transformer build thread

[jkeny]

Yea, maybe Richard would be interested in starting a thread on building trafos for DAC outputs/amp inputs - I would be keen to investigate further too!

Good that the chips arrived - hopefully before your ebay ones :)

[abraxalito]

is winding transformers difficult ?
id like to experiment more with them on the signal input to amp

Not so much difficult as testing of one's patience, which I suppose could be considered difficult. One thing that takes a while to get accustomed to is handling the wire - although the transformers you listened to weren't wound with particularly thin wire because they were designed for headphones, the optimum transformers in a line-level signal path would be wound with much thinner wire. So the first few times you have a go with wire that thin (we're talking like 0.08mm diameter and below) you're going to snap it. Which is a significant cause of frustration.

they sure were impressive on the day

Agreed.

I'd be happy to start a thread on transformers if there's some interest. I did one on DIYA to which there was significant push-back, here - http://www.diyaudio.com/forums/class-d/ ... guide.html

[abraxalito]

gnd loop through monitor earth is a common one

Yes and also the monitor contains a switching power supply so its an 'aggressor' in EMC terms, throwing noise into the system.

as the one we tried on the soekris didn't work that great nor sounded good, think we concluded it was the low output of the soekris?
could be a cool solution to funky grounds in hifi

Right, didn't you mention the Soekris wasn't buffered so had an output impedance in the region of a kilo-ohm or something? Trafos really do need to be driven by lowish impedances, particularly those examples which were designed for headphones. An optimized line-level trafo would do somewhat better.

[jkeny]

is winding transformers difficult ?
id like to experiment more with them on the signal input to amp

Not so much difficult as testing of one's patience, which I suppose could be considered difficult. One thing that takes a while to get accustomed to is handling the wire - although the transformers you listened to weren't wound with particularly thin wire because they were designed for headphones, the optimum transformers in a line-level signal path would be wound with much thinner wire. So the first few times you have a go with wire that thin (we're talking like 0.08mm diameter and below) you're going to snap it. Which is a significant cause of frustration.

they sure were impressive on the day

Agreed.

I'd be happy to start a thread on transformers if there's some interest. I did one on DIYA to which there was significant push-back, here - http://www.diyaudio.com/forums/class-d/ ... guide.html

Thanks, it would be best if Nige & I read that thread so you don't have to repeat stuff you've already posted & then maybe start a trafo build thread?

[jkeny]

I see in your DIYA thread on trafos a lot of the pushback was coming from an Irish guy named voltwide - anybody know who he is?
However, he does link to Burklin who have a small (28mm X32mm) isolation transformer for €23 here https://www.buerklin.com/en/search?text=pikatron
The datasheet doesn't give much (enough?) info & it's in German but it's a 1:1 1Kohm primary 1Kohm secondary 40Hz-20KHz freq
Is something like this suitable for DAC output/amp input use?

I know that means that there's no impedance step up/down & the DAC's o/p stage will not therefore have an easier time driving an easier load which is what you theorise is one of the main benefits of o/p trafos.

[abraxalito]

I confess I'm ignorant as to what the 1kohm impedance spec means in practice, I'm searching online for answers to this. My guess is its something to do with the primary (shunt) inductance of the transformer but at what frequency I haven't a clue... It would certainly work for your DAC as the internal opamps of DAC chips can normally drive 1kohm and given that its an inductive impedance it'll rise with frequency.

There are two main benefits of output trafos - the load lightening effect as you've mentioned but also the isolation. The latter one was borne out nicely by the experiment we did on Nige's system.

[abraxalito]

Thanks, it would be best if Nige & I read that thread so you don't have to repeat stuff you've already posted & then maybe start a trafo build thread?

What would be most interesting to me would be if you and Nige and anyone else would post up any questions you have arising out of that thread (after you've all read it and attempted to digest it) then I'll have a go at filling in the missing details. xrk on there wanted to know more winding details but I ignored that as he seemed to lose his initial interest after the various negative thread contributions...

[jkeny]

From the datasheet the 1k seems to relate to source & load (the translation of the German words quelle & last). There's also a 200 ohm version.
Does this mean that is the impedance that the source will see driving the trafo & the load being driven will also see?
Being a 1:1 winding ratio means that it doesn't present a lighter load for the opamp output stage of a DAC to drive?

BTW, does the small sizes of these trafos (28X23X16mm) (18X14.5X13mm) suggest steel cores rather than ferrite?

[jkeny]

I have a question from your first post on that DIYA thread - if there are more questions it would probably be best to start a new thread - let's see how it goes?
My question is - I know what low frequency I want (20Hz) but how do I know what Volt-seconds I want? How does V-s translate into what we hear? Is it the speed of the rise time of the signal? Does this translate into transient response? How do we know what transient response we need - I would think as fast as possible would be the answer?

Turns out this is many questions rather than just one :)

[jkeny]

BTW, a good deal has just appeared today on DIYA http://www.diyaudio.com/forums/swap-mee ... ost4832808
A pair of line level Cinemag 15/15B trafo for £85 + shipping from UK.
These normally go for €180 each