transformer build thread

[abraxalito]

http://ie.farnell.com/pro-power/rrp-g-1 ... /dp/146183
Delivery usually takes about a month from china

That's a miniscule reel of wire for a 'Roadrunner' wiring pencil - only 38m which probably won't fill a single winding on a trafo. You'll need a reel with a few hundred metres at least.

[abraxalito]

not certain but at a glance and very primitive understanding there seems to be two banks of r's a pos and neg signal which are merged at the end of the ladder to provide the 1.4vrms
ive no idea what would happen if they were separated and used as pos and neg
maybe it dont work that way?

Correct, it dont work that way. The two banks are the designer's implementation of the 'Colinear' concept (see the PCM63's datasheet).

this is how they got the stock bal buffer out without a v- signal

Useful to see a typical 'engineering' solution using opamps which ignores the noise they create on the power supplies. The feedback resistors around the opamps represent loads which ensure that the opamp's output stage switches and puts higher order harmonics on the rails. These ultrasonics then couple into the signal via the 'decoupling' caps to the signal GND.

I've found to get opamps sounding good the feedback resistors need to be much higher value, which then means bipolar input opamps can't be used (due to noise with high source impedance). Even TL074s sound pretty decent using this trick.

[abraxalito]

@Richard - Doesn't the wire diameter have a bearing on the transformer behaviour apart from core size but maybe not so important for these low signal handling function?

Larger wire is going to have a bit more stray capacitance and larger cores will be more prone to hum pickup yep. But larger wire has lower DCR so its not all downside.

[nige2000]

http://ie.farnell.com/pro-power/rrp-g-1 ... /dp/146183
Delivery usually takes about a month from china

That's a miniscule reel of wire for a 'Roadrunner' wiring pencil - only 38m which probably won't fill a single winding on a trafo. You'll need a reel with a few hundred metres at least.

Although I dont like the way that sounds

maybe easier for you to pop some suitable wire and bobbins etc in a bag and send it over to us

[nige2000]

not certain but at a glance and very primitive understanding there seems to be two banks of r's a pos and neg signal which are merged at the end of the ladder to provide the 1.4vrms
ive no idea what would happen if they were separated and used as pos and neg
maybe it dont work that way?

Correct, it dont work that way. The two banks are the designer's implementation of the 'Colinear' concept (see the PCM63's datasheet).

this is how they got the stock bal buffer out without a v- signal

Useful to see a typical 'engineering' solution using opamps which ignores the noise they create on the power supplies. The feedback resistors around the opamps represent loads which ensure that the opamp's output stage switches and puts higher order harmonics on the rails. These ultrasonics then couple into the signal via the 'decoupling' caps to the signal GND.

I've found to get opamps sounding good the feedback resistors need to be much higher value, which then means bipolar input opamps can't be used (due to noise with high source impedance). Even TL074s sound pretty decent using this trick.

Ok thought it was a bit strange two banks of resistors merged

Although I never listened to the stock buffed outputs many was not impressed
removing them did improve the unbuffered out sq

[nige2000]

found this last night from the scrap heap
its a paul pang audio silver transformer
http://ppaproduct.blogspot.ie/2013/07/a ... -card.html

it takes the oscillator signal and curiously through an in series cap....

on the scope it looked kinda like this
post and pre transformer


it certainly provided a smoother sound
however on my modded pcs i prefered clk signal direct from oscillator because i felt there was a loss of resolution/timing

during some messing i found if the oscillator signal was ringing it lead to an unpleasant harsh sound and a sinewave type sounded smooth

[abraxalito]

Looks as though that might be a ferrite cored toroid, as I have some green cores a bit like it. Winding transformers on toroids isn't much fun at all beyond single digit turns numbers....

[nige2000]

Looks as though that might be a ferrite cored toroid, as I have some green cores a bit like it. Winding transformers on toroids isn't much fun at all beyond single digit turns numbers....

seems to be 10 turns primary and secondary
presume some sort of curved needle would be useful

is there some sort of jig that could be constructed to do the winding
with a little motor...

[abraxalito]

https://www.aliexpress.com/item/Hand-Wi ... 23086f657b

something like this but it requires elbow grease. Heavy brute, the shipping's more than the item.

[nige2000]

https://www.aliexpress.com/item/2016-hi ... 39524a3c1e

says free shipping
can the bobbins be mounted on a chuck?

i was thinkin more like duct tape, elastic bands and cordless drill