Authentic LO1166 Neve output transformer

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Spencerleehorton

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Hi All,

Just thought I'd document my journey with making my LO1166 output transformers for my Neve preamps.
Have tested the carnhills and my versions are meant to have twice the inductance of originals.
Will detail how they sound next week.

Regards

Spence.
 

Spencerleehorton

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I will be running protools out the spdif through dat machine then into patch bay.
From there I can patch in all my mic pres and outboard.
I have Sowter input txf () and Carnhills VTB1148 on one stereo 1290 preamp, the others are all 1290 with Sowter input txf.
I will run same beat from addictive drums and try and make sure levels are the same for all.
 

Spencerleehorton

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Hi All,

this is a little picture of the prototype, and though i would comment on a few things first of all.
The original transformer info states that the PRI inductance is 305mh and the SEC is 814mh, it doesn't state at what frequency this was measure at or at what amplitude?

I have measured the Carnhill VTB1148 at different frequencies and different amplitudes and have some results to work from.
So far the new prototype is coming out better in inductance. The spec sheet has been followed to the letter and the 5 + 6 winds resistance is different, the sheet details 21.72ohms but its actually only 12.73ohms it comes out at.
At 1khz 0.775v the prototype is PRI = 160mh SEC = 404mh as a comparison the Carnhill was PRI = 134mh SEC = 340mh
I havent put the txf in the clamp yet or done the nylon with the pins.

Im going to put in preamp and test against Carnhill now.

regards

Spence.
 

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Spencerleehorton

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Well all i can say is it sounds wonderful!!

Ive attached a very unscientific frequency read out but it does show what i'm hearing quite clearly.

The Carnhill VTB1148 is on the left and the New LO1166 is on the right.

From 8 - 16khz the new TXF seems to be much better.
also a nice little dip at around 300hz which the Carnhill doesn’t have, this helps to clean up the lower mids.
Low end seems to look a bit better as well.
This is only very basic readings but i can hear all of these points, so it has made quite a difference, so very promising.

regards

Spence.
 

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Spencerleehorton

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Ive got a few more Neve pre-amps to try this out on here so will post up some more frequency charts using some different sources.
Drums, bass, guitar, sinewave, white noise etc, see how they come out.
 

ruffrecords

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Re your measured inductance values:

1. With iron cores, inductance tends increase as frequency decreases. Without specifying the frequency of measurement, a manufacturer's figures for inductance are meaningless.

2. This is a gapped core so it can pass dc current. The size of the gap makes a lot of difference to the value of inductance.

3. This is a gapped core so it can pass dc and it does pass dc in the Neve class A output stage. The dc current reduces the effective inductance of the transformer. The only value of inductance that matters is the inductance when carrying the required dc current.

4. More inductance is always a good thing as long as it is not at the expense of HF performance.

5. I am not a transformer expert but I have picked up a few things along the way.

Cheers

Ian
 

Spencerleehorton

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Hi Ian,

Without sounding arrogant, all of what you have said I'm well aware of.

My question is, if cj or who ever has stated these inductance values, what frequency and at what amplitude were they taken at?
 

ruffrecords

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Spencerleehorton said:
Hi Ian,

Without sounding arrogant, all of what you have said I'm well aware of.

My question is, if cj or who ever has stated these inductance values, what frequency and at what amplitude were they taken at?

I guess you should ask them?

Cheers

Ian
 

Spencerleehorton

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HI All,

I think the frequency which the LO1166 sheet had measured the inductance was at 20hz, i have tested at 750mA at 20hz and i get about 380mH on PRI and 960mH on SEC, so its very close.
I have just wound a 10468 and tested and has come out very good, ive put it into a 1290 preamp and test by putting some drums though and it out performs the Sowter/Carnhill 1290 by a mile!!! bottom end is so much better, top end is lovely and clear and mid range less muddy and more defined.
 

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Potato Cakes

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Fantastic work!

If you have extras, I would pay you for a couple to compare to some other Neve preamps I've built. I have a couple other Neve style projects I'm slowly putting together and would be curious how they perform. Will they fit in a 1U high unit?

Thanks!

Paul
 

Spencerleehorton

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No they won’t fit in 1U, but that’s the sound trade off with all that iron!

Kosi, they sound very Neve is my point, I’ve compared to carnhills and used the original data sheet from CJ to produce a completely accurate version.
These have been tested against the carnhills and there is a lot of differences in inductance, DCR and frequency response.
These versions come out much better on every level.
 

Spencerleehorton

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HI All,

Finally coming to the end of this now, just waiting for the lacquer to dry over the weekend then the first batch is done!!!

What do you think?
 

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bruno2000

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Spencerleehorton said:
HI All,

Finally coming to the end of this now, just waiting for the lacquer to dry over the weekend then the first batch is done!!!

What do you think?

I think I'd like to try a couple........
Best,
Bruno2000
 

Murdock

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Spencerleehorton said:
HI All,

Finally coming to the end of this now, just waiting for the lacquer to dry over the weekend then the first batch is done!!!

What do you think?

looking good! too bad it won't fit into a 1U. what are the dimensions?
Would definitely be interested in a pair if they could somehow be fitted in there.
 

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