Most transparent (lundahl) transformer?

[metalockpick]

Hello, to complete my recording setup I'd like to build a as transparent as possible reamp box. Are there any recommendations out there of transparent 1:1 transformers, which don't really alter the transient response, the frequency response and have very low THD?

 

[metalockpick]

Lundahl makes very transparent transformers. 100 ohm source impedance? You may need a buffer to drive that transformer to keep your high end. LL7901 would likely be your best bet for what you are asking, and you can run the windings in series to make driving them w/,your DAW easier.
For VERY high level, I find that LL1577 is superior to JE-12 DBE in terms of clarity and lack of saturation.

 

[CJ]

7901 has a big core and low turns so you will need a truck to drive it,

and a truck driver.

i might be able to help you there,

I'm just an old blue collar, semi-crazy road scholar they tell me that I'm half insane
And I've been driving so long, I got diesel in my blood and ninety weight oil on my brain.
'Til they put me in the ground they'll never shut me down
Til I'm six feet under I'll be rolling thunder. jus sayin, wtf?

 

[eraz]

I do have a bunch of various lundahls, marinairs, sowter, richenbach, jensen, etc here. I should run them through their paces and see what is up. I have done it for myself and I am sure its already here a kajillion times. But I have never shared what we see, and I do bore so easily.

Would be great if you could share your findings! Or perhaps even do some reamps so we can hear by ourselves

 

[eraz]

Lundahl makes very transparent transformers. 100 ohm source impedance? You may need a buffer to drive that transformer to keep your high end. LL7901 would likely be your best bet for what you are asking, and you can run the windings in series to make driving them w/,your DAW easier.
For VERY high level, I find that LL1577 is superior to JE-12 DBE in terms of clarity and lack of saturation.

Excuse my lack of knowledge, but if the source impedance (my interface line output) is around 100ohm and the LL7901 is designed to work perfectly with 600ohm (according to the specs PDF), shouldn't I be good then?

7901 has a big core and low turns so you will need a truck to drive it,

and a truck driver.

i might be able to help you there,

I'm just an old blue collar, semi-crazy road scholar they tell me that I'm half insane
And I've been driving so long, I got diesel in my blood and ninety weight oil on my brain.
'Til they put me in the ground they'll never shut me down
Til I'm six feet under I'll be rolling thunder. jus sayin, wtf?

Same question here.
Thank you very much for your help!

 

[metalockpick]

Excuse my lack of knowledge, but if the source impedance (my interface line output) is around 100ohm and the LL7901 is designed to work perfectly with 600ohm (according to the specs PDF), shouldn't I be good then?

Same question here.
Thank you very much for your help!

 

[metalockpick]

That big xformer has 8 identical windings. Run 2-4 in series on the primary, same on secondary for 1:1. Big core means extremely high level B4 saturation, not that it's harder to drive.
Consumer/prosumer gear has notoriously cheap output drivers
You want input impedances 10x the source impedance. Don't get this confused with optimum load impedance. If your source imp is 100 Ohms, that's meant to drive a minimum 1000 ohm load, or higher (I.E, input to some other prosumer device).

 

[Mikaeel]

For the last three days I've been trying to find out which Lundahl transformer will actually work.
The main problem is the wide variety of output impedances of the line out's. I'm trying to achieve the same requirements: most transparent, linear, low noise impedance converter. I understand that many people like to hear transformer saturation, but this is not always desirable and/or appropriate. Unfortunately, we have to use transformers because only transformers can provide true Halvanic isolation (digital alternatives not discussed here).
So I tried to see if the LL1530 would be useful:

Please don't pay attention to the inductance values (I had to cheat and entered simulated values to check the transformation ratio). Ground is placed before the first coil, because for some reason LTSpice shows more than 1:7 step-up.
The idea here is to omit the output potentiometer, and control the output level from the audio interface or DAW. A -4db attenuator is used here to avoid saturation and maximum primary level.
But... I think this circuit will work for line outputs with an impedance of less than 20 ohms. For line outputs with other impedances I do not know what to choose from the Lundahl products. I don't like the idea of building an opamp based impedance converter for this transformer. Any ideas? Or maybe there is a better matching transformer from Lundahl? Unfortunately I'm not experienced enough to read their data sheets.

 

[Mikaeel]

Also I found this:





What do you think about using the LL1540 in a reamp box design?

 

[Cqwet Dbdfte]

If you search you may find better LTspice transformer models that include core effects. The simplified "K L1 L2 1" model leaves out pertinent stuff (core effects, capacitances, leakage inductance, etc), and is pretty much just a voltage isolation/step factor, but ok for a first approximation.

 

[CJ]

Best way to do this is to try them all and send the ones you don't like over to me for '"evaluation."

 

[Cqwet Dbdfte]

...or better yet, send them to me for recycling.

 

[Mikaeel]

Best way to do this is to try them all and send the ones you don't like over to me for '"evaluation."

I wish I had the budget to try all their products.
Here is test of the crappy chinese made transformer (for audio! all impedance match)