tresaino wrote: What I'm currently exploring is whether we can change step-up transformers from RCA to balanced (both in and out). Some people say that step-ups are also inherently balanced and therefore this is not a problem, however it has been said before that cartridges are 'differential' but not a true balanced device - as for that one would need a center tap on the cartridge coil.
Steerpike_jhb wrote: Absolutely you CAN! The only thing you need to pay attention to is to ensure symmetry throughout. A cartridge is as balanced as you can get. Centre tapping just causes problems and asymmetry.
It has taken me a year to get there, what you see/don’t see in the crappy box on top of my preamp are Lundahl LL1931 step-up transformers, connected in 1:16 and in ‘balanced’ mode.
I actually suspect the Lundahls are not connected in truly balanced but rather in differential mode, as I can see no third wirings on the XLR connectors or going to the ground tap on the back of the box. Useful information about the LL1931s and how to connect them can be found on their website: http://www.lundahl.se/pdfs/datash/1931.pdf
My original plan had been to rewire the Bent Audio step-up transformers from RCA to balanced mode, but John Chapman from Bent Audio responded that on the TX103 secondaries there were only 2 (and not 3) wires, therefore he could not rewire for a “true balanced” mode. He was obviously aware that cartridges do not have 3 wire balanced connections and are ‘differential’ but not a true balanced device, however he said he still felt better if the step-up transformer was connected in true balanced rather than in differential mode. The story went on and he was supposed to build a new pair of MUs in balanced mode for me, but in the end it didn’t work out and we lost contact, so I started to explore different avenues and ended up with Lundahls.
I won’t comment on the quality of sound here, as other people compared the Bent TX103s with the Lundahl LL1931s before me. Except to say that they are indeed extraordinarily transparent and that I am not looking for anything better.
What I want to comment on is the connection in ‘balanced/differential' mode and the resulting absolute, total silence – no hiss or hum whatsoever! Absolutely nothing, there is no difference in noise if I switch from the CD input to the phono input on the preamplifier. I have been playing with step-up transformers for quite some years by now, I love them but have to admit that all of them gave me at least some hiss or hum, particularly when I cranked up the volume or if the step-up ratio was on the higher side. Not any more, these Lundahls are as silent as it gets.
I don't think this was ever discussed here properly, but step-up transformers connected in balanced/differential mode are a small revolution to my ears.