Need output transformer (suggestion)

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owel

Well-known member
Joined
Jun 3, 2004
Messages
1,088
Location
Nashville, USA
I racked some Sony mic preamp and EQ, and the output I'm getting is about 13Vpp. I tried a Sowter output trafo (bought here at Prodigy pro!) and used it as 1:1.5 and I was able to bump it up to 17Vpp.

The problem is the Sowter 8751 output trafo won't fit inside my 1u case. Too tall!

Can you guys recommend an output transformer model that will fit inside a 1u case, with 1:1.5 step up?

Thanks!
 
:green:

http://recording.org/users/kev/sowter_TXs.htm

9160 Neve 1073 Line Output
Ratio 1:1.5. Sowter replacement design for Neve P/N L01166.
Optimised for voltage drive circuit. Max output level +27 dBu.
Total dc resistance ref secondary 37 ohms.
This is identical to type 8751 except we have used a 0.75 inch core instead if 1.0 inch.
Ideal for rack mounting. Size "OA" ( Width 40 mm.)
ST9160.jpg




Key differences with the 8751 is :
8751
Max output level +30 dBu.
Total dc resistance ref secondary 39 ohms.
Size "OB" (Width 46 mm)
9160
Max output level +27 dBu.
Total dc resistance ref secondary 37 ohms.
Size "OA" ( Width 40 mm.)
 
Thanks for the quick responses guys!

I checked the 9160 and it seems according to Sowter website it has the same height of 50mm just like the 8751. Bummer!

Lundahls don't have 1:1.5, only 1:2.... Will that be okay? I suppose so, my output will go from +18dB to +24dB....

Who's that KandK audio guy that visits the board?

I'm still open to suggestions... the cheaper the better... or maybe I should just go use opamps to create a balanced output driver... but don't really wanna do that... The Sony mic pre has Jensen input transformers so I want to make both input and outputs transformer-balanced....
 
> Sony mic preamp and EQ, and the output I'm getting is about 13Vpp.

What's the power supply and intended use of this Sony preamp?

What load are you driving? What load is the Sony made to drive?

What is wrong with +15dBm, that you need another 3.5dB (1:1.5)?
 
>What's the power supply and intended use of this Sony preamp?

It's a mic pre from the Sony MXP3036 console. The power supply is +18-0-18V. From the output of the preamp, it goes to the EQ module.

> What load are you driving? What load is the Sony made to drive?

I think they're made to drive 600ohms, but not sure... I don't have any specs. On the EQ module, it also has it's own driver stage.

> What is wrong with +15dBm, that you need another 3.5dB (1:1.5)?

Nothing wrong with +15dBm. Right now, I'm using buttachunk's MCI416 transformer 1:1 specs. The only 2 transformers I have to play with are the MCI and the 8751 Sowter.

I want transformer output so I can convert it from unbalanced to balanced without using opamps.
 
[quote author="Dan Kennedy"]The two Sowters are the same height, tall wise, but the 9160 is
thinner, which is why it fits in a single rack space where the other one
won't.[/quote]

Thanks Dan for the clarification.
 
If you want to use a transformer that will indeed fit, try a Lundahl LL1588. It can be connected 1:1 or 1:2.
 
[quote author="Dan Kennedy"]The two Sowters are the same height, tall wise, but the 9160 is
thinner, which is why it fits in a single rack space where the other one
won't.[/quote]
&
[quote author="Kev"]9160 Neve 1073 Line Output
Ratio 1:1.5. Sowter replacement design for Neve P/N L01166.
Optimised for voltage drive circuit. Max output level +27 dBu.
Total dc resistance ref secondary 37 ohms.
This is identical to type 8751 except we have used a 0.75 inch core instead if 1.0 inch.
Ideal for rack mounting. Size "OA" ( Width 40 mm.)[/quote]

Apart from the height & level-difference of those two Sowter-TXs
& despite the 'identical' above, I was still wondering if there's any
noticable difference in sound between the 9160 & 8751 ?

Dunno, no such thing as somewhat lesser lows for instance?

Thanks,

Peter
 
glad you noticed that post

obviously the low end at high level
AND 600 and lower loads
... is where the smaller size could make a difference
Saturation and Distortion are a possible differences ... and the phase
AS for how this changes the sound and to what degree
you really have to try these things to know for yourself

there are other variables and then there is personal taste
 
[quote author="Kev"]glad you noticed that post

obviously the low end at high level
AND 600 and lower loads
... is where the smaller size could make a difference
Saturation and Distortion are a possible differences ... and the phase
AS for how this changes the sound and to what degree
you really have to try these things to know for yourself

there are other variables and then there is personal taste[/quote]

Agreed of course, there'll be no ready-made answers (one's always hoping :wink: but knowing at the same time it wouldn't make complete sense if they were really existing).

The notion I have of those gapped beasts is that they're able to deliver much more signal than the next box or DAW could handle, so likely the eventual limitations at high level (thanks for pointing out :thumb: ) won't be that big a problem.... they're all still not sweating.

But thinking of the analogy of say a 25W vs a 100W gtr-amp, one often would go for the lower power to get the nice nasty goodies quicker.
That thought just struck me as a possible reason to go for the smaller 9160. And the 1HE box, but 2HE would fine by me as well.

Thanks,

Peter
 
The bigger/smaller core will also change the high end a tad, since you now have a different cross section on the coil, and therefore leakage will change a bit. I had a Linx output in here a few days ago but forgot to check the leakage. It weighed in at 1.38 lbs. Resonance was higher than stock Neve.
Huge core.
Took a lot of generator to drive the low end.
The ecitiation knee will cjange with the bigger core. There will be more non linearty at the lowest signal levels, as the core needs more juice to get all the domains swinging.
 
[quote author="CJ"]The bigger/smaller core will also change the high end a tad, since you now have a different cross section on the coil, and therefore leakage will change a bit. I had a Linx output in here a few days ago but forgot to check the leakage. It weighed in at 1.38 lbs. Resonance was higher than stock Neve.
Huge core.[/quote]

Thanks. :thumb: How to see that, the bigger cored TX passing less highs ? Or just different ?

And another cheers to that Lemmy-avatar. It gives the feeling that you're constantly being looked at; the Mona Lisa pales in comparison :wink:
 
I ran a few simple checks on one of my Lynx Neve type output transformers last night. I used my BelMerit CM225 digital LC meter, FWIW.

Lynx has two primaries: violet-gray and orange-brown. Single secondary: blue-yellow.

Inductance:
v-g = 402mH
o-br = 417mH
bl-y = 1242mH

Leakage inductance (with instructions from CJ):
y-bl = 1700uH with v-g shorted, o-br shorted
y-bl = 1600uH with v-g shorted, o-br open
o-br = 345 uH with v-g shorted, y-bl shorted
o-br = 29uH with v-g shorted, y-bl open
o-br = 634uH with v-g open, y-bl shorted

Leakage capacitance (all connections open)
v-o = 13.86nF = 0.01386uF
v-bl = 277pF

Hope this is of some interest to someone...

A P
 

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