Old Audio Transformers For Tube Preamps

[sarakisof]

Hello folks, being in the middle of the process for the Gyraf G9 tube pre / di (not p2p) , i am looking for other options than those suggested for input/output trannies. Old ones but something i could find on cheap, by cannibalising other circuits.

http://www.gyraf.dk/gy_pd/g9/g9_sch.gif

Most guys build those with OEPs (cheap but "new" modern sound) or Lundahls (expensive). There are some others having used old Beyer 1:5 for input and Edcors out with good, fat "mojo" results. So i am looking for smthng similar but you know those Beyers nowadays tend to be priced too.

So here we are for a general discussion maybe, not only for the G9. For example, i found those trannies for a good price. Could they be used somewhere in G9? If not, what are they could be good a option for? They are 1:1+1. A passive di maybe?

What about transformers from old military radios? They are all rock solid, well made and would give a great mojo for sure but most of them are narrow frequency spec as designed for radio use. But i am sure there are some pretty good in terms of freq range too. Or from other stuff, apart from all those well known "pro audio" wsw Siemens, Telefunken, tab etc. from past era. Maybe there is old consumer stuff out there waiting for us. 

[sarakisof]

Edit: Forgot the datasheet. Here it comes

[iainpunk]

i hope you understand that old transformers don't sound different right? if you want to have ''transformer mojo'' in the sound, get one that's rated for a too low voltage, this makes the transformer saturate, especially at low frequencies.
i have done a bunch of experimenting with chopping slots partially through the transformer core to make it saturate at lower levels for a transformer fuzz, its weird and sounds nasty in a not so cool way.

anyway, i recommend getting a new, modern one! or if you are creative, you could use a mains transformer.

cheers, Iain

[sarakisof]

 Yeap ok, but let's say i could find old gear or military surplus stuff, what specs i should look for G9? I am a bit confused here. Some say any 1:5-1:10 for input and 2:1-5:1 for output should be fine. Then again i was ready to use a Beyer 35536  1:5 for input and the same for output (backwards) and they stopped me saying Beyer should only go for input, no for output as the level is to high. But I don't get this last one.

Ps. I think that old irons is smthng we cannot find today and that this has smthng to do with a different sound compared to nowadays, I'm not saying better, but different for sure. There are people having spent many years studying and trying to reproduce the way, materials etc used in old coils. Some prefer them, some others don't. I personally believe like in pick ups , that all those things count, coils, bobbins, cores, iron, insulating material etc etc

[FiveseveN]

I personally believe

But do you have any proof or at least some first hand experience or are you chasing something someone else has convinced themselves (and presumably you) is true?

[sarakisof]

Having A/B listened in friend's studio to some preamps in the past by using in one channel new and in the other old trannies almost always preferred the old ones. OEPs for example were too aggressive for my ears. I have also rewinded many old broken guitar and bass pickups while winded also some of them (same) with new enamel wire. Again i preferred the old ones. Just a personal preference.

But the topic was about smthng else. I was asking about how a 1:5 tranny could work as input and not as 5:1 output in G9 circuit. Knowing that we want about 600:10K input and 2.4K:600 output..

[rankot]

Is it so important to use in/out tranny, or one can use dedicated in/out ICs, like INA163 or DRV134?

[iainpunk]

Having A/B listened in friend's studio to some preamps in the past by using in one channel new and in the other old trannies almost always preferred the old ones. OEPs for example were too aggressive for my ears. I have also rewinded many old broken guitar and bass pickups while winded also some of them (same) with new enamel wire. Again i preferred the old ones. Just a personal preference.

But the topic was about smthng else. I was asking about how a 1:5 tranny could work as input and not as 5:1 output in G9 circuit. Knowing that we want about 600:10K input and 2.4K:600 output..

i have done numerous double blind tests of different types of components with my old colleagues at the venue where i used to volunteer. (everything from op amps and diodes to guitar tone caps and transformers). if i were a betting man, i'd bet that you can't tell the difference between most 10:1 transformers when doing a double blind test, let alone hear which is old or new, given that i supply the transformers from my own collection. i have quite the collection of transformers (about 35), and some have characteristics that sound ''more vintage'' whilst being brand new and others are form the 1920's and sound clear like brand new ones, its just a matter of choosing the right transformer, regardless of age.
i don't think mil surp is a good trafo source, most of the time, they don't care about Hi-Fi, but about saving weight and cost.

i don't see why you can't use the 5:1 on both the in and output, should be fine.

Rankot, the transformers are because the voltage that comes out of the last SRPP stage is quite high and low enough impedance that it can drive a reasonably heavy load, with an output transformer of 5:1, the output impedance is about 150 Ohm. it just doesn't make sense to use an output chip when you already have an push-pull output tube stage.

cheers, Iain

[rankot]

But why not INA163 for input?

[amptramp]

You might be looking at some pricey stuff here.  Hammond has several series of broadcast-quality transformers with series numbers 560, 800A, 850A, 1140, 140EX.  They also have cheaper interstage transformers in the 124 series but it does not have the low frequency response that would match what you already have.  Check here:

https://www.hammfg.com/electronics/transformers/audio

[rankot]

And why not using OEP transformers? They are available and cheap.

[iainpunk]

And why not using OEP transformers? They are available and cheap.

this

Having A/B listened in friend's studio to some preamps in the past by using in one channel new and in the other old trannies almost always preferred the old ones. OEPs for example were too aggressive for my ears....

[Derringer]

FWIW, I'm a novice with the fancy equipment but I did build a pair of tube mic-pres this past summer. One has a Jensen input with edcor output and the other has edcor in and edcor out. They're different circuits so I can't really compare the Jensen to the Edcor fairly. However, both pres sound good to my ears. Get some transformers that work, that you're comfortable paying for, and build the thing. Maybe build it in a way that you could swap transformers at a later time. After it's built, keep an eye out for fancy mojo transformers, pick one up when you find a deal and swap it in to see what's what.

And I remember pouring over that Gyraf schem, among many others, when I was figuring out what to try design-wise.

Oh ... and if you do go the edcor input route, you'll have to get crafty with how you mount it. The OT's have mounting tabs but the Input I bought did not. I ended up making a little cradle out of FR4

[PRR]

https://www.amazon.com/Shure-A85F-Transformer-Female-4-Inch/dp/B0006NMUHW

[rankot]

https://www.amazon.com/Shure-A85F-Transformer-Female-4-Inch/dp/B0006NMUHW

I can't find any specs for that one. What is it's frequency range?

Also, did anyone tried Neutrik transformers for microphone preamps, like this, for example: https://www.canford.co.uk/Products/21357/23-002_NEUTRIK-NTM4-TRANSFORMER-Analogue-audio-PCB-microphone-input

[PRR]

> I can't find any specs for that one. What is it's frequency range?

You wanted cheap, auction, old military. You want specs too??

Buy a couple. They are universally useful for stage audio. They do not sound like bad specs.

They come out of Asia now and flood America and West Europe. I'm sure there are places they are hard to find.