can hear that aren't measurable beyond a simple frequency response. .. There's also too many things to measure in this instance like inter-modulation distorion etc... The problem is I would have to measure at all the different gain settings. The harmonic distortion response is not flat either, the transistor distortion typically tens to distort the higher frequencies first before the low frequencies due to the NFB loop. That's part of the "sheen" sound I like so much.

The heritage audio module was doing it in spades just like my vintage modules before I moved it to the 19" case!

Case is grounded properly and the same PSU. The only thing changed was unsoldering the transformers like I mentioned above.

Anyways, I love the HA module they really nailed the sound perfectly. I also have 10 vintage 1073 modules now as well that I have had for a year or so. I prefer the HA module over some of the vintage units. They all sound a little different from each other and allot of them have the "ladder switch revision'' witch uses fixed feedback on the 283 card. Sounds a little different.

I sold all my AMS modules about a year ago, there was way too many inconsistencies. Some modules would sound really good, some sounded like crap. You also gotta keep in mind they all go through AMS test department before they leave the factory.